Motoyama & Davis: Smith's Anesthesia for Infants and Children, 7th ed.

PART TWO – General Approach to Pediatric Anesthesia

Chapter 14 – Pediatric Regional Anesthesia

Allison Kinder Ross

  

 

Safety Issues, 459

  

 

Regional Anesthesia in the Anesthetized Child, 459

  

 

Age-Related Changes in Neurotoxicity, 460

  

 

Risk of Infection, 460

  

 

Compartment Syndrome, 460

  

 

Local Anesthetics in Children, 460

  

 

Local Anesthetics and Risks of Toxicity, 461

  

 

Reviews of Safety of Regional Anesthesia in Children,464

  

 

Advantages of Regional Anesthesia in Children, 465

  

 

Central Neuraxial Blockade, 465

  

 

Spinal Anesthesia, 465

  

 

Caudal Anesthesia, 468

  

 

Continuous Caudal Catheters,474

  

 

Epidural Anesthesia, 475

  

 

Peripheral Nerve Blocks, 477

  

 

Upper Extremity Nerve Blocks, 478

  

 

Lower Extremity Nerve Blocks, 482

  

 

Continuous Peripheral Nerve Catheters, 492

  

 

Ilioinguinal/Iliohypogastric Nerve Block,492

  

 

Penile Nerve Block, 494

  

 

Intercostal Block, 495

  

 

Paravertebral Nerve Block, 496

  

 

Blocks of the Face and Scalp, 498

  

 

Intravenous Regional Anesthesia, 499

  

 

Topical Anesthesia, 500

  

 

Miscellaneous Pediatric Regional Anesthetic Blocks, 501

  

 

Summary, 501

The practice of pediatric regional anesthesia has evolved over the past century from the study of spinal anesthetics in infants and children to an integral part of a sophisticated multispecialty practice involving continuous local anesthetic infusions with patient-controlled analgesia based on age-appropriate pharmacokinetics. Performing regional anesthetics in children may be perceived as difficult because of the age-related variations in anatomy and depth of structures. In addition, other issues, such as increased risk of toxicity of local anesthetics and lack of appropriate equipment, may present challenges to many practitioners when it comes to performing regional anesthesia in a child. To safely practice regional anesthesia in children, it is important to understand the safety issues regarding the pharmacokinetics of local anesthetics and their additives, to have knowledge of the anatomy in children of different ages, and to be aware of the indications and complications of the specific regional blocks.

▪ SAFETY ISSUES

There are five major safety concerns regarding administering regional anesthesia to children:

  

1.   

Need for children to be anesthetized for placement of the regional block

  

2.   

Age-related changes regarding neurotoxicity

  

3.   

Risks of infection

  

4.   

Ability of regional anesthesia to mask an underlying compartment syndrome

  

5.   

Proper use of local anesthetics and risk of local anesthetic toxicity

▪ REGIONAL ANESTHESIA IN THE ANESTHETIZED CHILD

Perhaps the biggest difference between adult and pediatric regional anesthesia other than the obvious size discrepancies is that children typically receive their regional anesthetic while they are under general anesthesia. This practice remains controversial outside of the pediatric arena ( Bromage, 1996 ; Bromage and Benumof, 1998 ; Rosenquist and Birnback, 2003 ). Part of this criticism was based on a closed-claim case report of a woman who developed paraplegia following the placement of an epidural while she was under general anesthesia. As was pointed out in editorials by Fischer (1998) and by Krane and others (1998) , this particular case, however, does not support the argument that the general anesthetic was the basis for the bad outcome. The actual cause of the paraplegia remains unknown, and there were many factors that could have led to such an outcome, such as previous lumbar laminectomy, unsuccessful initial attempts for epidural placement, placement of a thoracic epidural catheter, multiple episodes of intraoperative hypotension, and the presence of air in the thoracic region at the spinal cord on magnetic resonance imaging (MRI). Bromage and Benumof made the assumption that the patient could have warned the practitioners of a problem had she not been under general anesthesia. This also assumes that the patient's sedation would have been at a level that would have allowed her to provide warning signs. Although these assumptions may have some basis of defense, difficult block placement by inexperienced practitioners, use of air for loss of resistance, and intraoperative hypotension are all major risk factors for adverse outcome whether general anesthesia is present or not. Further, because of differences in patient cooperation, the practice of performing a regional anesthetic in children differs greatly from placing a block in an adult. The practice of performing regional anesthetic blocks during general anesthesia in children, including thoracic epidural blocks, is an accepted practice as long as the individual has the proper training and expertise. Over 50 international pediatric anesthesiologists signed the editorial by Krane and others to support the placement of blocks in anesthetized children. In fact, “it would be considered malpractice to perform such techniques in patients who were not fully anesthetized” ( Dalens, 1999 ) and “any performance of a block in an agitated and moving child is not only unethical, but could be dangerous when the needle approaches the delicate nervous structures” ( De Negri et al., 2002 ).

Rosenquist and Birnback wrote an editorial in response to a large retrospective study of 4298 adult thoracic surgical patients who underwent lumbar epidural catheter placement while under general anesthesia ( Horlocker et al., 2003 ). In this large series, there were no neurologic complications including radicular symptoms or persistent paresthesias. Rosenquist and Birnback, however, echoed the sentiments of Bromage and Benumof that the risk-benefit ratio does not support the use of epidural blocks in anesthetized patients; they also stated that epidural blocks have been used in anesthetized children for over a decade and that “extrapolation of pediatric data to adult practice is not warranted and offers no reassurance” (2003).

In children who are under general anesthesia or who are heavily sedated, it may be difficult to recognize intravascular injection of a local anesthetic. For this reason, the practice of test dosing with a local anesthetic with the addition of epinephrine has been readdressed and should be a common practice ( Tobias, 2001 ). It is also argued that an anesthetized child cannot warn the practitioner of a significant paresthesia and that there is the potential risk of neurologic injury from intraneural placement of a needle or anesthetic. This is a hypothetical risk that has not been supported by reports of large series of pediatric regional anesthetics ( Pietropaoli et al., 1993 ; Goldman, 1995 ; Giaufre et al., 1996 ).

▪ AGE-RELATED CHANGES IN NEUROTOXICITY

The use of local anesthetics and neurotoxicity on the developing nerve is an area that continues to be addressed. Animal data have demonstrated that all local anesthetics are potentially neurotoxic, and this neurotoxicity parallels their anesthetic potency ( Selander, 1993 ). The factors that contribute to the mechanism of the neurotoxicity include the concentration of the local anesthetic and the time of exposure of the nerve to the local anesthetic. This is important in children, particularly in neonates, who may be at the greatest risk of direct neurotoxicity during nerve development and should not receive the higher concentrations of local anesthetics. Studies on rabbit nerve fibers have demonstrated an increased sensitivity to the blocking effects of local anesthetics in young nerves ( Benzon et al., 1988 ). Additional in vitro biologic investigation has demonstrated that lidocaine, bupivacaine, mepivacaine, and ropivacaine all are capable of producing growth cone collapse and neurite degeneration (Radwan, 2002). However, the incidence of growth cone collapse with bupivacaine and ropivacaine is insignificant compared with lidocaine and mepivacaine. Additional investigation in this area is imperative to better understand the mechanisms behind neural injury and how it may affect nerves in children of different ages.

▪ RISK OF INFECTION

Another safety consideration is the practice of preparing the skin before a regional block to reduce the risk of infection. Before placing any block, sterile preparation of the skin should be performed, but this is particularly important for central blocks to reduce the risk of meningitis or epidural abscess. The use of povidone-iodine, although useful for cleansing the skin before a regional block, may be harmful to the very sensitive skin of an infant. The povidone-iodine should also be allowed to dry and not be carried centrally with the needle into the epidural or subdural spaces. After the block has been placed, the iodine should be washed from the skin to avoid iodine burns. Chlorhexidine is recommended over the use of povidone-iodine as it has been shown to decrease colonization when used in young children for epidural catheter placement ( Kinirons et al., 2001 ; Wagner and Prielipp, 2003). The actual risk of infection from regional techniques, however, is extremely low. For indwelling caudal catheters, the incidence of catheter tip colonization is 20% versus 4% for indwelling epidural catheters ( McNeely et al., 1997 ). No patients with bacterial colonization of the catheters exhibited systemic signs of infection. Strafford and others (1995) studied 1620 children who received epidural catheters. There were no infections in the children who had the catheters placed for postoperative analgesia and only one significant infection in an immunosuppressed child who received a catheter on a long-term basis for pain secondary to her malignancy ( Strafford et al., 1995 ). Giaufre and others (1996), in a prospective study of over 24,000 regional techniques performed in children by members of the French-Language Society of Pediatric Anesthesiologists, reported no infections.

▪ COMPARTMENT SYNDROME

A concern often cited for failure to perform a regional anesthetic in pediatric patients for orthopedic procedures is the risk of an unrecognized compartment syndrome. The theory behind this concern is that the local anesthetic in the regional block may mask the initial symptoms of the sensation of pressure in the limb, which may lead to unrecognized compartment syndrome ( Dunwoody et al., 1997 ). Case reports in children have demonstrated that a successful epidural block with a low concentration of local anesthetic does not mask the symptoms of compartment syndrome. They recommended that one should perform serial examinations on children to assess the operated extremity in the presence of good analgesia. Another option in a high-risk child is to measure compartmental pressures postoperatively in children who would clearly benefit from infusions of local anesthetic, such as those who have undergone microvascular surgery or amputation.

▪ LOCAL ANESTHETICS IN CHILDREN

There are age-related changes in local anesthetic pharmacoki netics and pharmacodynamics. There are two classes of local anesthetics: the amides and the esters. Amides undergo enzymatic degradation in the liver. Local amide anesthetics should be used carefully in children, particularly in neonates and infants, as they may lack the ability to distribute and metabolize these agents effectively. Ester anesthetic agents are metabolized by plasma cholinesterase and have less age-related changes in metabolism.

Amide-class local anesthetics include lidocaine, etidocaine, prilocaine, mepivacaine, bupivacaine, levobupivacaine, and ropivacaine. Although all of these agents have been used for regional anesthesia in adults, etidocaine, mepivacaine, and prilocaine are rarely used in children. The choice of local anesthetic depends not only on the desired onset time and duration of action of the regional block but also on the safety of the agent.

Amide anesthetics are primarily protein bound in the plasma. Bupivacaine, levobupivacaine, and ropivacaine are more than 90% bound to the plasma proteins α1-acid glycoprotein (high affinity for local anesthetics) and albumin (high volume and relatively low affinity for local anesthetics). It is the free or unbound fraction of the local anesthetic that is physiologically active and is responsible for its effect on the cardiovascular and central nervous systems. Infants less than 6 months of age have decreased levels of plasma proteins, which results in a larger free fraction of local anesthetic and consequently places this age group at a greater risk of toxicity from these agents ( Lerman et al., 1989 ; Berde, 1992 ). As an infant matures, the plasma proteins increase and the plasma free fraction of the drug decreases. Adult levels of protein binding are reached at about 1 year of age ( Fig. 14-1 ). Of interest is that α1-acid glycoprotein levels increase in response to surgical stress, and the increased α1-acid glycoprotein ultimately decreases the free fraction of local anesthetic agent. This occurs even when total plasma concentration appears to be near toxic levels (Tucker, 1994, 1996 [263] [261]; Booker, 1996) . Metabolism of amide local anesthetics occurs via the liver's cytochrome P450 system. These enzymes reach adult activity by the first year of life. The immaturity of liver enzymes in neonates and infants contributes to the decreased clearance of amide local anesthetics seen in this time period.

 
 

FIGURE 14-1  A, Age-related changes in the plasma concentration of α1-acid glycoprotein. B, Age-related changes in the plasma free fraction of bupivacaine.  (From Mazoit JX, Denson DD, Samii K: Pharmacokinetics of bupivacaine following caudal anesthesia in infants.Anesthesiology 68:387, 1988.)

 

 

 

Ester anesthetics (e.g., chloroprocaine and tetracaine) depend on plasma esterases for their elimination. Similar to the decreased levels of plasma proteins in neonates and infants, there are decreased levels of plasma esterases as well ( Zsigmond and Downs, 1971 ). This, however, has not been shown to be of clinical significance, and tetracaine is commonly used for spinal anesthetics in premature infants for inguinal hernia repairs. Chloroprocaine, although not a commonly used pediatric local anesthetic, has been used for caudal anesthesia. It is thought to afford a greater level of safety than amide anesthetics because of its rapid metabolism ( Henderson et al., 1993 ; Tobias et al., 1996 ).

▪ LOCAL ANESTHETICS AND RISKS OF TOXICITY

Children may be at increased risk of toxicity of local anesthetics because of their relatively increased cardiac output and increased systemic uptake of the agent. This increased systemic uptake may result in direct central nervous system (CNS) toxicity by increasing the amount of local anesthetic available to cross the blood-brain barrier. In addition, increased systemic uptake can cause direct cardiac toxicity. Lidocaine at plasma levels of 2 to 4 mcg/mL acts as an anticonvulsant, but at 10 mcg/mL, it produces convulsions ( Dalens, 1995 ). Neonates, for example, manifest symptoms of neurotoxicity such as depressed Apgar scores from lidocaine at umbilical venous blood concentrations of 2.5 mcg/mL, significantly lower than the 5 mcg/mL that is associated with neurotoxicity in adults ( Foldes et al., 1960 ;Shnider and Way, 1968 ; Ralston and Shnider, 1978 ; Tucker, 1986 ).

In unmedicated patients, initial symptoms of neurotoxicity include headache, somnolence, vertigo, and perioral or lingual paresthesia. These symptoms and any objective signs of neurotoxicity such as tremors, twitching, shivering, or actual convulsions may not be detected in infants and children under general anesthesia. Diagnosis of local anesthetic toxicity under general anesthesia can be made with indirect signs such as muscular rigidity, hypoxemia without other causes, unexplained tachycardia, dysrhythmias, or cardiovascular collapse. General anesthetics are protective from the CNS effects, but general anesthetics are not protective against cardiac toxicity and may even further contribute to the toxicity ( Badgwell et al., 1990 ).

Cardiac toxicity occurs as the local anesthetic prevents the fast inward sodium channels in the myocardium from opening. Manifestations of toxicity from bupivacaine consist of dysrhythmias with evidence of high degree of conduction block, widening of the QRS, torsades de pointes, ventricular tachycardia related to reentry phenomena, or major cardiovascular collapse with decreased myocardial contractility ( de La Coussaye et al., 1992 ). Bupivacaine may produce cardiac and CNS toxicity at serum concentrations of 2 mcg/mL in children ( Tucker, 1986 ; Dalens and Mazoit, 1998 ). Although 2 mcg/mL is considered the toxic threshold for bupivacaine in children, and 4 mcg/mL in adults, the true toxic concentration of unbound bupivacaine is unknown in humans ( Knudsen et al., 1997 ; Luz et al., 1998 ;Meunier et al., 2001 ; Berde, 1993 ).

Bupivacaine

Bupivacaine is a racemic mixture of equimolar amounts of R (+)-bupivacaine and S (-)-bupivacaine. Racemic bupivacaine had been the only amide local anesthetic with long duration and therefore the most commonly used amide local anesthetic in children. Pharmacokinetic studies of a single dose of racemic bupivacaine (2.5 mg/kg) injected in the caudal space have demonstrated differences between infants and children (Ecoffey et al., 1985; Desparmet et al., 1987 ; Mazoit et al., 1988 ). Infants have a greater volume of distribution (3.9 L/kg versus 2.7 L/kg), an increased elimination half-life (7.7 versus 4.6 hours), and decreased clearance (7.1 versus 10.0 mL/kg per min) compared with older children ( Table 14-1 ). Although side effects from bupivacaine are rare, they can be serious, ranging from CNS excitation to cardiovascular collapse from direct cardiotoxicity. Case reports of possible toxicity of racemic bupivacaine secondary to continuous infusions of bupivacaine were reported in the early 1990s (Agarwal et al., 1992 ; McCloskey et al., 1992 ). In the report of McCloskey and others, children had continuous caudal infusions of 0.25% bupivacaine at doses between 1.67 and 2.5 mg/kg per hr. One neonate sustained bradycardia and hypotension, and two older children developed seizures. Bupivacaine serum concentrations at the time of the event ranged between 5.6 and 20.3 mcg/mL. In the cases reported by Agarwal and others (1992) , one child who developed a seizure had an intrapleural catheter with a bupivacaine infusion rate of 0.5 mg/kg per hr. The seizure occurred with a plasma bupivacaine level of 5.6 mcg/mL. The other child in this report had a continuous bupivacaine epidural infusion at 1.25 mg/kg per hr, and seizures occurred with a plasma bupivacaine level of 5.4 mcg/mL. All children in the reports from McCloskey and Agarwal had plasma bupivacaine levels that exceeded the toxic threshold of bupivacaine (2-4 mcg/mL).


TABLE 14-1   -- Summary of pharmacokinetics of local anesthetics in children

Agent

Block/Dose

Age of Child

Cmax (mg/L)

Tmax (min)

Vd (L/kg)

CI (m L/kg per min)

t1/2(hr)

Reference

Bupivacaine

Caudal 2.5 mg/kg

1 to 6 mo

(0.55 to 1.93)

(10 to 60)

3.9 ± 2.0

7.1 ± 3.2

7.7 ± 2.4

Mazoit and others, 1988

 

Epidural infusion 0.2 mg/kg per hr

11 mo to 15 yr

NM

NM

NM

6.49 (3.96 to 11 11)

3.36 ± 0.93

Desparmet and others, 1987

 

Caudal 2.5 mg/kg

0 to 5 mo

1.109 (0.6 to 2.195)

60 (30 to 240)

NM

NM

2.75 (1.7 to 4.4)

Hansen and others, 2001

 

Caudal 2.5 mg/kg plus epinephrine 2.5 mcg/mL

 

1.102 (0.449 to 1.909)

60 (60 to 360)

 

 

6.05 (3.97 to 8.95)

 

 

Ilioinguinal/iliohypogastric 2 mg/kg (0.5%)

2 to 16 yr

2.2 ± 1.0

24 ± 11.9

NM

NM

3.6 ± 1.8

Ala-Kokko and others, 2002

Ropivacaine

Caudal 2 mg/kg

1 to 8 yr

0.47 ±0.16

60 (12 to 249)

2.4 ± 0.7

7.4 ± 1.9

3.2 ±0.8

Lonnqvist and others, 2000

 

Caudal 2 mg/kg

<1 yr

0.73 ± 0.27

60 (15 to 90)

NM

NM

NM

Wulf and others, 2000

 

 

1 to 5 yr

0.49 ±0.21

52.5 (30 to 120)

 

 

 

 

 

Caudal 2 mg/kg

0 to 3 mo

0.748 (0.425-1.579)

NM

2.12 ±0.75

3.1 ± 1.6

5.1

Hansen and others, 2001

 

 

3 to 12 mo

0.604 (0.41-1.278)

 

(all infants)

(all infants)

(all infants)

 

 

Epidural 1.7 mg/kg

3 to 11 mo

0.61 (0.55 to 0.725)

60 (60 to 120)

2.37 (9%)

4.26 (9%)

NM

McCann and others, 2001

 

 

1 to 4 yr

0.64 (0.54 to 0.75)

60 (30 to 90)

2.37 (9%)

6.15 (11%)

NM

 

 

Epidural infusion 0.4 mg/kg per hr

0.3 to 7.3 yr

NM

NM

3.1 (2.1 to 4.2)

8.5 (5.8 to 11.1)

4.9 (3 to 6.7)

Hansen and others, 2000

 

Ilioinguinal/iliohypogastric 2 mg/kg (0.75%)

2 to 16 yr

1.5 ± 0.8

35 ± 15.4

NM

NM

6.5 ± 4.4

Ala-Kokko and others, 2002

 

Ilioinguinal/iliohypogastric 3 mg/kg (0.5%)

1 to 12 yr

1.5 ± 0.93

45 (15 to 64)

NM

NM

2.0 ±0.7

Dalens and others, 2001

Values are stated either with ± SD value, or with ranges or partition coefficients in parentheses.

Cmax> peak plasma concentration; Tmax, time to peak plasma concentration; Vd, volume of distrib ution; Cl, plasma clearance; t½., terminal half-life; NM, not measured.

 

 

 

An editorial by Berde (1992) addresses the false generalization that children are more resistant to local anesthetic toxicity than are adults. Although earlier studies involving children noted no evidence of toxicity in patients with plasma concentrations of bupivacaine from 1 to 7 mcg/mL, the use of benzodiazepines in those children may have been protective ( McIlvaine et al., 1988 ). Badgwell and others (1990) reported greater resistance to toxicity in 2-day-old piglets compared with older piglets. However, the direct application of this study to neonates is difficult because neonates have lower plasma protein concentrations and lower bupivacaine clearance. Berde recommended (1) that maximal allowable doses of local anesthetics should not be exceeded ( Table 14-2 ), (2) infusion rates should be reduced in children with risk factors for seizures, and (3) the maximal allowable doses should be reduced by at least 30% for infants less than 6 months of age ( Berde, 1992 ).


TABLE 14-2   -- Maximal allowable dosing guidelines of local anesthetics

Local Anesthetic

Single Dose (mg/kg)

Continuous Infusion Rate (mg/kg per hr)

Continuous Infusion Rate in Infants <6 Months of Age[‡] (mg/kg per hr)

Bupivacaine

3

0.4 to 0.5

0.2 to 0.25

Levobupivacaine

3[*]

0.4 to 0.5

0.2 to 0.25

Ropivacaine

3[*]

0.4 to 0.5

0.2 to 0.25

Lidocaine

5

1.6

0.8

Lidocaine with epinephrine[†]

7

NA

NA

Modified from Berde, 1992 .

NA, not applicable.

 

*

Maximal allowable dose may be up to 4 mg/kg (under investigation).

Epinephrine added to local anesthetic at 5 mcg/mL or 1:200,000.

Rate should be reduced by additional 30% after 48 hours in infants.

