Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

CHAPTER 21 – The Pediatric Patient

Doreen Soliman, MD,
Franklyn Cladis, MD,
Peter Davis, MD

  

 

Physiology

  

 

Cardiac Physiology

  

 

Respiratory Physiology

  

 

Temperature Regulation

  

 

Renal Physiology

  

 

Pain and Perioperative Stress Response

  

 

Nervous System

  

 

Meningomyelocele

  

 

Otolaryngology

  

 

Congenital Laryngeal Webs and Atresia

  

 

Choanal Atresia

  

 

Cystic Hygroma

  

 

Craniofacial Anomalies

  

 

Clefts

  

 

Synostosis

  

 

Hypoplasia

  

 

Surgical Correction of Craniofacial Anomalies

  

 

Mediastinal Masses

  

 

Congenital Malformations of the Lung

  

 

Bronchogenic and Pulmonary Cysts

  

 

Congenital Cystic Adenomatous Malformation

  

 

Pulmonary Sequestration

  

 

Congenital Lobar Emphysema

  

 

Congenital Diaphragmatic Hernia

  

 

Tracheoesophageal Fistula

  

 

Abdominal Wall Defects

  

 

Omphalocele and Gastroschisis

  

 

Prune Belly Syndrome

  

 

Bladder and Cloacal Exstrophy

For neonates to survive in the extrauterine environment, a series of adaptations must occur. These adaptations or physiologic transitions have profound implications. These adaptations are interdependent on each other and include (1) conversion of the cardiovascular circulation from a parallel circulation to one in series; (2) establishment of a functional residual capacity and maintenance of an air exchange; (3) regulation of fluid and electrolytes in the presence of an immature kidney and the absence of a placenta; and (4) temperature homeostasis in an organism easily overwhelmed by its environment. All of these physiologic or transitional tasks can be further compromised by the presence of surgical or medical diseases. The transition from neonate to infant is characterized by maturation of all of its organ systems and occurs over weeks to months. However, the relative immaturity of these organ systems in infants, compared with adults, creates challenges for the anesthesiologist. To understand how best to approach uncommon diseases of the infant, a basic understanding of normal physiology is required.

PHYSIOLOGY

Cardiac Physiology

Transitional Circulation/Pulmonary Vascular Resistance

The transition from fetal to neonatal circulation is characterized by a change from parallel circulation (cardiac output contributes to both pulmonary and systemic perfusion, simultaneously allowing mixing of oxygenated and deoxygenated blood) to one that occurs in series (cardiac output contributes to either pulmonary or systemic perfusion with minimal admixture). High pulmonary vascular resistance (PVR) and relatively low systemic vascular resistance (SVR) also characterize fetal circulation. In utero, oxygenated blood from the placenta is transported to the fetus via the umbilical vein ( Fig. 21-1 ). Blood from the gastrointestinal tract combines with the umbilical vein to become the ductus venosus, which drains into the inferior vena cava (IVC). Blood from the IVC enters the right atrium and preferentially crosses the foramen ovale to the left atrium and left ventricle, thereby providing slightly more oxygenated blood for cerebral circulation. The superior vena cava (SVC) drains into the right atrium and is pumped primarily to the systemic circulation via the ductus arteriosus. Less than 10 percent of combined ventricular output contributes to pulmonary flow.[1] A series of events occur at birth that change fetal (parallel) circulation into neonatal circulation (series).

 
 

FIGURE 21-1  Course of the fetal circulation in late gestation. Note the selective blood flow patterns across the foramen ovale and the ductus arteriosus.  (From Greeley WJ, Steven JM, Nicolson SC: Anesthesia for pediatric cardiac surgery. In Miller RD [ed]: Miller's Anesthesia, 6th ed. Philadelphia, Churchill Livingstone, 2005, p 2007, with permission.)

 

 

 

During delivery PVR decreases and SVR increases, allowing for a significant increase in pulmonary blood flow. The increase in SVR occurs secondary to separation from the placenta. The decrease in PVR occurs for several reasons. With the onset of lung ventilation, there is a decrease in the mechanical compression of the alveoli and an increase in Po2. [2] [3] At birth, the mechanical distention of the alveoli coupled with the increased oxygen tension results in a precipitous decrease in PVR. The changes in PVR are mediated by biochemical factors, including nitric oxide and prostaglandin. In the newborn period, the pulmonary vessels exhibit a highly reactive tone. Maintenance of an elevated PVR is lethal to the neonate. Pulmonary vasoconstriction with right-to-left shunting in response to hypoxia, hypercarbia, sepsis, and acidosis can cause severe hypoxemia and death.

With a decrease in PVR, pulmonary blood flow and venous return to the left atrium increase. The increase in left atrial pressure and flow closes the foramen ovale. Over the next few months of life, PVR decreases even further. Hypoxemia and acidosis are two important factors that affect PVR. An increase in PVR can lead to right-to-left shunting across the foramen ovale and ductus arteriosus. This persistence of an elevated PVR can lead to further hypoxemia and tissue acidosis. Thus, hypoxemia and acidosis can lead to a vicious cycle of increased PVR, increased right-to-left shunting, increased hypoxemia, increased tissue acidosis, and further increase in PVR and shunting.

The neonatal myocardium is immature and continues its development after birth. Many functional differences between the neonatal and adult myocardium are directly related to the immaturity of the neonatal tissue components.[4] At delivery and extending into the neonatal period, there are fewer contractile elements and there is less elastin in the newborn's myocardium, resulting in a decreased contractile capacity and decreased ventricular compliance, respectively. Fetal myocardium has limited ability to generate the equivalent contractile force as the adult myocardium throughout the entire range of the length-tension curve. The consequence is a reduced capacity to adapt to increases in preload or afterload. [5] [6] This does not mean the stroke volume is fixed. There is echocardiographic evidence that the immature heart, while limited, is able to increase stroke volume.[7] Because of this immaturity, the neonatal heart has a diminished capacity to handle significant volume loads and more easily develops ventricular overload and failure.

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Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

Respiratory Physiology

A significant difference between neonatal and adult respiration is oxygen consumption. Neonatal oxygen consumption is two to three times greater than that of the adult (5 to 8 mL/kg/min vs. 2 to 3 mL/kg/min).[8] This contributes to the rapid oxygen desaturation observed in infants during periods of apnea or hypoventilation.

The neonatal/infant lung is less compliant than the adult lung. The immature lung in the pediatric patient is characterized by small and poorly developed alveoli with thickened walls and decreased elastin. The amount of elastinin the lung continues to increase until late adolescence.[9] Before and after late adolescence, pulmonary elastin is decreased. Elastin provides elasticity to the lung, without which there is airway collapse. Because infants and older adults have less elastin, they are prone to alveolar collapse. [9] [10] The closing capacity, the lung volume at which there is airway collapse, occurs at a larger lung volume in the very young and the very old ( Fig. 21-2 ). In the infant, airway closure can occur before end exhalation, resulting in atelectasis and right-to-left transpulmonary shunting. In contrast to the pediatric lung, the pediatric chest wall is more compliant than the adult chest wall. The increased amount of cartilage in pediatric ribs accounts for this. This increased chest wall compliance may help contribute to airway collapse because negative intrathoracic pressure can result in chest wall collapse.

 
 

FIGURE 21-2  Closing capacity in relation to age. The difference between functional residual capacity (FRC) and closing capacity is charted against age. Note that closing capacity is greater than FRC in children younger than 5 years old and adults older than 45 years old. (From Mansell A, Bryan C, Levison H: Airway closure in children. J Appl Physiol 1972;33:771-774, with permission.)

 

 

 

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Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

Temperature Regulation

Neonates and infants are at increased risk of thermoregulatory instability because they are more prone to heat loss and they have a decreased ability to produce heat. They are at increased risk of heat loss because of their large surface area to volume ratio.[11] They also have decreased ability to restrict heat loss secondary to limited vasoconstriction compared with adults.[12] The primary method of heat production in the neonate and infant consists of nonshivering thermogenesis. This compensates poorly for heat loss. Nonshivering thermogenesis occurs primarily in brown fat, which may be decreased in premature neonates. This mechanism can also be inhibited by inhalational agents. [13] [14] Nonshivering thermogenesis is mediated by norepinephrine. Norepinephrine is a potent pulmonary vasoconstrictor. Consequently cold stresses can cause elevations to PVR and provide a mechanism for right-to-left shunting. Shivering thermogenesis assumes a less significant role in infants. Temperature stability can be ensured by using neonatal warming lights, forced warm air blankets, intravenous fluid warmers (if large amounts of fluids or blood products are given) increasing the ambient temperature of the operating room and keeping the infant covered.

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Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

Renal Physiology

In the first few days of life a major physiologic priority of the neonate is to lose weight as a result of a reduction in extracellular body water. This physiologic weight loss usually is a function of an isotonic contraction of body fluids. Perturbations of this process can affect infant morbidity and mortality.

The neonatal kidney develops its full complement of nephrons by 36 weeks' gestation. The glomerular filtration rate is lower in the neonate (approximately 25% of adult value) and achieves adult values within the first few years of life. Tubular function in the neonate is also limited; consequently, a glomerular to tubular imbalance is present in the first few years of life as well.

Neonates have limited capacity to concentrate their urine. When challenged, term infants can concentrate to 800 mOsm/kg of plasma water, whereas preterm infants can concentrate to 600 mOsm/kg of plasma water. Neonates have diminished end organ responsiveness to vasopressin, whereas fluid-challenged term infants and premature infants can dilute their urine to 50 and 70 mOsm/kg of plasma water, respectively. Thus, excessive fluid restriction and overhydration can result in dehydration and intravascular volume overload. Renal sodium losses are inversely related to gestational age and disease states (hypoxia, respiratory distress, acute tubular necrosis, and hyperbilirubinemia can exacerbate these losses).

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Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

Pain and Perioperative Stress Response

Pain and stress have been shown to induce significant physiologic and behavioral consequences. Newborns and infants are capable of mounting a hormonal response to the stress of their illness. [15] [16] A better understanding of the causes, mechanisms, and treatments of pain during development has provided clinicians with a wide array of techniques to safely manage procedural and postoperative pain. [17] [18] [19] The nervous system at birth displays hypersensitivity to sensory stimuli in comparison to that of the nervous system of the mature adult. In neonates, thresholds of response to mechanical and thermal stimulation are reduced and further sensitization can occur with sustained or repetitive stimulation, which is different from the mature nervous system.[20] Structural and functional changes in the peripheral and central nervous systems that take place in the postnatal period involve alterations in expression, distribution, and function of receptors, ion channels, and neurotransmittors.[21] These changes can profoundly affect the character of nociceptive responses at different stages of development. Perinatal brain plasticity is affected by this sensitization and increases the vulnerability of the neonatal brain to early adverse experiences. These adverse experiences lead to abnormal neurologic development and behavior. [22] [23]

A multimodal approach to pain management is necessary and may involve pharmacologic and nonpharmacologic methods.[24] The use of nonopioid analgesics (acetaminophen, nonsteroidal anti-inflammatory drugs), opioids, local anesthetics, and regional techniques provides a balanced analgesic approach to pain management.

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Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

NERVOUS SYSTEM

Meningomyelocele

Meningomyelocele (MMC) is a defect of neural tube development occurring around the fourth week of gestation. The incidence of MMC is 0.5 to 1.0 per 1,000 live births. The etiology is multifactorial but may occur secondary to folate deficiency, exposure to toxins (valproic acid, carbamazepine), and genetic disorders (trisomy 13 and 18). This is the most common neural tube defect and is characterized by lack of development of the layers that naturally cover and protect the spinal cord, resulting in protrusion of the meninges through the bony defect overlying the cord. The sac created by the protruding meninges may (MMC) or may not (meningocele) contain nerve tissue. The defect may occur anywhere along the spinal cord, but the lumbosacral region is the most common site. Defects at the thoracic and cervical region occur rarely. MMC results in neurologic injury below the level of the lesion. The neurologic injuries can include paraplegia, urinary and fecal incontinence, and sexual dysfunction; however, there is considerable clinical variation.

Associated Anomalies.

The most common associated neurologic anomaly is the Chiari 2 malformation, which is characterized by downward herniation of the cerebellar vermis and the fourth ventricle. Infants with Chiari 2 malformations can present with clinical evidence of brain stem compression, resulting in a weak cry, poor swallowing, poor feeding, aspiration, apnea, and opisthotonus ( Fig. 21-3 ). Older children may present with neurologic symptoms involving the upper extremity. Hydrocephalus can occur in as many as 85% of patients with lumbar MMC. The etiology of the hydrocephalus is not clear but may occur secondary to anatomic abnormalities associated with the Chiari malformation and/or abnormal cerebrospinal fluid (CSF) absorption.[25] Other associated anomalies include clubfeet, Klippel-Feil syndrome, hydronephrosis, exstrophy of the bladder, and congenital heart defects.

 
 

FIGURE 21-3  MR image of a patient with Chiari II malformation. Note the upward herniation of the cerebellum as indicated by the short arrow. The curved arrow indicates downward herniation of the brainstem through the foramen magnum. The thin long arrow marks the foramen magnum.

 

 

Pathophysiology

Most children with MMC survive into early adulthood.[26] Thirty percent of the deaths in the first two decades of life are secondary to respiratory complications. These complications are largely attributable to hydrocephalus and Chiari 2 malformation.[27] In the first few weeks of life, infants with MMC require immediate repair to prevent infection, further neurologic injury, and dehydration.

Anesthetic Considerations (Preoperative).

Infants with MMC present to the operating room for primary repair of their MMC. Later in life they present for ventriculoperitoneal shunts (VPS), VPS revisions, tethered cord repairs, and posterior spine fusions.

The anesthetic management of the infant with MMC begins with a complete preoperative assessment. Infants with Chiari 2 malformations may be at risk for apnea and aspiration. Preoperative echocardiography and renal ultrasound may be part of the evaluation to rule out congenital heart defects and hydronephrosis. Examination of the neck may reveal decreased range of motion secondary to Chiari 2 malformation and/or Klippel-Feil sequence. An assessment of the patient's volume status is important, given the risk of significant intraoperative third space losses from the open skin defect. Laboratory data can be tailored to the needs of the infant, but at least a blood glucose value should be checked. Bleeding can occur secondary to tissue dissection. A hemoglobin/hematocrit type and screen may be performed preoperatively ( Table 21-1 ).


TABLE 21-1   -- Anesthetic Considerations with Meningomyelocele and Occipital and Nasal Encephalocele

Pathology

Associated Anomalies

Anesthetic Issues

Meningocele

Chiari 2 malformation

Preoperative labs: blood glucose, hemoglobin, type and screen

 

Apnea

 

 

 

Preoperative labs: blood glucose, hemoglobin, type and screen, and renal ultrasound, echocardiogram

Meningomyelocele

Hydrocephalus: VPS

Airway management: possible decreased neck extension from Chiari 2 and Klippel-Feil (rare), intubation may be lateral decubitus to protect neural elements

 

Congenital cardiac defects

 

 

Genitourinary

 

 

Klippel-Feil

Hypothermia risk: full access heating blanket, neonatal warming lights

 

 

Latex precautions

 

 

Postoperative apnea

 

 

Preoperative labs: blood glucose, hemoglobin, type and screen

Occipital encephalocele

As above

Airway management: head positioning for mask ventilation and intubation may be more difficult secondary to location of neural elements

 

 

Preoperative labs: blood glucose, hemoglobin, type and screen

Nasal encephalocele

As above

Airway management: may be difficult to mask ventilate secondary to nasal defect

 

 

Craniotomy: consider an arterial catheter.

