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

 

PART THREE – Clinical Management of Special Surgical Problems

Chapter 20 – Anesthesia for Pediatric Plastic Surgery

Jayant K. Deshpande,Kevin Kelly,
Matthew B. Baker

  

 

Craniofacial Reconstruction, 723

  

 

Preoperative Management, 723

  

 

Induction of Anesthesia, 728

  

 

Intraoperative Management, 729

  

 

Postoperative Management, 732

  

 

External Fixation and Osseous Distraction Devices,732

  

 

Special Considerations for Pierre Robin Sequence,732

  

 

Cleft Lip and Cleft Palate Repair, 733

  

 

Summary, 735

In this chapter, the anesthetic considerations of the most common plastic surgical procedures are summarized. Common surgical problems with practical suggestions and discussions of anesthetic technique and anesthetic concerns are offered.

Plastic surgical procedures range from minor cosmetic repairs to extensive major reconstructive surgery. Frequently, reconstructive surgery is a staged procedure. Consequently, these patients make numerous visits to the operating room. The anesthesiologist should visit the patient preoperatively to assess the child's fears and anxieties. In addition, the anesthesiologist should provide reassurance and, when necessary to assessing the child, provide adequate premedication (see Chapters 7 and 10 , Psychological Aspects of Pediatric Anesthesia and Induction of Anesthesia and Maintenance of the Airway).

▪ CRANIOFACIAL RECONSTRUCTION

Children who undergo craniofacial reconstruction may have disorders ranging from synostosis of a single cranial suture with resultant abnormal skull formation to congenital anomalies, such as Apert's, Crouzon's, and other syndromes, which may involve multiple skull sutures and other facial anatomic anomalies ( Box 20-1 ). Despite the sometimes significant craniofacial deformations present in these children, their underlying neurodevelopmental status and general health are often quite normal (Figs. 20-1 to 20-4 [1] [2] [3] [4]. The goal of surgical intervention is to improve the anatomy and geometry of the cranium and face and thereby permit normal brain growth and to minimize subsequent abnormal psychosocial development. Since the 1990s, surgical and anesthetic techniques have evolved sufficiently to allow repair to be performed during late infancy or early toddlerhood. Early repair has resulted in excellent surgical outcomes and possibly psychosocial development of the child.

BOX 20-1 

Partial List of Syndromes and Conditions Commonly Associated With Craniofacial Anomalies

  

 

Apert's syndrome

  

 

Cleidocranial dysostosis

  

 

Congenital craniosynostosis

  

 

Craniofacial hemangioma/other vascular malformations

  

 

Crouzon's syndrome

  

 

Goldenhar's syndrome

  

 

Hemifacial microsomia

  

 

Mandibular dysostosis

  

 

Maxillofacial deformities

  

 

Neurofibromatosis

  

 

Pfeiffer's syndrome

  

 

Plagiocephaly

  

 

Treacher Collins syndrome

 
 

FIGURE 20-1  Cranium with normal sutures and skull bones.

 

 

 
 

FIGURE 20-2  Craniosynostosis results in abnormal skull growth with the deformity determined by which suture is prematurely fused. Skull growth is inhibited perpendicular to the fused suture. The dotted line represents the normal skull configuration. A, Unilateral fusion of the coronal suture producing a flattening of the affected side and contralateral frontal bossing. B, Bilateral coronal synostosis causing a widened foreshortened skull. C, Metopic craniosynostosis produces a triangularly shaped forehead. D, Sagittal synostosis causes an elongation and narrowing of the cranium.

 

 

 
 

FIGURE 20-3  These 3-DCT scans of a child's skull show the location of normal sutures. Concentric circles are imaging artifacts.

 

 

 

 

FIGURE 20-4  Six 3-DCT scans of the heads of children with cranial deformities. Concentric circles are imaging artifacts. A, Brachycephaly with bilateral coronal suture synostosis; B, plagiocephaly or unilateral coronal synostosis; C, scaphocephaly or sagittal suture synostosis; and D, trigonocephaly or metopic suture synostosis.