 

 

Levobupivacaine

Levobupivacaine is the S(-)-enantiomer of bupivacaine and is less toxic to the CNS or heart than is racemic bupivacaine ( Mazoit et al., 1993 ; Graf et al., 1997 ; Huang et al., 1998 ). The decreased risk of cardiotoxicity from levobupivacaine has been shown in healthy adult volunteers after intravenous administration of either levobupivacaine or racemic bupivacaine ( Bardsley et al., 1998 ). Although similar intravenous studies have not been done in children, animal and human studies suggest less toxicity and equipotency of levobupivacaine compared with bupivacaine ( Mather and Chang, 2001 ; McLeod and Burke, 2001 ; Gristwood, 2002 ). Pharmacokinetic studies of levobupivacaine have not been completed in children.

Ropivacaine

Ropivacaine has shown promise in pediatric patients with the onset times similar to bupivacaine and durations of actions that are similar or perhaps slightly longer than bupivacaine (DaConceicao et al., 1998, 1999 [53] [54]; Ivani et al., 1998 , 2002; Lonnqvist et al., 2000 ; Hansen et al., 2001 ; Locatelli et al., 2005 ). There remains controversy as to the potency of ropivacaine compared with bupivacaine and adult studies do not correlate with pediatric studies ( Ivani, 2002 ). Although not confirmed, ropivacaine at 0.2% exhibits the same analgesic effect as 0.25% in children, perhaps because of the intrinsic vasoconstrictive activity that is evident at the lower concentrations used in children ( Ivani, 2002 ). Ropivacaine has less risk of CNS and cardiac toxicity than bupivacaine. In fact, inadvertent intravenous ropivacaine in a 1-year-old child failed to produce neurotoxic or cardiotoxic signs or symptoms ( Thong et al., 2000 ). In a pharmacokinetic study of ropivacaine in children aged 1 to 8 who were administered 1 mL/kg 0.2% ropivacaine for caudal block, the free plasma concentrations were well below toxic levels ( Lonnqvist et al., 2000 ). Clearance of the drug was 7.4 mL/kg per min and the terminal half-life was 3.2 hours. Hansen and others (2001) studied the pharmacokinetics of caudal ropivacaine in infants less than 1 year of age (see Table 14-1 ). In this study, infants less than 3 months of age were com pared with the infants aged 3 months to 1 year ( Hansen et al., 2001 ). Although the maximum free concentration of ropivacaine was significantly higher in the younger age group (99 mcg/L versus 38 mcg/L), the total and free plasma concentrations in all of the children less than 1 year old were within the range of concentrations previously reported in adults and older children ( Lonnqvist et al., 2000 ; Wulf et al., 2000 ).

Reducing Risks of Toxicity

There are several safety measures that can reduce the risks of toxicity from local anesthetics in children. One primary safety measure is to avoid overdosing by adhering to recommendations for maximal allowable doses. For a bolus injection, the maximal recommended dose of lidocaine is 5 mg/kg. Because epinephrine decreases the uptake and absorption of local anesthetic, the dose of lidocaine can be increased to 7 mg/kg when epinephrine (5 mcg/mL) is added to the local anesthetic. Because levobupivacaine and ropivacaine have intrinsic vasoconstriction properties, the addition of epinephrine does not increase the maximal recommended dose. The maximal allowable bolus dose for bupivacaine, ropivacaine, and levobupivacaine is 3 mg/kg ( Agarwa l et al., 1992 ; McCloskey et al., 1992 ). Recommendations for maximal dosing of continuous infusions are presented in Table 14-2 and are the same for bupivacaine, levobupivacaine, and ropivacaine ( Berde, 1992 ). For epidural infusions, the infusion rates should not exceed 0.4 to 0.5 mg/kg per hr for patients greater than 6 months of age, and the recommendation for neonates is not to exceed 0.2 to 0.25 mg/kg per hr. Based on the clearance of bupivacaine and using the guidelines in Table 14-2 , the plasma concentrations should remain below 2.5 mcg/mL and therefore below the toxic level of 4 mcg/mL in adults and recommended level of less than 2 mcg/mL in children. ( Tucker, 1986 ; Desparmet et al., 1987 ; Mazoit et al., 1988 ; Berde, 1993 ). These infusions assume a loading dose of 2 to 2.5 mg/kg of bupivacaine and should be reduced by 25% in patients with risk factors for seizures (e.g., past history of febrile seizures, hypomagnesemia, and hyponatremia) ( Agarwal et al., 1992 ; Berde, 1992 ).

In addition to dosing guidelines, the risk of toxicity is also affected by hypothermia, hypoxia, hypercarbia, acidosis, or hyperkalemia ( Broadman, 1996 ). These factors enhance the toxicity of local anesthetics via different mechanisms. Another factor that leads to increased toxicity is the speed of injection of the local anesthetic agent. Rapid injections can cause toxicity by resulting in a high peak that may not allow for the adaptation of sodium channels against the local anesthetic action.

When combined, the toxicities of two local anesthetics are additive. If the maximal allowable dose of one local anesthetic has been reached, another local anesthetic agent should not be delivered ( Giaufre et al., 1996 ). Although combinations of local anesthetics may be a common practice at some centers, maximal allowable dosing should be calculated for each of the anesthetics used and decreased based on the relative percentages of each.

The choice of local anesthetic is a clinical decision. In general, lower concentrations of local anesthetics such as 0.25% bupivacaine or levobupivacaine and 0.2% ropivacaine may be used in infants and small children, and higher concentrations such as 0.5% bupivacaine, levobupivacaine, or ropivacaine should be reserved for older children. Higher concentrations result in longer duration of action and increased motor block. In young children, there is a risk of direct local anesthetic toxicity on developing nerves ( Selander, 1993 ; Lambert et al., 1994 ; Radwan et al., 2002 ). The age at which this is no longer a concern is unknown.

Test Dosing

Before injecting local anesthetics, it is essential to determine that the agent not be injected into the intravascular space. The absence of blood aspiration when administering a pediatric block is not a reliable indicator that the needle is not in a vessel. Infants, in particular, may be at greatest risk of intravascular injection ( Freid et al., 1993 ; Ved et al., 1993 ; Flandin-Blety and Barrier, 1995 ). Although clinical practice has relied on a “test dose” to elicit a tachycardia when the test drug is inadvertently injected systemically, the test dose was often considered unreliable in the anesthetized patient ( Desparmet et al., 1990 ). In the study of Desparmet and others of children anesthetized with halothane, only 16 of 21 children who received a test dose of 0.1% lidocaine with epinephrine 1:200,000 had an increase in heart rate that was greater than 10 beats per minute (bpm). When using halothane anesthesia, an increase of 20 bpm with prior administration of atropine improves the efficacy of the test dose. Isoproterenol has also been used as a test drug, and although it is a more reliable indicator of an intravascular injection in patients anesthetized with halothane ( Perillo et al., 1993 ; Kozek-Langenecker et al., 1996 ), the safety of isoproterenol with neuraxial administration has not been determined. The validity of test dosing has been studied and reviewed (Tanaka and Nishikawa, 1998, 1999 [248] [249]; Tobias, 2001 ). Using sevoflurane anesthesia, Tanaka and Nishikawa (1998, 1999 [248] [249]) were able to demonstrate that an increase in heart rate of 10 bpm, an increase change in T-wave amplitude of 25%, or blood pressure increase of greater than 15 mm Hg defines a positive test dose. Prior administration of atropine did not affect these criteria.

A test dose can be a useful tool for identifying intravascular injection when the appropriate criteria are used. The test dose should not, however, be a replacement for slow incremental dosing of the total volume of the local anesthetic, attention to vital signs, and electrocardiographic monitoring throughout the drug administration. A recommended test dose under sevoflurane anesthesia is 0.1 mL/kg of the chosen local anesthetic with epinephrine 5 mcg/mL added but not to exceed 3 mL. A heart rate increase of 10 bpm, a systolic blood pressure increase of 15 mm Hg, a T-wave amplitude increase of greater than 25% from baseline, or bradycardia should alert the practitioner to possible intravascular injection (Tanaka and Nishikawa, 1998; 1999 [248] [249]; Freid et al., 1993 ; Fisher et al., 1997 ; Tobias, 2001 ).

Another advantage of epinephrine administration in regional anesthesia is that, in addition to being a reliable marker for intravascular injection, the use of epinephrine decreases systemic absorption of the local anesthetic (Eyres et al., 1983, 1986 [87] [88]). Children may be at increased risk of local anesthetic toxicity from increased systemic absorption because of their relatively higher cardiac output and regional blood flow. In a study comparing bupivacaine with epinephrine 5 mcg/mL to bupivacaine alone in children for fascia iliaca block, Doyle and others (1997) demonstrated that the peak plasma concentration was lower in the bupivacaine with epinephrine group (0.35 mcg/mL versus 1.1 mcg/mL) and that the time to peak concentration was more gradual (20 minutes versus 40 minutes from injection).

▪ REVIEWS OF SAFETY OF REGIONAL ANESTHESIA IN CHILDREN

Despite the issues of the safety of regional anesthesia in children, as previously mentioned, studies have shown that the risks and complications in regional anesthesia in children are quite low and often preventable ( Dalens and Hasnouai, 1989 ; Pietropaoli et al., 1993 ; Giaufre et al., 1996 ; Dalens and Mazoit, 1998 ). The largest of these studies was published by the French-Language Society of Pediatric Anesthesiologists (ADARPEF) ( Giaufre et al., 1996 ). This prospective report covered 1 year and included 24,409 regional blocks in children. Central blocks accounted for greater than 60% of the blocks, whereas peripheral nerve blocks and local anesthetic techniques made up the remaining 38%. There were only 25 complications that occurred in the study, and all of the complications occurred in children who received central blocks. The overall complication rate of regional anesthesia was 0.9 per 1000.

The most common complications from regional blockade were inadvertent dural puncture (n=8), inadvertent intravascular injection of local anesthetic (n=6), technical problem (n=3), and overdosage of local anesthesia leading to dysrhythmias (n=2). In addition, two children had transient paresthesias, one child had apnea after central morphine, and one child had a skin lesion after a caudal anesthetic administration. In this study, there were no deaths secondary to any of the complications. The conclusion from this study of regional anesthesia in children was that complications were rare and minor and that they occurred most often in the operating room where they were readily managed. In addition, when appropriate, a peripheral nerve block may be preferable to a central block.

The use of appropriately sized equipment for pediatric regional blocks cannot be overemphasized. The ease of performing a block in a small child is enhanced with the use of shorter, smaller-gauge needles that allow for exact placement. Eleven of the reviewed 23 complications in the large ADARPEF safety study could be contributed to the use of inappropriate equipment.

In a retrospective review of 24,005 regional anesthetics administered over a 10-year period, Flandin-Blety and Barrier (1995) reported 108 events without sequelae (0.45%). In this review, there were five events that resulted in severe neurologic injury, including tetraplegia in three children, paraplegia in one child, and one child with cerebral lesions. All five of the children were healthy and less than 3 months of age. Four of the five children had loss of resistance to air used for their technique to identify the epidural space. The true pathophysiologic causes for the neurologic injuries in these children are unknown, but the authors recommended that air not be used to identify the epidural space and that a lower concentration of epinephrine, such as 2.5 mcg/mL, be used to avoid possible ischemic injury. In addition, the authors recommended that the indications for regional anesthesia be reconsidered in children less than 18 months of age due to their incomplete myelination of neuronal fibers.

▪ ADVANTAGES OF REGIONAL ANESTHESIA IN CHILDREN

There are advantages to the use of regional anesthesia that are evident and continue to increase the popularity of its practice. The use of regional anesthesia in combination with general anesthesia results in reduced concentrations of potent inhaled agents and reduced or absent use of opioids resulting in quick recovery times and less nausea and vomiting ( Dalens and Hasnaoui, 1989 ; Yaster and Maxwell, 1989). In addition, regional anesthesia suppresses the neuroendocrine responses to surgery compared with general anesthesia alone ( Murat et al., 1988 ; Wolf et al., 1993 ). Regional anesthesia as the sole technique for inguinal hernia repair has been shown to decrease the incidence of postoperative apnea in former preterm infants ( Welborn et al., 1990 , 1991; Cote et al., 1995 ; Krane et al., 1995 ). Although large numbers of outcome studies are lacking, regional anesthetic techniques have been shown to decrease the incidence of postoperative complications and reduce hospital stay ( McNeely et al., 1997 ;Miller et al., 2002 ).

In addition to the advantages that regional anesthesia may offer, regional techniques have also been used for therapeutic purposes. Patients have received regional blocks for vascular insufficiency related to meningococcemia, Kawasaki's disease, erythromelalgia, and sickle cell disease ( Edwards et al., 1988 ; Anderson et al., 1989 ; Tobias et al., 1989 ; D'Angelo et al., 1992 ; Yaster et al., 1994 ; Tobias, 2002 ). Lumbar sympathetic block has been used for infants and children with ischemic limbs secondary to arterial or intravenous infiltration ( Sanchez et al., 1988 ), and stellate ganglion block has been effective for upper extremity ischemia ( Lagade and Poppers, 1984 ; Parris et al., 1991 ). Regional anesthesia has also been a therapeutic tool in the treatment of postdural puncture headache. Epidural blood patches have been used successfully in a variety of children for this indication ( Ylonen and Kokki, 2002 ).

Copyright © 2008 Elsevier Inc. All rights reserved. - www.mdconsult.com

Motoyama & Davis: Smith's Anesthesia for Infants and Children, 7th ed.

Copyright © 2005 Mosby, An Imprint of Elsevier

▪ CENTRAL NEURAXIAL BLOCKADE

Central blockade is performed in children for many of the same reasons that it is performed in adults, such as bilateral lower extremity, abdominal, and thoracic procedures. There are risks and benefits to performing central blocks that are inherent to the type of block chosen. Central blocks that are commonly performed in children include spinal blocks and epidural blocks. Epidural blocks may be placed at the caudal, lumbar, and tho racic levels. Contraindication to central blockade includes a child on anticoagulation therapy, a patient with a preexisting coagulopathy, or a patient or parent who refuses to consent to the procedure. Guidelines regarding regional anesthesia and anticoagulation therapy in adults may be useful for guiding the management of the child with similar concerns ( Horlocker et al., 2003) ( Table 14-3 ).

TABLE 14-3   -- American Society of Regional Anesthesia and Pain Medicine Guidelines for neuraxial anesthesia in patients receiving thromboprophylaxis

Antiplatelet Medication

Subcutaneous Heparin

Intravenous Heparin

Low-Molecular-Weight Heparin

Warfarin

Thrombolytics

Herbal Therapy

No contraindication with NSAIDs; discontinue ticlopidine 14 days, clopidogrel 7 days, GP Ilb/IIIa inhibitors 8 to 48 hr in advance

No contraindication, consider delaying heparin until after block if technical difficulty anticipated

Heparinize 1 hr after neuraxial technique, remove catheter 2 to 4 hr after first heparin dose; no mandatory delay if traumatic

Twice-daily dosing: LMWH 24 hr after surgery, regardless of technique; remove neuraxial catheter 2 hr before first LMWH dose. Single daily dosing: Needle placement 12 hr after LMWH; first postoperative dose 4 to 12 hr; catheters removed 10 to 12 hr after LMWH and 4 hr prior to next dose; postpone LMWH 24 hr if traumatic

Document normal INR after discontinuation (prior to neuraxial technique): remove catheter when INR<1.5 (Initiation of therapy)

No data on safety interval for performance of neuraxial technique or catheter removal follow fibrinogen level

No evidence for mandatory discontinuation prior to neuraxial technique; be aware of potential drug interactions

NSAIDs, nonsteroidal anti-inflammatory drugs; GP Ilb/IIIa, platelet glycoprotein receptor Ilb/IIIa; INR, international normalized ratio; LMWH, low-molecular-weight heparin. Reprinted from HorlockerTT, Wadel DJ, Benson H, et al.: Regional anesthesia in the anticoagulated patient: defining the risks. Reg Anes th Pain Med 28:172, 2003. With permission from the American Society of Regional Anesthesia and Pain Managements.

 

 

 

▪ SPINAL ANESTHESIA

Spinal anesthesia was probably the earliest form of regional anesthesia that was considered a useful practice for children ( Bainbridge, 1901 ; Tyrell-Gray, 1909 ). Since that time, spinal anesthetics have become an important anesthetic technique for reducing the incidence of postoperative apnea in premature and ex-premature infants ( Harnik et al., 1986 ; Welborn et al., 1990 ; Krane et al., 1995 ; Somri et al., 1998 ). Infants who have continuing apnea at home or hematocrit less than 30% are at particular risk for postoperative apnea ( Cote et al., 1995 ). Spinal anesthesia may also reduce the need for postoperative mechanical ventilation in those infants who are less than 60 weeks' postconceptual age after hernia repair ( Huang and Hirshberg, 2001 ). The ability of a spinal anesthetic to densely block the dermatomes involved in inguinal hernia repair has kept this regional technique a popular choice in pediatric anesthesia for inguinal surgery. Often a spinal anesthetic combined with liberal clear liquids until 2 hours before the procedure and a pacifier intraoperatively are sufficient to keep an ex-premature infant comfortable while undergoing inguinal hernia repair. However, any ex-premature infant up to 44 weeks' postconceptual age, and up to 60 weeks' postconceptual age if the infant has risk factors such as anemia or ongoing apnea, should be a candidate for overnight monitoring after their surgery regardless of whether a pure regional technique was used.

Although spinal anesthesia may be used in any age group, there are relatively few true indications for a spinal anesthetic in older children. Older children may be at increased risk of postdural puncture headaches ( Wee, 1996) .

Anatomy

The anatomic differences between an infant and a young child or adult are clinically significant and must be taken into consideration when performing a spinal technique. The dural sac in a newborn ends at S3, and the conus medullaris may be located at L3 ( Plate 14-1 ). To avoid the risk of spinal cord puncture in a neonate, a spinal should be performed at the L4-5 interspace. After the first year of life, the spinal cord is in its adult position with the dural sac at S1 and conus medullaris at L1.

 
 

PLATE 14-1  Comparisons between levels of the conus medullaris and the dural sac in the infant versus the older child or adult.

 

 

Technique

To perform a spinal anesthetic, one may position the infant on the side with the back flexed but with the head extended to avoid airway compromise. Some practitioners prefer to have the awake neonate or infant in the sitting position to improve success of the block by increasing the chance of good cerebrospinal fluid (CSF) flow through the needle by increasing the hydrostatic pressure. In either position, it is important that an assistant keep a firm grasp of the awake infant during the placement of the spinal block. An assistant with a firm hold increases the likelihood of a successful block and decreases the chance of complications.

A sterile prep and a clear plastic drape are used so that the anatomy may be seen. For neonates and infants, a 1½-inch 22-gauge spinal needle is inserted at the L4-5 interspace ( Plate 14-2 ). The stylet of the needle should be in place when inserted during the pass through the skin. This avoids the remote risk of an epidermoid tumor ( Shaywitz, 1972 ; Barnitzky et al., 1977 ). Using this size needle in this age group, one should be able to feel the resistance as the needle enters the ligamentum flavum; then a “pop” should be felt as the needle enters the dura. The stylet is removed to check for the flow of CSF. In an infant positioned in the lateral position, if no CSF is evident after what seemed to be appropriate needle placement, the infant can be placed in the sitting position. This change in position may improve CSF flow once the subdural space is entered.

 
 

PLATE 14-2  Performance of spinal anesthetic in the neonate. Note how the back is flexed, but the neck remains extended for airway patency. IC, iliac crest.

 

 

In children over 2 years of age, a longer needle with a smaller gauge may be used. The smaller gauge needle may decrease the incidence of PDPH but may also make it more difficult for the practitioner to feel the distinctive pop of the needle through the ligamentum flavum. In addition, the smaller size needle may inhibit the flow of CSF.

After confirmation of position into the subarachnoid space as evident by free flow of CSF through the needle, the local anesthetic solution is slowly injected. After the injection, the needle is removed and the child is placed in the supine position. It is extremely important that the child remain supine and that the legs not be raised for any reason, including placement of an electrocautery pad. Lifting the child causes the local anesthetic to migrate and results in a high spinal level ( Wright et al., 1990 ).

Dosing

The total volume of CSF in a neonate is 4 mL/kg compared with 2 mL/kg in an adult, and the hydrostatic pressure is 30 to 40 mm H2 O, lower than that of an adult. In addition, almost half of the total CSF volume is in the spinal subarachnoid space, whereas only one fourth of the total volume in adults is found in the spinal region. These factors play an important part of dosing spinal blocks as the local anesthetics are quickly diluted by the CSF in a neonate upon injection. Infants require higher volumes based on weight, but the duration of action of spinal blocks is shorter than that in adults ( Rice et al., 1994 ).

Although there have been many different dosing regimens used over the years, tetracaine, either with or without epinephrine, is a commonly used local anesthetic for spinal anesthesia. Rice and others (1994) studied 100 infants to determine the duration of spinal block, and the authors compared three groups: lidocaine (3 mg/kg with epinephrine), tetracaine (0.4 mg/kg plain), and tetracaine (0.4 mg/kg with epinephrine). The duration in the lidocaine with epinephrine group was 56 ± 2.5 minutes; in the tetracaine plain group, 86 ± 4 minutes; and in the tetracaine with epinephrine group, 128 ± 3 minutes.

The following guidelines may be used for dosing spinal blocks in infants. If using 1% tetracaine, a dose of 0.5 mg/kg mixed in an equivalent amount of 10% dextrose to make the solution hyperbaric should provide at least 90 minutes of surgical analgesia. Yaster and Maxwell (1989) suggested that regardless of the infant's weight, 1.5 to 2 mg of tetracaine is the minimal effective dose ( Yaster and Maxwell, 1989 ). To achieve 5 mg/mL tetracaine, mix 1 mL of 1% tetracaine with 1 mL of D10W. The delivered volume is then 0.3 to 0.4 mL for infants less than 10 kg in weight. If 0.01 mL/kg of epinephrine is added to 0.75 to 1 mg/kg of hyperbaric tetracaine, surgical analgesia can be extended to 90 to 120 minutes. Bupivacaine can also be used for spinal blockade. A dose of bupivacaine, 0.5 to 0.6 mg/kg of either isobaric or hyperbaric bupivacaine, provides an average of 80 minutes of surgical analgesia ( Dalens, 2000 ). Dosing of bupivacaine should be reduced for infants and young children who are greater than 5 kg in weight due to changes in CSF volume. For infants 5 to 15 kg, the dose of hyperbaric bupivacaine or tetracaine is 0.4 mg/kg or 0.08 mL/kg, and for children greater than 15 kg, the dose of bupivacaine or tetracaine is 0.3 mg/kg or 0.06 mL/kg ( Dalens, 1995 ).