 

 

Positioning: may be positioned head up or sitting; consider a central venous catheter.

 

 

Postoperative ventilation may be required secondary to airway edema or blood in the upper airway.

 

 

Induction.

Anesthesia can be induced with intravenous induction agents or a standard inhalational agent. Standard intravenous induction agents include atropine, sodium pentothal, or propofol and a neuromuscular blocking agent. Succinylcholine has been administered to patients with MMC without any reported increase in serum potassium levels.[28] Airway management may be more challenging in the infant with MMC because of associated neck pathology (Chiari malformation, Klippel-Feil), positioning, and increased association with short tracheas.[29] Positioning during airway management and laryngoscopy is critical to avoid pressure and subsequent injury to the neural placode. The infant can be induced and intubated on the side or supine, provided there is appropriate support to the back to protect the neural elements. Towels can be rolled and used to support the infant when supine. The neural cord defect can also be placed in a donut-shaped small gel head ring to allow the infant to be supine without causing pressure to be placed on the neural elements. The trachea may be short in infants with MMC.[29] Attention must be paid to identifying the carina and properly positioning the endotracheal tube to prevent endobronchial intubation.

Maintenance.

Anesthesia can be maintained with an inhalational agent and nitrous oxide. Remifentanil may be advantageous given its rapid clearance, short terminal half-life, and nonaccumulating properties.[30]Subsequent use of intraoperative neuromuscular blocking agents is not recommended because nerve stimulation by the neurosurgeons is sometimes performed to identify neural tissue. The open skin defect can occupy a large portion of surface area and can result in significant third space fluid losses. These infants are also at risk for hypothermia because of the relatively large area of exposed skin and may require resuscitation with room temperature fluids. Maintaining a warm room and using a full access forced warm air blanket can reduce this risk. Because the patient is positioned prone for the primary closure, the face, eyes, and extremities must be appropriately padded and protected.

Regional Anesthesia.

Spinal anesthesia has been reported for the primary repair of lumbosacral MMCs. Infants with thoracic lesions were excluded. The initial introduction of intrathecal local anesthetic was by the anesthesiologists. The dural puncture was performed at the most caudad region of the defect, with a hyperbaric mixture of tetracaine. The block was supplemented by the neurosurgeons, if needed, and a pacifier along with intravenous midazolam was provided for those infants who remained unsettled after supplementation. Fourteen infants were successfully anesthetized and surgically corrected. Half required supplementation of local anesthetic. Two of the 14 had postoperative apnea, and no new neurologic events were noted immediately after surgery.[31]

Latex Precautions.

Latex sensitization is increased in children with myelodysplasia. Pittman and colleagues studied the prevalence of latex specific IgE among children with MMC: 47% of the children with MMC had antibodies against latex, compared with 15% of the chronically ill control group, and 3.8% of the medical control group.[32] Using epicutaneous skin testing, Shah and colleagues demonstrated latex sensitization in 44% of children and adolescents with MMC: 21% of these children had a history of clinical latex allergy. Age and number of surgical procedures were significantly correlated with latex sensitization.[33] Patients with latex allergies often have additional allergies. Most commonly these are secondary to repeated antibiotic exposure, but reports of sensitization to opioids and neuromuscular blocking agents have been reported.[34]

Postoperative Considerations.

Infants with meningomyelocele may be at increased risk of postoperative apnea. Extubation after primary repair of the defect may take place in hemodynamically stable infants who are awake and can maintain their airway. Infants should recover in a monitored setting with respiratory and cardiac monitors.

Fetal Surgery.

Prenatal intervention had been proposed, initially in an attempt to improve neurologic and urologic function. Earlier animal studies suggested an improvement in postnatal function. However, in humans there was no significant improvement in lower leg function. It appears that the benefit derived from early fetal intervention may be a reduction in hindbrain herniation and shunt-dependent hydrocephalus.[35]

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Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

OTOLARYNGOLOGY

Congenital Laryngeal Webs and Atresia

Congenital laryngeal webs are uncommon and have an estimated incidence of 1 in 10,000 births. Most laryngeal webs are glottic with extension into the subglottic area. The laryngeal web is a result of a failure to recanalize the laryngeal inlet at about 10 weeks' gestation. The symptoms vary according to the location of the web and the degree of involvement ( Fig. 21-4 ; Table 21-2 ). Symptoms are related to vocal cord dysfunction and range from mild hoarseness to aphonia. Most webs involve the anterior glottis and are generally thin and associated with mild hoarseness and minimal airway obstruction. With laryngoscopy the vocal folds are visible. Subglottic webs are infrequent, and supraglottic webs are rare. Complete congenital laryngeal atresia is incompatible with life unless an emergency tracheotomy is carried out in the delivery room. Complete congenital atresia is associated with tracheal and esophageal anomalies ( Fig. 21-5 ).[36]

 
 

FIGURE 21-4  Medium congenital glottic web. This is a medium-sized, thicker congenital anterior glottic web.  (Courtesy of Charles Bluestone, MD.)

 




TABLE 21-2   -- Signs and Symptoms of Congenital Laryngeal Webs

  

 

Phonatory abnormalities: A high-pitched or absent cry occurs with glottic anomalies. A muffled cry is characteristic of supraglottic obstruction.

  

 

Stridor

  

 

Severe airway obstruction that is associated with increased work of breathing (retractions), tachypnea, apnea, and cyanosis

From Gerber ME, Holinger LD: Congenital laryngeal anomalies. In Bluestone CD, Stool SE, Alper CM, et al (eds): Pediatric Otolaryngology, 4th ed. Philadelphia, Elsevier, 2003, vol 2, pp 1460-1472.

 

 

 
 

FIGURE 21-5  Laryngeal atresia.  (Courtesy of Charles Bluestone, MD.)

 



Diagnosis/Differential Diagnosis

Signs and symptoms of infants with congenital laryngeal webs include disorders of phonation, stridor, and airway obstruction. Table 21-3 outlines the different pathologic processes that may mimic the symptoms of congenital laryngeal webs.


TABLE 21-3   -- Disorders that Mimic Laryngeal Webs

  

 

Laryngomalacia

  

 

Congenital subglottic stenosis

  

 

Laryngeal and laryngotracheoesophageal clefts

  

 

Vascular anomalies (hemangiomas)

  

 

Vocal cord paralysis

 

 

Treatment.

Thin anterior webs and webs in the glottic area may require incision and dilatation. If the web involves the subglottic larynx, the anterior cricoid plate is usually abnormal. In these instances treatment requires an external approach with division of the web and the cricoid plate and the use of cartilage grafting.[37]

Anesthetic Management ( Table 21-4 )

A systematic approach to evaluation of the airway is essential. Flexible fiberoptic nasopharyngolaryngoscopy and rigid laryngoscopy and bronchoscopy are needed to fully assess the airway. Because anesthetic agents can affect vocal cord motion, flexible fiberoptic nasopharyngolaryngoscopy is used to assess vocal cord mobility with the patient awake or lightly sedated.


TABLE 21-4   -- Anesthetic Management of Laryngeal Web

  

 

Experienced anesthesiologist and ear nose and throat surgeon

  

 

Operating room equipped with airway emergency equipment

  

 

Careful communication with the surgeon and anesthesiologist

  

 

Fasting protocols observed except for emergencies

  

 

Anticholinergics: glycopyrrolate, 5 to 10 ìg/kg, or atropine, 10 mcg/kg

  

 

Topical anesthesia with lidocaine 1%

  

 

Dexamethasone, 0.5 to 1 mg/kg

  

 

Postoperative care: humidified oxygen therapy

 

 

An experienced endoscopist and anesthesiologist should provide the care for these infants, in an operating room fully equipped for managing pediatric airway emergencies. Communication between the surgeon and the anesthesiologist is of paramount importance.[38] Intravenous access can be established after the induction of general anesthesia using inhalational agents. Sevoflurane or halothane can be used, although the former has been associated with fewer side effects.[39] Anticholinergic agents are recommended for rigid bronchoscopy to decrease secretions and minimize the risk of bradycardia. Topical anesthesia of the vocal cords and the trachea is used as an adjunct. Lidocaine 1% has a short duration of action (10 minutes).[40]

Total intravenous anesthesia, including remifentanil and propofol, can be used for maintenance of anesthesia.[41] The choice of spontaneous or controlled ventilation depends on the severity of airway obstruction.[42] Spontaneous ventilation is probably the ventilation mode of choice in patients with severe airway compromise. Intravenous dexamethasone, 0.5 to 1.0 mg/kg, should be administered to treat potential airway edema. In cases of severe stenosis, cricotracheal resection requires postoperative nasotracheal intubation and mechanical ventilation for 5 to 14 days. This postoperative care requires the use of sedation, neuromuscular blockade, and intensive care monitoring to avoid accidental endotracheal extubation. Prolonged use of neuromuscular blockade can result in residual muscle weakness, which may compromise or delay planned extubation.[43]

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Choanal Atresia

Choanal atreasia occurs in approximately 1 in 7,000 live births. Ninety percent of the atresias are bony, and 10% are membranous. Abnormal embryogenesis of neuroectodermal cell lines may explain choanal atresia. The primitive face develops from five facial prominences ( Fig. 21-6 ). The frontonasal prominence is responsible for nasal development from week 3 to 10 of gestation. Migrating neural crest cells form the nasal or olfactory placode, which are convex thickenings on the frontonasal prominence. The primitive nasal pit is formed from a central depression in these placodes. Mesenchymal proliferation around the nasal placode allows horseshoe-shaped medial and lateral prominences to develop and fuse to form the nostril. The nasal pits grow backward.[44]

 
 

FIGURE 21-6  A, The five facial prominences: frontonasal process, paired mandibular processes, and paired maxillary processes. B, Fusion of the medial and lateral nasal processes.  (From Losee JE, Kirschner RE, Whitaker LA, Bartlett SP: Congenital nasal anomalies: A classification scheme. Plast Reconstr Surg 2004;113:676-689, with permission.)

 

 

 

Choanal atresia is thought to result from the persistence of bucconasal and buccopharyngeal membranes or an insufficient excavation of the nasal pits. Postnasal cavity outlet obstruction is more common. Fifty percent of patients with choanal atresia have other congenital anomalies.[45] Choanal atresia may be partial or one of a constellation of congential abnormalities known as the CHARGE association (coloboma, heart disease, atresia [choanal], retarded growth, genital abnormalities, ear deformity). Choanal atresia can be unilateral or bilateral. Because neonates are obligate nose breathers, bilateral choanal atresia frequently presents as immediate onset of respiratory distress. Obstruction of the nasal cavity can present with apneic episodes and “cyclic” cyanosis, which are exacerbated by feeding and improved with crying.[46]

The initial presentation of the newborn with bilateral choanal atresia is the immediate onset of respiratory distress. The relationship between the neonatal tongue and the palate perpetuates this obstruction. The use of an oral airway or McGovern nipple (a nipple modified with enlarged perforations at the tip) acts as an alternative temporary airway. Unilateral choanal atresia is usually asymptomatic, except for unilateral mucoid discharges.

Diagnosis.

Inability to pass a 6-Fr catheter through the nasal cavity to more than 32 mm, coupled with an endoscopic examination, verifies the suspected diagnosis. Axial computed tomography (CT) remains the study of choice to delineate the type of atresia and aid with operative planning (transpalatal vs. transnasal approach). Adequate preparation of the patient before scanning by aspirating secretions and the use of decongestant drops helps ensure the best quality radiographic result. Associated craniofacial syndromes can be found in Table 21-5 .


TABLE 21-5   -- Craniofacial Associations with Choanal Atresia

  

 

CHARGE association (coloboma, heart defects, atresia of choanae, retarded growth or development of the central

  

 

nervous system, genitourinary ear anomalies, or deafness)

  

 

Apert syndrome: craniosynostosis, syndactylism, difficult airway

  

 

Fraser syndrome: laryngeal/tracheal stenosis, congenital heart disease, genitourinary anomalies, renal agenesis/hypoplasia

From Papay FA, McCarthy VP, Eliachar I, et al: Laryngotracheal anomalies in children with craniofacial syndromes. J Craniofacial Surg 2002;13:351-364.

 

 

 

Treatment.

Ninety percent of patients have bone involvement, whereas in 10% the obstruction is membranous. For bilateral choanal atresia surgical correction occurs in the neonatal period and involves a transnasal correction using CO2 or neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers. The nasal passage is stented open for 3 to 5 weeks to improve airway patency. The surgical technique generally involves an endoscopic approach where a vertical mucosal incision is made in the posterior bony septum and a perforation within the atresia plate is created ( Fig. 21-7 ). This perforation is then amenable to serial dilatation.[47]

 
 

FIGURE 21-7  Choanal atresia. A, Choanal atresia in a neonate. The atresia plate on the right side has just been perforated. B, The situation after the opening in the atresia plate has been enlarged.  (Courtesy of Charles Bluestone, MD.)

 



A transpalatal approach has also been used for bony and bilateral atresia. However, the disadvantages of the transpalatal approach are the procedure's long operative time and large blood loss. Additionally, malocclusion occurs in 50% of patients and oronasal fistulas are not uncommon. In patients with unilateral choanal atresia surgical treatment is usually carried out at any time during childhood. The surgical approach can be transnasal or transpalatal.[48]

Anesthetic Considerations.

Anesthetic concerns for infants undergoing choanal surgery involve age-appropriate concerns as well as management of a difficult airway. In addition, for infants having the CHARGE association any underlying cardiac issue must be addressed. The airway is secured with an oral RAE tube after an inhalational or intravenous induction. The anesthetic agent is titrated to allow the patient to be extubated as awake as possible with the patient's airway reflexes intact. However, if the procedure has been lengthy, airway edema is present, or hemodynamic instability is present, then the patient should remain intubated until these issues have resolved.

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Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

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Cystic Hygroma

Cystic hygroma is a congenital cystic lymphatic malformation. It is caused by congenital dysplasia of lymphatics but may be secondary to hamartoma or true neoplasm. The lesion is rare, occurring in 1 in 12,000. Clinically, a cystic hygroma occurs most often (60% to 70%) in the neck ( Fig. 21-8 ). Typically, the neck mass develops in the posterior triangle. If it develops higher in the neck (suprahyoid), it can occupy the anterior triangle and may be associated with intraoral lesions. Suprahyoid lymphangiomas are more likely to involve the mouth and cause feeding problems and airway obstruction.[49] Infection or hemorrhage into the cyst can also cause acute airway compromise. Twenty percent of cystic hygromas occur below the clavicles in the axillae or the mediastinum. Mediastinal extension can cause respiratory symptoms. Usually, cystic hygromas are diagnosed at birth; however, many are diagnosed during prenatal ultrasound.

 
 

FIGURE 21-8  Neonate with a large neck mass consistent with cystic hygroma.  (From Zitelli BJ, Davis HW: Atlas of Pediatric Physical Diagnosis, 4th ed. St. Louis, Mosby, 2002, p 560, with permission.)

 



Anesthetic Management.