 

 

The perioperative care of children undergoing craniofacial reconstruction requires an informed and collaborative team of health care providers. Pediatric plastic surgeons and neurosurgeons work in tandem to remove and rearrange the skull deformity while avoiding potential trauma to the underlying brain, venous sinuses, and blood vessels. Specialists in cranio-oromaxillofacial surgery and otolaryngology often comprise active members of the team, particularly if reconstruction of the midface or jaw is required. Experienced anesthesiologists are crucial members of the team, as perioperative management requires balancing possible conflicting issues, such as brain protection and reducing cerebral edema while maintaining an adequate circulating blood volume ( Box 20-2 ). Timely postoperative care, including anticipating and preventing complications, requires that the pediatric intensivist and critical care nurses are familiar with the surgical and perioperative management plan. Children who have undergone plastic surgery of the head and neck often need speech therapy, physiotherapy, and possible psychological support after surgery. The child's primary care physician, along with the plastic surgeon, must know how to deal with these complex issues and how to act as the child's and family's advocate in order to coordinate the multiple care providers.

BOX 20-2 

Common Perianesthetic Challenges of Craniofacial Surgery

  

 

Difficult airway

  

 

Difficult to maintain patent airway during surgery

  

 

Field avoidance

  

 

Head position often 90 to 180 degrees away from anesthesiologist

  

 

Massive blood loss

  

 

Can approach or exceed 1 blood volume

  

 

Massive fluid shifts and difficult fluid management

  

 

As a result of considerable blood loss, and significant evaporative losses from exposed dura and brain during long procedure

  

 

Temperature control

  

 

Hypothermia likely because of exposed dura and brain during long procedure

  

 

Potential positional trauma from prolonged procedure

  

 

Precautions must be taken to prevent nerve and skin injury

  

 

Risk of air embolism from exposed skull and venous channels

  

 

Postoperative care issues

  

 

Including ongoing coagulopathy

  

 

Management of the difficult airway

  

 

Potential need for mechanical ventilation

  

 

Family support and care

▪ PREOPERATIVE MANAGEMENT

During the preoperative visit, the anesthesiologist should become familiar with the child's underlying pathophysiology, as well as the parents—expectations and anxieties and the child's personality (seeChapter 7 , Psychological Aspects of Pediatric Anesthesia). The history should provide information regarding current medications, allergies, asthma, recent upper respiratory tract infections, and previous anesthetic and surgical experiences. Difficult intubation is a major concern in these patients. The anesthesiologist should be aware that previous reconstructive surgery may have altered the airway anatomy dramatically (e.g., development of temporomandibular joint [TMJ] ankylosis). The presence of somnolence, nausea, vomiting, episodes of apnea or bradycardia, or cranial nerve dysfunction (especially visual disturbances) suggests increased intracranial pressure.

Fortunately, young children with craniosynostosis rarely develop intracranial pressure problems because the skull can expand in another direction during the postnatal period in order to compensate for the decreased growth perpendicular to the suture that is fused ( Heeckt et al., 1993 ; Siddiqi et al., 1995 ). This skull expansion does, however, add to the skull deformity. Hydrocephalus can be seen in children with cranial stenosis and should be treated prior to cranial reconstruction to avoid complications. If hydrocephalus is present and a history of seizures is documented, then blood levels of anticonvulsant should be determined proportionately. Some congenital syndromes may also be associated with anomalies of the heart or lungs; in these instances, details of any cardiopulmonary involvement must be elicited.