Complications

Complications during spinal anesthesia in children are uncommon. In the ADARPEF study, an intravascular injection during spinal anesthesia was the only reported complication in 506 cases ( Giaufre et al., 1996 ). One complication that is associated with spinals, as well as with inadvertent subarachnoid entry during the administration of an epidural block, is postdural puncture headache (PDPH). Although considered to be a rare occurrence in children, this event may actually be more common than originally thought. In fact, the incidence of PDPH following lumbar puncture has varied from 10% to 50% in children aged 10 to 18 years ( Wee, 1995 ; Oliver, 2002 ). The onset of symptoms from a PDPH typically occurs within 48 hours with the hallmark symptom being a frontal or an occipital headache that is postural in nature. The cause of PDPH is most likely a persistent leakage of spinal fluid that causes a net decrease in CSF volume and intracranial pressure. The supine position helps to alleviate the symptoms of PDPH by decreasing the effect of gravity on the CSF leak. To reduce the risk of PDPH, smaller-gauge needles are used and the needle is inserted with the bevel parallel to the longitudinal fibers of the dura ( Kokki and Hendolin, 1996 ). If a diagnosis of PDPH is made, simple measures such as bed rest and hydration can decrease the volume of CSF loss. In addition, analgesics to reduce the headache and intravenous caffeine may be administered. Caffeine is effective because of its ability to cause cerebrovascular vasoconstriction resulting in decreased cerebral blood flow. In one study, when caffeine was used prophylactically in adults, visual analog pain scores and analgesic demand following PDPH were lower ( Yucel, 1999) .

If conservative measures are ineffective in treating PDPH after 48 hours, an epidural blood patch should be considered. An epidural blood patch requires that blood be drawn in a sterile fashion from a peripheral vein. The blood is then injected into the epidural space under aseptic technique. An epidural blood patch is most effective 48 to 72 hours after the dural puncture and may be ineffective if performed immediately after dural tap due to high leakage of CSF that may interfere with blood clotting ( Oliver, 2002 ). In a child who is awake during the placement of an epidural blood patch, the practitioner should stop the injection either once the child feels discomfort or pressure in the back. If a child is anesthetized during the performance of an epidural blood patch, no more than 0.3 mL/kg of blood should be injected into the epidural space ( Ylonen, 2002) .

Total spinal block with respiratory arrest and bradycardia is another complication of spinal anesthesia ( Desparmet, 1990 ). The preganglionic sympathetic blockade that is commonly seen in adults secondary to a high spinal is not typically seen in children, particularly in infants ( Oberlander et al., 1995 ; Finkel, 2003 ; Somri, 2003) . Dohi and others (1979) were the first to describe the lack of hemodynamic changes following spinal block–induced sympathetic blockade in children. They found that children less than 5 years of age had little to no hemodynamic response to a T3 level tetracaine spinal anesthetic, whereas children greater than 8 years had cardiovascular responses that were more similar to those of adults. The mechanism for this lack of hemodynamic sympathectomy was postulated to be the immaturity of the sympathetic nervous system as well as differences in CSF volume and spinal cord surface area. In addition, it is also possible that the smaller blood volume that is present in the lower extremities of a young child compared with that of an adolescent or adult may account for less venous pooling and therefore less hemodynamic change ( Dohi et al., 1979 ; Dohi and Seino, 1986 ). Despite the typical lack of cardiovascular compromise, neonates may occasionally require ventilatory support or pharmacologic intervention due to a high spinal with a resulting blockade of the cardiac accelerator fibers and/or decrease in stimulation of the right atrial stretch receptors ( Wright et al., 1990 ). Investigation has shown that even former premature infants in the absence of fluid loading tolerate high spinal anesthesia with minimal autonomic changes ( Oberlander et al., 1995 ).

▪ CAUDAL ANESTHESIA

By far the most commonly used regional block in pediatric practice is the caudal epidural block. The reasons for the success of this regional technique are the ease of performing the block and the extensive safety record of its use in children. The caudal block is the easiest block to perform and to teach. Schuepfer and others (2000) evaluated the technical skills of residents in anesthesiology to determine the learning curve for performing a caudal block in a child. They found that there was a high success rate of performing a caudal anesthetic in a child after performing only a limited number of cases. Caudal blocks have great utility in ambulatory surgical patients and for inpatients. They can be administered as a single injection or as a continuous infusion. A caudal block can be used for any surgery that is performed on the lower abdomen or lower extremities, such as procedures involving innervation from the sacral, lumbar, and lower thoracic dermatomes. Commonly performed pediatric surgery such as inguinal hernia repair and orchiopexy with der matomal distribution below T-10 makes the caudal block a useful adjunct to the anesthetic. Caudal blocks result in improved patient pain scores compared with scores of patients with general anesthesia alone ( Londergan et al., 1994 ). Single-shot caudal anesthesia, when combined with postoperative ketorolac administration, allows children who have undergone intravesical ureteroneocystostomy to be discharged on postoperative day 1 ( Miller et al., 2002 ). For outpatient urologic procedures, caudal block with light general anesthesia was superior to local nerve block or general anesthesia alone. Patients with caudal blocks had lower pain scores and lower postoperative pain medication requirements ( Londergan et al., 1994 ). Single-shot caudal anesthesia has also been used in ex-premature infants as the sole anesthetic to decrease the incidence of postoperative apnea and to avoid the use of general anesthesia and narcotics ( Bouchut et al., 2001 ).

The practice of placing a caudal block before incision would seem likely to improve postoperative care by providing preemptive analgesia. The benefits of providing preemptive analgesia through regional block have not been confirmed in pediatric caudal studies. Holthusen and others (1994) noted that there were no significant differences in cumulative postoperative analgesic requirements or cumulative pain scores between children having caudal blocks placed either before or after their circumcision. In a separate study comparing two groups of children who received caudal blocks for clubfoot repair,Goodarzi (1996) noted that there were no significant differences in the time to first postoperative analgesic administration or in cumulative analgesic requirements for the first 48 hours between the group that received the block before incision and the group that received the block after the incision. However, it should be realized that placing the caudal at the end of the procedure does not allow the benefit of lower inhaled anesthetic agent concentrations to be used intraoperatively.

There are relative contraindications to performing caudal anesthetics in children. These include the presence of a pilonidal cyst, or abnormal superficial landmarks at the sacral level. The presence of any of these may suggest that the dural sac and cord may not be in their normal anatomic positions. Absolute contraindications include true meningomyelocele of the sacrum or meningitis. Hydrocephalus and intracranial tumors decrease intracranial compliance and are considered relative contraindications to caudal or epidural anesthesia. Progressive degenerative neuropathy is not an absolute contraindication, but it carries medicolegal implications.

Anatomy

The caudal space is the result of a defect due to the nonfusion of the fifth sacral vertebral arch. This area of the nonfusion forms the sacral hiatus, the entry into the caudal epidural space. The landmarks around the sacral hiatus are the sacral cornua, the posterior superior iliac spines, and the coccyx ( Plate 14-3A, B ). To find the sacral hiatus, one palpates the sacral cornua and the indentation that is immediately caudal and in the midline. If the cornua are difficult to palpate, the general area of the sacral hiatus may be found by palpating the two posterior superior iliac spines, and assuming that a line between these would be the base of an equilateral triangle, the apex should be at the location of the sacral hiatus.

 

 

PLATE 14-3  A, Posterior anatomy of the caudal space. B, Lateral view of the caudal space and needle insertion.

 

 

The caudal space itself lies underneath the sacrococcygeal ligament that runs through the sacral hiatus under the skin. Around 7 years of age, the child's caudal space begins to become more angulated and may be difficult to enter. Although it is possible to perform a caudal block in adolescents and adults, the formation of a presacral fat pad in puberty adds to the difficulty of placing the block. It should be remembered that the distance from the skin to the caudal space in neonates is minimal ( Fig. 14-2 ) and that because the dural sac may extend to S3 in neonates, the possibility of entering the dural sac in this age group is increased.

 
 

FIGURE 14-2  Depths to perineural, epidural and subarachnoid spaces according to age.  (From Dalens B [ed]: Regional Anesthesia in Infants, Children and Adolescents. Philadelphia, Williams & Wilkins, 1995, p. 32.)

 

 

 

Technique

The choice of needle to be used depends on whether the caudal anesthetic is to be a single-shot or whether additional dosing will be required. For a single-shot caudal, it is advantageous to use a short-beveled needle with a stylet. One may also use needles such as blunt 22-gauge or intravenous catheters that do not have stylets; however, there is a remote risk of developing an epi dermal inclusion cyst or tumor if the epidermis is carried through the shaft of the needle into the neuraxial space ( Shaywitz, 1972 ). A Crawford needle is similar to an epidural Touhy needle as it has a stylet and is blunt, but a Crawford needle's bevel is in alignment with the shaft of the needle so that a catheter exits the needle in a straight line rather than at an angle, such as with a Touhy. The Crawford needle is ideal for either single-shot local anesthetic injection or for placement of a caudal epidural catheter.

With the child in the lateral position, flex the hips with the dependent leg less flexed than the top leg for the Simm's position. Near the cephalad margin of the gluteal crease, feel for the sacral cornua and the sacral hiatus, a depression immediately inferior to the cornua and in the midline. This is the sacral hiatus ( Plate 14-4 ). After sterile preparation and drape, identify the sacral hiatus again with the nondominant gloved hand and place the needle into the skin in the midline at a 45° angle to the skin aiming cephalad. Resistance might be felt as the sacrococcygeal ligament is penetrated with a “pop” once the needle has passed into the epidural space. If using a single-injection technique, local anesthetic may be delivered once the sacrococcygeal ligament has been pierced. Frequent aspiration for blood and/or CSF should occur as small movements may result in misplacement of the tip of the needle. If using an intravenous catheter for entry into the caudal space, the angle of the needle must be dropped once the sacrococcygeal ligament has been pierced to align the needle and intravenous catheter with the epidural space. The needle should then be advanced approximately 2 to 3 more mm so that the catheter can be directly threaded into the epidural space. After a negative aspiration for blood and CSF, the local anesthetic should inject easily without resistance. A finger should palpate the skin cephalad to injection to ensure that the agent is not being injected subcutaneously. Although air has been used to check for crepitus after injection, this practice is not recommended due to the risk of air embolism ( Guinard and Borboen, 1993 ; Schwartz and Eisenkraft, 1993 ).

 
 

PLATE 14-4  Performance of caudal block. SC, sacral cornua; PSIS, posterior superior iliac spine; SH, sacral hiatus; TC, tip of coccyx. Note that an equilateral triangle is formed with the fingertips from PSIS to PSIS to needle insertion at SH.

 

 

Dosing

For a single-shot caudal anesthetic that does not have repeat dosing, the goal is to provide the appropriate intraoperative level and a prolonged postoperative analgesia ( Plate 14-5 ). Although there have been formulas developed for determining levels for injection of a single-shot caudal, delivery of 1 mL/kg of local anesthetic with epinephrine 1:200,000 provides a thoracic level with a duration of 4 to 6 hours depending on the local anesthetic chosen ( Armitage, 1979 ). Although one would never inject 1 mL/kg of local anesthetic in the epidural space of an adult, the anatomy of the caudal epidural space in a child is such that a high volume is needed in order to fill the loosely packed space and to spread to reach the appropriate dermatomes. The caudal space communicates freely with the perineural spaces of the spinal nerves, which allows a lower concentration of local anesthetic to be effective. Dosing guidelines may be found in Table 14-4 . Although convention suggests that an increased volume of local anesthetic should be required for adequate block and duration of action, a study found that there was no advantage to increasing the volume of local anesthetic over 0.7 mL/kg ( Schrock et al., 2003) . In children 1 to 6 years of age undergoing inguinal hernia repair, Schrock and others (2003) compared three groups, all of whom received 0.175% bupivacaine administered at different volumes (0.7 mL/kg, 1 mL/kg, and 1.3 mL/kg). The durations of action as determined by first postoperative analgesic were similar for all three groups: 4.2, 3.6, and 4.8 hours, respectively. In addition, there were no differences among the groups with regard to first time to void, ambulate, or discharge. However, in another study, Verghese and others (2002) noted that 1 mL/kg of 0.2% bupivacaine was more effective than a smaller volume of 0.8 mL/kg of 0.25% bupivacaine in blocking the peritoneal response of spermatic cord traction during orchidopexy. The quality of postoperative analgesia, however, was similar in the two groups.

 
 

PLATE 14-5  Dermatomal distribution of different volumes of local anesthetic for single-shot caudal block.

 

 


TABLE 14-4   -- Recommendations for dosing caudal and epidural blocks.

 

Concentration

Dose

Possible Additives

Single-dose caudal

0.175% to 0.5%

0.75 to 1.25 mL/kg not to exceed 3 mng/kg

Epinephrine 2.5 to 5 mcg/mL

Clonidine 1 to 2 mcg/kg

Morphine 30 to 70 mcg/kg

Continuous caudal or lumbar epidural catheters

0.1% to 0.25%

0.4 mL/kg per hr or 0.2 to 0.4 mg/kg per hr

Fentanyl 2 to 5 mcg/mL

Hydromorphone 5 to 10 mcg/mL

Continuous thoracic epidural

0.1% to 0.25%

0.3 mL/kg per hr or 0.1 to 0.2 mg/kg per hr

Fentanyl 2 to 5 mcg/mL

Hydromorphone 5 to 10 mcg/mL

Bupivacaine, levobupivacaine, or ropivacaine may be used. Greater concentrations and larger doses should be reserved for levobupivacaine or ropivacaine. Doses and concentrations should be reduced in infants. Children less than 2 years of age who receive morphine centrally require 24-hour monitoring after its delivery.

 

 

 

The recommended concentration of bupivacaine for a single-shot caudal is 0.125% to 0.25%. However, Gunter and others (1991) , in a dose-range study, concluded that 0.175% offered the best combination of analgesia and rapid recovery with the least number of side effects. When performing single-shot caudal anesthesia in ex-premature infants for hernia repair, a combination of agents has been shown to be successful ( Bouchut et al., 2001 ). A mixture of 0.5 mL/kg of 1% lidocaine, along with 0.5 mL/kg of 0.5% bupivacaine, was used in 25 infants. This combination provided surgical analgesia for 60 minutes. However, 1 of the 25 infants developed a total spinal block and 2 children developed postoperative apnea.

Some information is available on the use of the newer local anesthetics for caudal anesthesia in infants and children. Ropivacaine has been evaluated in children for caudal anesthesia and has been found to provide a similar onset and analgesic duration to bupivacaine ( Ivani et al., 1998 ). In some studies, compared with bupivacaine, ropivacaine produced less of a motor block at 0.25% and 0.375% concentrations ( DaConceicao and Coelho, 1998 ; DaConceicao et al., 1999 ). When 0.2% ropivacaine, 0.25% levobupivacaine, and 0.25% bupivacaine were compared in children for caudal anesthesia, postoperative analgesia was not significantly different among the groups, nor was the time for the first postoperative analgesic ( Ivani et al., 2002 ). The only difference was a slight reduction in the incidence of motor block in the ropivacaine group.

When using 1 mL/kg of 0.2% ropivacaine, free plasma concentrations were well below toxic levels ( Lonnqvist et al., 2000 ). To determine the effective concentration of ropivacaine for single-shot caudal analgesia, Bosenberg and others (2002) compared 1 mL/kg of 0.1%, 0.2%, and 0.3% ropivacaine in 110 children aged 4 to 12 years. The median time to first analgesic was 3.3, 4.5, and 4.2 hours in the groups, respectively. Pain scores were significantly higher in the 0.1% group compared with the 0.3% group. Motor block was 0%, 13%, and 28% in the 0.1%, 0.2%, and 0.3% groups, respectively. Bosenberg and others concluded that although 1 mL/kg of ropivacaine is effective for postoperative pain in children after inguinal surgery, the lower concentration of 0.1% is not effective, and the higher concentrations result in a higher rate of motor block.

In other dosing studies with ropivacaine, Koinig and others (1999) compared 0.75 mL/kg of 0.5% ropivacaine, 0.25% ropivacaine, and 0.25% bupivacaine in children aged 1.5 to 7 years undergoing inguinal hernia repair. The remarkable finding in this study was the duration of analgesia afforded by 0.5% ropivacaine. The duration in the ropivacaine 0.5% group was 1440 minutes, whereas the 0.25% ropivacaine and 0.25% bupivacaine groups were 208 minutes and 220 minutes, respectively.

Levobupivacaine, the S(-)-enantiomer of bupivacaine, has also been put into clinical practice as an alternative to bupivacaine. Ivani and others (2002) compared 1 mL/kg of caudal 0.25% levobupivacaine with 0.2% ropivacaine and 0.25% racemic bupivacaine in children and noted no significant difference in intraoperative or postoperative analgesia among the three groups ( Ivani et al., 2002 ). In children less than 2 years of age, a dose of 2 mg/kg of 0.25% levobupivacaine had similar efficacy to racemic bupivacaine and levobupivacaine had a duration of action of 7.3 hours ( Taylor et al., 2003 ). Ivani and others (2003) noted the optimum concentration of levobupivacaine at 1 mL/kg for single-shot caudal anesthesia without any additive was 0.2%. This dose provides 118 minutes of postoperative analgesia compared with 60 minutes with 0.125% and 158 minutes with 0.25%. The advantage of using 0.2% over 0.25% was the decreased incidence of motor blockade. Dosing guidelines for levobupivacaine are similar to those for bupivacaine (see Table 14-4 ).

Caudal Additives

One of the disadvantages of caudal anesthesia is the relatively short duration of postoperative analgesia in children, even when using long-acting local anesthetics. Many agents have been studied in an attempt to find an additive that would prolong the duration of analgesia for single-shot caudal anesthesia.

Epinephrine

The use of epinephrine for regional anesthetic techniques in children was discussed earlier in this chapter. It is recommended that epinephrine be added to single-dose local anesthetics at a dose of 5 mcg/mL or a concentration of 1:200,000. The hypothetical disadvantage of the use of epinephrine is vasoconstriction and possible cord ischemia from impaired flow to the artery of Adamkiewicz ( Cook and Doyle, 1996 ). An epinephrine dose of 2.5 mcg/mL or a concentration of 1:400,000 may be used as an additive for central blocks ( Flandin-Blety and Barrier, 1995 ).

Epinephrine serves as a marker for intravascular injection and decreased systemic absorption of local anesthetic. In addition, epinephrine may prolong the duration of a regional block. Warner and others (1987) compared children aged 3 months to 17 years receiving single-shot caudal block with 0.5 mL/kg bupivacaine 0.25%. One group received the bupivacaine plain and the other group had epinephrine 5 mcg/mL added to the local anesthetic. Epinephrine prolonged the duration of analgesia of the caudal block compared with the blocks that did not include epinephrine. The duration of analgesia decreased with increasing age with the greatest effect on children less than 5 years of age. Children aged 5 or less had a mean duration of analgesia 10 to 13 hours longer if epinephrine was in the solution. In children aged 6 to 10 years, epinephrine increased the duration of effect by 2 to 3 hours, whereas in children older than 11 years, epinephrine increased the block by 1 to 2 hours. However, in other studies, epinephrine has not been shown to prolong a caudal block with bupivacaine ( Fisher et al., 1993 ; Cook et al., 1995 ).

Ketamine

Preservative-free ketamine has been described for caudal use in children to prolong a bupivacaine block following hernia surgery. Naguib and others (1991) compared three groups of children receiving either plain bupivacaine 0.25%, ketamine 0.5 mg/kg, or bupivacaine 0.25% plus ketamine 0.5 mg/kg. The group that received only ketamine 0.5 mg/kg had superior analgesia and longer duration of action than the group that had received plain 0.25% bupivacaine. The ketamine group also had similar analgesia and duration of action to the group that received the combination of ketamine and bupivacaine. No postoperative behavior changes were noted in the ketamine groups. These findings have been confirmed in subsequent studies using ketamine 0.5 mg/kg as an additive to either bupivacaine 0.25% or ropivacaine 0.2% in the caudal space ( De Negri et al., 2001 ; Weber and Wulf, 2003 ). Cook and others (1995) studied children aged 1 to 10 years who received caudal anesthesia using 0.25% bupivacaine 1 mL/kg with the addition of either ketamine 0.5 mg/kg, clonidine 2 mcg/kg, or epinephrine 5 mcg/mL. The ketamine group had a mean duration of analgesia of 12.5 hours compared with 5.8 hours for the clonidine group and 3.2 hours for the epinephrine group. When used alone in the caudal space, ketamine at this dose of 0.5 mg/kg had a shorter duration of action than bupivacaine 0.25% with 1:200,000 epinephrine, but ketamine 1 mg/kg provided surgical and postoperative analgesia that was equivalent to bupivacaine ( Marhofer et al., 2000 ).

Hager and others (2002) reported on the use of ketamine for caudal analgesia without local anesthetic and compared a group that received ketamine 1 mg/kg with two other groups who received, in addition to ketamine, clonidine 1 or 2 mcg/kg. The ketamine group had a mean duration of postoperative analgesia of 13.3 hours. When clonidine 1 mcg/kg or 2 mcg/kg was added to the ketamine, the mean duration was 22.7 hours and 21.8 hours, respectively. This particular study prompted a letter to the editor by Eisenach and Yaksh (2003) that stressed concern over the performance and publications of studies that subjected healthy children to agents that have not had adequate preclinical toxicity studies. Eisenach and Yaksh further discussed the potential risks of neurotoxicity using S(+)-ketamine in the epidural space without significant benefits to the otherwise healthy child. The response to this letter from the authors of the study defended their position with a number of reports on ketamine in the epidural space (Marhofer and Semsroth, 2003 ). The issue remains controversial as pointed out in a systematic review of nonopioid additives by Ansermino and others (2003) . This review summarized the findings of randomized control trials performed on children using nonopioid additives in the caudal space and concluded that although clonidine, ketamine, and midazolam increase the duration of analgesia, the potential for neurotoxicity remains a concern with ketamine and midazolam. They also concluded that the routine use of nonopioid adjuvants for elective outpatient surgery had not been shown to improve patient outcome.