During the preoperative evaluation, infants with feeding difficulties should be suspected of having intraoral lesions. Those with respiratory symptoms or coughing should be evaluated for mediastinal involvement with a chest radiograph or CT. Delay in the evaluation should be minimized because the lesions can grow rapidly. The primary anesthetic concern during induction is airway management. Inhalational induction can be performed, but difficulty with both ventilation and intubation has been described.[50] A nasopharyngeal airway may help open the airway and restore ventilation. If preoperative examination suggests difficulty with both ventilation and intubation, consideration should be given to performing an awake or a sedated fiberoptic nasal intubation. Other options include sedated placement of a laryngeal mask airway (LMA) with subsequent fiberoptic intubation, blind nasotracheal intubation, or a sedated tracheostomy.

The surgical resection of a cystic hygroma can be associated with significant blood loss. Intraoperative management should focus on maintaining normovolemia and normothermia. Intravascular access with two large intravenous catheters and an arterial catheter may be required to manage the resuscitation. Central venous access from the neck or chest may not be possible depending on the location of the lymphangioma. Femoral venous cannulation should be considered as an alternative. Fluid shifts and third space fluid losses may be significant. Maintenance of body temperature can be achieved with warming lights, fluid warmers, and forced warm air blankets. Surgical resection may involve manipulation of the vagal nerve, which can result in bradycardia. Evaluation at the end of surgery will determine the feasibility of early extubation. Infants with difficult intubation, significant fluid shifts, or hemodynamic instability should remain intubated and undergo recovery in the intensive care unit. Vocal cord dysfunction can occur secondary to nerve injury from the surgical dissection and should be considered if acute airway obstruction occurs after extubation.

Management of prenatally diagnosed cystic hygromas may involve delivery via the EXIT (ex-utero intrapartum treatment) procedure. During the EXIT procedure the head and torso of the fetus are delivered and the airway is secured while uteroplacental support is maintained. [51] [52] Intubation can be achieved with direct laryngoscopy. If this is impossible because of the anatomy, rigid bronchoscopy or tracheostomy can be performed ( Fig. 21-9 ). Tracheostomy may be very difficult if the mass repositions or covers the trachea.

 
 

FIGURE 21-9  Rigid bronchoscopy performed during the EXIT procedure on a neonate with cystic hygroma. (Courtesy of Laura Myers, MD.)

 

 

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CRANIOFACIAL ANOMALIES

Craniofacial anomalies are characterized by congenital or acquired deformities of the cranial and/or facial skeleton. Craniofacial anomalies, although rare, make up a considerably diverse group of defects. The incidence of all of the anomalies may be difficult to determine because they include only those defects that are well defined. An estimated 1200 persons per year are born with these defects. In the past 2 decades the surgical repairs have advanced significantly and now include the surgical expertise from multiple fields. These specialties include plastic surgery, neurosurgery, oral maxillofacial surgery, otorhinolaryngology, dentistry, orthodontics, speech pathology, genetics, and anesthesiology. The goal of surgical intervention is to restore both form and function.

The classification of craniofacial anomalies is very difficult because of their variability, rarity, and degree of severity and lack of understanding of the etiology and pathogenesis. The Committee on Nomenclature and Classification of Craniofacial Anomalies of the American Cleft Palate Association has proposed the following classification: (1) clefts, (2) synostosis, (3) hypoplasia, (4) hyperplasia, and (5) unclassified.[53]

Clefts

Craniofacial clefts involve a defect of the underlying cranial and/or facial skeleton. This group of deformities has been best classified by Tessier, who uses the orbit as the center of the defect from which the clefts radiate like the spokes of a wheel ( Fig. 21-10 ). Cleft lip and palate are the more commonly recognized examples of craniofacial clefts. Treacher Collins syndrome, which is also known as mandibulofacial dysostosis, is an example of a craniofacial cleft that involves clefts 6, 7, and 8 (see Figs. 21-10 and 21-11 [10] [11]).

 
 

FIGURE 21-10  Tessier classification of rare craniofacial clefts. Using orbit as center of reference, clefts are oriented like spokes of wheel, with those caudad to the orbit considered facial and those cephalad considered cranial. For descriptive purposes, those clefts involving two regions are designated by two numbers (e.g., 4, 10), the sum of which is typically 14. Bony clefts (B) are usually reflected in soft tissue (A).  (From Whitaker LA, Bartlett SP: Craniofacial anomalies. In Jurkiewicz J, Krizek T, Mathes S, Ariyan S [eds]: Plastic Surgery: Principles and Practice. St. Louis, Mosby, 1990, p 109, with permission.)

 



 
 

FIGURE 21-11  Child with Treacher Collins syndrome.  (From Losee JE, Bartlett SP: Treacher Collins syndrome. In Lin KY, Ogle RC, Jane JA [eds]: Craniofacial Surgery: Science and Surgical Technique. Philadelphia, WB Saunders, 2001, pp 288-308, with permission.)

 



Treacher Collins syndrome was first described in 1846 by Thompson and was further elaborated by Treacher Collins. This is a rare syndrome of facial clefting and is transmitted in an autosomal dominant pattern. The syndrome is characterized by poorly developed supraorbital ridges, aplastic/hypoplastic zygomas, ear deformities, cleft palate (in one third), and mandibular and midface hypoplasia ( Fig. 21-11). From birth, issues of airway adequacy take priority. The hypoplastic maxillae and mandible along with choanal atresia and glossoptosis all contribute to varying degrees of airway obstruction. Tracheostomy may be required during infancy for those at highest risk of obstructive sleep apnea and sudden infant death syndrome (SIDS).[54] Aside from cleft lip and palate repair, the timing of major reconstruction typically occurs during childhood or adolescence when the cranio-orbital-zygomatic bony development is nearly complete. Infants and children with Treacher Collins syndrome can have congenital cardiac defects.

Anesthetic Considerations.

Anesthetic concerns specific to this syndrome primarily involve the airway. Infants and children with Treacher Collins syndrome may be very difficult or impossible to mask ventilate and/or intubate, and this airway difficulty may increase with age.[55] Several techniques have been successfully used to safely manage the airway in these infants. The LMA has been used to successfully ventilate a newborn with Treacher Collins syndrome for an extended period of time.[56] Direct laryngoscopy, regardless of the blade used, may be difficult. The Bullard laryngoscope has been used successfully.[57] The LMA has also been used to assist in the intubation of these children. [58] [59] Given the potential for difficult mask ventilation and intubation, this population may be best managed with a sedated fiberoptic intubation or a sedated tracheostomy. Another concern for the anesthesiologist is protecting the patient's eyes. Because of the maxillary and zygomatic hypoplasia, prone positioning may increase the risk of orbital compression and perioperative blindness.

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Synostosis

Craniosynostosis is defined as a premature closure of one or more of the cranial sutures. This results in abnormalities in the size and shape of the calvarium, cranial base, and orbits and constitutes a diverse group of deformities. The craniosynostoses not only affect cosmetic appearance but also can affect brain growth, intracranial pressure (ICP), and vision, resulting in developmental delay, increased ICP, and visual loss. The synostoses are classified based on head shape, not the involved suture ( Fig. 21-12 ).

 
 

FIGURE 21-12  Typical patterns of craniofacial morphology associated with craniosynostosis. A, Turribrachycephaly. B, Plagiocephaly. C, Trigonocephaly. D, Scaphocephaly.  (From Whitaker LA, Bartlett SP: Craniofacial anomalies. In Jurkiewicz J, Krizek T, Mathes S, Ariyan S [eds]: Plastic Surgery: Principles and Practice. St. Louis, Mosby, 1990, p 119, with permission.)

 



Craniosynostosis can occur by itself (simple) or as a major component of a syndrome (complex or syndromic). Five syndromes are associated with craniosynostosis. They include Apert, Pfeiffer, Saethre-Chotzen, Carpenter, and Crouzon syndromes. Table 21-6 lists the various syndromes and their associated anomalies and anesthetic concerns. Four of the five are categorized as acrocephalosyndactylies because they involve deformities of the head (cephalo) and extremities (syndactaly). Crouzon's syndrome does not have musculoskeletal anomalies as part of the syndrome. Infants and children with synostosis present to the operating room for cranial vault remodeling to reduce ICP, prevent brain injury, and enhance appearance. Repair of syndromic craniosynostosis may be more complicated and appears to be associated with increased blood loss. The etiology of the increased bleeding is unclear, but it might be related to the length of surgery.[60]


TABLE 21-6   -- Anesthetic Considerations with Craniofacial Syndromes

Syndrome

Affected Suture

Clinical Features

Anesthetic Issues

Apert syndrome

Coronal

HEENT: turribrachycephaly, midface hypoplasia, orbital hypertelorism, cleft palate in 30%, occasional choanal atresia and tracheal stenosis, airway obstruction

Preoperative labs: hematocrit, type and screen

 

 

Cardiac: congenital heart disease occurs in 10%; may include ventricular septal defect, pulmonary stenosis

Airway management: may be very difficult mask ventilation because of midface hypoplasia, choanal atresia, and tracheal stenosis; may be difficult intubation secondary to facial anomalies and decreased neck mobility

 

 

Genitourinary: hydronephrosis in 3%, cryptorchidism in 4.5%

Cardiac: emphasis on balancing pulmonary and systemic blood flow, de-air intravenous lines, endocarditis prophylaxis

 

 

Musculoskeletal: syndactyly of the hands and feet, fusion of digits 2 to 4, fusion of the cervical vertebrae can occur

Musculoskeletal: cervical fusion may decrease neck extension; syndactyly may make vascular access difficult

 

 

Neurologic: mental retardation common, may have elevated intracranial pressure

Neurologic: caution with premedication if elevated intracranial pressure

 

 

Dermatologic: acne vulgaris common

 

Pfeiffer syndrome

Coronal and occasionally sagittal

HEENT: tower skull, midface hypoplasia, orbital hypertelorism, proptosis, choanal atresia uncommon

Preoperative labs: hematocrit, type and screen

 

 

Pulmonary: obstructive sleep apnea

Airway management: no reported cases of difficult intubation; airway obstruction may occur intraoperatively or postoperatively

 

 

Cardiac: may have cardiac defects

Cardiac: emphasis on balancing pulmonary and systemic blood flow, de-air intravenous lines, endocarditis prophylaxis

 

 

Musculoskeletal: usually mild syndactyly involving broad thumbs and great toes; rarely ankylosis of the elbow occurs; fusion of cervical vertebrae reported

Musculoskeletal: cervical fusion may decrease neck extension; syndactyly may make vascular access difficult

 

 

Neurologic: generally normal but mild developmental delay can occur; may have increased intracranial pressure

Neurologic: caution with premedication if elevated intracranial pressure; eyes require protection if ocular proptosis present

Saethre-Chotzen syndrome

Coronal and others

HEENT: brachycephaly, maxillary hypoplasia, orbital hypertelorism, beaked nose, occasional cleft palate

Preoperative labs: hematocrit, type and screen

 

 

Genitourinary: renal anomalies and cryptorchidism

Airway management: no reported cases of difficulty with ventilation or intubation

 

 

Musculoskeletal: short stature, mild syndactyly; cervical fusion possible

Musculoskeletal: cervical fusion may decrease neck extension; syndactyly may make vascular access difficult

 

 

Neurologic: mild developmental delay; rare increased intracranial pressure

Neurologic: caution with premedication if elevated intracranial pressure

Carpenter syndrome

Coronal and others

HEENT: tower skull, down-thrust eyes, orbital hypertelorism, low-set ears, small mandible

Preoperative labs: hematocrit, type and screen

 

 

Cardiac: cardiac defects common (ventricular and atrial septal defects)

Airway management: small mandible may make intubation difficult; obesity may make ventilation difficult

 

 

Genitourinary: hypogonadism

Musculoskeletal: syndactyly may make intravenous access difficult

 

 

Musculoskeletal: syndactyly of hands and feet

Neurologic: caution with premedication if elevated intracranial pressure

 

 

Neurologic: developmental delay common but variable, may have increased intracranial pressure

 

 

 

Other: obesity

 

Crouzon Syndrome

Coronal, lambdoid, others

HEENT: frontal bossing, tower skull, midface hypoplasia, beaked nose, hypertelorism, ocular proptosis, airway obstruction can occur

Preoperative labs: hematocrit, type and screen

 

 

Neurologic: occasional mild developmental delay, may have increased intracranial pressure

Airway management: may be a difficult intubation; may have airway obstruction during awake or sleep states; caution with premedication

 

 

 

Neurologic: caution with premedication if elevated intracranial pressure; eyes require protection if ocular proptosis present

 

 

Apert syndrome is part of a group of craniofacial disorders, referred to as acrocephalosyndactylies, that are characterized by craniofacial and extremity anomalies. There is an autosomal dominant pattern of inheritance. The etiology of the syndrome is from a mutation with the fibroblast growth factor receptor-2 gene (FGFR2).[61] The characteristic features of Apert's syndrome include turribrachycephaly (high steep flat forehead and occiput), midface hypoplasia, and orbital hypertelorism ( Fig. 21-13 ). Cleft palate occurs in approximately 30%. Choanal atresia and occasionally tracheal stenosis have been reported and can cause airway obstruction. Congenital cardiac disease is one of the more common associated visceral anomalies, occurring in approximately 10%. Genitourinary anomalies (hydronephrosis, cryptorchidism) also occur in 10% of patients with Apert's syndrome.[62] Severe synostosis can result in increased ICP and, if uncorrected, developmental delay. Syndactyly of the hands and feet often present as the fusion of digits 2 to 4, which can make intravenous access difficult. Cervical spine fusion has been reported in Apert's syndrome and may make endotracheal intubation even more challenging if there is decreased neck mobility.[63] Many children with Apert's syndrome have been intubated uneventfully. However, suboptimal laryngoscopic views secondary to abnormal anatomy may require flexible fiberoptic intubation. The LMA may also be a reasonable adjunct in those patients who are difficult to ventilate or intubate. However, to date there are no reported cases of their use in infants and children with Apert's syndrome. The clinical features and the anesthetic implications of Apert's syndrome and the other acrocephalosyndactylies are outlined in Table 21-6 . Unlike Apert's syndrome, the other acrocephalosyndactylies are not typically associated with difficult airways. However, midface hypoplasia is common in these infants and may cause significant upper airway obstruction intraoperatively and postoperatively.[64]

 
 

FIGURE 21-13  Child with Apert syndrome.  (From Buchman SR, Muraszko KM: Syndromic craniosynostosis. In Lin KY, Ogle RC, Jane JA [eds]: Craniofacial Surgery: Science and Surgical Technique. Philadelphia, WB Saunders, 2001, pp 252-271, with permission.)

 



Crouzon's disease, also known as craniofacial dysostosis, is also part of the syndromic craniosynostosis. These infants present with craniofacial anomalies without visceral or extremity involvement. The anomalies can result in significant airway obstruction that may require early tracheostomy. Crouzon's disease results from a mutation in the FGFR2, the same gene that causes Apert's syndrome. Table 21-6outlines the main clinical features and anesthetic issues. During infancy these patients may present to the operating room for tracheostomy and/or cranial vault remodeling.

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Hypoplasia

Hypoplasia of the craniofacial skeleton is a category of craniofacial anomalies characterized by hypoplasia or atrophy of a portion of the craniofacial soft tissue and skeleton. Pierre Robin sequence and hemifacial microsomia (including Goldenhar's syndrome) are examples of these anomalies.

Pierre Robin sequence is characterized by retrognathia, glossoptosis (tongue falling to the back of the throat), and airway obstruction and probably occurs secondary to a fixed fetal position in utero that inhibits mandibular growth. Management of this sequence is dependent on the severity of respiratory distress and airway obstruction. Those infants with mild obstruction and minimal respiratory distress who can continue to feed may require prone positioning only or no intervention at all. For more severe respiratory distress, the tongue can be surgically attached to the lower lip (tongue lip adhesion) to decrease airway obstruction and allow time for the mandible to grow.

Anesthetic Management.

Airway management in the infant with Pierre Robin sequence can be very challenging because of difficulty with mask ventilation and intubation. The LMA has been successfully used to ventilate and to assist in the intubation of these patients.[65] Nasal intubation with the flexible fiberoptic scope has also been described.[66] In infants who present with significant difficulty with ventilation or intubation, aside from oral pharyngeal and nasal airways, a suture (0-silk) can be placed at the base of the tongue to displace the tongue anteriorly to assist with ventilation or intubation.

Hemifacial microsomia is characterized by unilateral or asymmetrical development of the facial bones and muscles and frequently involves the ear. This manifests as hypoplasia of the malar-maxillary-mandibular region and usually involves the temporomandibular joint. The defect occurs from an anomaly of the first and second branchial arches and is believed to be secondary to a fetal vascular accident. Goldenhar's syndrome is a subset of hemifacial microsomia and is composed of hemifacial microsomia, epibulbar dermoid, and/or rib or vertebral, anomalies. The vertebral pathology can involve the cervical vertebrae and can significantly reduce the cervical range of motion. Other associated anomalies of hemifacial microsomia include cardiac (ventricular septal defect, tetralogy of Fallot, coarctation), renal, and neurologic defects (hydrocephalus). Patients with hemifacial microsomia can have significant upper airway obstruction and obstructive sleep apnea.

Anesthetic Management.

Airway management is a major concern in these patients. Mask ventilation may be difficult because of the facial asymmetry. Intubation is more challenging because of micrognathia, asymmetrical mandibular hypoplasia, and potentially from decreased cervical range of motion. This difficulty may decrease with age but may increase after surgical reconstruction. Successful ventilation and intubation of an infant with Goldenhar's syndrome has been reported with an LMA and flexible fiberoptic scope.[67]

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Surgical Correction of Craniofacial Anomalies

Surgical correction of these anomalies is performed to improve form and function and to minimize disability. Airway obstruction, increased ICP, developmental delay, and visual loss are some of the pathologic processes that may be corrected or prevented with appropriate surgical intervention. Several procedures are performed to correct these deformities. They include strip craniectomy, cranial vault remodeling, frontal-orbital advancement, midface advancement (Le Fort I, Le Fort III, monoblock advancement), and distraction osteogenesis. Strip craniectomy, cranial vault remodeling, and frontal-orbital advancement are surgical approaches to correct craniosynostosis. The goal is to release the synostotic sutures and open up the cranium to allow brain growth and development. Strip craniectomy involves less blood loss but because of premature refusion is usually reserved only for patients with sagittal synostosis. The surgical approach for these three procedures is through a bicoronal incision. Subperiosteal dissection allows access to the upper facial skeleton for surgical manipulation ( Fig. 21-14 ). These procedures are performed during the first year of life. They can involve significant blood loss, and preparations to ensure patient safety include adequate intravenous access and availability of blood products.

 
 

FIGURE 21-14  Bicoronal incision (A) with extensive subperiosteal dissection (B) provides access for surgical manipulation of upper facial skeleton.  (From Whitaker LA, Bartlett SP: Craniofacial anomalies. In Jurkiewicz J, Krizek T, Mathes S, Ariyan S [eds]: Plastic Surgery: Principles and Practice. St. Louis, Mosby, 1990, p 107, with permission.)

 



Mandibular advancement procedures are frequently performed to correct appearance, malocclusion, and airway obstruction. These procedures are not routinely performed in the infant. Generally these surgeries take place during early to late childhood.

Distraction osteogenesis is a technique that was developed to create bone elongation by creating a bone cut (osteotomy) and distracting the two ends. It was first developed and utilized by orthopedic surgeons but was not used for craniofacial surgery until 1992 when McCarthy described distraction osteogenesis to lengthen the human mandible.[68] This technique has now been used in many children to distract the mandible and midface ( Fig. 21-15 ). Distraction of the mandible and midface can be used to correct appearance and to correct upper airway obstruction. Airway obstruction has been corrected using distraction osteogenesis in infants as young as 14 weeks old.[69]

 
 

FIGURE 21-15  Mandibular distractor in an infant with Pierre Robin sequence.  (Courtesy of Joseph E. Losee.)

 



Anesthetic Management.

The anesthetic management of infants with craniofacial anomalies begins with a complete preoperative evaluation. The history should define the anomaly and identify if there is an associated syndrome. Infants and children with syndromes may have more difficult airways, other organ involvement, and more complicated surgical repair with more bleeding. Associated anomalies that can present a challenge to the anesthesiologist include facial and airway features that make mask ventilation and intubation difficult. Airway pathology can also cause obstruction, and some of these children have obstructive sleep apnea. History of fatigue or sweating with feedings, cyanosis, and syncope are suggestive of an underlying cardiac anomaly. Cardiac pathology is associated with some of the syndromes (e.g., Treacher Collins, Apert, Pfeiffer, Carpenter, and hemifacial microsomia). Some of these infants and children may have increased ICP. This may manifest as headaches, vomiting, and somnolence.

A thorough airway examination may be difficult to perform on an infant. Features that may predict difficulty with mask ventilation include midface hypoplasia and enlarged tongues. In addition, a small mandibular space, decreased jaw opening and translocation, and decreased neck flexion and extension predict difficult intubation. The rest of the examination should focus on identifying heart murmurs. In infants with syndactyly, identifying potential intravenous and arterial access sites is critical. For reconstructions that involve significant blood loss a preoperative hematocrit and type and crossmatch should be performed. Former premature infants and infants younger than 1 month old should have their glucose level monitored. Premedication can be performed for most children older than the age of 1 but is rarely necessary in those younger than 10 months old. Children with evidence of airway obstruction or increased ICP should not receive a premedicant. Endocarditis prophylaxis should be considered in those patients with congenital heart disease.

Airway management in these patients may be very challenging. As previously stated, the difficulty may present during attempts at ventilation, intubation, or both. Fortunately, difficult airways are not common. However, the incidence is higher in those patients with congenital syndromes and in those patients who have had previous reconstruction. Many techniques have been successfully described in infants; these include using the Bullard laryngoscope, LMA, flexible fiberoptic scope, and retrograde intubation. [57] [66] [70] A combination of techniques may be required to secure the airway. For example, the LMA has been used to facilitate the passage of the fiberoptic scope and endotracheal tube.[58] Some infants with craniofacial anomalies require tracheostomy because of significant upper airway obstruction. [64] [71] Adequate preparation entails having all of the necessary equipment available and having personnel who are trained and experienced to use these airway instruments. It may also mean having a pediatric otorhinolaryngologist immediately available.

Several intraoperative considerations exist when managing the anesthetic for craniofacial repairs. Often these procedures are long and expose infants to the risks of hypovolemia, hypothermia, blood loss, and venous air emboli. The craniofacial procedures performed during the first year of life include cranial vault remodeling, fronto-orbital advancement, strip craniectomy, and distraction osteogenesis. The cranial-based procedures can involve significant blood loss because of the duration of the procedure and also because of complications such as entering the sagittal sinus. Nearly 90% to 100% of the infants undergoing these procedures will require a blood transfusion.[72] Even the strip craniectomy, which is typically performed to correct sagittal synostosis and results in less blood loss, can still produce significant hemorrhage. Infants are particularly at risk of being exposed to transfusions because they can present to the operating room at the nadir of their physiologic anemia (2 to 3 months of age). Preparation for these procedures requires a baseline hematocrit and a type and crossmatch. Adequate intravenous access needs to be obtained for resuscitation. In an infant, at least two large-bore (22 to 18 gauge) peripheral intravenous catheters should provide adequate access. Arterial pressure monitoring is recommended for beat-to-beat analysis of blood pressure and intravascular volume status, as well as for blood gas monitoring.

Techniques to minimize blood loss have been proposed and include preoperative recombinant erythropoietin, acute normovolemic hemodilution, induced hypotension, electrocautery, aprotinin, and use of a cell saver. Preoperatively, recombinant erythropoietin may decrease the transfusion requirements in infants having craniosynostosis repair. The reported dose of erythropoietin is 300 to 600 units/kg given subcutaneously one to three times per week, along with oral iron supplementation. Erythropoietin is started three weeks before surgery. A prospective study of once-weekly dosing decreased the incidence of transfusion in infants having craniosynostosis repair from 93% to 57%.[60]

Aprotinin, a serine protease inhibitor, may also decrease perioperative blood loss and transfusion requirements during craniofacial procedures. In a prospective randomized and blinded placebo-controlled study evaluating the effect of aprotinin in infants and children having cranial vault remodeling and frontal orbital advancements, D'Errico and coworkers noted a reduction in the amount of packed red blood cells being transfused intraoperatively and postoperatively in those receiving aprotinin. However, the number of patients requiring transfusion was not reduced.[73] No adverse events were reported.

In the past, the use of cell saver has been reported as being impractical for small pediatric patients because of the size of the receptacle.[74] Recently, the cell saver reservoirs are available in sizes as small as 55 mL. This technology may reduce the rate of autogenous blood transfusion in infants having craniofacial surgery. In a prospective analysis evaluating the use of cell saver with a 55-mL pediatric bowl in patients pretreated with erythropoietin, only 30% of those infants having cranial vault remodeling required allogenic blood.[75]

Venous air embolism (VAE) is a potential complication of craniofacial and neurosurgical procedures. It can present as hemodynamic instability and can result in death. VAE can occur commonly in pediatric patients having cranial-based procedures. A prospective study using a precordial Doppler in infants and children having craniosynostosis repair detected VAE in 82% of the patients. Thirty-one percent developed hypotension secondary to VAE, but none developed cardiovascular collapse.[76] This is higher than the previously reported incidence of 66%.[77] Infants may be at increased risk of VAE because they can hemorrhage significantly during cranial vault remodeling, resulting in low central venous pressures. In addition, the relatively large size of the infant head may raise the surgical site above the level of the heart, thereby increasing the pressure gradient for air entrainment. Some advocate the placement of central venous catheters to monitor the trend of central venous pressures and minimize the risk of air embolism. However, there are no data that suggest central venous pressure monitoring decreases the risk of VAE. Management of VAE begins with preventing hypovolemic states by providing adequate volume resuscitation and using a precordial Doppler for early detection of VAE. Lowering the head of the bed, flooding the surgical field with saline, applying bone wax, discontinuing nitrous oxide, and providing inotropic support are all measures that have been utilized to acutely manage VAE.

Craniofacial procedures can be very long, lasting several hours. Complications resulting from long surgical procedures include skin breakdown, neuropathic injury, and hypothermia. Attention must be paid to the initial setup to ensure adequate positioning and padding to minimize these intraoperative injuries. Infants having cranial vault remodeling may be positioned prone, and attention to protecting the face and eyes is important. Patients with syndromes that alter the architecture of the midface may present a challenge when placed prone because adequately protecting the face and eyes may be more difficult. An example of the initial setup is shown in Figure 21-16 . The infant is placed on a full access Bair hugger to minimize hypothermia, and the surgical site (head) is then isolated from the body using plastic drapes. This not only minimizes convective and radiant heat losses but also prevents conductive heat loss to a wet bed from irrigation and blood. Blood products should be warmed through a fluid warmer before administration (except for platelets).

 
 

FIGURE 21-16  Operating room setup for posterior cranial vault remodeling. Note application of forced warm air plastic sheets to separate the head from the body. This creates a barrier to fluids (blood, prep solution, irrigation). Special attention to avoid ocular pressure is essential.  (Courtesy of Joseph E. Losee.)

 



Postoperative Management.

The postoperative management of infants having craniofacial surgery depends on coexisting morbidities and the procedure performed. Infants who have had distractors placed may have a more difficult airway after extubation because of location of the device. Mask ventilation can be very difficult with mandibular distractors. Airway equipment, including appropriately sized LMAs, should be available after extubation. External maxillary distractors are not typically placed in infants. However, their use in older children can make access to the airway more challenging, and personnel and equipment to remove part of the device are important in the operating room.[78] Infants having cranial vault remodeling and frontal orbital advancements can experience significant blood loss intraoperatively. Providing these patients are adequately resuscitated and are hemodynamically stable, they can often be extubated in the operating room. Infants with difficult airway, significant airway obstruction, or who have experienced intraoperative complications may benefit from delayed extubation in the intensive care unit/operating room after their condition has stabilized. Ongoing blood loss is common after major craniofacial surgery, and infants may require repeat transfusions in the immediate postoperative setting. Other complications include cerebral edema,[79] visual changes,[80] CSF leak,[81] infection,[82]electrolyte abnormalities (hyponatremia),[79] metabolic acidosis, and transfusion reactions.

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MEDIASTINAL MASSES

Mediastinal masses in infants and children present a diagnostic and therapeutic dilemma to the medical team caring for them. Careful communication between the oncologists, pediatric surgeons, anesthesiologists, radiologists, and intensivists is important for a favorable outcome. An understanding of the pathology, clinical presentation, diagnosis, imaging, and treatment is instrumental in the efficient and safe care of these children with mediastinal masses.

Anatomic Considerations.

A classification of mediastinal masses based on location is presented in Table 21-7 . The anterior mediastinum is the zone posterior to the sternum, anterior to the pericardium, superior to the diaphragm, and inferior to the plane through the sternomanubrial junction. Anterior mediastinal masses are common in children. The most common anterior mediastinal masses are teratomas, thymomas, and lymphomas (Hodgkin's and non-Hodgkin's lymphoma). They account for approximately 40% of the tumors. The middle mediastinum is defined by the pericardium and origins of the great vessels. The posterior mediastinum is outlined by the pericardium and great vessels anteriorly, the vertebral column posteriorly, and the parietal pleurae laterally. Generally, neurogenic tumors occur in the posterior mediastinum, of which neuroblastoma is the most common.[83]

TABLE 21-7   -- Mediastinal Tumors

 

Benign

Malignant

Anterior

Thymoma

Thymic carcinoma

 

Thymic cyst

Thyroid carcinoma

 

Thymolipoma

Seminoma

 

Thymic hyperplasia

Mixed germ cell

 

Thyroid

Lymphoma

 

Cystic hygroma

Thymic carcinoid

 

Parathyroid adenoma

 

 

Foramen of Morgagni hernia

 

Middle

Benign adenopathy

Lymphoma

 

Cysts

Metastases

 

Esophageal

Esophageal cancer

 

Hiatal hernia

Thyroid carcinoma

 

Cardiac and vascular structures

 

 

Lipomatosis

 

 

Cardiac and vascular structures

 

 

Cardiophrenic fat pad

 

 

Foramen of morgagni hernia

 

 

Ectopic thyroid

 

Posterior

Neurofibroma

Neuroblastoma

 

Schwannoma

 

 

Foramen of Bochdalek hernia

 

 

Meningocele

 

From Yoneda KY, Louie S, Shelton DK: Mediastinal tumors. Curr Opin Pulm Med 2001;7:226-233.

 

 

 

Pathology.

Anterior mediastinal masses have been reported mostly in older children, but there are several cases reported in infants. [84] [85] [86] Most masses in children younger than 2 years of age are benign. Malignant masses are more frequently found in older children and are mostly lymphomas, Hodgkin's and non-Hodgkin's, as well as neurogenic tumors. [87] [88]

Masses of the mediastinum surround the large airways, heart, and great vessels. Compression of the airways and great vessels can result in respiratory and cardiovascular symptoms.