Clonidine

Clonidine, an α2-adrenergic agonist, at 1 to 2 mcg/kg has been used with success and may result in an additional 4 to 6 hours of analgesia when combined with bupivacaine ( Lee and Rubin, 1994 ; Constant et al., 1998 ). Ivani and others (2000) also demonstrated a beneficial effect of clonidine when added to ropivacaine. In this study, 0.1% ropivacaine plus clonidine 2 mcg/kg provided superior analgesic quality to a caudal block compared with 0.2% ropivacaine without clonidine. The true mechanism of analgesic action of clonidine remains unknown, but there is evidence that it has both central and peripheral sites of action ( Ivani et al., 2002 ). Although clonidine may cause some sedation, particularly at the higher doses, and although the sedation has not been considered clinically significant in studies, caudal clonidine has been implicated in case reports as a cause of apnea in neonates ( Breschan et al., 1999 ; Bouchut et al., 2001 ).

De Negri and others (2001) compared ketamine with clonidine to determine which agent would most effectively prolong a ropivacaine caudal anesthetic. Children 1 to 5 years of age received 0.2% ropivacaine 2 mg/kg, ropivacaine plus clonidine 2 mcg/kg, or ropivacaine plus ketamine 0.5 mg/kg for caudal anesthesia. Postoperative analgesia was significantly longer in the ropivacaine with ketamine group (701 minutes) compared with the ropivacaine with clonidine group (492 minutes) and the ropivacaine plain group (291 minutes). There were no clinically significant side effects in any of the groups. These findings were similar to the study by Cook and others (1995) that compared clonidine 2 mcg/kg with ketamine 0.5 mg/kg as additives to 0.25% bupivacaine caudal anesthesia.

Tramadol

Tramadol is an analgesic that acts centrally at opioid receptors and has been compared with bupivacaine alone and a tramadol-bupivacaine combination for caudal analgesia ( Prosser et al., 1997 ; Batra et al., 1999 ; Gunduz et al., 2001 ). At a dose of 1 mg/kg of tramadol added to bupivacaine, patients had lower pain scores and longer durations of analgesia compared with bupivacaine alone ( Batra et al., 1999 ). At a tramadol dose of 2 mg/kg added to bupivacaine, some children had sedative effects; however, this was not considered to be clinically significant ( Gunduz et al., 2001 ). Caudal tramadol 2 mg/kg provides reliable postoperative analgesia similar to caudal morphine 30 mcg/kg for children undergoing herniorrhaphy ( Ozcengiz et al., 2001 ).

Neostigmine

The use of neostigmine in the epidural space is a relatively new concept in children. Its action may be attributed to either direct action on the spinal cord via inhibition of the breakdown of acetylcholine in the dorsal horn or by peripheral antinociceptive effect ( Shafer et al., 1998 ; Yang et al., 1998 ). A study in children compared three groups to determine the effectiveness of neostigmine 2 mcg/kg as a caudal analgesic for hypospadias repair, either alone or in combination with bupivacaine ( Abdulatif and El-Sanabary, 2002 ). The groups received 1 mL/kg of either 0.25% bupivacaine plain, bupivacaine with neostigmine 2 mcg/kg, or neostigmine 2 mcg/kg plain. The combination of bupivacaine and neostigmine provided superior analgesia to either of the other two groups and a mean duration of 22.8 hours compared with 8.1 hours in the bupivacaine plain group and 5.2 hours in the neostigmine plain group.

Opioids

Opioids have been commonly used in caudal blocks with or without local anesthetic agents. There are two distinct classes of opioids: hydrophilic and lipophilic. In general, hydrophilic opioids such as morphine are capable of rostral spread, whereas lipophilic opioids such as fentanyl remain more localized to their area of injection. This difference accounts for the greater incidence of sedation and respiratory depression that occurs with hydrophilic agents.

Opioids may be used to improve the quality and duration of a block, but there are advantages and disadvantages to spinal axis opioids ( Lonnqvist et al., 2002 ). The major disadvantage of opioid additives is the risk of respiratory depression. In children less than 1 year of age, the risk of respiratory depression from caudal morphine is significantly higher than that in children greater than 1 year of age ( Valley and Bailey, 1991 ). In this study of 138 children who had received 70 mcg/kg of caudal morphine, the incidence of clinically significant respiratory depression was 8%. Ten of the 11 children with respiratory depression were less than 1 year of age and weighed less than 9 kg. Seven of the 11 patients also received intravenous opioids. All episodes of respiratory depression occurred within 12 hours of the caudal morphine injection. Therefore, spinal axis opioids are contraindicated in ambulatory surgical patients. Additionally, patients under 1 year of age and patients receiving supplemental intravenous opioids should be carefully monitored postoperatively.

Another disadvantage of neuraxial opioids is the increased incidence of postoperative pruritus, nausea, and vomiting. Although fentanyl 1 mcg/kg may prolong a caudal block, the incidence of pruritus and vomiting also increases ( Constant et al., 1998 ). In one study, the investigation was actually halted due to the unacceptable incidence of postoperative vomiting in a group of children who had received caudal buprenorphine ( Khan et al., 2002 ). Urinary retention is a side effect of caudal morphine and required urinary catheterization in 30% of children in one study using 70 mcg/kg morphine ( Irving et al., 1993 ). Another reason for the avoidance of neuraxial opioids is the availability of alternative additives. As previously discussed, additives such as clonidine and ketamine have been used as adjuncts for central blockade with success and result in fewer side effects compared with opioids.

Despite the pitfalls of using opioids as a component of central blockade, the practice continues because of the relative advantages these agents offer. Preservative-free morphine more than doubles the duration of a single-shot bupivacaine caudal ( Krane et al., 1987 ). In a study of children aged 1 to 16 years, there was a slightly greater incidence of urinary retention, pruritus, and nausea in the group that received caudal morphine, but there was no evidence of delayed respiratory depression even at doses of 100 mcg/kg in this age group. A caudal morphine dose of 30 mcg/kg has been recommended for children to provide the advantage of increased analgesic duration with decreased incidence of side effects, particularly respiratory depression ( Krane et al., 1989 ). In children who were undergoing open-heart procedures, a dose of 75 mcg/kg morphine provided lower pain scores and decreased incidence of atelectatic changes on radiography compared with a control group that had not received caudal morphine ( Rosen and Rosen, 1989 ). Plasma levels of morphine given via the caudal route peak at 21 ± 4.8 ng/mL approximately 10 minutes after injection ( Wolf et al., 1991 ). These levels are lower than that associated with systemic administration of morphine.

Lipophilic opioids do not offer the same risk of respiratory depression as hydrophilic agents. The disadvantage of the lipophilic agents is the shorter duration of postoperative analgesia than what is provided by morphine, and there may actually be no benefit to the addition of fentanyl to local anesthetic for a single-shot caudal. In most reports, caudal fentanyl 1 mcg/kg has not been shown to increase the duration of analgesia produced by 0.125% bupivacaine, 0.25% bupivacaine, or 2% lidocaine ( Jones et al., 1990 ; Campbell et al., 1992 ; Joshi et al., 1999 ; Baris et al., 2003 ). In contrast, Constant and others (1998) demonstrated the prolongation of analgesia in a study in which fentanyl 1 mcg/kg was added to a mixture of bupivacaine and lidocaine in children aged 6 to 108 months. The mean duration of analgesia in the fentanyl group was 253 ± 105 minutes compared with 174 ± 29 minutes in the control group without fentanyl. Vomiting occurred in 4 of 15 of the children who had extradural fentanyl and 0 of 14 in the children who had not received fentanyl.

Fentanyl and morphine were compared for efficacy and side effects in children aged 1 to 16 years ( Lejus et al., 1994 ). The children all received a preincision epidural dose of 0.5% bupivacaine 0.75 mL/kg and then were divided into two groups. The morphine group received a preoperative bolus of epidural morphine 75 mcg/kg and the same morphine bolus dose 24 hours later. The fentanyl group received 2 mcg/kg before incision, followed by a continuous infusion of 5 mcg/kg per day. The group that received the fentanyl infusion had comparable analgesia to the morphine group with less pruritus (20% versus 53%) and less nausea and vomiting (0% versus 33%).

Complications

Complications from caudal anesthesia include risks during the performance of the block, risks from injection of local anesthetic, and side effects from the agents used. During the performance of a caudal block, the needle could be accidentally placed into the intravascular space, subarachnoid space, or sacral marrow. The incidence of intravascular injection should be decreased with the use of a short-beveled needle, and a test dose should provide information as to whether the needle is intravascular or in the vascular marrow ( Dalens and Hasnaoui, 1989) . The detection of a subarachnoid injection may be difficult if CSF is not clearly seen upon aspiration before local anesthetic injection. In the safety study of Giaufre and others (1996) , inadvertent dural puncture was the most frequent complication. In the event the subarachnoid space has been entered, it is possible to reintroduce a needle for a caudal anesthetic; however, the agent should be injected very slowly to avoid the possible migration of local anesthetic solution into the subdural space through any previous puncture sites.

Children differ from adults in that hypotension secondary to centrally delivered local anesthetics is not generally a significant side effect from caudal or neuraxial regional anesthesia. Even without intravascular volume loading before the administration of a central blockade, hypotension is typically not observed in children less than 5 years of age ( Dohi et al., 1979 ; Dohi and Seino, 1986 ). This may be due to either the immature sympathetic nervous system or the fact that the lower extremities, in proportion to overall body size, do not provide a significant volume for venous pooling.

Studies have been performed in children to investigate the hemodynamic response to caudal analgesia. Doppler studies to investigate hemodynamic changes have demonstrated that cardiac output does not change during caudal anesthesia in infants ( Payen et al., 1987 ). However, a study to investigate pulmonary Doppler flow revealed that the pulmonary flow velocity changes during caudal anesthesia, presumably secondary to an increase in pulmonary artery resistance ( Ozasa et al., 2002 ). Because the change may have reflected local anesthetic–induced vasoconstriction, the authors concluded that caudal epidural anesthesia is not recommended in children with pulmonary hypertension.

Urinary retention, although a concern, is not considered a frequent side effect in single-shot caudal anesthetics. Fisher and others (1993) reviewed the postoperative voiding interval in children who received either bupivacaine caudal blocks with and without epinephrine or ilioinguinal hypogastric nerve blocks. In this study, they noted no significant difference in the time to micturition among these groups. Although the range of times to first micturition varied widely from 25 to 630 minutes, no children required any intervention for urinary retention.

Complications from intravascular injection and accumulation of local anesthetics have previously been discussed.

▪ CONTINUOUS CAUDAL CATHETERS

Intraoperatively, an indwelling catheter may be placed in the caudal epidural space. These catheters allow for additional dosing of the local anesthetic agents at the end of the procedure or in the recovery area before catheter removal. A repeat dose or a second dose of local anesthetic can safely be administered 90 to 120 minutes after the initial dose as long as maximal allowable dosing is not exceeded in that time period. In addition, continuous caudal block may be used as an alternative to spinal anesthesia in the ex-premature infant who is at risk for postoperative apnea while undergoing inguinal hernia repair. This technique has been used with success with and without a concomitant general anesthetic ( Henderson et al., 1993 ; Peutrell and Hughes, 1993 ; Tobias et al., 1996 ).

The presence of a caudal catheter allows for continued postoperative pain management in children. Continuous infusions, although commonly used because of their ability to provide complete postoperative analgesia, have come under scrutiny because of a lack of prospective outcome studies that demonstrate benefit ( Chalkiadis, 2003 ). Audits of postoperative infusions have demonstrated that 17% to 22% of patients require premature termination of the infusions. In 67% of these patients, the termination was due to an unacceptable rate of side effects or complications ( Wilson and Lloyd-Thomas, 1993 ; Wood et al., 1994 ). This high rate leads one to question the benefit of neuraxial analgesia over intravenous analgesia ( Chalkiadis, 2003 ). Side effects may be greater for lipophilic infused epidural opioids (e.g., fentanyl), because the catheter tip must be positioned at the interspace corresponding to the dermatomes of the surgical procedure. Another issue that argues against placing and maintaining a continuous epidural catheter includes the dissatisfaction in children of having a motor block. There may also be an increased incidence of postoperative urinary retention and pruritus in children who receive infusions of neuraxial opioids ( Lloyd-Thomas and Howard, 1994 ).

Although these side effects are not necessarily dangerous, they do result in increased workload for medical staff, additional medications, and child/parent distress. More serious issues with continuous caudal infusions include the rare risks of epidural hematomas, epidural infection and abscesses, or respiratory depression from central opioids. In addition, there is the cost factor of the epidural catheter kits, the operative time to insert the caudal catheters, urinary catheters, and postoperative costs for pharmacy, nursing, on-call staff, and a pain service. For these reasons, it has been suggested that continuous infusions be reserved for those children who would truly receive a direct benefit.

Technique

The anatomy, a continuous catheter via the caudal route and entry into the caudal space have been described previously. In threading a caudal catheter, the space should first be dilated with a push of preservative-free normal saline. The catheter is then threaded through the needle until the tip of the catheter reaches the estimated desired level. The caudal approach to placing a lumbar or thoracic catheter in infants was described by Bosenberg and others (1988) . Because of the loosely packed fat in the epidural space, a catheter should advance easily. If resistance is felt, it is most likely due to the catheter coiling or doubling back in the epidural space. In older children who may have more densely packed epidural fat, the use of a catheter with a stylet may increase the success rate ( Gunter and Eng, 1992 ). In addition to using a catheter with a stylet, other means of improving success of this technique are to dilate the space with preservative-free normal saline before catheter placement, flexing the hips to straighten the spine, and utilizing fluoroscopy to ensure proper catheter tip position.

If an angiocath has been used for insertion of the catheter, the catheter may be withdrawn, twisted, and advanced through the plastic introducer until the desired position as determined by radiography is obtained. Catheters should not be withdrawn through metal needles due to the risk of shearing the catheter into the epidural space. Success in placing a thoracic catheter via the caudal route is variable. In a study of 86 infants who had caudal placement of a thoracic catheter that was confirmed by radiographs, the positions of 28 of these catheters were considered to be inadequate ( Valairucha et al., 2002 ). Of the 28, 10 were determined to be in the high thoracic or cervical regions and were able to be pulled back, 17 were coiled in the lumbosacral area, and 1 was outside the epidural space in the presacral area. Radiographic confirmation of catheter tip position for thoracic catheters that are threaded from the caudal route is essential.

Dosing

Continuous caudal catheters that have their tip in the sacral or lower lumbar areas are dosed differently from those that have been threaded to the low to mid-thoracic levels. Suggestions for dosing may be found in Table 14-4 . Continuous caudal catheters require large volumes of local anesthetic to fill the loose caudal epidural space and to spread the anesthetic cephalad to the desired dermatomal level. It is important to refer to the maximal allowable dosing recommendations so that these rates are not exceeded in an attempt to “drive up” the epidural block from the caudal space (see Table 14-2 ). Bupivacaine, ropivacaine, and levobupivacaine may be used for continuous caudal anesthesia, with or without additives. It is possible to improve the analgesia of a continuous caudal catheter by including a hydrophilic opioid such as preservative-free morphine or hydromorphone to the infusion.

In addition to a continuous infusion, there is the ability for children to benefit from patient-controlled epidural analgesia. Patient-controlled analgesia allows the patient to receive analgesia literally at the press of a button. Its popularity in children initially began in the late 1980s with intravenous opioids and has expanded to local anesthetic infusions for a variety of blocks. For patient-controlled analgesia to be effective, a patient or provider must be able to identify pain and push a button that signals a pump to deliver a preset amount of the local anesthetic solution. This pump is programmed in advance to deliver a bolus amount based on weight criteria and is set to adhere to specific time and dosage limits. In addition to the bolus that is delivered in response to the push of the button, the pump is capable of infusing a continuous background rate of local anesthetic solution. In a study of children who had undergone a total of 132 procedures in whom patient-controlled epidural analgesia was used postoperatively, more than 90% had satisfactory analgesia with no significant adverse effects ( Birmingham et al., 2003 ). This study confirmed that children as young as age 5 have the cognitive ability to understand the use of patient-controlled analgesia.

Complications

Complications of continuous caudal infusions are typically secondary to the agent that is being delivered. The risk of local anesthetic toxicity has been discussed, and there is ample evidence that the use of bupivacaine at doses over 0.2 mg/kg per hr in infants and 0.4 mg/kg per hr in children greater than 6 months of age may lead to neurotoxicity or cardiovascular collapse ( Agarwal et al., 1992 ; Berde, 1992 , 1993; McCloskey et al., 1992 ).

In addition to the risk of serious complications, minor complications such as urinary retention, muscle weakness, itching, or nausea and vomiting can occur. Lowering the concentrations of local anesthetics and avoiding opioids in the central infusion can reduce the risk of these side effects. This regimen, however, puts the patient at greater risk of experiencing postoperative pain.

Continuous indwelling caudal catheters would seem to be an obvious setup for fecal contamination and infection. When caudal catheters have been compared with epidural catheters, caudal catheters were found to have a greater incidence of colonization of bacteria (20% versus 4%), with Staphylococcus epidermidis being responsible for the vast majority of colonization ( McNeely et al., 1997 ). In addition, four of the nine caudal catheter tips that were colonized also involved gram-negative bacteria. Of interest, caudal catheter tip colonization was not predicted by duration of catheterization, skin inflammation, or dressing contamination. None of the children developed signs of epidural infection either in the hospital or during 3-month follow-up. Another study demonstrated the absence of epidural abscess or clinically significant infection from indwelling catheters for postoperative pain ( Strafford et al., 1995 ). An option for children who are to have prolonged analgesia provided by a continuous caudal or epidural catheter is to tunnel the catheter under the skin ( Aram et al., 2001 ). Catheters that have been tunneled under the skin should provide for a more long-term infusion of agents by providing decreased chance of catheter dislodgment and protection against colonization and infection.

▪ EPIDURAL ANESTHESIA

Epidural anesthesia is commonly used for those procedures that involve surgery of the mid to upper abdomen and thorax that are less amenable to a continuous caudal anesthetic. Children who have procedures that have higher morbidity rates such as Nissen fundoplication may benefit from perioperative epidural analgesia ( McNeely et al., 1997 ; Wilson et al., 2001 ). Postoperative complications and hospital stay may be reduced with the use of an epidural for this procedure compared with opioid analgesia alone. In addition, the use of epidural anesthesia is associated with a significantly reduced stress response to surgery in children, as determined by lower cortisol levels and plasma epinephrine levels ( Murat et al., 1988 ; Wolf et al., 1993 ).

Although lumbar epidural blocks are commonly used, thoracic epidural blocks should be performed only by practitioners who are experienced in their use and should be reserved for children with pulmonary disease or those who are to undergo a surgical procedure in the thoracic area or upper abdominal area that is associated with significant postoperative pain. As discussed, under continuous caudal anesthesia, a catheter may be threaded from the caudal space cephalad to the thoracic region to provide more site-specific analgesia without the risks associated with placing a needle in the thoracic spine. However, threaded catheters from the caudal space are frequently malpositioned. In older children, a thoracic epidural inserted between T4 and T8 should attenuate the stress response associated with thoracic surgery and provide optimal postoperative analgesia ( Hammer, 2001 ). Thoracic epidural catheters that are placed intraoperatively by the surgeon before wound closure for anterior spinal fusion and instrumentation for scoliosis have been shown to be safe and effective ( Jason Lowry et al., 2001 ).

Anatomy

The epidural space in children is divided into sacral, lumbar, thoracic, and cervical levels. The caudal block enters at the sacral level. A lumbar epidural needle/catheter is typically placed at the L3-4 interspace, which in older children is found in the midline of a line that may be drawn between the two iliac crests. Although these landmarks are accurate in older children, the intercrestal line may actually cross the L5-S1 interspace in neonates and the L4-5 interspace in infants up to a year of age because of the lag of the growth of the spinal cord (see Plate 14-1 ). Because of the developmental changes that occur with the spinal cord and dural sac positions, placing an epidural catheter below the level of the intercrestal line (e.g., caudal area) may decrease the risk of a wet tap in a neonate or young infant.

Epidural pressures differ depending on the age of the patient. Infants have narrow epidural spaces and are more likely to exhibit leak around an epidural catheter from a backflow of solution if injected too quickly ( Vas et al., 2001 ). Even at slow injection rates, epidural pressures in infants are higher than in adults.

The anatomy of the thoracic spine is similar to that of the lumbar spine with some exceptions. The spinous processes in the thoracic area are longer and the interspinous spaces narrower ( Plate 14-6 ). These differences necessitate that the epidural needle be placed at a sharper angle in a cephalad direction. The ligaments in the thoracic area are more lax and may be more difficult to discern during needle placement compared with performing a lumbar needle insertion. Most important, the spinal cord occupies most of the spinal canal in the thoracic area, leaving little margin for error once the needle reaches the epidural space.

 
 

PLATE 14-6  Anatomy of the epidural space.  (From Brown DL: Atlas of Regional Anesthesia. WB Saunders, Philadelphia, 1992, p. 286.)

 



The depth to the epidural space at the L2-3 level is approximately 10 mm at birth, and this depth increases with age in a linear fashion. The approximate expected distance from the skin to the epidural space in children aged 6 months to 10 years is approximately 1 mm/kg body weight ( Bosenberg, 1995 ). Approximate depths from the skin to the lumbar and thoracic epidural spaces for the different ages are referenced in Figure 14-2 .