Clinical Presentation.

The signs and symptoms depend on the size and location of the mediastinal mass and on the extent of compression of the tracheobronchial tree and the cardiovascular system.[89] Symptoms related to compression of the tracheobronchial tree include cough, dyspnea, and orthopnea. The symptoms are generally exacerbated when the child is in the supine position. Signs of respiratory compromise include stridor, cyanosis, wheezing, and decreased breath sounds. Compression of the cardiovascular system manifests as fatigue, headaches, fainting spells, and orthopnea and may cause SVC obstruction or SVC syndrome (edema of the head and neck; distended neck veins and collateral veins on the chest wall; plethora; cyanosis of the face, neck, and arms; proptosis; and Horner's syndrome.[90] Symptoms of cerebral edema from venous hypertension can occur with SVC obstruction and include headaches, syncope, and lethargy ( Table 21-8 ).


TABLE 21-8   -- Clinical Findings in Patients with Mediastinal Masses

History

Physical Examination

Laboratory

Airway

Cough

Decreased breath sounds

Chest radiograph (posteroanterior and lateral to look for tracheal deviation or compression)

Cyanosis

Wheezing

 

Dyspnea

Stridor

 

Orthopnea

Cyanosis

Flow-volume loops supine and sitting

Cardiovascular

Fatigue

Neck or facial edema

Chest radiographic changes in cardiac silhouette

Faintness

Jugular distention

 

Headache

Papilledema

Echocardiogram done supine and sitting

Shortness of breath and orthopnea

Blood pressure changes or changes in pallor with postural changes

 

Cough

Pulsus paradoxus

 

From Pulleritz J, Holzman RS: Anaesthesia for patients with mediastinal masses. Can Anaesth Soc J 1989;36:681-688.

 

 

 

Diagnosis.

Procurement of tissue for diagnosis of mediastinal masses can be achieved by several methods. Fine-needle aspiration biopsy can be performed by experienced interventional radiologists. However, this procedure carries a 15% inconclusive result.[91] This requires surgical biopsy to ascertain the diagnosis. Surgical approaches depend on the location of the mass. Consideration should always be given to collecting tissue from a remote location, such as a cervical lymph node or pleural fluid, under local anesthesia. If these sites are not possible then a tissue sample will need to be collected from the mediastinum. Anterior mediastinotomy (Chamberlain procedure), in which the second or third interspace is incised for exposure, allows access to the anterior mediastinum, right paratracheal, and aortopulmonary areas. [91] [91] Mediastinoscopy and thoracoscopy with video assistance have become widely accepted for the diagnosis and management of mediastinal disease. If local anesthetic techniques are not possible and the patient is considered at high anesthetic risk, empirical therapy with irradiation or corticosteroids may be considered. A brief preoperative course of radiation has been described in patients believed to be at highest risk of perioperative complications. Anesthesia was safely provided to all of the patients, and the tissue sample was still adequate to make a diagnosis.[92]Limiting the duration of treatment or shielding an area of the tumor from the radiation may improve the chances of a tissue diagnosis. However, empirical therapy can alter the tissue and should be considered as a last resort.

Preanesthetic Evaluation.

Many mediastinal tumors are asymptomatic and are first noted on routine chest radiography. In some studies only 30% of children with Hodgkin's disease demonstrated symptoms.[93] Chest CT with iodinated contrast is the study of choice to determine the location and extent of compression of adjacent structures in the chest. Magnetic resonance imaging (MRI) is superior to CT for imaging nerve plexus and blood vessels. MRI is useful when iodinated contrast is contraindicated or in the diagnosis of thyroid masses.[94] When cardiovascular structures are involved, echocardiography, contrast medium–enhanced CT, or cardiac MRI is essential. Echocardiography may provide dynamic information regarding ventricular compression and performance. Pulmonary function testing in the supine and sitting position is important in determining the extent of airway compromise. The supine position tends to exacerbate the respiratory compromise. Intrathoracic obstruction causes distortion of the maximal expiratory flow rate, whereas extrathoracic obstruction causes distortion of the inspiratory flow rate. An equal reduction of both inspiratory and expiratory flow rates is affected by fixed lesions. In patients with mediastinal masses pulmonary function testing reveals both an obstructive and a restrictive impairment ( Fig. 21-17 ).[95]

 
 

FIGURE 21-17  Expiratory flow volume loops in an 8-year old with an anterior mediastinal mass. Note the reduction in maximum flows that improves after 4 days of chemotherapy.  (From Shamberger RC, Holzman RS, Griscom NT, et al: CT quantitation of tracheal cross-sectional area as a guide to the surgical and anesthetic management of children with anterior mediastinal masses. J Pediatr Surg 1991;26:138-142.)

 

 

 

The essential component of the preanesthetic evaluation is to identify those patients at highest risk of perioperative respiratory and cardiovascular complications. One study suggests that the narrowing of the trachea and bronchi to less than 50% predicted on CT indicates an increase in anesthetic risk.[96] In another study all children with anterior mediastinal masses who demonstrated tracheal cross-sectional areas greater than 50% predicted or a peak expiratory flow rate greater than 50% predicted underwent uneventful general anesthesia.[95] The only symptom that appears to correlate with cross-sectional area of the airway is orthopnea. In the previous study, no patients with a cross-sectional area of the airway greater than 50% demonstrated orthopnea; and in several cases, orthopnea was the only symptom that consistently preceded respiratory collapse on induction of anesthesia. [86] [97] [98] In adults it appears that those with cardiorespiratory signs and symptoms, both obstructive and restrictive abnormalities on pulmonary function tests, and those with tracheal compression greater than 50% are at greatest risk of having early postoperative life-threatening complications.[98]

Anesthetic Management.

Several reports have described the risk of life-threatening airway obstruction and cardiovascular collapse during general anesthesia in patients with mediastinal masses. [86] [98] [100] These catastrophic outcomes occur because of the physiologic changes that occur during general anesthesia. During general anesthesia, lung volume is reduced owing to loss of inspiratory muscle tone, as well as to the loss of the tethering effect that the expanded lung has on the airway. The normal transpleural pressure gradient that distends the airway during inspiration is diminished, and this further compromises the airway caliber. During spontaneous ventilation, the diaphragm moves caudad. While the patient is paralyzed with neuromuscular blocking agents the diaphragm shifts cephalad at the end of expiration.[100] This change further compromises the airway. The size of the infant may magnify the physiologic consequences of anterior mediastinal masses. The increased cartilaginous component of the ribs increases the compliance of the thoracic wall, making it less likely to support the weight of a tumor. Also, a reduction in an already small airway will significantly increase airway resistance (the Poiseuille equation demonstrates that the resistance of laminar flow in a tube is inversely proportional to the fourth power of the radius).

Laminar gas flow through a narrow airway is best maintained with spontaneous ventilation.[100] Positive-pressure ventilation and airway obstruction disrupt laminar flow and increase the resistance to gas flow in the airways. An inspired mixture of helium and oxygen decreases resistance to gas flow through the airways because of helium's lower density compared with oxygen.[101] During turbulent flow, the pressure gradient required to produce a given gas flow becomes directly proportional to the density of the gas. Also helium's lower density increases the likelihood of laminar flow, thus reducing resistance further.[101] Heliox (helium-oxygen) has been described in a 3-year-old patient with a large symptomatic anterior mediastinal mass who underwent general anesthesia with an LMA.[102]

For patients undergoing diagnostic procedures or catheter placement, an effort should be made to perform the procedure under local anesthesia with sedation. General anesthesia can be performed safely; however, there needs to be a high index of suspicion for respiratory and cardiovascular complications. The induction of anesthesia can be achieved with either intravenous or inhalational techniques. The emphasis should be on maintaining spontaneous ventilation. Airway management with mask, LMA, and endotracheal tube has been described. [103] [104] Reinforced armor tubes have also been described to help maintain airway patency, and rigid bronchoscopy may become necessary should complete airway collapse occur. [84] [85] [105] In older children who require intubation but are clinically too tenuous for general anesthesia, a fiberoptic intubation can be accomplished with sedation and topical anesthesia of the airway. The Chamberlain approach has been performed under sedation with local anesthetic infiltration in children and should be considered for those at greatest risk of complications. In patients with respiratory compromise, intravenous access should be secured before the start of anesthesia and in patients with SVC syndrome intravenous access should be secured in the lower extremities. Because the supine position during induction of anesthesia may compromise an already tenuous airway, patients with mediastinal masses should be positioned in a semi-sitting position. If severe airway obstruction develops, the patient should be placed in the prone or lateral position. Patients who are believed to be at greatest risk of cardiovascular collapse should be considered preoperatively for cardiopulmonary bypass ( Fig. 21-18 , Table 21-9 ).

 
 

FIGURE 21-18  Algorithm for anesthetic management of the child with an anterior mediastinal mass. CBC, complete blood count; CPB, cardiopulmonary bypass; CT, computed tomography; CXR, chest radiograph; LP, lumbar puncture; PICU, pediatric intensive care unit; SVC, superior vena cava.  (Adapted from Hammer GB: Anaesthetic management for the child with a mediastinal mass. Pediatr Anesth 2004;14: 95-97, with permission.)

 

 

 


TABLE 21-9   -- Anesthetic Considerations for Management of Mediastinal Masses

  

 

Evaluate with computed tomography, echocardiography, pulmonary function tests, chest radiography.

  

 

Attain intravenous access in the lower extremity if superior vena cava syndrome is present.

  

 

Prepare to change position lateral or prone.

  

 

Maintain spontaneous ventilation.

  

 

Have rigid bronchoscope available.

  

 

Have cardiopulmonary bypass on standby.

 

 

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Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

CONGENITAL MALFORMATION OF THE LUNG

Bronchogenic and Pulmonary Cysts

Bronchogenic cysts occur from abnormal budding of bronchial tissue. The cysts may occur anywhere from the mediastinum to the periphery, depending on when they separate during embryogenesis. They can be classified as mediastinal (central) or pulmonary (peripheral). Mediastinal cysts are more common and are usually located in the paratracheal and paraesophageal area, with the majority occurring between the trachea and the esophagus. The majority of pulmonary (peripheral) cysts occur in the lower lobes. Bronchogenic cysts may be filled with air or mucoid or serous fluid. [106] [107] Although unlikely, they may communicate with the tracheobronchial tree. Most patients are asymptomatic, but if symptoms do occur they are related to airway, respiratory, and cardiovascular compromise from cyst enlargement or from infection. Infection may present as chronic cough, fever, and recurrent pneumonia.[107] Diagnosis is made with chest radiography and chest CT. The management of symptomatic patients is surgical resection ( Table 21-10 ).

TABLE 21-10   -- Anesthetic Management of Bronchogenic Cysts

  

 

Preoperative Evaluation of Bronchogenic Cysts

  

 

History: may have respiratory symptoms, cough, fever, recurrent lung infections

  

 

Chest radiography/computed tomography: evaluate location and size of cyst, evaluate for cardiac compression

  

 

Laboratory: hematocrit, type and screen, oxygen saturation

  

 

Anesthetic Management

  

 

Consider single lung ventilation if fluid-filled cyst.

  

 

Consider avoiding nitrous oxide.

 

 

Anesthetic Management.

Concerns regarding the anesthetic management include respiratory compromise secondary to cyst expansion from positive-pressure ventilation and/or nitrous oxide and spillage of cyst contents into the airway. A review of the anesthetic management of 24 cases of bronchogenic cysts indicated that these complications do not occur as commonly as previously thought. All of the patients in this case series received muscle relaxation and positive-pressure ventilation intraoperatively, and no problems were encountered. There were three reports of excessive tracheal secretions that may have been related to drainage of fluid-filled cysts. Repeated suctioning was required, but no airway compromise was reported. The use of one lung ventilation was not described.[107] Spillage of cyst fluid in the airway with transient oxygen desaturation has been reported after induction of anesthesia. Lung isolation was also not employed in this case.[108] During the anesthetic management of bronchogenic cysts, lung isolation techniques may be advantageous, particularly with the manipulation of fluid-filled cysts. Whereas positive-pressure ventilation and the use of nitrous oxide appear to be reasonably well tolerated, it is unclear just how much risk they present.

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Congenital Cystic Adenomatous Malformation

Congenital cystic adenomatoid malformation (CCAM) occurs secondary to an abnormal overgrowth of terminal bronchioles with a lack of mature alveoli, bronchial glands, and cartilage.[109] They are rare and occur at an estimated incidence of 1:25,000 to 1:35,000.[110] These cysts communicate with the tracheobronchial tree. CCAMs may be made up of a solid mass or a cystic structure that may consist of a single large dominant cyst or multiple cysts. Stocker classified CCAMs into three groups based on size and the histology of the cyst lining. Associated anomalies include renal agenesis and dysgenesis and prune belly syndrome. Clinical signs and symptoms at presentation depend largely on the size of the mass. The cystic lesions communicate with the tracheobronchial tree and may behave like a ball-valve effect, becoming distended secondary to gas trapping. In-utero compromise with anasarca and ascites may occur if the lesion is large enough to impair fetal circulation. Compression of surrounding structures can result in lung hypoplasia. Neonates and infants may present with significant respiratory distress, requiring immediate resection. Patients presenting after the neonatal period often develop recurrent pulmonary infections localized to one lobe.[111] Diagnosis is made by clinical symptoms, chest radiography, and chest CT ( Fig. 21-19 ). In-utero diagnosis is made during prenatal ultrasound. Definitive treatment is surgical removal of the affected lobe ( Table 21-11 ).

 
 

FIGURE 21-19  Microcystic adenomatoid malformation seen on plain film (A), CT (B), and surgical specimen (C).  (From Zitelli BJ, Davis HW: Atlas of Pediatric Physical Diagnosis, 4th ed. St. Louis, Mosby, 2002, p 565, with permission.)

 




TABLE 21-11   -- Anesthetic Management of Congenital Cystic Adenomatous Malformation (CCAM)

  

 

Preoperative Evaluation

  

 

History: symptoms depend on size of mass, respiratory distress (may be severe), recurrent lung infection

  

 

Chest radiography/computed tomography: evaluate location and size of CCAM

  

 

Laboratory: hematocrit, type and screen, oxygen saturation

  

 

Associated Anomalies

  

 

Renal agenesis or dysgenesis

  

 

Prune belly syndrome

  

 

Anesthetic Management

  

 

Spillage of CCAM contents can occur into airway; consider single-lung ventilation.

  

 

CCAM can expand; consider avoiding nitrous oxide; consider single-lung ventilation

 


Anesthetic Management.

Communication of the CCAM with the tracheobronchial tree potentially increases the anesthetic risk. Positive-pressure ventilation and nitrous oxide may expand the lesion and cause cardiovascular and respiratory compromise. Spillage of cyst contents during anesthesia and obstruction of the endotracheal tube have also been reported.[108] Induction of anesthesia by an inhalational anesthetic with spontaneous ventilation may be preferential, but maintaining spontaneous ventilation during thoracotomy or thoracoscopy is very difficult and not feasible. Lung isolation may be ideal because it not only minimizes the risk of cyst overinflation during positive-pressure ventilation but also minimizes the risk of exposure to cyst contents should it rupture. Lung isolation in neonates and infants can be achieved either with purposeful mainstem intubation of the right or left bronchus or with placement of a 5-Fr bronchial blocker. The advantage of the bronchial blocker is that it may allow better protection from drainage of cyst contents into the contralateral lung. However, neither option for lung isolation allows suctioning, oxygenation, or continuous positive airway pressure (CPAP) to the isolated lung.