Technique

With the child in the lateral position and knees and hips flexed, the line that joins the two iliac crests crosses the body of S1 in neonates, L5 in infants, L4-5 in young children, and L4 in older children and adolescents ( Busoni and Messeri, 1989 ) ( Plate 14-7 ). After sterile prep and drape, the needle should be placed in the midline between the spinous processes that are closest to the line that crosses the iliac crests. If performing a lumbar epidural puncture, the spinous processes require the needle to be directed slightly cephalad but mostly perpendicular to the skin. The needle is advanced slowly with one hand firmly against the child's back and holding the portion of the needle that is entering the child's skin. This is to avoid any inadvertent and rapid advancement of the needle. The needle passes through skin, subcutaneous tissue, supraspinous ligament, interspinous ligament, and then ligamentum flavum before entering the epidural space as illustrated in Plate 14-6 . Because of the risk of air embolus, a continuous loss of resistance technique using saline rather than air to confirm the epidural space is the recommended approach (Sethna and Berde, 1993 ).

 
 

PLATE 14-7  Performance of the epidural block. IC, iliac crest; SP, spinous process.

 

 

The ability to feel entry into the ligamentum flavum and the loss of resistance as the epidural space is entered are more subtle in infants than in adults. Once the epidural space is entered and there is negative aspiration for CSF or blood, the local anesthetic with epinephrine should be injected as an initial test dose before delivering the planned dose of local anesthetic. Compared with adults, epidural pressures differ in children, particularly in infants ( Vas et al., 2001 ). Based on the relationship between the volume and rate of injection of local anesthetics in infants and the epidural pressure, a slow rate of injection is used, perhaps 0.5 mL/min.

To place a thoracic epidural, the child is placed in the lateral decubitus position. After sterile prep and drape, the point of needle insertion is the midpoint of the spinous processes at the chosen level. The needle should be at a 45- to 60-degree angle aiming cephalad until resistance is felt as the spinous ligaments are encountered. A syringe to detect loss of resistance to saline is attached and the needle is continuously advanced slowly with light pressure on the plunger of the syringe. A sudden loss of resistance indicates needle placement in the epidural space. One of the hallmarks of a successful thoracic epidural needle placement is the ease at which a catheter is threaded in this area. It should pass easily and without resistance.

Equipment

Appropriate-sized equipment is readily available for epidural placement in children. Short Touhy needles and small-gauge catheters, with and without metal helixes, are available. The main disadvantage of a small-gauge catheter is that they increase resistance to continuous infusions of local anesthetics. Postoperatively this can result in frequent alarm of the infusion pump.

Dosing

Epidural catheters are typically placed with the plan to continue their use in the postoperative period. Because the tip of the epidural catheter should be in close proximity to the level of surgery and because the lumbar/thoracic epidural space is more compact than the caudal space, the initial bolus of local anesthetic that is required for lumbar and thoracic epidural blocks is smaller (0.3 to 0.5 mL/kg) than the volumes required for a caudal injection. Approximately 90 minutes after the initial bolus, a continuous infusion may be initiated with care to stay within dosing guidelines (see Table 14-2 ). Commonly used local anesthetics for epidural analgesia are bupivacaine, levobupivacaine, and ropivacaine. Recommendations for epidural dosing may be found in Table 14-4 .

When using 0.25% bupivacaine at a rate of 0.08 mL/kg per hr in the lumbar epidural space in children aged 11 months to 15 years, Desparmet and others (1987) demonstrated that the terminal half-life ranges from 164 to 270 minutes and that total body clearance is similar to that after single caudal injection. Larsson and others (1994) studied bupivacaine infusions in 12 infants. In infants, bupivacaine infusions at rates of 0.5 to 0.83 mg/kg per hr for 12 hours resulted in marked increases in plasma bupivacaine concentrations. Larsson also noted possible toxic reactions in 3 of the 12 infants and suggested these infusion rates were excessive for this age group.

The pharmacokinetics of epidural ropivacaine were assessed after a single injection of 1.7 mg/kg via a lumbar epidural catheter ( McCann et al., 2001 ). The median peak plasma concentrations of ropivacaine were 610 mcg/L in infants aged 3 to 11 months and 640 mcg/L in children aged 12 to 48 months. In both groups of children the median peak plasma concentration was reached in 60 minutes. The calculated clearance of ropivacaine was 4.26 mL/kg per min in infants and 6.15 mL/kg/min in older children. There was no ropivacaine toxicity observed in either group. When ropivacaine 0.2% at 0.4 mg/kg per hr was delivered as a continuous lumbar or epidural infusion for 36 to 96 hours, Hansen and others (2000) noted no clinically significant side effects in 18 pediatric patients aged 4 months to 7 years. In this study, the volume of distribution of epidural ropivacaine was 3.1 L/kg, total clearance was 8.5 mL/kg per min, and the elimination half-life was 4.9 hours (see Table 14-1 ).

Epidural Additives

The advantage of adding clonidine to single-shot caudal blocks has been demonstrated, but only recently has there been investigation of its use for continuous epidural analgesia. In a study of 60 children who received a low lumbar epidural catheter for hypospadias repair, a postoperative infusion of ropivacaine alone versus ropivacaine with varying doses of clonidine was compared. In this study, plain ropivacaine 0.1% at 0.2 mg/kg per hr or ropivacaine 0.08% at 0.16 mg/kg per hr plus either clonidine 0.04, 0.08, or 0.12 mcg/kg/hr was evaluated ( De Negri et al., 2001 ). The children who received the ropivacaine with the higher clonidine doses in the 0.08 to 0.12 mcg/kg per hr range had improved pain scores, longer time to first analgesic, and reduced total supplemental analgesics. In addition, these patients had no evidence of sedation or other side effects.

The use of neuraxial opioids was discussed in detail in the section on caudal analgesia. In a study designed to assess the efficacy of preoperative epidural morphine, 21 children were randomized to either receive 30 mcg/kg epidural morphine after induction of general anesthesia but before surgical incision or to not receive an epidural injection. Both groups were given intraoperative infusions of sufentanil and postoperative Patient Controlled Analgesia (PCA) with morphine. The group that had received preoperative epidural morphine, in comparison with the control group without epidural morphine, had lower pain scores and decreased total analgesic requirements postoperatively without increased side effects ( Kiffer et al., 2001 ).

Epinephrine is a commonly used additive for single-shot epidural blocks because of its ability to decrease systemic absorption and perhaps prolong the block while adding an additional level of safety. For continuous infusions, these benefits must be weighed against the theoretical risks of vasoconstriction of spinal vessels. A study by Kokki and others (2002) compared a combination of ropivacaine and sufentanil with and without epinephrine 2 mcg/mL in a population of children. The group of children who had epinephrine in their postoperative epidural infusions had significantly lower infusion requirements and fewer side effects.

Complications

As discussed for caudal catheters, the risk of infection is very low. Although there have been case reports of epidural abscess, short-term epidural catheterization for postoperative courses do not appear to have the same risk of infection as those that may be placed for chronic pain ( Strafford et al., 1995 ). In 1620 chil dren studied over a 6-year period who received epidural catheters, there were no infections or epidural abscesses in catheters that had been placed for postoperative pain management. There was only one epidural abscess found in this study, and that was in an immunosuppressed child with terminal malignancy who had Candida colonization of the epidural space that had been invaded by tumor and who had an indwelling catheter for control of pain from her malignancy. When catheters have been removed and cultured, the incidence of catheter-tip colonization in epidural catheters is 4%, lower than that found in caudal catheters at 20% (McNeeley et al., 1997).

Copyright © 2008 Elsevier Inc. All rights reserved. - www.mdconsult.com

Motoyama & Davis: Smith's Anesthesia for Infants and Children, 7th ed.

Copyright © 2005 Mosby, An Imprint of Elsevier

▪ PERIPHERAL NERVE BLOCKS

The goal of placing peripheral nerve blocks (PNBs) is to specifically target analgesia to the location of the surgery so that side effects may be kept to a minimum ( Ross et al., 2000 ). The safety of performing such blocks has been established, and it has been recommended by ADARPEF that peripheral blocks be used in place of central blocks when appropriate ( Giaufre et al., 1996 ). In their safety study of regional anesthetics in children, there were no complications in the 9396 children who received PNBs or local anesthesia. Despite these findings, PNBs are underused in children, probably related to inexperience and the perception that they may be difficult to perform or may be hazardous.

Success of placing PNBs is often a function of knowledge of the anatomy and use of the appropriate equipment (Sethna and Berde, 1992 ). Insulated needles with a nerve stimulator are typically used for peripheral nerve blockade because they allow precise location of the nerve independent of the nerve's depth. With insulated needles, the field of current is localized to the needle's tip. Unsheathed needles may be less expensive and result in successful blocks, but the current is distributed not only to the needle's tip but also along the shaft of the needle. The required stimulatory current is greater (up to 2 mA) (Bosenberg, 1995 ). For upper extremity nerve blocks, a 1- or 2-inch insulated needle will suffice. Lower extremity blocks may require the use of longer needles, particularly for sciatic blocks in adolescents. Another practical consideration in performing a PNB with a nerve stimulator is that the use of neuromuscular blockers abolishes the ability to elicit muscle stimulation with a peripheral nerve stimulator. The peripheral nerve stimulator should be capable of delivering 0.1 to greater than 1.5 mA and be set to 2 Hz. The positive electrode of the nerve stimulator should be placed at least 10 cm from the nerve to be blocked and preferentially on the opposite limb.

To locate a nerve or plexus, one should begin with the nerve stimulator set at 1 to 1.2 mA and advance the needle until the desired motor response is achieved. The voltage may then be decreased. When the voltage is decreased to less than 0.5 mA, the motor response should be diminished but still present. One may need to make further fine adjustments in the needle's position in order to continue muscle stimulation of the appropriate muscle group at the lower voltage. However, an increase in voltage may be required to relocate the nerve if muscle stimulation is completely lost. Once the nerve stimulator's voltage is less than 0.5 mA and slight muscle stimulation results, then local anesthetic is injected. If the needle is in the correct position, the muscle stimulation should cease immediately. If there is intense muscle stimulation with 0.2 mA, the possibility of intraneural needle placement must be considered. Consequently, the needle should be withdrawn and readvanced carefully. In anesthetized children, the placement of a needle into a nerve would not be detected, so this warning sign of intense muscle stimulation at lower voltage is significant. In addition, one should look for other warning signs of intraneural injection such as difficulty with injection and increased heart rate with injection.

Surface nerve mapping has been used in children to improve the ability to locate a peripheral nerve or plexus and may be a useful practice, particularly in patients with abnormal anatomy and in infants who may be at higher risks of complications from regional anesthesia ( Bosenberg, 2002) . Nerve surface mapping is performed by setting the nerve stimulator at a frequency of 1 to 2 Hz and the current between 3 to 4 mA. The positive electrode should be at least 10 cm from the nerve to be mapped, and the negative electrode or alligator clamp that would normally be attached to the block needle is instead pressed against the skin at right angles across the suspected path of the nerve. Once a point of maximal motor response is found, a mark may be placed to indicate where the insulated needle may be inserted for regional blockade.

In children who are anesthetized, it is not possible to reliably test the success of a PNB; however, one may increase the voltage of the nerve stimulator after local anesthetic injection to determine that there is loss of stimulation. Although subtle, it is also possible to determine success of motor block by comparing the flaccidity of the blocked limb with the muscle tone of the contralateral extremity. Vasodilation and/or increased skin temperature, when present in the blocked limb, may be a more reliable indicator of a successful block, but its absence does not mean that the block is unsuccessful. The absolute determinant of a successful block is the absence of response to the surgical incision. Most PNBs, independent of the agent used, should provide total analgesia to the desired nerve or plexus within 20 minutes of the local anesthetic injection.

Dosing of PNBs is discussed with regard to the individual block. Independent of the local anesthetic delivered, the addition of epinephrine to the solution should provide additional safety when performing the block. As previously discussed, not only does the addition of epinephrine to the local anesthetic solution have the potential to serve as a marker for intravascular injection; it may also decrease overall absorption of the local anesthetic. In a study of 20 children who were to undergo unilateral surgery of the thigh, patients were administered a fascia iliaca block using 2 mg/kg bupivacaine either with or without epinephrine 5 mcg/mL ( Doyle et al., 1997 ). The median maximum plasma bupivacaine concentration in the group without epinephrine was 1.1 mcg/mL compared with 0.3 mcg/mL in the group of patients in whom epinephrine was added to the bupivacaine. Not only did the epinephrine group have a significantly lower peak plasma level, but the onset time to peak plasma concentration was more gradual for the group with epinephrine.

The majority of PNB techniques are similar to those of adults. The differences from adult practice are presented here, along with blocks that are more directed to children.

▪ UPPER EXTREMITY NERVE BLOCKS

Upper extremity blocks may be used for surgery of the shoulder, arm, and hand. Specifically, brachial plexus blocks below the clavicle, including the axillary approach, are suitable for surgery on the hand and those blocks above the clavicle are useful for surgery on the shoulder and upper arm ( Plate 14-8 ). Depending on the approach to the plexus, it is also possible to provide total analgesia to the hand with blocks above the clavicle.

 
 

PLATE 14-8  Dermatomal distribution of brachial plexus.

 

 

Anatomy

The brachial plexus contains the anterior branches of spinal roots C5 through T1 ( Plate 14-9 ). In the neck, these branches run between the anterior and middle scalene muscles and are enclosed in a fascial sheath. They then form three trunks (superior, middle, inferior) that exit the interscalene groove and run behind the subclavian artery. As they exit the interscalene groove, these cords form an anterior and aposterior division. The divisions then unite to form lateral, posterior, and medial cords, depending on their relation to the axillary artery. There is a natural separation between the supraclavicular and infraclavicular plexus at the coracoid process that ultimately affects spread of local anesthetic ( Vester-Andersen et al., 1986 ). At the level of the axilla exist the peripheral nerves that innervate the arm. The radial nerve supplies the dorsal aspect of the upper extremity below the shoulder including the thumb and dorsal aspects of the index, middle, and fourth fingers. The musculocutaneous nerve provides innervation to the biceps of the upper arm and cutaneous innervation to the lateral forearm. The median nerve innervates the majority of the forearm, as well as the ventral aspects of the second, third, and lateral portion of the fourth fingers, and the medial portion of the thumb. The ulnar nerve is more limited to the hand and innervates the lateral aspect of the fourth finger and all of the fifth finger.

 
 

PLATE 14-9  Brachial plexus anatomy.

 

 

Axillary Block

Axillary block is the most common approach to the brachial plexus in children and is suitable for procedures on the hand such as syndactyly repair and finger reimplantation ( Plate 14-10 ). Advantages of performing an axillary block include the simplicity of the anatomy, ease of placement, and low risk of complications ( Tobias 2001) . Disadvantages include the need for a patient to be able to abduct the arm for access to the axilla and the inability to block the musculocutaneous nerve 40% to 50% of the time because it branches higher in the axilla than the ulnar, median, and radial nerves. Because the musculocutaneous nerve innervates the lateral side of the forearm, it may need to be blocked separately for surgical procedures that involve that nerve's distribution. Many approaches for an axillary block have been described and used in children. In a study to compare a single-injection versus a multiple-injection technique in children, unlike in adults, there was no difference in block quality found between the two techniques ( Carre et al., 2000 ). This study also confirmed that using either technique, separate block of the musculocutaneous nerve is still required if necessary for the surgical site.

 
 

PLATE 14-10  Dermatomal distribution of axillary block.

 

 

In a study to assess the efficacy of the timing of an axillary block, 55 children received 2 mg/kg of 0.25% bupivacaine either before surgical incision or immediately after surgery but before emergence (Altintas et al., 2000 ). Thirty-two percent of children in the presurgical group required no additional analgesics within the first 24 hours compared with 83% in the postsurgical group that required no additional analgesics. Although cumulative pain scores were higher in the presurgical group, both groups had effective analgesia.

Technique

A one-injection technique for axillary nerve block is accomplished by first palpating the axillary artery ( Plate 14-11 ). The needle is then inserted immediately adjacent and superior to the artery high in the axilla, at a 30- to 45-degree angle aimed toward the midpoint of the clavicle ( Plate 14-12 ). One may feel a “pop” as the plexus sheath is entered. Using a nerve stimulator, and after evidence of muscle stimulation in the hand is observed, local anesthetic is injected. A longitudinal swelling immediately beneath the skin as the local anesthetic fills the sheath may appear. This may occur especially in infants and young children. This swelling disappears quickly as the anesthetic spreads proximally into the sheath, and this swelling should not be confused with a subcutaneous injection. Subcutaneous injection does not have a longitudinal distribution and does not disappear quickly.

 
 

PLATE 14-11  Anatomy for axillary block.

 

 

 
 

PLATE 14-12  Performance of the axillary block. AA, axillary artery; PM, pectoralis muscle.

 

 

After the local anesthetic has been delivered and the needle removed, the arm should be adducted, thus releasing the pressure of the head of the humerus from the fossa. This motion along with holding distal pressure at the site of injection promotes proximal spread of the local anesthetic into the sheath. With a single-injection technique, all of the local anesthetic is delivered in one location. With a multiple-injection technique, the nerves are individually anesthetized by locating at least two of them individually using the nerve stimulator. Either technique may miss the musculocutaneous nerve because it exits the sheath proximal to the other three distal nerves. For this reason, a separate block of the musculocutaneous nerve is generally required. The musculocutaneous nerve is blocked by directly inserting the needle into the belly of the coracobrachialis muscle while looking for stimulation of biceps. In addition, if a surgical tourniquet is to be used and the patient is not having a general anesthetic, then the intercostobrachial nerve should be blocked. This is accomplished by placing a subcutaneous ring of local anesthetic high around the inner aspect of the arm.

Complications

There should be few complications when performing an axillary block. There is the rare risk of hematoma and nerve compression, and for this reason a transarterial approach may not be recommended in children. If inadvertent axillary artery puncture occurs, firm pressure should be applied for at least 5 minutes to avoid formation of hematoma and subsequent vascular insufficiency ( Merril et al., 1981 ). Other complications may include relative distortion of anatomy after the first injection of local anesthetic in the axillary region or inadvertent overdosage of local anesthetic when multiple-injection techniques are used ( Dalens, 1995 ). However, these complications were not reported in the pediatric study by Carre and others (2000) .

Lateral Vertical Infraclavicular Block

A lateral vertical infraclavicular brachial plexus (LVIBP) block was introduced for pediatric use because the block can be performed without arm abduction. In addition, the block is more reliable in anesthetizing the musculocutaneous nerve, and the block provides better analgesia of upper arm compared with an axillary block ( Fleischmann et al., 2003 ) ( Plate 14-13 ). Although other infraclavicular approaches were considered too hazardous because of the risk of pneumothorax, the more lateral and vertical approach developed by Kapral and others (1999) provides a safe distance between puncture site and pleura. This technique has been used in adults and children and has been shown to provide a greater spectrum of block than the axillary approach ( Kapral et al., 1999 ; Fleischmann et al., 2003 ). The indications for a lateral infraclavicular block are the same as those for axillary block.

 
 

PLATE 14-13  Dermatomal distribution of lateral vertical infraclavicular brachial plexus block.

 

 

Technique

With the child in the supine position, the upper arm should remain next to the trunk and the elbow flexed 90 degrees so that the forearm is on the abdomen. One palpates the coracoid process and, using a nerve stimulator, inserts a 1-inch 24-gauge insulated needle 0.5 cm distal to the coracoid process in a perpendicular or vertical direction while continuously aspirating for blood and/or air (Plates 14-14 and 14-15 [18] [19]). Once appropriate stimulation has been determined and continuous aspiration for blood and/or air has been negative, local anesthetic solution is then injected. There is no need to block the musculocutaneous nerve separately when this approach is used.

 
 

PLATE 14-14  Anatomy for lateral vertical infraclavicular brachial plexus block.

 

 

 
 

PLATE 14-15  Performance of lateral vertical infraclavicular brachial plexus block. CP, coracoid process; C, clavicle.

 

 

Complications

Complications using this approach are rare. There may still be risk of inadvertent pleural or vascular puncture, but these risks should be less than with other approaches to the brachial plexus.

Interscalene Block

An interscalene block may be used for surgery of the shoulder and upper arm with success in children. An interscalene block also anesthetizes the musculocutaneous nerve reliably, but there is less reliability of blocking the ulnar nerve than with the other nerve blocks. This is because the ulnar nerve's origin is in the lower portion of the plexus. Interscalene blocks are used infrequently in children because of the perceived higher risk of complications and side effects.

Technique

With the patient supine and the head turned in the opposite direction, the posterior border to the sternocleidomastoid muscle may be palpated. Immediately inferior to this and at the level of the cricoid cartilage, the interscalene groove should be identified by rolling the fingers behind the sternocleidomastoid muscle. The needle is inserted at a 90-degree angle to the skin with a slight caudal angle to elicit distal contractions. If the phrenic nerve is stimulated, the diaphragm contracts, which indicates that the needle is too anterior. Once appropriate muscle stimu lation is observed at the proper voltage, local anesthetic is injected.

Complications

Complications of interscalene block include pneumothorax, epidural injection, or intrathecal injection. Vertebral artery puncture may also occur with the risk of local anesthetic delivery directly to the CNS, resulting in CNS toxicity. In addition, there is a high risk of phrenic nerve block with paralysis of the hemidiaphragm. Phrenic nerve block is not well tolerated, especially in infants or patients with underlying respiratory compromise ( Kempen et al., 2000 ). Unilateral vocal cord paralysis may also occur and result in airway compromise. Sympathetic blockade with Horner's syndrome is a common side effect of interscalene blocks.

Parascalene Block

The parascalene approach to the brachial plexus was developed by Dalens (1995) to provide effective analgesia to the shoulder and upper arm while minimizing the risks of vertebral artery puncture, dural puncture, and/or pneumothorax, that is, risks associated with an interscalene block. The parascalene block is similar to the interscalene approach, but by changing the insertion and direction of the needle, major structures in the neck are avoided ( Plate 14-16 ). This block has been found to be easy to perform, with a 97% success rate in children on the first or second attempt ( Dalens et al., 1987 ).