Standard surgical exposure is achieved via a thoracotomy. However, the development of smaller equipment has allowed this procedure to occur less invasively via a thorascopic approach. The potential advantages include less pain and faster recovery, with potentially shorter hospital stays. Lung isolation may facilitate the surgeon's exposure, and some centers routinely employ this technique. The CCAM has also been removed while the fetus is on uteroplacental support during the EXIT procedure.[112]

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Copyright © 2005 Saunders, An Imprint of Elsevier

Pulmonary Sequestration

Pulmonary sequestration is characterized by a segment of lung tissue that is ectopic and serves no ventilatory function. It does, however, have its own vascular supply that typically arises from the thoracic or abdominal aorta.[113] Venous drainage has been reported through the pulmonary, azygous, or portal veins. Unlike the cystic malformations of the lung, sequestrations have no tracheobronchial communications and are not at risk of spillage of contents or expansion. There are two types of pulmonary sequestrations: intralobar and extralobar. The intralobar or intrapulmonary sequestration is located within a lobe and has no distinct pleural covering. Extralobar sequestrations have their own pleural covering and are associated with other congenital anomalies in 50% of cases. Some of these anomalies include communication with the gastrointestinal tract, duplication of the colon and ileum, cervical vertebral anomalies, pulmonary hypoplasia, diaphragmatic defects, and bronchial atresia of right upper lobe with anomalous pulmonary venous drainage. Sequestration with anomalous pulmonary venous drainage has the characteristic appearance of a wedge shape along the right heart border resembling a scimitar on chest radiography ( Fig. 21-20 ).[113]

 
 

FIGURE 21-20  Chest radiograph demonstrating scimitar syndrome in a child with pulmonary sequestration.  (From Zitelli BJ, Davis HW: Atlas of Pediatric Physical Diagnosis, 4th ed. St. Louis, Mosby, 2002, p 134, with permission.)

 



Clinically, these two types of sequestrations present differently. Often intralobar sequestrations are asymptomatic and may not present until later childhood or adolescence.[114] Extralobar sequestrations usually present before the age of 2. Symptoms include cough, pneumonia, and failure to thrive. Plain radiographs will identify sequestrations but are unable to discern between intralobar and extralobar sequestrations. Angiography provides definitive diagnosis and identifies the arterial supply and venous drainage. MRI and angiography (MRA) may provide high-definition images and may replace the need for angiography.[115]

Surgical resection is the treatment of choice for symptomatic sequestration. Asymptomatic patients may also benefit from resection to prevent the occurrence of infection. Because of its separate pleural covering, removal of extralobar sequestrations can be performed without sacrificing surrounding lung tissue. Lobectomy, however, is usually required to resect intralobar sequestrations because of the intimate relationship with normal lung.[116]

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Congenital Lobar Emphysema

Congenital lobar emphysema is characterized by overinflation of a pulmonary lobe secondary to an in-utero bronchial ball-valve obstruction. The bronchial obstruction may occur because of intrinsic or extrinsic compression. Defects of the bronchial wall cause the intrinsic obstruction. This defect usually occurs in the upper lobes and is caused by a deficiency in the quantity or quality of the cartilage in the bronchial wall.[117] Extrinsic compression is usually from cardiac or vascular abnormalities. These abnormalities may include tetralogy of Fallot, patent ductus arteriosus, and vascular rings or slings. Other causes of extrinsic obstruction include intrathoracic masses (teratoma), enlarged lymph nodes, and bronchogenic cysts.[117] Congenital cardiac deformities occur in approximately 15% of patients with congenital lobar emphysema[118] ( Table 21-12 ).

TABLE 21-12   -- Anesthetic Management of Congenital Lobar Emphysema

  

 

Preoperative Evaluation

  

 

Signs and symptoms: respiratory distress, cyanosis

  

 

Computed tomography: rule out vascular rings and slings, intrathoracic masses

  

 

Chest radiography: evaluate size and location of emphysematous lobe

  

 

Laboratory: hematocrit, type and screen, oxygen saturation

  

 

Associated Anomalies

  

 

Cardiac: congenital heart disease 15%

  

 

Differential Diagnosis

  

 

Tension pneumothorax

  

 

Bronchial obstruction: foreign body, mucus plug

  

 

Anesthetic Management

  

 

Maintain spontaneous ventilation; consider lung isolation.

  

 

Avoid nitrous oxide.

 

 

Most cases of congenital lobar emphysema are diagnosed by 6 months of age. Thirty-three percent are diagnosed at birth and 50% are diagnosed by 1 month.[119] Respiratory distress and cyanosis are the most common presenting symptoms. Chest radiography reveals a large emphysematous lobe with ipsilateral atelectasis. These findings may be misinterpreted as a tension pneumothorax.[120] The differential diagnosis also includes bronchial obstruction from a foreign body or mucus plug. Accurate diagnosis is important because surgical management of a foreign body or mucus plug would be bronchoscopy, not thoracic surgery.

Anesthetic Management.

Definitive treatment for congenital lobar emphysema is lobectomy and is usually performed in patients with hypoxemia (Pao2 < 50 mm Hg), despite supplemental oxygen.[119] Rarely, cases have been described that have resolved spontaneously.[121] The primary concern during the anesthetic management of these patients is the deleterious effects of positive-pressure ventilation. Positive-pressure ventilation may expand the emphysematous lobe and cause respiratory and cardiovascular collapse. Maintaining spontaneous ventilation when feasible and employing lung isolation techniques may minimize this risk. Nitrous oxide is also contraindicated because of the risk of expansion of the emphysematous lobe.

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Congenital Diaphragmatic Hernia

Congenital diaphragmatic hernia (CDH) is characterized by a defect in the diaphragm that allows the herniation of abdominal contents into the thoracic cavity. The defect occurs on the left in about 85% of cases, and the most common form is the herniation through a left posterolateral defect or foramen of Bochdalek. Herniation through the anterior foramen of Morgagni occurs in only 2%. The incidence of CDH is approximately 1 in 3000 to 5000 births ( Fig. 21-21 ).[130] A typical chest radiographic finding of bowel content herniation into the left thorax is demonstrated in Figure 21-22 .

 
 

FIGURE 21-21  Congenital diaphragmatic hernia at postmortem showing obliteration of the left pleural cavity and severe compression of the right heart and lung.  (From Zitelli BJ, Davis HW: Atlas of Pediatric Physical Diagnosis, 4th ed. St. Louis, Mosby, 2002, p 563, with permission.)

 



 
 

FIGURE 21-22  Chest radiograph of congenital diaphragmatic hernia.  (From Zitelli BJ, Davis HW: Atlas of Pediatric Physical Diagnosis, 4th ed. St. Louis, Mosby, 2002, p 563, with permission.)

 



The severity of disease correlates with the timing of the diagnosis, the size of the defect, and the associated anomalies. Diagnosis prior to 25 weeks' gestation and large defects (lung to head ratio < 1 and liver herniation into the thorax) have been correlated with increased mortality. [123] [124] Associated anomalies can occur in as many as 40% to 50% of cases of CDH.[124] The most common of these involve the central nervous system and the cardiac system. Congenital cardiac defects may include ventricular outflow tract obstructions (hypoplastic left heart syndrome, tetralogy, coarctation) as well as atrial and ventricular septal defects.[125] Genitourinary, gastrointestinal, and chromosomal abnormalities also occur in 23%, 17%, and 10%, respectively ( Table 21-13 ). [127] [128]


TABLE 21-13   -- Anomalies Associated with Congenital Diaphragmatic Hernia

  

 

Central nervous system (meningomyelocele, hydrocephalus)

  

 

Congenital heart disease (atrial and ventricular septal defects, coarctation, tetralogy of Fallot)

  

 

Gastrointestinal (malrotation, atresia)

  

 

Genitourinary (hypospadias)

From David TJ, Illingworth CA: Diaphragmatic hernia in the southwest of England. J Med Genet 1976;13:253.

 

 

 

The failure of the fusion of the pleuroperitoneal membrane allows the abdominal contents to enter the thoracic cavity during the 10th week of gestation. This in-utero compression prevents lung development and causes alveolar and vascular hypoplasia. The degree of pulmonary hypoplasia depends on the size of the defect and the duration of the compression. Typically, both lungs are involved, even though the defect is unilateral. A controversial theory regarding the embryology of CDH states that the initial defect is primary pulmonary hypoplasia with secondary diaphragmatic defect.[128]Regardless of the etiology, the result is alveolar and vascular hypoplasia. Medial thickening occurs in the preacinar and intra-acinar arterioles, causing an increase in pulmonary vascular resistance, which ultimately contributes to persistent pulmonary hypertension. Pulmonary hypertension is a significant determinant of mortality in neonates with CDH.

Other entities may mimic CDH ( Table 21-14 ), such as a large CCAM near the diaphragm. Abdominal ultrasound or a CT can help determine the integrity of the diaphragm. Diaphragmatic eventration may occur secondary to birth trauma or anterior horn cell neuropathy (Werdnig-Hoffman disease) and can be diagnosed by demonstrating paradoxical diaphragmatic excursion on ultrasonography or fluoroscopy.[129]


TABLE 21-14   -- Differential Diagnosis of Congenital Diaphragmatic Hernia

  

 

Congenital cystic adenomatous malformation

  

 

Diaphragmatic eventration (trauma, Werdnig-Hoffman disease)

 

 

Medical Management.

The goal of medical management consists primarily of maintaining adequate oxygenation and ventilation, but most important, it is to avoid iatrogenic barotrauma from mechanical ventilation ( Table 21-15). At the time of delivery, the patient should be endotracheally intubated. An effort should be made to minimize bag-mask ventilation before intubation to reduce the risk of gastric expansion. Immediately after intubation, the gut should be decompressed and vascular access should be obtained. The umbilical vein and artery may be utilized or a right radial arterial catheter (for preductal arterial blood gas analysis) and a central venous catheter may be placed. Preductal and postductal measurement of oxygenation should be performed to assess the degree of right-to-left shunting, a surrogate marker of pulmonary hypertension. Shunting through the ductus arteriosus is suggested if the preductal Pao2 is 15 to 20 mm Hg higher than the postductal Pao2. Shunting at the level of the foramen ovale will decrease the predicted value of the preductal Pao2 and will not produce a gradient when compared with the postductal Pao2. Preductal saturation also reflects cerebral oxygenation. The ventilatory strategy should achieve a preductal oxygen saturation of greater than 85%, while maintaining a Paco2 of 45 to 55 mm Hg and a pH greater than 7.3, with peak inspiratory pressures less than or equal to 25 cm H2O.[130] Neonates who require peak pressures greater than 25 cm H2O for adequate oxygenation may need to be ventilated with high-frequency oscillatory ventilation (HFOV) to minimize the risk of ventilator-associated barotrauma.


TABLE 21-15   -- Medical Management of Congenital Diaphragmatic Hernia

  

 

Airway

  

 

Endotracheal intubation

  

 

Breathing

  

 

Decompress stomach.

  

 

Ventilation goal: positive inspiratory pressure < 25 cm H2O, preductal SaO2 > 85%, PaCO2 45-55 mm Hg pH > 7.3

  

 

Consider high-frequency oscillatory ventilation if unable to

  

 

oxygenate with pressures < 25 cm H2O.

  

 

Circulation

  

 

Cardiac echocardiography to:

  

 

Exclude congenital heart disease

  

 

Assess right ventricular function

  

 

Assess pulmonary hypertension

  

 

Assess right-to-left shunting at ductal level

 

 

Permissive hypercarbia was first proposed by Wung in 1985 for infants with persistent fetal circulation. In many centers this strategy has been adopted for neonates with CDH.[131] Hypercarbia and ductal shunting may be tolerated by the neonates with CDH, provided there is adequate right-sided heart function and systemic perfusion. Adequate right-sided heart function can be evaluated with echocardiography, and adequate systemic perfusion can be demonstrated with normal lactate levels, mixed venous saturation greater than 70%, and the absence of a metabolic acidosis. Patients with evidence of persistent pulmonary hypertension with elevated right ventricular pressures, or preductal oxygen saturation less than 85%, may require a trial of nitric oxide (iNO). Although there may be a response to iNO in neonates with CDH, there are no clear data that this impacts on survival.[132] Neonates with right ventricular dysfunction and low systemic pressures may require intravenous fluids and inotropic support. Predictors of outcome during the initial resuscitation are inexact. The inability to achieve a preductal Pao2 greater than 100 mm Hg predicted 100% mortality in one study.[133] Apgar scores and birth weight have also been described to predict mortality in neonates with CDH.[134]

The benefit of extracorporeal membrane oxygenation (ECMO) on the morbidity and mortality of CDH is controversial. Some centers reported significant improvement in survival with the introduction of ECMO.[135] This has to be tempered with the fact that some centers have experienced the same survival statistics without the use of ECMO.[136] There is also significant morbidity associated with the use of ECMO. Anticoagulation with heparin to prevent clot formation in the ECMO circuit and platelet activation and consumption increase the risk of bleeding. Bleeding may cause significant morbidity if this occurs in the central nervous system, and bleeding may complicate attempts at surgical correction while on ECMO. Inclusion criteria for ECMO include gestational age greater 34 weeks, weight greater than 2 kg, presence of reversible disease, and predicted mortality of greater than 80%. Neonates with an oxygenation index (OI = Fio2 × mean airway pressure × 100/Pao2) greater than 40 to 50 may represent those at greatest risk (> 80%) of mortality. Intraventricular hemorrhage more than grade II or those with another life-threatening congenital anomaly should be excluded from ECMO.[137] ECMO is considered in neonates with progressive hypoxia, hypercarbia, and persistent pulmonary hypertension who have failed other attempts at medical correction, including iNO, inotropic support, or opening the ductus with prostaglandin E1.[130] A review of all of the published data has indicated that there may be a short-term benefit with the use of ECMO but there may not be a long-term benefit because of the associated morbidity.[138]

Surgical Management.

In the past it was believed that CDH represented a neonatal emergency requiring immediate surgical decompression of the thorax. Postoperatively, patients experienced a “honeymoon” period of brief improved oxygenation. This was soon followed by worsening hypoxia secondary to increased pulmonary vascular resistance and increased right-to-left shunting.[139] The poor outcomes with immediate repair raised the question of whether these patients should be stabilized preoperatively before surgical repair. To date there are no clear data to support delayed repair over early surgical intervention. A prospective randomized trial evaluated the importance of timing on survival and incidence of ECMO between early (6 hours) versus late (96+ hours) surgery and found no difference between the groups.[139a] All of the existing published data were reanalyzed in a Cochrane Database Systematic review in 2003 and again there was no clear advantage demonstrated with delayed surgical repair after medical stabilization.[139b]

Most often the surgical approach is through a subcostal incision. The majority of the repairs take place through a left-sided incision. After the abdominal contents are removed from the thoracic cavity, the bowel is eviscerated from the abdominal cavity to expose the defect. The diaphragmatic defect may be closed primarily or with a Gore-Tex patch. After the abdominal contents are replaced, there may be a significant elevation in abdominal pressure with surgical wound closure.[139] A silo may be required to gradually reintroduce the abdominal contents.