 
 

PLATE 14-16  Dermatomal distribution of parascalene block.

 

 

Technique

With the child supine and a roll under the shoulders, the arm should be adducted next to the trunk and the head turned to the opposite side. The primary landmarks are Chassaignac's tubercle (transverse process of C6) and the midpoint of the clavicle. Draw a line between these two structures and insert a needle at the junction of the upper two thirds and lower third of this line (Plates 14-17 and 14-18 [21] [22]). This insertion spot should be at the level of the cricoid process near the external jugular vein. The approximate depth to the parascalene brachial plexus from the skin is different for different ages of children (see Fig. 14-2 ). Using low voltage, and once appropriate stimulation has been achieved, the local anesthetic solution is then injected.

 
 

PLATE 14-17  Anatomy for parascalene block.

 

 

 
 

PLATE 14-18  Performance of parascalene block. TP, transverse process of C6; MC, midpoint of clavicle.

 

 

Complications

Complications using the parascalene approach are rare but may include venous puncture, Horner's syndrome, and hemidiaphragmatic paralysis secondary to phrenic nerve paralysis.

Dosing of Upper Extremity Blocks

Various local anesthetics either alone or in combination have been used for upper extremity blocks. For prolonged analgesia, bupivacaine, levobupivacaine, or ropivacaine should be used. Because the brachial plexus is not highly vascular, the uptake of local anesthetic is less than that of pleural or central blocks; however, the maximal allowable doses of local anesthetic must be determined and the block dosed accordingly. When concentrations were compared, bupivacaine 2 mg/kg versus 3 mg/kg delivered for axillary block in children resulted in plasma levels of 1.35 mcg/mL and 1.84 mcg/mL, respectively ( Campbell et al., 1986 ). These values are well below the toxic range. To compare 0.2% ropivacaine with 0.25% bupivacaine, Thornton and others (2003) administered 0.5 mL/kg to children for axillary block. There was no significant difference between the two groups in pain scores, time to first analgesic, or total analgesic in 24 hours. The median time to first dose of analgesic was 7.25 hours in the ropivacaine group and 9.3 hours in the bupivacaine group. In general, if using 0.25% to 0.5% bupivacaine or levobupivacaine or 0.2% to 0.5% ropivacaine, the lower concentrations should be used in children 5 years of age or less at a volume of 0.5 mL/kg. Epinephrine 5 mcg/mL should be added to the solution to assist in identifying intravascular injection and to decrease the absorption of the local anesthetic. Using these dosing guidelines, approximately 4 to 12 hours of analgesia should be achieved ( Table 14-5 ).


TABLE 14-5   -- Recommendations for dosing of peripheral nerve blocks

Regional Technique

Bolus Dose (mLμ/kg)[*]

Continuous Infusion (mLμ/kg per hr)

Axillary Parascalene

0.2 to 0.5 0.2 to 0.4

0.1 to 0.2 0.1 to 0.2

Femoral or lateral femoral cutaneous

0.3 to 1

0.15 to 0.3

Fascia iliaca

0.5 to 1

0.15 to 0.3

Lumbar plexus

0.5 to 1

0.15 to 0.3

Sciatic

0.3 to 1

0.15 to 0.3

Ilioinguinal/iliohypogastric

0.25

NA

Penile block

0.1

NA

Paravertebral

0.5

0.2 to 0.25

NA, not applicable.

Bupivacaine, levobupivacaine, or ropivacaine may be used. For bolus dosing, lower concentrations such as 0.2% to 0.25% should be used in infants and young children, whereas concentrations of 0.375% to 0.5% should be used in children >5 to 8 years of age. For continuous infusions, lower concentrations such as 0.1% to 0.2% of all agents are acceptable.

 

*

Epinephrine 1:200,000 should be added to singl-shot peripheral nerve blocks except for penile block.

 

▪ LOWER EXTREMITY NERVE BLOCKS

Although caudal block is the most commonly performed pediatric regional anesthetic technique, lower extremity nerve blocks often provide analgesia to the lower limbs with a more direct effect ( McNicol, 1986 ; Dalens, 1995 ; Ross et al., 2000 ; Tobias, 2003 ). Lower extremity blocks are performed by anesthetizing the lumbar and/or sacral plexus.

The lumbar plexus is located in the psoas compartment that lies in the paravertebral space ( Plate 14-19 ). The union of the anterior rami of lumbar nerves L1-4 constitutes the primary input of the lumbar plexus with a small portion of the twelfth thoracic nerve. As the plexus emerges from the paravertebral space, it divides into three nerves: the femoral, the lateral femoral cutaneous, and the obturator. Although the iliac vessels run anterior to the iliac fascia, these three nerves remain posterior to the fascia. The femoral nerve is a mixed nerve with motor innervation to the quadriceps muscles and sensory innervation to the anterior and medial thigh. A branch of the femoral nerve, the saphenous nerve, provides innervation below the knee to the medial aspect of the lower leg and foot near the saphenous vein. The lateral femoral cutaneous nerve is a sensory nerve with innervation to the lateral thigh, and the obturator nerve is primarily motor to the leg adductors with some sensory to the lower medial thigh and knee.

 
 

PLATE 14-19  Anatomy and distribution of lumbar plexus. LFC, lateral femoral cutaneous nerve.

 

 

The sacral plexus is derived from the anterior rami of L4, L5, and S1-3 and gives rise to the sciatic nerve and the posterior cutaneous nerve of the thigh ( Plate 14-20 ). The sciatic nerve is a mixed nerve that provides motor and sensory innervation to the posterior aspect of the thigh and the majority of the lower leg. As the sciatic nerve travels down the posterior thigh, it branches into the common peroneal and posterior tibial nerves.

 
 

PLATE 14-20  Anatomy and distribution of sacral plexus.

 

 

Specific blocks of the lower extremity are described.

Lateral Femoral Cutaneous Nerve Block

Although an isolated block of the lateral femoral cutaneous nerve (LFC) is rarely needed, it may be blocked to provide analgesia for muscle biopsy of the vastus lateralis muscle during malignant hyperthermia testing ( Wedel, 1989 ). An LFC block may also be used in combination with a femoral nerve block in high-risk children in place of a general anesthetic for complete analgesia for muscle biopsies of the thigh ( Rosen and Broadman, 1986 ; Maccani et al., 1995 ).

Anatomy

The LFC arises from second and third lumbar nerves and travels deep to the iliacus fascia toward the anterior superior iliac spine until it emerges under the fascia lata in the upper thigh. It is a pure sensory nerve that innervates the lateral thigh to the knee, including some terminal branches at the patellar plexus. ( Plate 14-21 .)

 
 

PLATE 14-21  Dermatomal distribution of lateral femoral cutaneous block.

 

 

Technique

No nerve stimulator is required to block the LFC as the LFC is purely a sensory nerve. In the infrainguinal approach, a blunt 22-gauge needle is inserted perpendicular to the skin aiming in the direction of the nerve inferolaterally 0.5 to 1 cm below the inguinal ligament and medial to the anterior superior iliac spine ( Plate 14-22 ). A pop is felt as the needle pierces the fascia lata. Local anesthetic is then injected in a fanlike manner ( McNicol, 1986 ).

 
 

PLATE 14-22  Performance of lateral femoral cutaneous block. ASIS, anterior superior iliac spine; IL, inguinal ligament.

 

 

Complications

There are no known serious complications from an isolated LFC except direct nerve trauma.

Femoral Nerve Block

A femoral nerve block may be used for any above-the-knee surgery of the lower extremity that requires analgesia of the majority of the thigh ( Plate 14-23 ). This includes analgesia for femur fracture (Ronchi et al., 1989 ). The block is simple to perform either with or without a nerve stimulator; however, a nerve stimulator should not be used in an awake child with a femur fracture due to the pain that may occur with muscle contraction from nerve stimulation.

 
 

PLATE 14-23  Dermatomal distribution of femoral nerve block, “3 in 1,” with percentages of complete block of individual nerves. LFC, lateral femoral cutaneous nerve.

 

 

Anatomy

The femoral nerve is derived from lumbar nerves 1 to 3 and enters the thigh within the femoral triangle below the inguinal ligament. The approximate depth to the femoral nerve from the skin should be reviewed (see Fig. 14-2 ). The nerve is immediately lateral to the femoral artery and is covered by the fascia lata and fascia iliaca ( Plate 14-24 ).

 
 

PLATE 14-24  Anatomy of femoral nerve block.

 

 

Technique

With the child supine and the feet rotated outward, the femoral artery is palpated immediately below the inguinal ligament. The needle is inserted with a slight cephalad angle to the skin at 0.5 to 1 cm below the inguinal ligament and 0.5 to 1 cm lateral to the artery ( Plate 14-25 ). As the needle pierces the fascia lata, a distinct pop is felt. If a nerve stimulator is used, the desired muscle response should be contraction of the mid quadriceps with a “patellar kick.” If there is muscle stimulation medial to the mid patella at the thigh adductors, the needle is slightly adjusted laterally. If there is lateral muscle stimulation, the needle is adjusted slightly medially. Because of the close proximity of the femoral vessels, continuous aspiration for blood should be performed in order to detect intravascular entry. Once the desired location of the needle is achieved, local anesthetic is then injected.

 
 

PLATE 14-25  Performance of femoral block. IL, inguinal ligament; FA, femoral artery; U, umbilicus. Needle insertion is 0.5 to 1 cm lateral to artery.

 

 

A “3-in-1” block is a modification of a femoral nerve block. This technique anesthetizes the LFC and obturator nerve, which lie more proximal in the sheath. The 3-in-1 technique is accomplished by performing a femoral nerve block and promoting proximal spread. The landmarks and needle insertion are exactly the same as for a simple femoral block with the exception that the volume of local anesthetic is increased and distal pressure is used to promote cephalad spread to the lumbar plexus by means of using the femoral sheath as a conduit. When compared with a fascia iliaca compartment block (see later), a 3-in-1 approach can result in a higher failure rate ( Dalens et al., 1989 ). In a study by Dalens and others, the 3-in-1 block was successful in anesthetizing the femoral nerve 100% of the time. However, completely blocking the LFC and obturator was successful in only 20% of the children. In this study, Dalens and others noted that the successful blocks of the LFC and obturator nerves in the 3-in-1 group were not due to proximal spread of the local anesthetic but instead may have been due to a fascia iliaca–like spread of the local anesthetic.

Complications

Complications from femoral or 3-in-1 blocks are uncommon but may include puncture of the femoral artery. In that event, pressure should be applied for at least 5 minutes to avoid the formation of a large hematoma.

Fascia Iliaca Compartment Block

The fascia iliaca block provides analgesia of the femoral, lateral femoral cutaneous, and obturator nerves ( Plate 14-26 ). Compared with the 20% effectiveness of the 3-in-1 block, a fascia iliaca block may be effective in more than 90% of children ( Dalens et al., 1989 ). Fascia iliaca blocks are useful for all above-the-knee lower extremity surgeries because of their ability to anesthetize this region in its entirety. In addition, the fascia iliaca block reliably anesthetizes the femoral branch of the genitofemoral nerve, the sensory nerve supply to Scarpa's triangle. Because of its ability to block the upper leg, the fascia iliaca compartment block can be used in combination with intravenous sedation or nitrous oxide for children who are undergoing muscle biopsy of the thigh.

 
 

PLATE 14-26  Dermatomal distribution of fascia iliaca block, with relative percentages of successful block of individual nerves by this approach. LFC, lateral femoral cutaneous nerve.

 

 

Anatomy

The three distal nerves of the lumbar plexus'the femoral, lateral femoral cutaneous, and obturator nerves'all emerge from the psoas muscle and run along the inner surface of the fascia iliaca ( Plate 14-27 ). A fascia iliaca compartment block delivers local anesthetic between the fascia iliaca and iliacus muscle, where it spreads to bathe the three nerves.

 
 

PLATE 14-27  Anatomy of fascia iliaca block. LFC, lateral femoral cutaneous nerve.

 

 

Technique

With the child in the supine position, the inguinal ligament is located by drawing a line from pubic tubercle to anterior superior iliac spine. Divide the inguinal ligament into thirds. At the junction of the lateral third and medial two thirds of the inguinal ligament, drop a line inferiorly 0.5 to 2 cm and perpendicular to the ligament. This is the point of needle insertion ( Plate 14-28 ). A blunt needle is used and is inserted perpendicular to the skin. There is no need for a nerve stimulator because the goal is to find the area behind the iliacus fascia for anesthetic injection, not to locate a specific nerve. Two pops are felt as the needle first pierces the fascia lata and then the fascia iliaca. If light pressure is placed upon the plunger of the syringe, a loss of resistance is felt as the fascia iliaca is pierced. With the needle in the correct position, local anesthetic solution is injected.

 
 

PLATE 14-28  Performance of fascia iliaca block. ASIS, anterior superior iliac spine; IL, inguinal ligament; FA, femoral artery. Needle insertion is 0.5 to 2 cm below inguinal ligament.

 

 

Complications

Complications during a fascia iliaca block might include isolated femoral block if the injection is too medial; otherwise, there are no known major complications from performing a fascia iliaca block.

Lumbar Plexus Block

Similar to the fascia iliaca compartment block, a lumbar plexus block provides analgesia to the three major nerves of the lumbar plexus ( Plate 14-29 ). This block is useful for any surgery that may occur on the upper leg due to its complete ability to anesthetize that region. This block also anesthetizes the distal branches of the lumbar plexus, including the iliohypogastric, ilioinguinal, and genitofemoral nerves that innervate the groin area, applicable to many pediatric surgical procedures.

 
 

PLATE 14-29  Dermatomal distribution of lumbar plexus block.

 

 

Anatomy

The lumbar plexus lies in the psoas compartment between the two masses of the psoas muscle that attach to the vertebrae and is surrounded by fascia that is derived from fascia iliaca ( Plate 14-30 ). The approximate depth from the skin to the lumbar plexus in the different ages is noted (see Fig. 14-2 ).

 
 

PLATE 14-30  Anatomy of lumbar plexus block. PSIS, posterior superior iliac spine.

 

 

Technique

In a study of 50 children aged 6 months to 16 years undergoing hip and upper lower extremity procedures, Dalens and others (1988) compared two techniques of lumbar plexus block. In group 1, a modification by Chayen of a psoas compartment block was used. In this technique a needle was inserted at the midpoint of a line connecting the spinous process of the fifth lumbar vertebra and the posterior superior iliac spine. There were difficulties with needle insertion in 7 of 25 children, and 23 of the 25 children had epidural spread of local anesthesia. In the second group, a modification of Winnie's approach was used. In this technique, a needle was inserted at the intersection of the line drawn to connect the iliac crests and a line drawn through the posterior superior iliac spine parallel to the spinous processes ( Plate 14-31 ). There were no problems with needle insertion, and all 25 patients exhibited a unilateral lumbar plexus block distribution. Sacral distribution occurred in 23 of the 25 children as these two plexuses are found in the same anatomical plane.

 
 

PLATE 14-31  Performance of lumbar plexus block. PSIS, posterior superior iliac spine; IC, iliac crest; SC, spinal column. Note that the needle is considerably lateral to spinal column.

 

 

Although both techniques provided effective analgesia to the lumbar plexus, the Chayen approach resulted in epidural spread rather than isolated lumbar plexus. Because of the greater ease of performance of the modified Winnie technique, this technique is further described for use in children.

Modified Winnie Approach to the Lumbar Plexus

With the child in the lateral position, block side up, the knees and thighs are flexed. Two lines are drawn (1) to connect the two iliac crests and (2) ipsilateral posterior superior iliac spine running cephalad and parallel to the spinous processes. The needle is inserted perpendicular to the skin at the intersection of the two lines (see Plate 14-31 ). The needle is advanced through the quadratus lumborum. If contact is made with a transverse process, the needle is then directed slightly more cephalad until a strong contraction of the mid (not lateral or medial) quadriceps with a “patellar kick” is apparent. If hamstring contractions are observed, the needle is then directed slightly more laterally. If there is isolated hip movement, the psoas has been directly stimulated. If the quadriceps and hamstrings are contracting simultaneously, the needle should be directed more cephalad to stimulate the lumbar rather than sacral plexus.

Complications

Although complications are rare, they may be serious if the needle is advanced too deeply into the retroperitoneum. Retroperitoneal hematoma is a significant risk, and continuous aspiration for blood should be done during performance of the block. The highest incidence of major bleeding after peripheral regional anesthetic techniques has been found to occur after a psoas compartment block (Horlocker et al., 2003 ).

Sciatic Nerve Block

A sciatic nerve block is indicated for surgical procedures that involve the lower extremity below the knee. When used in combination with blocks of the lumbar plexus, the lower extremity may be blocked in its entirety.

Anatomy

The sciatic nerve is derived from the anterior rami of L4-S3 and is the largest nerve in the body (see Plate 14-20 ). It emerges through the greater sciatic foramen to run between the greater trochanter of the femur and the ischial tuberosity before taking its position in the thigh posterior to the quadriceps femoris. If the sciatic nerve is blocked in its proximal position, this also anesthetizes the posterior femoral cutaneous nerve (a branch of ventral rami of S1-3). This nerve innervates the posterior thigh above the knee and the hamstring muscles. The sciatic nerve primarily consists of two nerves'the tibial and common peroneal nerves'which travel in a common sheath in the posterior upper portion of the leg. These nerves divide near the popliteal fossa and innervate the leg below the knee.

Approaches to the Sciatic Nerve

Several approaches to the sciatic nerve have been described in children. The posterior, anterior, and lateral approaches have been compared with respect to ease of performance, efficacy of block, and rate of complications ( Dalens et al., 1990 ). The overall success rate of all three approaches exceeded 90%. However, there were fewer difficulties reported with the posterior approach. The posterior approach resulted in an 88% success rate on first attempt compared with 78% for lateral approach and only a 62% success rate on first attempt for anterior approach. In addition, vascular punctures occurred only in children who underwent an anterior approach. Because of the higher success rate of the posterior approach and the completeness of analgesia of sciatic and posterior branches ( Plate 14-32 ), the posterior approach is described here. However, the reader is prompted to review the lateral approach especially for use in children who are unable to be positioned for the other approaches to the sciatic nerve (Dalens, 1995 ).

 
 

PLATE 14-32  Dermatomal distribution of posterior sciatic block.

 

 

To block the sciatic nerve using the posterior approach, a modification of Labat's technique was developed by Dalens and others (1990) . The child is placed in the lateral position with the side to be blocked uppermost and the upper leg flexed at both the hip and knee. Using a nerve stimulator and insulated needle, the point of needle insertion is at the midpoint of the line that extends from the tip of the coccyx to the greater trochanter of the femur. The needle should be perpendicular to the skin with slight angulation toward the lateral ischial tuberosity (Plates 14-33 and 14-34 [37] [38]). The approximate depth to the sciatic nerve using the posterior approach changes with age (see Fig. 14-2 ). Using a nerve stimulator, the motor response is a movement in the patient's foot. Plantar flexion indicates stimulation of the tibial nerve. Dorsiflexion or eversion at the ankle indicates stimulation of the peroneal nerve. Once the appropriate muscle is elicited, local anesthetic is injected.

 
 

PLATE 14-33  Anatomy for posterior sciatic block.

 

 

 
 

PLATE 14-34  Performance of posterior sciatic block. TC, tip of coccyx; GT, greater trochanter.

 

 

Complications of the posterior approach to the sciatic nerve include vascular puncture of gluteal vessels. Constant aspiration for blood should be maintained during performance of the block to avoid this complication.

The Raj block was developed in 1975 and is similar to the posterior approach ( Raj et al., 1975 ). This approach anesthetizes the sciatic nerve slightly more distal than with the classic posterior approach (Plate 14-35 ). This block is performed in the supine child with the leg to be blocked lifted and flexed at the hip and knee ( Plate 14-36 ). The needle is inserted at the midpoint between the ischial tuberosity and greater trochanter in the sciatic groove ( Plate 14-37 ). Once appropriate muscle stimulation with less than 0.5 mA is seen at the foot, local anesthetic is injected. The advantage to this block is the reliability of the landmarks and simplicity of the block itself. By flexing the hip, the Raj technique brings the sciatic nerve closer to the skin. This improves the likelihood of a successful block, especially in obese children and adolescents.

 
 

PLATE 14-35  Dermatomal distribution of Raj approach to sciatic nerve block.

 

 

 
 

PLATE 14-36  Anatomy for Raj approach to sciatic nerve.

 

 

 
 

PLATE 14-37  Performance of Raj sciatic block. IT, ischial tuberosity; GT, greater trochanter.

 

 

popliteal fossa block may be used for procedures of the distal lower extremity and anesthetizes the sciatic nerve more distally in the leg and just proximal to the knee ( Kempthorne and Brown, 1984 ) (Plate 14-38 ). Near the popliteal fossa, the sciatic nerve divides into the common peroneal nerve and posterior tibial nerve. The common peroneal nerve runs anteriorly to wrap around the head of the fibula, while the posterior tibial nerve travels down the posterior lower leg ( Plate 14-39 ). In approximately 10% of the population, the branching of the sciatic nerve occurs more proximal to the popliteal fossa and high in the posterior thigh. For this reason, there may be a variable success rate in blocking the sciatic at this level, but both nerves are usually blocked by this approach due to a common epineural sheath that envelops the two nerves ( Vloka et al., 1997 ). Advantages to the popliteal approach include the relative superficial location of the sciatic nerve to the skin and the decreased risk of intraneural injection, as the sciatic nerve is not fixed against any bony structures in this location. To easily access the popliteal fossa, the patient may remain in the supine position and the leg to be blocked is lifted with the knee and thigh flexed. The child may also be turned to the lateral position and the leg to be blocked positioned uppermost. The superior triangle of the popliteal fossa has as its boundaries the semimembranosus and semitendinosus tendons medially, the biceps femoris tendon laterally, and the popliteal crease inferiorly. The needle is inserted 45 degrees to the skin aiming cephalad and just lateral to the midline of the popliteal triangle ( Plate 14-40 ).