Fetal surgery for CDH was initiated after animal models demonstrated a reversal of lung hypoplasia when diaphragmatic hernias were corrected in utero.[140] Fetal repair in humans was first described in 1990.[141] Overall success of the open fetal approach was limited by maternal morbidity, which included premature rupture of membranes and preterm labor. Fetal intervention was only considered for those fetuses at highest risk of mortality. Research during the late 1970s introduced the concept of tracheal occlusion to reverse the lung pathophysiology from diaphragmatic herniation. This concept resulted in a fetal strategy in humans to temporarily occlude the trachea in utero until birth (PLUG—Plug the Lung Until it Grows). [145] [146] [147] However, this strategy and variations of this strategy have not demonstrated any survival advantage over standard postnatal medical management.[145]

Anesthetic Management ( Table 21-16 ).

Preoperative assessment of the neonate with CDH should begin with an evaluation of the degree of respiratory compromise and pulmonary hypertension. Attention to the type of ventilatory support and associated blood gas values is important. Consideration should be given to using the newborn intensive care unit ventilator or HFOV if there is any concern about achieving adequate ventilation. Cardiovascular evaluation should focus on identifying any congenital heart defects and the degree of right-to-left shunting, pulmonary hypertension, and right ventricular performance. Severe pulmonary hypertension can result in severe hypoxia, decreased cardiac output, and metabolic acidosis. This information can be provided from echocardiography and preductal and postductal blood gas analysis. Associated neurologic findings include MMC and hydrocephalus. Premature neonates are at risk for the development of intraventricular hemorrhages. This will exclude them from ECMO because of the anticoagulation. Head ultrasounds are routinely performed in this population and should be performed before ECMO cannulation. Hematologic issues require maintaining an adequate hemoglobin (approximately 12 mg/dL) and checking for vitamin K administration at birth. Some of these patients may be on diuretics. An electrolyte panel should be performed to evaluate for hypokalemia. The neonate will already have a nasogastric or orogastric tube in place. If not, this should be placed to decompress the stomach.


TABLE 21-16   -- Anesthetic Management of Congenital Diaphragmatic Hernia

  

 

Preoperative Evaluation

  

 

Place oral or nasogastric tube.

  

 

Evaluate severity of pulmonary hypoplasia and pulmonary hypertension.

  

 

Ventilation: what ventilation requirements exist? Preductal saturation < 85%? Right ventricular strain on echocardiography?

  

 

Echocardiography: to evaluate right ventricular function, right-to-left shunting, and pulmonary hypertension

  

 

Chest radiography: evaluate size of hernia

  

 

Laboratory: arterial blood gas analysis, hematocrit, type and screen, preductal and postductal oxygen saturation, vitamin K given? Hypokalemia from diuretics?

  

 

Anesthetic Management

  

 

Monitors: arterial catheter, preductal and postductal pulse oximeter, precordial on contralateral chest

  

 

Avoid nitrous oxide.

  

 

Decompress stomach.

  

 

Use endotracheal intubation.

  

 

Ventilation goal: positive inspiratory pressure < 25 cm H2O, preductal SaO2 > 85%, PaCO2 45-55 mm Hg, pH > 7.3

  

 

Maintain normothermia.

  

 

Administer bicarbonate to maintain normal pH.

  

 

Continue inhalational nitric oxide if used preoperatively.

  

 

Administer dextrose intravenous solution.

  

 

Opioid-based anesthetic; consider epidural analgesia.

  

 

Consider contralateral pneumothorax if clinical deterioration occurs.

 

 

Intraoperative management consists of first ensuring adequate room temperature and utilizing either warming lights or a forced warm air blanket to maintain normothermia. Induction of anesthesia has been described using both intravenous and inhalation techniques. Given the risk of aspiration and the resulting injury to already immature lungs, a rapid-sequence intubation may be preferred after the gastric tube is suctioned and the neonate is preoxygenated. If there appear to be any barriers to safe intubation such as a difficult airway, then an awake intubation may be safest. Positive-pressure mask ventilation should be minimized to prevent gaseous distention of the stomach.

In addition to the standard monitors, a preductal arterial catheter should be placed, but an umbilical artery catheter may also be used. Both preductal and postductal pulse oximeters should be placed, and a precordial stethoscope on the contralateral chest can be used to identify a pneumothorax. If central venous access is attempted, consideration should be given to avoid the internal jugular veins, because these may be future cannulation sites for ECMO.

The hallmark of medical management of these patients is to minimize the risk of iatrogenic ventilatory injury. Peak pressures should not exceed 25 to 30 cm H2O. An opioid-based anesthetic has been described and may minimize the surgical stress and pulmonary vascular lability.[146] Muscle relaxation is typically employed to facilitate surgical exposure and abdominal closure. Nitrous oxide is not used because of the risk of bowel distention. This could impair ventilation while the bowel is in the thoracic cavity and may impede abdominal closure once the abdominal contents are replaced in the abdominal cavity. Nitrous oxide can also accelerate the onset of a pneumothorax. Contralateral pneumothorax is a potential intraoperative complication and needs to be considered if there is an acute clinical deterioration. Pulmonary hypertension can be managed by maintaining a normal pH, Pao2, and Paco2 and minimizing hypothermia and surgical stress. Sodium bicarbonate may need to be administered to treat acidosis and/or to alkalinize the blood and thereby treat pulmonary hypertension. If iNO is used preoperatively, it should be continued in the operating room. Epidural analgesia has been described in the anesthetic management of neonates with CDH. This option for intraoperative and postoperative management may best be suited in those with smaller defects who likely will not require prolonged ventilation or anticoagulation for ECMO.[147]

Despite the advances in the medical and surgical care of fetuses and neonates with CDH, the mortality still remains significant. Delayed surgery, HFOV, iNO, ECMO, and fetoscopic surgery have not been proven to significantly improve the overall mortality. A recent outcome study demonstrated a mortality of 62% that did not vary statistically despite the introduction of ECMO, iNO, surfactant, and delayed surgery.[140] The concept of permissive hypercarbia and gentle ventilation may have had the most significant impact on survival in neonates with CDH. Some centers have observed an improvement in survival from 50% to 75% to 90%, with the introduction of this ventilation strategy. [131] [151]

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Tracheoesophageal Fistula

Tracheoesophageal fistula (TEF) is a generalized term for a condition characterized by esophageal atresia with or without a communication (fistula) between the esophagus and the trachea. There are several anatomic variations that cannot all be described by one definition. Esophageal atresia is the most common esophageal anomaly, occurring in approximately 1 in 2000 to 1 in 5000 live births. Prematurity and polyhydramnios are associated with TEF. The inability to swallow amniotic fluid in utero results in polyhydramnios. Associated anomalies occur in 30% to 50%. Mortality varies from 5% to 60%. Recent analysis indicates a survival rate of approximately 95%.[149] Morbidity and mortality are increased in infants with severe coexisting congenital anomalies and prematurity. Cardiac and pulmonary anomalies appear to be the most significant with those children, with severe congenital cardiac anomalies and respiratory complications requiring mechanical ventilation at highest risk.

Classification.

Gross created a classification system in 1953.[150] This classification outlines five types of esophageal atresia with and without fistula (types A to F) ( Fig. 21-23 )

 
 

FIGURE 21-23  Gross's classification of esophageal atresia without fistula (A), esophageal atresia with proximal fistula (B), esophageal atresia with distal fistula (C), esophageal atresia with proximal and distal fistula (D), tracheoesophageal fistula without atresia (E), and esophageal stenosis (F).  (From Ulma G, Geiduschek JM, Zimmerman AA, Morray JP: Anesthesia for thoracic surgery. In Gregory GA [ed]: Pediatric Anesthesia, 4th ed. Philadelphia, Churchill Livingstone, 2002, p 440, with permission.)

 

 

 

  

 

A—Esophageal atresia without fistula

  

 

B—Esophageal atresia with communication of the upper esophageal segment to the trachea

  

 

C—Esophageal atresia with communication of the lower esophageal segment to the trachea

  

 

D—Esophageal atresia with both upper and lower esophageal segments communicating with the trachea

  

 

E—No esophageal atresia but there is a tracheoesophageal fistula

  

 

F—Esophageal stenois without fistula

Type C is the most common, occurring in approximately 85% of TEFs.

Infants with esophageal atresia are unable to manage their oral secretions and present with excessive oral and nasal salivation, choking, coughing, and regurgitation with first feeding. The tracheoesophageal communication results in gastric dilatation and aspiration of gastric contents. Pneumonia (of the right upper lung) and pneumonitis can occur, as well as respiratory compromise from gastric dilatation. These patients can present with cyanosis and apnea. Tracheomalacia can also occur, resulting in a barking cough.[151]

Associated Anomalies.

Associated anomalies occur in 30% to 50% of patients with TEF. A common association is the VATER complex.[152] This mnemonic leaves out cardiac anomalies. A more appropriate complex name would be VACTERL.

Vertebral anomalies

Anorectal/intestinal anomalies (atresia)

Cardiac anomalies: incidence of 14% to 24%. The most common lesions are ventricular septal defect, coarctation, tetralogy of Fallot, and atrial septal defect.

Tracheoesophageal fistula

Esophageal atresia

Renal and radial anomalies

Limb

Diagnosis of TEF is based on clinical signs and symptoms. The inability to pass an orogastric catheter into the stomach and a chest radiograph showing the catheter in the proximal esophageal pouch confirms the diagnosis. Gastric air may or may not be present, depending on the anatomy of the lesion.

Surgical Management.

Surgical management consists of identifying and ligating the TEF and then anastomosing the atretic esophagus. If the gap between the esophageal segments is large enough to prevent a primary anastomosis, a staged repair is performed. This may consist of interposing a segment of colon or upward movement of the stomach.[153]

The primary goal in the preoperative period is to prevent pulmonary complications. These infants should be kept NPO. Prone or lateral positioning with the head of the bed at 30 degrees may reduce the risk of aspiration. A nasoesophageal catheter should be attached to suction. Pneumonia should be treated, and a gastrostomy to vent the stomach should only be considered in the infant with immature lungs or respiratory distress syndrome. Intubation is avoided, if possible, to minimize gastric distention. Metabolic acidosis should be treated before surgical repair. Lastly, associated anomalies need to be identified and evaluated. This evaluation may include echocardiography, abdominal ultrasound, and radiographs of the spine and extremities. These infants may already have central intravenous access for total parenteral nutrition. Routine preoperative blood work should include a hemoglobin, type and crossmatch, and glucose determination.

Anesthetic Management.

The principal issues that dictate anesthetic management include the risk of aspiration, negative effects of positive-pressure ventilation before ligation of the fistula, management of associated anomalies, including prematurity, and surgical technique (thoracotomy) ( Table 21-17 ).


TABLE 21-17   -- Anesthetic Management of Tracheoesophageal Fistula

  

 

Tracheoesophageal Fistula

  

 

Signs and symptoms: respiratory distress, coughing, choking, unable to pass oral catheter into stomach; pneumonia, pneumonitis

  

 

Radiographs of spine and upper extremities: evaluate vertebral and radial anomalies

  

 

Chest radiography: radiopaque oral catheter in proximal esophagus, gastric gas pattern

  

 

Echocardiography: evaluate cardiac defects

  

 

Imaging: renal ultrasound

  

 

Laboratory: hematocrit, type and screen, oxygen saturation, glucose

  

 

Associated Anomalies

  

 

VACTER association:

  

 

Vertebral anomalies

  

 

Anal atresia

  

 

Cardiac defects

  

 

Tracheoesophageal fistula

  

 

Radial/renal anomalies

  

 

Anesthetic Management

  

 

Preoperative management: oral esophageal suctioning, maintain NPO, gastrostomy tube for respiratory distress syndrome or immature lungs; may require endotracheal intubation; treat metabolic acidosis

  

 

Monitoring: arterial catheter

  

 

Induction: maintain spontaneous ventilation until fistula is isolated (mainstem intubation, bronchial blocker)

  

 

Complications

  

 

Obstruction of endotracheal from secretions, purulent drainage, blood, or mechanical bend

  

 

Atelectasis

 

 

Standard monitoring includes electrocardiography, pulse oximetry, noninvasive blood pressure, temperature, and capnography. An arterial catheter may be beneficial in the infant with significant pulmonary disease and/or cardiac disease. An esophageal stethoscope placed over the left chest will facilitate the detection of endotracheal tube migration into the right mainstem bronchus. Positioning for definitive surgical repair requires left lateral positioning for a right thoracotomy.

Aspiration and gastric distention with respiratory embarrassment are the initial concerns during induction of anesthesia. In medically unstable infants, a gastrostomy may be required before induction to relieve gastric distention, and an awake intubation may be considered. In patients who are stable, an intravenous or mask induction can be performed. Positive-pressure ventilation should be minimized to small tidal volumes, or spontaneous ventilation should be maintained if possible. Presence of a gastrostomy may slow mask inductions, requiring transient partial clamping of the tube. Endotracheal tube positioning is important to minimize gastric distention. Usually the fistula inserts along the posterior aspect of the trachea just above the carina. Proper positioning can be achieved by purposefully placing the endotracheal tube into the right mainstem bronchus and then slowly withdrawing until breath sounds are just heard at the left axillae. Placement can also be confirmed with a fiberoptic bronchoscope. Other options for minimizing gastric distention include placement of a balloon-tipped catheter (Fogarty, 2 to 3 Fr) into the fistula, either from above (through the trachea, next to endotracheal tube) or from below via the gastrostomy (5 Fr). The Fogarty catheter can be placed from above during bronchoscopy by the surgeon to evaluate the location of the fistula and other anatomic anomalies.[154] Occasionally massive gastric distention can occur, resulting in respiratory compromise and cardiovascular collapse, requiring an emergency gastrostomy. The risk of gastric distention increases with the size of the fistula. Muscle relaxation has been described successfully in the anesthetic management of TEF in those with smaller fistulas.[155] Fistulas that are large or are located near the carina may benefit from isolation with a Fogarty catheter.

Once the fistula is isolated, muscle relaxation and controlled ventilation can be used. A frequently occurring problem is hypoxemia. Hypoxemia can occur secondary to right mainstem intubation, ETT obstruction from secretions, drainage from lung infections, and bleeding. In addition, kinking of the bronchus or even the trachea by surgical manipulation can occur, as well as atelectasis of the retracted lung during surgical exposure. Recruitment maneuvers to reexpand the lungs may be necessary to improve intraoperative oxygenation. A forced air heating blanket is used to prevent hypothermia. Dextrose-containing intravenous solution is provided to prevent hypoglycemia. Extubation at the end of surgery may minimize manipulation of the anastomosis from the ETT, but respiratory distress syndrome or pneumonias may require prolonged intubation. Intravenous opioids are effective for intraoperative and postoperative pain management, but regional anesthesia is advantageous to avoid opioids and the risk of postoperative respiratory depression. Providing there are no significant vertebral anomalies, a caudal catheter can be placed and threaded to the thoracic region. The catheter's position can be confirmed by injecting low ionic strength contrast medium (0.5 mL Omnipaque 180).[156]

Postoperative Considerations.

Postoperative concerns include the management of an orogastric tube that will be marked to the level of the esophageal anastomosis. There should be no suctioning beyond this point to prevent disruption of the anastomosis. Also, head extension can put tension on the anastomosis and should be minimized.