 
 

PLATE 14-38  Dermatomal distribution of popliteal fossa block.

 

 

 
 

PLATE 14-39  Anatomy of popliteal fossa block.

 

 

 
 

PLATE 14-40  Performance of popliteal block. SM, semimembranosus/semitendinosus tendons; BF, biceps femoris; ML, midline.

 

 

The distance from the popliteal fold to needle insertion is estimated based on weight. If the weight is less than 10 kg, the distance is 1 cm; if the weight is 10 to 20 kg, the distance is 2 cm ( Konrad and Johr, 1998 ). Each 10 kg of body weight should move the needle cephalad in the triangle approximately 1 cm. Muscle stimulation of the foot in either the common peroneal or posterior tibial distribution is acceptable; however, posterior tibial stimulation may be a more reliable indicator of successful placement. Local anesthetic is injected once appropriate stimulation is apparent at less than 0.5 mA.

Konrad and Johr (1998) sought to determine a system for standardization of popliteal fossa block. They performed the block in 50 children between the ages of 2 months and 18 years. They determined that the minimal distance to the sciatic nerve in the popliteal fossa was 13 mm, and the depth did not vary significantly in patients weighing less than 35 kg but did increase for children weighing more than 35 kg. All of the blocks in the study were successful, and there were no complications. Vascular puncture was avoided due to the lateral position of the needle in relation to the popliteal vessels.

Tobias and Mencio (1999) provided analgesia in 20 children for foot and ankle surgery by performing popliteal fossa blocks at the completion of the surgical procedure. When using 0.75 mL/kg of 0.2% ropivacaine, the duration of analgesia was between 8 and 12 hours.

Ankle Block

An ankle block is a simple block that provides analgesia to the foot for procedures such as toe removal or simple reconstructive surgery.

Anatomy

There are five nerves that innervate the foot that must be blocked for analgesia of the foot in its entirety ( Plate 14-41 ). The saphenous nerve is found near the saphenous vein on the medial side of the dorsum of the foot and is somewhat superficial in its location. It innervates the skin surrounding the medial malleolus. Following the dorsum of the foot, and near the anterior tibial artery, runs the deep peroneal nerve, which is responsible for the innervation of the web space between the first and second toes. As the name implies, this nerve runs deep and is found near the tibia and between the extensor hallucis longus and anterior tibial artery. Immediately lateral to the deep peroneal nerve, but found superficially, is the superficial peroneal nerve. This nerve innervates the medial and lateral aspects of the dorsum of the foot. The plantar innervation of the foot is supplied by the tibial and sural nerves. The tibial nerve is found immediately posterior to the posterior tibial artery and medial malleolus, and thesural nerve is located posterior to the lateral malleolus.

 
 

PLATE 14-41  Anatomy for ankle block.

 

 

Technique

To perform an ankle block, each of the five nerves is blocked using a 25-gauge needle. With the child supine, the saphenous nerve is blocked by injecting 1 to 5 mL local anesthetic solution subcutaneously near the saphenous vein anterior to the medial malleolus. The deep peroneal nerve is blocked by inserting the needle lateral to the extensor hallucis longus tendon near the tibial artery and advancing the needle until it contacts the tibia. The needle should then be withdrawn slightly and 1 to 5 mL local anesthetic injected. The superficial peroneal nerve is blocked with a subcutaneous ring of local anesthetic across the lateral dorsum of the foot. The patient's foot then should be positioned so that the two posterior nerves may be blocked for complete analgesia of the foot. The tibial nerve is blocked midway between the medial malleolus and the calcaneus posterior to the tibial artery. The sural nerve is blocked midway between the lateral malleolus and the calcaneus. Each of the posterior nerves should receive 1 to 5 mL local anesthetic solution.

Dosing

To ensure complete analgesia to the foot with a duration of action greater than 4 hours, bupivacaine, ropivacaine, or levobupivacaine 0.5% should be used. The volumes delivered at each nerve depend on the age and size of the patient. The larger volumes are reserved for adolescents, but maximal dosing guidelines should not be exceeded. Epinephrine should not be added to the solution due to the risk of peripheral vasoconstriction.

Complications

Risks during performance of an ankle block should be rare. Because of the proximity of vessels, frequent aspiration for blood should be performed during injection. In addition, the use of epinephrine for an ankle block, particularly in an infant or a young child, should be avoided to reduce the possibility of ischemia secondary to loss of perfusion to the distal foot.

Dosing of Lower Extremity Blocks

The volumes of local anesthesia depend on the nerves to be blocked. For femoral nerve blocks, 0.3 to 0.75 mL/kg are administered, whereas for plexus blocks, volumes of 1 mL/kg are frequently needed (see Table 14-5 ). The duration of action of local anesthesia is dependent on the anesthetic concentration and age of the patient. When used in combination, local anesthetics are additive. It is important not to exceed maximal allowable dosing (see Table 14-2 ).

▪ CONTINUOUS PERIPHERAL NERVE CATHETERS

Indwelling catheters may be placed for peripheral nerve analgesia for those procedures that result in significant and prolonged postoperative pain or when vascular insufficiency is a risk. Although there is no extensive literature on placing continuous catheters for peripheral nerves or plexus anesthesia in children, there is equipment available that is suitable for these younger patients. Options of catheter placement include a modification of a Seldinger technique with placement of a wire over a needle and then a catheter over the wire such as a 3 or 4 Fr Cook central line catheter. There are also commercially available continuous catheter kits that allow for catheter insertion after the plexus has been localized with a nerve stimulator. Examples of these kits that allow for continuous catheter placement in children include a system using a short 18-gauge insulated Touhy needle through which a 20-gauge catheter may be threaded (B. Braun, Bethlehem, PA). There are also systems available that use a catheter-over-needle approach where a 20-gauge introducing catheter similar to an intravenous cannula fits over a 22-gauge insulated needle. Once the stimulation is achieved, the cannula is inserted into the sheath, the needle removed, and then a styletted 24-gauge catheter is threaded into the sheath for continuous infusion.

There is little information on the continuous infusions of local anesthetics in upper extremity catheters in children, but dosing of an indwelling catheter for brachial plexus anesthesia should adhere to maximal allowable dosing guidelines as set forth in Table 14-2 . Typical doses should start at 0.1 to 0.2 mL/kg per hr of either bupivacaine or levobupivacaine 0.125% to 0.25% or ropivacaine 0.1% to 0.2% (see Table 14-5 ). Increases in the infusion rate may be made as needed as long as the maximal infusion rate does not exceed 0.2 mg/kg per hr in infants less than 6 months or 0.4 mg/kg per hr in children older than 6 months. It would be unusual, however, for peripheral nerve catheter infusions to reach maximum limits. There has been a case report that describes the use of an axillary catheter for a child with epidermolysis bullosa simplex who required placement of an external fixator ( Diwan et al., 2001 ). The practitioners managed this catheter for 2 days with bolus injections of 0.125% bupivacaine 0.5 mL/kg every 8 hours with success.

Continuous catheters have been used for the lower extremity in children, most commonly for femur fractures of patients in the intensive care unit setting ( Johnson, 1994 ; Tobias, 1994 ). Johnson used an epidural catheter in the femoral sheath and delivered 0.125% bupivacaine at 0.3 mg/kg per hr. In these patients, plasma bupivacaine concentrations were well below toxic levels. Using a Seldinger technique and a 3 Fr 8-cm single-lumen central line catheter (Cook Critical Care, Bloomington, IN), Tobias administered continuous infusions of 0.15 mL/kg/hr of 0.2% bupivacaine to four children with femur fractures and closed head trauma. The catheters provided adequate analgesia in the intensive care unit setting for 4 to 6 days and there were no complications.

To provide more complete analgesia of the upper portion of the leg, catheters may also be placed in the lumbar plexus or fascia iliaca compartments. Sciard and others (2001) , using nerve stimulation, placed 20-gauge plexus catheters (Pajunk, Albany, NY) in the lumbar plexus of children and administered continuous infusions of 0.2% ropivacaine at 0.33 to 0.4 mg/kg per hr. Paut and others (2001)inserted 20-gauge catheters (Contiplex; B. Braun, Melsungen, Germany) through 55-mm cannulas into the fascia iliaca compartment and administered continuous infusions of 0.1% bupivacaine at a rate of 0.135 ± 0.03 mg/kg per hour. The plasma bupivacaine levels at 24 and 48 hours were not significantly different at 0.71 mcg/mL and 0.84 mcg/mL, respectively. The authors concluded that the bupivacaine plasma concentrations at the rates used in their study for a continuous fascia iliaca block are within safety margins. Ivani and others (2003) reported a case of a 21-day continuous infusion via a continuous sciatic catheter in a 3-year-old boy with subtotal foot amputation. Using an infusion of 0.4 mg/kg per hr of 0.2% ropivacaine with clonidine 0.12 mcg/kg per hr, there was total pain relief and no complications.

The use of disposable pumps for continuous delivery via a peripheral catheter of local anesthetic solutions has become popular in the adult population for outpatient orthopedic surgery. Dadure and others (2003) described the use of the disposable elastomeric pumps in 25 children aged 1 to 15 years receiving continuous infusion via catheters in the popliteal, femoral, or axillary sheaths. A continuous infusion of 0.2% ropivacaine was used at a rate of 0.1 mL/kg per hr. The median pain score for all children was 0 up to 48 hours, and there were no adverse events.

▪ ILIOINGUINAL/ILIOHYPOGASTRIC NERVE BLOCK

Ilioinguinal/iliohypogastric (ILIH) nerve block provides analgesia to the inguinal area and provides good perioperative pain relief for patients undergoing such procedures as inguinal hernia repair, orchiopexy, and hydrocelectomy ( Hannallah et al., 1987 ; Casey et al., 1990 ; Fisher et al., 1993 ). Early studies compared the use of an ILIH block for children aged 1 to 7 years for inguinal hernia repair. The block was performed after induction of anesthesia but before surgical incision. When compared with general anesthesia without the block, the group of patients who received an ILIH nerve block ambulated earlier and required less analgesia in the immediate postoperative period. The ILIH block group also required less analgesia for the following 48 hours after surgery ( Langer et al., 1987 ).Hannallah and others (1987) studied the efficacy of an ILIH block for orchiopexy surgery. They found no advantage to performing a caudal block over ILIH block for orchiopexy surgery as there were no significant differences between the groups in postoperative pain scores, postoperative vomiting, or time to meet discharge criteria. These results have been duplicated in other studies with no differences found between the ILIH groups and caudal groups with respect to postoperative pain scores, analgesic requirements, or times to micturition ( Fisher et al., 1993 ; Splinter et al., 1995 ). However, in a similarly designed study, Somri and others (2002) noted that caudal anesthesia was significantly more effective than ILIH in decreasing plasma catecholamine levels for postorchidopexy.

Casey and others (1990) investigated the effectiveness of an ILIH nerve block for inguinal hernia repair and compared this with simple installation of bupivacaine into the surgical wound. There was no difference between the ILIH nerve block group and the wound installation group with regard to pain scores, analgesic requirements, or recovery or discharge times. In a study to assess the effectiveness of 0.5% bupivacaine (2 mg/kg) in patients receiving either an ILIH nerve block, wound infiltration, or a combination of wound infiltration and nerve block, Anatol and others (1997) noted that all three patient groups had effective analgesia and that there were no differences in pain scores or analgesic requirements among the three groups.

Anatomy

The ilioinguinal and iliohypogastric nerves originate from the lumbar plexus and pierce the transversus abdominis muscle. The iliohypogastric nerve then takes its course between the transversus and internal oblique muscles and the ilioinguinal runs between internal oblique and external oblique. They pass superficial to transversus abdominus near the anterior superior iliac spine where they can be blocked before running their separate courses to innervate the inguinal region and upper scrotum ( Plate 14-42 ). The spermatic cord also receives innervation from the genital branch of the genitofemoral nerve that originates from lumbar plexus, usually at L1 or L2.

 
 

PLATE 14-42  Anatomy for ilioinguinal/iliohypogastric nerve block.

 

 

Technique

The ilioinguinal and iliohypogastric nerves may be blocked in their location near the anterior superior iliac spine. If performed before incision, a sterile preparation of the skin is done and a blunt 22- or 25-gauge needle is inserted 1 cm superior and 1 cm medial to the anterior superior iliac spine ( Plate 14-43 ). The needle is initially directed posterolaterally to contact the inner superficial lip of the ileum and then withdrawn while injecting local anesthetic during needle movement. Once the skin is reached, the needle is redirected toward the inguinal ligament (ensuring that the needle does not enter the ligament) and local anesthetic is injected after a “pop” is felt as the needle penetrates the oblique muscles. The needle should also be directed towards the ambilicus to deliver local anesthetic in the same plane. If the block is to be performed at the end of surgery, the surgeon may anesthetize the nerves under direct vision. The nerves lie at the lateral border of the incision. Lim and others (2002) determined that there is no added advantage to a single-shot versus double-shot ILIH nerve block.

 
 

PLATE 14-43  Performance of ilioinguinal/iliohypogastric nerve block. ASIS, anterior superior iliac spine; U, umbilicus. A field block is performed in the direction of the arrows and inferiorly toward the inguinal ligament.

 

 

Dosing

Bupivacaine 0.25% in a volume of 4 to 6 mL was used in a study by Hannallah and others (1987) that included males between the ages of 18 months and 12 years, while Casey and others (1990) used 0.25 mL/kg of bupivacaine 0.25% for children aged 2 to 10 years for hernia repair. Both of these studies cited good postoperative pain relief for these children. Although the maximum duration of analgesia is unknown from these studies, in the study by Casey and others (1990) effective analgesia was still present 180 minutes postoperatively. Levobupivacaine has been compared with placebo for patients aged 6 months to 12 years undergoing inguinal herniorrhaphy. In this study, Gunter and others (1999) noted that 0.25 mL/kg of 0.5% levobupivacaine was effective for ILIH block and was associated with a longer time to rescue analgesic administration and lower pain scores compared with children who had received no block. Dalens and others (2001) evaluated the effectiveness and pharmacokinetic profile of 0.5% ropivacaine 3 mg/kg for ILIH nerve block in children aged 1 to 12 years of age undergoing inguinal surgery. They noted that this dose provided satisfactory pain relief and peak ropivacaine plasma concentrations were 1.5 ± 0.93 mg/L. These levels were well below the toxic level.

Complications

Although complications from an ILIH nerve block are generally rare and minor, there have been case reports of colonic and small bowel perforation ( Johr and Sossai, 1999 ; Amory et al., 2003 ). Inadvertent femoral nerve blockade and motor block of the quadriceps may occur if the local anesthetic solution spreads below the inguinal ligament during the block placement. This can yield a block similar to the fascia iliaca block ( Roy-Shapiri et al., 1985 ).

▪ PENILE NERVE BLOCK

A penile nerve block includes techniques such as subpubic nerve block, dorsal nerve block, and subcutaneous ring block and may be used for procedures on the distal penis including circumcision and uncomplicated hypospadias repair. Investigations have shown that newborns have a decreased stress response when undergoing circumcision with the benefit of a penile block. A ring block may be more effective than either a dorsal nerve block or local anesthetic cream ( Maxwell et al., 1987 ; Stang et al., 1988 ; Lander et al., 1997 ; Butler-O'Hara et al., 1998 ; Hardwick-Smith et al., 1998 ). In addition, a subcutaneous ring block may result in a lower incidence of complications compared with a dorsal nerve block ( Broadman et al., 1987 ). The subpubic nerve block blocks the nerves before they enter the base of the penis. This block is less likely to disrupt the vascular or penile structures. Holder and others (1997) compared the subcutaneous ring block in boys undergoing circumcision with a group of boys who had a subpubic block. The group anesthetized with the subpubic block had significantly lower pain scores. In addition, three boys in the subcutaneous ring block group had tissue distortion from the block that affected surgical conditions.

When using a penile block for boys undergoing hypospadias repair, Chhibber and others (1997) have shown that placing the block before incision and repeating the block at the end of surgery provided better postoperative pain control than did placing the block only once (i.e., either before or after the surgical procedure).

Anatomy

The distal two thirds of the penis is supplied by the dorsal nerves, which are branches of the pudendal nerve ( Plate 14-44 ). The pudendal nerve arises from the sacral plexus. The dorsal nerves are located near the dorsal vessels and are surrounded by Buck's fascia.

 
 

PLATE 14-44  Anatomy for dorsal nerve penile block.

 

 

Technique

Subcutaneous Ring Block

A simple approach for blocking the dorsal nerves to the penis is the subcutaneous ring block. A skin wheel of local anesthetic (without epinephrine) is injected circumferentially around the base of the penis but superficial to Buck's fascia.

Dorsal Penile Block

A dorsal penile nerve block may be performed by injecting local anesthetic directly at the nerves as they run on each side of the penis at the level of the symphysis pubis ( Plate 14-45 ). Using a 25-gauge needle, Buck's fascia is pierced and local anesthetic (without epinephrine) is injected at the 10:30 and 1:30 o'clock positions at the base of the penis. Due to the close proximity of the dorsal vessels, frequent aspiration for blood during the local anesthetic injection is necessary.

 
 

PLATE 14-45  Performance of dorsal nerve block. PS, pubic symphysis. Points of needle insertion are at 10:30 and 1:30 o'clock at the base of the penis.

 

 

Subpubic Block

To perform a subpubic block, the penis is gently pulled downward and the needle is inserted perpendicular to the skin 0.5 to 1 cm lateral to the midline and caudal to the symphysis pubis. As the needle is advanced, it is directed slightly medially and caudally until Scarpa's fascia is crossed. Once that “give” is felt and assuming a negative aspiration for blood, local anesthetic is delivered.

Dosing

The most important point to remember about dosing a penile block is to NEVER USE EPINEPHRINE. The penis is an end organ and the use of epinephrine may lead to necrosis. For all techniques of providing penile nerve block, bupivacaine 0.25%, levobupivacaine 0.25%, or ropivacaine 0.2% may be used to provide analgesia with a duration of 4 to 6 hours. A subcutaneous ring block should be dosed so that there is subcutaneous evidence of local anesthetic injection around the base of the penis, but the dose must not exceed the maximal allowable recommendations for single injection (see Table 14-2 ). For a dorsal nerve block or subpubic block, approximately 0.1 mL/kg of local anesthetic is injected at each site. Sfez and others (1990) have shown that for a penile block, with 0.1 mL/kg at each injection site of either 0.25% bupivacaine or a 1:1 mixture of 0.25% bupivacaine with 1% lidocaine, serum local anesthetic concentrations were well below the toxic range.

Complications

As previously mentioned, epinephrine should never be used when performing a penile block as this may lead to significant vasoconstriction and ischemia ( Berens and Pontus, 1990 ). Hematoma formation may occur from puncture of the dorsal vessels during dorsal nerve block. This can result in necrosis of the tip of the penis ( Sara and Lowry, 1984 ). When performed properly, a subcutaneous ring block should be void of complications with the exception of tissue edema at the base of the penis. Tissue edema may affect the surgical conditions if the block is performed before the surgical procedure.

▪ INTERCOSTAL BLOCK

Intercostal nerve block provides limited analgesia after thoracotomy, upper abdominal procedures, rib fractures, and insertion of chest tubes. An intercostal block may be useful for these indications in the perioperative arena or in an emergency department or intensive care unit setting.

Anatomy

The intercostal nerves arise paravertebrally from the first 11 thoracic spinal nerves and are located in a groove that is found underneath the corresponding rib and shared with the intercostal vessels ( Plate 14-46 ). Gray and white rami communicantes branch off from the spinal nerves and adjoin the sympathetic ganglia before entering the intercostal space. The intercostal space contains the intercostal nerve, artery, and vein and is bordered by the intercostal muscles.

 
 

PLATE 14-46  Anatomy of intercostal nerves.

 

 

Technique

To adequately anesthetize the intercostal nerves near their origin, the block is performed lateral to the paraspinous muscles toward the posterior axillary line. The child should be in the lateral decubitus position with the arm elevated so that the posterior axillary line is easily accessed ( Plate 14-47 ). After sterile prep, insert a 25-gauge needle (length depends on age of child) through the skin, less than 1 cm below that of the lower border of the rib aiming cephalad to make contact with the rib itself. The needle is then withdrawn and advanced to “walk under” the inferior border of the rib until there is a feel of a slight loss of resistance as the muscles are penetrated ( Fig. 14-3 ). The nerve is located immediately inferior to the vessels but in close proximity that requires frequent aspiration during injection of local anesthetic. To improve success of analgesia, the intercostal nerves two segments above and two segments below should be blocked in addition to the segment corresponding to incision. Although a single injection of an increased volume of 10 mL per segment has been shown to spread to multiple intercostal spaces in adults, this is not a common practice in children ( Moorthy et al., 1992 ).

 
 

PLATE 14-47  Performance of intercostal block. PAL, posterior axillary line; S, scapula; R, inferior border of rib. Needle is directed to contact inferior border of each rib to be blocked and then “walked off” posteriorly.

 

 

 
 

FIGURE 14-3  Needle advancement for performance of an intercostal nerve block.

 

 

Dosing

A dose of 0.1 to 0.15 mL/kg per interspace (maximum of 3 mL per interspace) of local anesthetic agent is injected after negative aspiration. Bupivacaine 0.25%, levobupivacaine 0.25%, or ropivacaine 0.2% should provide 8 to 12 hours of analgesia.

Complications

Complications of intercostal block include pneumothorax, vascular puncture, and epidural or spinal local anesthetic spread. Spread of local anesthetic to the epidural or spinal spaces may occur if the injection travels through a dural sleeve covering the spinal root and may be more common in the posterior approach compared with more anterior approaches. In addition, there may be increased risk of local anesthetic toxicity from systemic uptake or inadvertent vascular puncture compared with other PNBs due to the close proximity of the intercostal vessels to the nerve.