Postoperative complications include anastomotic leak, tracheomalacia or bronchomalacia, stricture, pneumonia, and pneumothorax.[157] Complications can also occur secondary to underlying medical conditions and result in significant morbidity and mortality. All patients who have undergone TEF repair are considered to have esophageal dysmotility and gastroesophageal reflux.

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ABDOMINAL WALL DEFECTS

Omphalocele, gastroschisis, and bladder and cloacal exstrophy are various forms of congenital abdominal wall defects. Congenital abdominal wall defects present a peculiar challenge to neonatologists, surgeons, and anesthesiologists. The optimal management of neonates with anterior wall defects depends on the careful prenatal assessment of these patients, as well as the experience and knowledge of the defect's natural history. A multidisciplinary approach can improve neonatal outcome.

Omphalocele and Gastroschisis

Gastroschisis and omphalocele are congenital defects of the anterior abdominal wall that differ in many aspects. The diagnostic distribution between the two entities is important because of the associated abnormalities. Omphaloceles have a much higher incidence of associated abnormalities ( Fig. 21-24 ). Omphaloceles have associated cardiac, neurologic, genitourinary, skeletal, or chromosomal abnormalities in two thirds of patients. In addition, gastrointestinal anomalies are frequent. Prematurity occurs in 60% of patients with abdominal wall defects ( Table 21-18 ).

 
 

FIGURE 21-24  A, Infant with an omphalocele. Note how abdominal wall contents are enclosed in a sac-like structure that is related to the umbilical cord. B, Infant with gastroschisis. Note the thickened abdominal viscera and the position of the umbilical cord.  (From Keljo DJ, Gariepy CE: Anatomy, histology, embryology, and developmental anomalies of the small and large intestine. In Feldman M, Friedman LS, Sleisenger MH [eds]: Sleisenger & Fordtran's Gastrointestinal and Liver Disease, 7th ed, 2002, p 1651, with permission.)

 

 

 


TABLE 21-18   -- Comparison of Gastroschisis and Omphalocele

 

Gastroschisis

Omphalocele

Incidence

1: 10,000

1: 4,000–7,000

 

Intact umbilical cord and evisceration of bowel through a defect in the abdominal wall right of the cord

Herniation of bowel and liver thorough umbilical wall covered by membranes unless ruptured liver and other organs

Sac

No membrane covering (sac absent)

Present

Associated Organs

No

 

Associated Anomalies

Intestinal atresia 25%

Chromosomal anomalies

 

Cryptorchidism 31%

Trisomy 18, 13, 15, and 21

 

 

Beckwith-Wiedemann syndrome

 

 

Pentalogy of Cantrell

 

 

Prune belly syndrome

Maternal Age

< 25 yr

Older

Smoking and Alcohol Use

Yes

No

Teratogens

Acetaminophen, aspirin, pseudoephedrine use in pregnancy: Yes

No

Congenital Heart Disease

12%

24%

Prematurity

40%-67%

10%-23%

 


Anatomy and Embryology.

These defects are thought to result from an imbalance between cell proliferation and apoptotic cell death. The apoptotic cell death in the region of the umbilical ring results in relative growth delay in that region, whereas rapid development of the foregut causes herniation of the bowel through the umbilical stalk.

In gastroschisis, the abdominal wall forms in a dysplastic fashion owing to decreased cell deposition or vascular abnormality. This results in the formation of a thin area in the abdominal wall to the right of the umbilicus. This area ruptures from increased intra-abdominal pressure. Another explanation is that gastroschisis represents a rupture of the hernia of the umbilical cord that occurs at the weakest point of the hernia sac, the site where the right umbilical vein involutes. Patients with omphalocele present with a central defect of the umbilical lining, and the abdominal contents are contained within a sac.[158]

Clinical Management.

Prognosis for the infant with gastroschisis is determined by the condition of exteriorized bowel. Elective cesarean section, especially for gastroschisis, was advocated to prevent bowel trauma. However, data from 15 publications dealing with the mode of delivery were analyzed and it was concluded that cesarean section had no distinct advantage over vaginal delivery with regard to neonatal outcome.[158]Bowel damage has been attributed to exposure to amniotic fluid and constriction at the abdominal wall defect. Preterm delivery may be advisable for patients with increasing bowel distention. The risk of prematurity should be weighed against the potential advantage of preterm delivery to salvage the bowel.

Surgical Repair.

Initial management for neonates with abdominal wall defects is focused on newborn resuscitation, fluid and electrolyte maintenance, temperature homeostasis, and protection of the eviscerated organs. After the infant is stabilized, which includes administration of broad-spectrum antibiotics, protection of the eviscerated organs with wrapped fluids, impermeable dressings, and intravenous hydration, the neonate is brought to the operating room for either a primary closure or a staged repair.

Anesthesia is induced with intravenous agents, and the patient's trachea is intubated. The major intraoperative concerns include (1) fluid requirements, (2) temperature regulation, (3) cardiovascular stability, and (4) increased intra-abdominal pressure. Large third space losses can be associated with anterior wall defects, in both the preoperative and intraoperative period. Hypothermia is a frequent complication and is multifactorial. The infant's ongoing fluid requirements, increased evaporative water loss, and increased radiant heat loss are all major contributing factors. Cardiovascular instability can result from both the ongoing water and heat losses, as well as the instability associated with the normal changes that occur with the transition from a fetal- to an adult-type circulation. In addition, cardiovascular compromise can occur from the increase in intra-abdominal pressure that occurs with the reduction of the eviscerated organs.

The surgical approach to treatment involves decompressing the intestines, nasogastric suction, and anorectal irrigation. The goal of surgical management is reduction of abdominal contents and the approximation of the fascial edges and skin coverage. Primary closure is attempted if abdominal pressure does not impair ventilation, venous return, cardiac output, or perfusion to the gut, kidneys, and lower extremities. Because the reduction of the intestinal contents can create a high increased intra-abdominal pressure, compromise to the organs, as well as compromise of the inferior vena cava, blood return can occur. Monitoring of gastric pressure, bladder pressure, and arterial venous pressure has been advocated. [162] [163] If primary repair is not feasible, then a staged repair with a silo is placed. A prosthetic silo is sutured to the fascial edges of the defect, and in days to weeks the abdominal contents are reduced back into the abdomen. At completion, the silo is removed and the ventral hernia or abdominal wall defect is repaired. In the postoperative period the major concerns center on nutrition, sepsis, and intestinal obstruction.

Anesthetic management of patients with abdominal wall defects involves the use of intravenous and/or inhalational anesthetic agents. Increased intra-abdominal pressure can result in reduced drug clearance; consequently, infusions of fentanyl and sufentanil can lead to drug accumulation and prolonged drug effect. Remifentanil, an opioid that is metabolized by plasma and tissue esterases and has an ultrashort duration of action, can be an ideal anesthetic agent for neonates. Muscle relaxants should be used to help facilitate abdominal closure. In those patients in whom primary closure cannot be achieved, postoperative ventilation may be necessary. During abdominal closure monitoring of the patient's airway pressure and blood pressure help to determine whether a primary repair or staged repair is necessary. In addition, central venous pressure monitoring can also be used to detect caval compression and increased intra-abdominal pressure.

Postoperative management is a function of the surgical procedure and any associated congenital abnormality. In infants with large intraoperative fluid requirements or infants suspected of having elevated intra-abdominal pressures, mechanical ventilation should continue until diuresis has occurred or until the increased intra-abdominal pressure resolves.

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Prune Belly Syndrome

Prune belly syndrome (PBS, triad syndrome, Eagle-Barrett syndrome, abdominal muscular deficiency) presents with a lax, wrinkled abdominal wall.[161] PBS is a specific constellation of anomalies that involve an abdominal wall deficient in muscular tissue, dilated urinary tracts, bilateral cryptorchidism, pulmonary hypoplasia due to in-utero impaired drainage of the bladder and oligohydramnios, gastrointestinal abnormalities, and orthopedic (musculoskeletal) disorders (congenital dislocation of the hip, scoliosis, pectus excavatum, clubfeet, congenital muscular torticollis, renal osteodystrophy).[162]The pathogenesis of PBS arises from the effects of intrauterine urethral obstruction associated with olighydramnios.[163] Oligohydramnios produces limited intrauterine space leading to fetal compression and resultant deformities. Clinically, patients with PBS vary widely. They can have significant respiratory compromise secondary to pulmonary hypoplasia and a decreased ability to cough. There is evidence that they can also develop restrictive lung disease secondary to the absence of abdominal musculature.[164] Because of these defects, they may have recurrent respiratory tract infections and may be more prone to postoperative respiratory complications. [168] [169] In severe forms death occurs in the neonatal period. Some patients may have no pulmonary hypoplasia but significant renal involvement and failure to thrive. Other patients may have an abnormally appearing urinary tract but normal renal function. Anesthetic management is determined by the patient's underlying pulmonary and renal status.

In patients with impaired renal function, selection of anesthetic agents is important. Although renal insufficiency has no effect on the choice of inhaled anesthetic agents, renal insufficiency can alter a patient's response to muscle relaxants and intravenous opioids. The kidneys have a minor role in the elimination of most opioids. Fentanyl has been administered to anephric patients without untoward effects. Alfentanil kinetics are variable in patients with renal failure.[167]

Morphine kinetics are unchanged in patients with renal failure; however, its metabolites, morphine-3-glucuronide and morphine-6-glucuronide, are significantly prolonged. Because the 6-glucuronide is pharmacologically active, it can lead to respiratory depression. Meperidine is mainly metabolized by the liver, but its principal metabolite, normeperidine, is pharmacologically active, causes CNS excitability (tremors, myoclonus, and seizures), and is excreted by the kidney. The elimination half-life is double in patients with renal failure. Although renal excretion of meperidine plays a minor role in adults, Chan and colleagues noted that patients with renal disease had higher plasma concentrations, longer elimination half-lives, decreased protein binding, and large volumes of distribution.[168]

Neuromuscular blocking agents are generally excreted in the urine and bile. In patients with renal failure, the sensitivity of the neuromuscular junction does not appear to be affected. Atracurium and cisatracurium, which undergo Hoffman elimination and enzymatic hydrolysis, are not affected by patients with renal disease. Vecuronium and rocuronium clearance can be prolonged in patients with renal failure. In patients with renal failure and low levels of plasma pseudocholinesterase, mivacurium administration may result in a prolonged effect. Pancuronium elimination, half-life, and duration of action are also prolonged in patients with renal disease.

The depolarizing drug succinylcholine is relatively contraindicated in patients with renal failure. Because serum potassium level increases in patients after its administration, acute life-threatening hyperkalemia can occur in patients with an elevated serum potassium concentration.

The use of sevoflurane in patients with renal failure does not appear to be unsafe. Sevoflurane is metabolized in vivo to inorganic fluoride and hexafluoroisopropanol, whereas in vitro sevoflurane is degraded by soda lime or Baralyme to compound A. Both intravenous fluoride levels and compound A have been associated with nephrotoxicity.[169] However, nephrotoxicity does not appear to occur in humans.[170] Reasons for this lack of nephrotoxicity may be related to sevoflurane's low solubility, its rapid elimination, and the small amount of intrarenal metabolism that sevoflurane undergoes.[171]Compound A is a product of sevoflurane degradation produced by alkaline hydrolysis in the presence of soda lime or Baralyme. Although compound A has produced histologic changes in rats, a nephrotoxic effect of compound A in humans is lacking. Although preexisting renal insufficiency is a risk factor for postoperative renal dysfunction, neither high-flow nor low-flow sevoflurane anesthesia in patients with preexisting renal disease appears to alter renal function compared with isoflurane. [175] [176]

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Bladder and Cloacal Exstrophy

Bladder and cloacal exstrophy are rare but devastating anomalies. Bladder exstrophy is a developmental defect seen in 1 in 40,000 live births, whereas cloacal exstrophy is found in about 1 in 200,000 births.

Embryology.

Bladder exstrophy is a defect of the caudal fold of the anterior abdominal wall. It results from persistence of the cloacal membrane, preventing cephalad migration of the mesoderm to the midline during development. When the cloacal membrane eventually degenerates, it leaves behind a midline defect.

A small defect may cause epispadias alone, whereas a large defect leads to exposure of the posterior bladder wall.[174] Classic exstrophy is characterized by wide pubic separation and an exposed bladder. Cloacal exstrophy involves the urinary and gastrointestinal tract. OEIS refers to the association of bladder exstrophy with omphalocele, exstrophy of the bladder, imperforate anus, and spinal defects such as myelomeningocele.[175] Diastasis of the pubis and absence of the genitalia are frequent findings in patients with cloacal exstrophy, neural tube defects are present in 50% of infants, and congenital short bowel syndromes occur in 20% ( Fig. 21-25 ).[176]

 
 

FIGURE 21-25  Cloacal exstrophy. Female newborn showing omphalocele, prolapsed ileocecal valve, and symmetrical bladder halves.  (From Gearhart JP: Exstrophy, epispadias, and other bladder anomalies. In Walsh PC [ed]: Campbell's Urology, 8th ed. Philadelphia, WB Saunders, 2002, p 2177.)

 



Diagnosis.

Prenatal sonographic diagnosis reveals absence of the bladder as well as associated genitourinary anomalies.[177] Cloacal exstrophy has been identified due to associated neural tube defects, omphalocele, or splaying of the pubic rami. Prenatal diagnosis of bladder or cloacal exstrophy should be followed by a careful search for other chromosomal and structural anomalies. Parental counseling by a multidisciplinary team should address issues of continence and possible sex reassignment.

Treatment.

Reconstruction involves several surgical procedures. These include urologic and orthopedic surgeries. A three-stage approach is commonly used to repair the exstrophy complex. The first procedure is performed in the neonatal period and involves bladder closure, pubic symphysis approximation, and abdominal wall closure. The second-stage procedure later in infancy involves epispadias repair. The final procedure involves bladder neck reconstruction and is generally performed at the age when toilet training is begun.[178] Osteotomies are performed to allow approximation of the pubic symphysis to facilitate midline repair. This is followed by pelvic stabilization with traction and external fixation or with plate fixation.

Anesthetic Considerations.

Bladder and cloacal exstrophy repair need to be addressed at birth. The newborn will undergo the initial repair, and anesthetic considerations for the care of the newborn should be observed ( Table 21-19 ). Regional anesthesia can be utilized for intraoperative and postoperative pain management with a single shot caudal with injection of local anesthetic (bupivacaine 0.125% or ropivacaine 0.1%) with Duramorph (20 μg/kg). A catheter threaded to the lumbar level is another option for continuous epidural analgesia. A combined general and regional technique allows for the use of fewer inhalational agents and early extubation of the neonate. With the use of epidural narcotics the neonate needs to undergo recovery in a monitored environment. Spina bifida associated with cloacal exstrophy may be a contraindication for regional techniques.[179] Latex precautions should be observed in this patient population because 75% of children with bladder exstrophy are sensitized to natural rubber latex and develop a latex allergy. [183] [184]


TABLE 21-19   -- Anesthetic Considerations for Bladder and Cloacal Exstrophy

  

 

Care of the newborn

  

 

Prevention of heat loss: fluid warmers, forced air blankets

  

 

Glucose management: check blood glucose level

  

 

Fluid management for third space losses

  

 

Evaluation of other associated congenital anomalies

  

 

Regional anesthesia

  

 

Latex precautions

 

 

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

Fleisher: Anesthesia and Uncommon Diseases, 5th ed.

Copyright © 2005 Saunders, An Imprint of Elsevier

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