▪ PARAVERTEBRAL NERVE BLOCK

Paravertebral nerve block provides analgesia at specific dermatomes, and it is generally used for children who undergo unilateral procedures. Its use has been established in children and the main advantages include (1) localized pain control and (2) avoidance of large volumes of local anesthetic ( Lonnqvist and Olsson, 1994 ; Lonnqvist et al., 1995 ; Richardson and Lonnqvist, 1998 ). Continuous paravertebral block has been shown to be effective for pain management for patients following thoracotomies, renal surgery, and cholecystectomy. Paravertebral blocks may be superior to epidural anesthesia in patients undergoing unilateral renal surgery, resulting in fewer morphine requirements in the postoperative period ( Eng and Sabanathan, 1992 ; Lonnqvist, 1992 ; Lonnqvist and Olsson, 1994 ). Bolus injection of local anesthetic in the paravertebral space has been used successfully in children for inguinal surgery ( Eck et al., 2002 ). Paravertebral blocks may be used in any patient where intercostal nerve blocks would be appropriate. Other advantages to performing paravertebral block include the spread of analgesia beyond one dermatome and the ease of catheter insertion for postoperative pain.

Anatomy

The paravertebral space is a wedge-shaped area along the vertebral column that contains the intercostal nerve, its dorsal ramus, the rami communicantes, and the sympathetic chain. The anterior boundary of the paravertebral space is the parietal pleura, and posterior to it is the superior costotransverse ligament and laterally, the posterior intercostal membrane ( Fig. 14-4 ). There are equations to determine the depth of the paravertebral space based on body weight ( Lonnqvist and Hesser, 1993 ). The distance (in mm) from the spinous process to the paravertebral space = 0.12 × body weight (kg) + 10.2. The depth in mm from the skin to the paravertebral space = 0.48 × body weight (kg) + 18.7.

 
 

FIGURE 14-4  Anatomy of paravertebral space.  (From Eason MJ, Wyatt R: Paravertebral thoracic block: A reappraisal. Anaesthesia 34:638–642, 1979.)

 

 

 

When injecting local anesthetic into the paravertebral space, the local anesthetic may spread several dermatomes due to the potential for free communication between adjacent spaces. The exception to this, however, may be at the T12 level where the psoas major muscle inserts into the vertebral column. In human cadavers, the psoas muscle may be a limiting factor in spread of local anesthesia from the thoracic region to segments below T12 ( Lonnqvist and Hildingsson, 1992 ). For this reason, in the study of children undergoing paravertebral blocks for inguinal surgery, Eck and others (2002)administered two injections, one above T12 and the other injection below T12.

Technique

After sterile preparation and drape, with the child in the lateral position and the block side up, the spinous process of the level to be blocked is identified. The distance from the midline to the point of lateral puncture is approximately the same distance as the tip from one spinous process to another ( Plate 14-48 ). If using a single-injection technique, a blunt spinal needle is used. If a catheter is to be threaded, a Touhy needle is necessary. Using a loss of resistance technique to saline, the needle is placed the proposed distance from the midline at the level of the spinous process. As the needle is inserted perpendicular to the skin, it makes contact with the corresponding transverse process. The needle is then “walked” over the cephalad margin of the transverse process. With gentle pressure on the syringe plunger, loss of resistance occurs once the needle crosses the costotransverse ligament and entry is gained into the paravertebral space. The loss of resistance is similar to, but less distinct than, that of going through the ligamentum flavum during epidural placement. Once the paravertebral space is identified, local anesthetic is injected into the space, and a catheter can be threaded if a continuous technique is desired. Threading a catheter through a Touhy needle into the paravertebral space may require some manipulation and cephalad angulation of the bevel of the needle. In a child the catheter should not be threaded more than 2 to 3 cm. This avoids lateral placement of the catheter into an intercostal space and single dermatome analgesia.

 
 

PLATE 14-48  Performance of paravertebral block. SP, spinous process. Lateral distance to point of needle insertion from midline should be equal to distance between spinous processes (arrows).

 

 

Dosing

For a unilateral paravertebral block, a bolus dose of 0.5 mL/kg of local anesthetic provides reliable analgesia of four dermato mes ( Lonnqvist and Hesser, 1993 ). Bupivacaine 0.25%, ropivacaine 0.2%, or levobupivacaine 0.25%, all with epinephrine 5 mcg/mL, may be used for single injection. If multiple levels are to be blocked, it is important not to exceed the maximal allowable dosing recommendations (see Table 14-2 ). For continuous infusions, bupivacaine, ropivacaine, or levobupivacaine can be infused at a rate of 0.25 mL/kg per hr for most children or 0.2 mL/kg per hr for infants ( Cheung et al., 1997; Karmaker et al., 1996 ; Lonnqvist, 1992 ). Lower concentrations of 0.1 to 0.125% should provide adequate analgesia. Older children or adolescents may require 0.2 to 0.25%.

Infants with a mean age of 5.3 weeks who received a bolus of bupivacaine 0.25% followed by infusion at 0.5 mg/kg per hr had bupivacaine serum levels that were suggestive of considerable bupivacaine accumulation. Some patients reached potentially toxic levels ( Karmaker et al., 1996 ). In a similar study in younger infants (median age of 1.5 weeks), Cheung and others (1997) used a lower concentration, lower infusion rate and added epinephrine 1:400,000 in an attempt to decrease the uptake of local anesthetic. With an initial 1.25 mg/kg bolus of 0.25% bupivacaine, and an infusion of 0.125% at 0.25 mg/kg per hr, the mean serum concentration was 1.60 mcg/mL. Three patients had plasma bupivacaine measurements of > 3 mcg/mL between 30 and 48 hours. None of these patients had any sequelae.

Complications

In one series of 367 patients for paravertebral block, the failure rate was 10.7% in adults and 6.2% in children ( Lonnqvist et al., 1995 ). Complications of the block included hypotension (4.6%), vascular puncture (3.8%), pleural puncture (1.1%), and pneumothorax (0.5%). Of these complications, all the patients who had hypotension were adults, none of the patients who had a vascular puncture demonstrated local anesthetic toxicity, and only one of the patients who had a pleural puncture had a pneumothorax. This study suggested that the failure rate was comparable to that of epidural blocks but with a much lower incidence of hypotension and little risk of dural puncture. The overall safety of paravertebral blocks has been established, although this technique should be limited to those who are experienced in its use.

▪ BLOCKS OF THE FACE AND SCALP

Infraorbital Nerve Block

The infraorbital nerve consists of four branches. These branches innervate the upper lip and mucosa along the upper lip, the vermilion, the lateral inferior portion of the nose, and the lower lid of the eye. Blocking the infraorbital nerve provides effective analgesia for cleft lip repair ( Bosenberg and Kimble, 1995 ; Prabhu et al., 1999 ). This block is also useful for nasal procedures such as endoscopic sinus surgery, nasal septal reconstruction, and rhinoplasty.

Anatomy

The infraorbital nerve is a purely sensory nerve derived from the second maxillary division of the trigeminal nerve. The infraorbital nerve is a terminal branch that exits the skull through the foramen rotundum to enter the pterygopalatine fossa. Here it emerges from the infraorbital foramen to divide into its four branches'the superior labial, internal nasal, external nasal, and inferior palpebral nerves.

Technique

The intraoral approach to block the infraorbital nerve is achieved by advancing a 27-gauge needle along the inner surface of the lip and cephalad to the infraorbital foramen parallel to the maxillary premolar. To perform this block, first palpate the infraorbital foramen and pull the upper lip superiorly to allow room for the needle and syringe ( Plate 14-49 ). Keep a finger on the infraorbital foramen during needle advancement to provide accurate measurement to the desired space.

 
 

PLATE 14-49  Anatomy for infraorbital nerve block.

 

 

Dosing

A total volume of 0.5 to 1 mL of bupivacaine 0.25%, levobupivacaine 0.25%, or ropivacaine 0.2% with 1:200,000 epinephrine added is injected after negative aspiration for blood.

Complications

The most common side effect from performance of an infraorbital nerve block is swelling around the eyelid. To avoid this, pressure should be applied at the site of injection for 5 minutes. Other complications are rare.

Great Auricular Nerve Block

The mastoid and external ear are innervated by the great auricular nerve. Analgesia for otoplasty and tympanomastoidectomy is provided by blocking this nerve and leads to reduction in the perioperative use of opioids for these procedures ( Cregg et al., 1996 ; Suresh and Wheeler, 2002 ).

Anatomy

The great auricular nerve is a sensory nerve branch of the super ficial cervical plexus (C3). Its course at the level of the cricoid cartilage follows the posterior border of the belly of the clavicular head of the sternocleidomastoid muscle.

Technique

The great auricular nerve is blocked at the level of the cricoid cartilage (C6). The clavicular head of the sternocleidomastoid muscle is identified and local anesthetic is injected superficially along the belly of the muscle approximately 5 to 6 cm below the ear ( Plate 14-50 ).

 
 

PLATE 14-50  Anatomy for great auricular nerve block.

 

 

Complications

Complications from a great auricular nerve block may be significant and include intravascular injection due to the close proximity of the carotid artery and jugular veins. In addition, deep placement of the needle can result in phrenic nerve block, cervical plexus block, and Horner's syndrome.

Supraorbital and Supratrochlear Nerve Blocks

Anesthetizing the supraorbital and supratrochlear nerves can provide pain relief for procedures of the anterior scalp and forehead, including excision of skin lesions, neurosurgical procedures with incisions of the scalp or forehead, and laser therapy for hemangiomas ( Suresh and Wheeler, 2002 ).

Anatomy

The supraorbital and supratrochlear nerves are terminal branches of the ophthalmic division of the trigeminal nerve (V1). These nerves supply the forehead and the scalp anterior to the coronal suture. They are found immediately above the eyelid area, where the supraorbital nerve exits through the supraorbital foramen and the supratrochlear nerve exits the orbit between the trochlea and the supraorbital foramen ( Plate 14-51 ).

 
 

PLATE 14-51  Anatomy for supraorbital and supratrochlear nerve blocks.

 

 

Technique

These nerves are blocked using a 27-gauge needle. After identifying the supraorbital notch, the needle is inserted perpendicular to the skin at the notch until it contacts bone; it is then withdrawn slightly and local anesthetic is injected after negative aspiration. The supratrochlear nerve is blocked by withdrawing the needle back to the skin and aiming slightly medially.

Complications

Periorbital edema and ecchymosis are common side effects when performing blocks around the eye. To avoid this side effect, pressure can be applied to the supraorbital area for 5 minutes after the block has been placed.

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Motoyama & Davis: Smith's Anesthesia for Infants and Children, 7th ed.

Copyright © 2005 Mosby, An Imprint of Elsevier

▪ INTRAVENOUS REGIONAL ANESTHESIA

Intravenous regional anesthesia (IVRA), or Bier block, describes a technique whereby an extremity is anesthetized by injecting local anesthetic intravenously and containing it within the extremity by using a tourniquet. This technique is useful only for intraoperative analgesia because the effect of the local anesthetic dissipates with release of the tourniquet. Intravenous regional anesthesia has been used in children for forearm fracture reduction and is considered safe and effective for most procedures of distal extremities that require pain relief for a short period of time ( Davidson et al., 2002 ). IVRA should not be used for procedures that have a potential of lasting greater than 90 minutes.

Technique

A separate intravenous catheter is placed in the limb that is to be blocked and a double tourniquet is applied to this extremity. The limb should then be elevated and exsanguinated by wrapping the extremity with an elastic bandage beginning with the digits and proceeding toward the tourniquets ( Plate 14-52 ). If the limb is fractured, exsanguination with the bandage should be deleted in an awake child to avoid excessive pain. The proximal tourniquet is then inflated to greater than 50 mm Hg above the baseline systolic blood pressure ( Fitzgerald, 1976 ). If the operation is occurring on the lower extremity, inflation pressures should be closer to 100 mm Hg above systolic blood pressure. After proximal tourniquet inflation, local anesthetic is slowly injected into the venous cannula in the operative limb. Onset of block should occur within 5 minutes of injection. After testing for successful block, the procedure may begin. Once it is evident during the procedure that tourniquet pain is being experienced, the distal tourniquet is inflated. The proximal tourniquet may then be released. Tourniquet pain is typically not an immediate issue upon inflation of the distal tourniquet because that area remains anesthetized. Most children require sedation in addition to the IVRA.

 
 

PLATE 14-52  Intravenous regional anesthetic. IV, intravenous catheter; CD, compression dressing; DT, distal tourniquet; PT, proximal tourniquet.

 

 

At the end of the procedure, the distal tourniquet may be released for 15 seconds and then reinflated. The tourniquet may be released and reinflated two additional times. This allows some of the local anesthetic into the systemic circulation at short intervals to avoid local anesthetic toxicity from a large amount of local anesthetic being released all at once. There should remain at least one cuff inflated for at least 20 minutes after injection of the local anesthetic, regardless of the length of the procedure.

Dosing

Either lidocaine or prilocaine may be used for intravenous regional anesthesia. Bupivacaine is contraindicated due to its ability to produce cardiotoxicity if it reaches the systemic circulation. When dosing lidocaine 0.5% or prilocaine 0.5%, use 0.6 mL/kg for the upper extremity and 1 mL/kg for the lower extremity.

In a study of 249 children over 3 years of age, either lidocaine 0.5% or prilocaine 0.5% was used for reduction of forearm fracture ( Davidson et al., 2002 ). The dose used in this study was 0.6 mL/kg (or 3 mg/kg of local anesthetic). The group that had received the lidocaine had better analgesia than the prilocaine group with fewer cases of what was considered to be unacceptable pain during reduction of the fracture. There were no adverse events.

To improve block conditions, fentanyl 1 mcg/kg or pancuronium 0.01 mg/kg may be added to the local anesthetic solution. Although these additives are used in adults, they have not been proved to be beneficial in children.

Complications

Prilocaine can produce methemoglobinemia if injected systemically. Neurotoxicity and seizures may occur from lidocaine if the tourniquets fail or are released prematurely. For this reason, IVRA is not indicated for children with underlying seizure disorders. Children with sickle cell disease or vascular insufficiency should not receive IVRA because of the risk of prolonged tourniquet time.

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Motoyama & Davis: Smith's Anesthesia for Infants and Children, 7th ed.

Copyright © 2005 Mosby, An Imprint of Elsevier

▪ TOPICAL ANESTHESIA

Topical anesthesia may be applied to a child either by using a cream or local infiltration to anesthetize the skin or by using topical application of local anesthetics directly to mucous membranes.

Topical local anesthetic cream was developed in the 1990s and has found popularity in the pediatric population due to its ability to anesthetize the skin before minor procedures. EMLA (Eutectic Mixture of Local Anesthetic) cream, a mixture of prilocaine and lidocaine, was the first commercially available agent that would anesthetize intact skin to a depth of 5 mm ( Ehrenström et al., 1983) . This mixture of prilocaine and lidocaine results in an oil-in-water emulsion that has a total local anesthetic concentration of 5%. EMLA cream has been found to be effective for superficial procedures such as venipuncture, laser treatment of port wine stains, and neonatal circumcision ( Mannuksela and Korpela, 1986 ; Ashinoff and Geronemus, 1990 ; Taddio et al., 1997 ). EMLA cream has been found to reduce the neonatal physiologic response to circumcision compared with placebo, but it is not considered as effective as dorsal nerve block or penile ring block ( Lander et al., 1997 ; Taddio et al., 1997 ; Howard et al., 1999 ).

EMLA cream is applied to intact skin at least 1 hour before the time of the procedure and covered with an occlusive dressing ( Morgan-Hughes and Kirton, 2001 ). Heating the EMLA cream with an external heat pack after application has been shown to reduce the time to efficacy to 20 minutes, although a 60-minute waiting period is superior ( Liu et al., 2003 ). EMLA cream should not be applied to traumatized or inflamed skin or on mucous membranes because of its potential for rapid absorption and systemic toxicity.

ELA-Max has become commercially available for use as a topical anesthetic for minor procedures and has been marketed as having the advantage of requiring only 30 minutes to be effective. ELA-Max is a cream consisting of 4% liposomal lidocaine. In a study of 120 children to compare ELA-Max with EMLA during venipuncture, the local anesthetic creams were applied at either 30 or 60 minutes before the procedure ( Eichenfield et al., 2002 ). Both local anesthetic creams were effective, and the study demonstrated that a 30-minute application of ELA-Max without an occlusive dressing was as effective as a 60-minute application of EMLA with an occlusive dressing.

Local infiltration before minor procedures is effective as a method to provide pain relief during needle puncture or superficial incision. Although any local anesthetic can be used for injection, there is no benefit to using higher concentrations for most indications. Lidocaine 0.5% provides immediate analgesia to the site and is effective for 90 minutes. If a longer duration is desired for pain relief after the procedure, bupivacaine 0.25% may be used, which provides 2 to 3 hours of postprocedure analgesia. When using bupivacaine for local infiltration, one must be extremely careful to avoid injecting the local anesthetic into vascular structures. To decrease bleeding at the site during the procedure, epinephrine 2.5 to 5 mcg/mL is added to the local anesthetic solution. Plastic surgeons often increase the amount of epinephrine to 10 mcg/mL or 1:100,000 to keep the field clear of blood.

Maximal allowable dosing guidelines are the same for local infiltration as they are for other regional blocks. A total of 5 mg/kg of lidocaine, or 7 mg/kg lidocaine when epinephrine is added, can be used safely ( Berde, 1993 ). When using bupivacaine either with or without epinephrine, 3 mg/kg is the maximal allowable dose. A simple rule of thumb when using bupivacaine 0.25% (2.5 mg/mL) is to not exceed 1 mL/kg of local anesthetic solution; therefore, the child never receives more than 2.5 mg/kg.

To use local infiltration in a child who is awake, measures to decrease the pain on injection must be taken for greater success. The child should be secured to decrease movement upon injection and during the procedure. A small-gauge needle such as a 27 gauge should be used and the injection performed slowly to minimize the pain that occurs with dissection of the superficial layers of the skin during injection. To further minimize pain, sodium bicarbonate is added to the solution at 1 mL/10 mL of lidocaine to increase the pH of the solution to physiologic values ( Momsen et al., 2000 ). This buffered solution decreases the discomfort from the injection of the more acidic lidocaine without buffer ( Christoph et al., 1988 ; Orlinsky et al., 1992 ).

Topical anesthesia may be applied to the mucous membranes of the nose and nasopharynx to decrease the discomfort associated with bronchoscopies, nasotracheal intubation, nasogastric tubes, or nasal airways. Topical anesthesia to the mucous membranes may be delivered by several methods. Lidocaine is available as a 5% ointment or 2% jelly. For mucous membranes, the 2% jelly is easy to apply and can be used for a greater surface area due to its lower concentration. The jelly may be simply applied to the nares and the tube for passage into the nose, and pledgets with the lidocaine jelly applied to the tip can be gently placed posteriorly in the nasopharynx to anesthetize that region. Although there are methods of delivering lidocaine as a nebulizer or spray, it is difficult to control the amount delivered, and at concentrations of 4%, it is easy to overdose a small child with this method. Peak plasma concentrations that are above the toxic levels are reached within 1 minute following the application of the 4% lidocaine spray due to fast absorption ( Eyres et al., 1978 ). If this remains the preferred route for some practitioners, every attempt should be made to provide only the maximal allowable dose and to be alert for the potential of local anesthetic toxicity that can occur due to the high uptake from this vascular area.

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Motoyama & Davis: Smith's Anesthesia for Infants and Children, 7th ed.

Copyright © 2005 Mosby, An Imprint of Elsevier

▪ MISCELLANEOUS PEDIATRIC REGIONAL ANESTHETIC BLOCKS

In addition to the described regional anesthetic techniques, there are certainly many more that have not been included in their entirety because of either low use or high complications. Some of these blocks, however, do have specific applications and may have been reported for this reason. An example of this is the cervical plexus block. It is not commonly used in children, but Tobias described its use in two adolescents who had known difficult airways and were scheduled to undergo neck surgery (1999).

For tonsillectomy patients, local anesthetic has been used to provide posttonsillectomy pain relief in children. Local bupivacaine infiltration of 5 mL per tonsillar pillar of 0.25% bupivacaine has been shown to lower pain scores in children ( Jebeles et al., 1993 ). Smaller volumes, however, have not been shown to be as efficacious when 1.8 mL per tonsillar pillar has been used ( Schoem et al., 1993 ). A glossopharyngeal nerve block for posttonsillectomy pain was studied to determine its effectiveness and safety ( Bean-Lijewski, 1997 ). The block consists of an injection of bupivacaine 0.25% to 0.5% into each lateral pharyngeal space using a 22-gauge spinal needle. This trial was terminated after two of the four children who had received the block developed severe upper airway obstruction after tracheal extubation. The conclusion was that the volume and concentration of bupivacaine resulted in blockade of the recurrent laryngeal nerves and/or the hypoglossal nerves. This technique, therefore, is not recommended.

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Motoyama & Davis: Smith's Anesthesia for Infants and Children, 7th ed.

Copyright © 2005 Mosby, An Imprint of Elsevier

▪ SUMMARY

Regional anesthesia in children has progressed due to the development of improved local anesthetics, pediatric-sized equipment, and, most important, the knowledge that has been gained regarding patient safety and efficacy. As the field of regional anesthesia continues to develop, it may become the primary method of providing both intraoperative and postoperative analgesia, if strategies continue to diminish the risks and studies are carried out to promote the benefits ( Goldman, 1995 ; Dalens and Mazoit, 1998 ).

Experienced practitioners in pediatric regional techniques provide an important service to children. Additional research must be directed at outcome studies to determine the true risks and benefits of these techniques in large populations of children. With the appropriate training and the use of appropriate agents and equipment, the practice of pediatric regional anesthesia as a means of providing superior analgesia should continue to be an essential part of the overall care of children in the perioperative period.

Copyright © 2008 Elsevier Inc. All rights reserved. - www.mdconsult.com

Motoyama & Davis: Smith's Anesthesia for Infants and Children, 7th ed.

Copyright © 2005 Mosby, An Imprint of Elsevier

REFERENCES

Abdulatif and El-Sanabary, 2002. Abdulatif M, El-Sanabary M: Caudal neostigmine, bupivacaine, and their combination for postoperative pain management after hypospadias surgery in children.  Anesth Analg  2002; 95:1215.

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