The physical examination includes evaluation of the patient's mental status and vital signs. Any signs and symptoms of increased intracranial pressure must be noted. Cushing's triad—apnea, bradycardia, and hypertension ( Cushing, 1902 )—is rarely present in these children, but “sundowning” (which means pressing on an open fontanel causes the gaze to fall) or wide sutures are not uncommon in children with elevated intracranial pressure (see Fig. 18-8 in Chapter 18 , Anesthesia for Neurosurgery). Preoperative neurologic deficits should be documented. The examination of airway patency is also extremely important. The child may have limited ability to open the mouth, and the pharynx may be difficult to visualize. Micrognathia, retrognathia, or mandibular hypoplasia, commonly associated with syndromes such as Pierre Robin, Treacher Collins, Beckwith-Wiedemann, or Crouzon's, can make intubation difficult. Patients who have long-standing upper airway obstruction because of choanal atresia, mandibular hypoplasia, or other causes may have chronic hypoventilation and hypoxia. Patients with craniofacial anomalies and associated hydrocephalus may experience episodes of apnea and recurrent hypoxia (Handler, 1985 ). Such situations can produce pulmonary hypertension and subsequently lead to cor pulmonale ( Rabinovitch, 1989 ; Rosen, 1996 ). The evaluation of these patients should include an electrocardiogram and, possibly, an echocardiogram.

Preoperative laboratory evaluation includes determination of hematocrit and hemoglobin concentrations and, if there has been significant vomiting, determination of electrolyte levels. A therapeutic drug level should be documented for any patient receiving anticonvulsants. The results of other studies, including chest radiographs, electrocardiograms, and electroencephalograms, must be reviewed. Finally, the anesthesiologist should confirm that at least one blood volume equivalent of packed red blood cells is available in the blood bank before surgery.

Oral medications can be continued (especially anticonvulsant medications) up to and including the morning of surgery. In patients not at risk for increased intracranial pressure or significant airway obstruction, an oral preoperative sedative, such as midazolam (0.25 to 0.5 mg/kg), may be useful to ease anxiety and increase the ease of inhalation induction.

Before formulating a plan for intraoperative care, the anesthesiologist should have a clear understanding of the surgical plan. The surgical team frequently includes both a neurosurgeon and a plastic and reconstructive (craniofacial) surgeon. The anesthesiologist must know the nature and extent of the surgical procedure planned and the position the patient will be in on the operating table. The anesthetic plan should incorporate the usual considerations for any anesthetic in a child and must allow for special concerns relevant to the condition (see later discussion). These patients usually do not have a concomitant disease, such as gastroesophageal reflux, and fast preoperatively for a sufficient duration (i.e., clear fluid up to 2 hours prior to anesthesia) so that induction of anesthesia can proceed routinely.

▪ INDUCTION OF ANESTHESIA

Anesthesia usually can be induced by inhalation of volatile agents. Sevoflurane has evolved to be the preferred agent because of its rapid uptake and its association with relatively few airway complications during induction (see Chapter 10 , Induction of Anesthesia). Two large-bore peripheral intravenous catheters and an arterial cannula are placed after anesthesia induction. Occasionally a central venous catheter may be needed if peripheral venous access is insufficient or if the child's hemodynamic status is tenuous. Muscle relaxants facilitate intubation. A preformed oral (RAE) tube or an armored (anode) tube of the appropriate size is inserted and secured with benzoin and tape. Alternatively, the surgeon may wire the endotracheal tube in place around the teeth or to the mandible or maxilla. Occasionally, nasotracheal tubes are required for the operative procedure. These tubes are often secured by placing a suture firmly around the wall of the endotracheal tube and into the nasal septum. After the position of the tube is verified, the child can be mechanically ventilated. The eyes must be lubricated and the eyelids taped shut or sutured closed by the surgeon. Alternatively, scleral shields may be placed in both eyes to provide protection without interfering in the surgical field of vision. In addition to arterial blood pressure, heart tones, breath sounds, pulse oximetry (Spo2), end-tidal carbon dioxide tension (PETCO2), urine output, and body temperature are continually monitored. In patients with preexisting increased intracranial pressure, anesthetic management is modified to preserve cerebral perfusion pressure (see Chapter 18 , Anesthesia for Neurosurgery).

Induction of anesthesia in patients with airway abnormalities presents some distinct difficulties. The anatomic defects can restrict mouth opening, distort pharyngeal and laryngeal anatomy, and hinder the placement and securing of the endotracheal tube. For these children, intravenous access must be established before induction. In the presence of significant airway abnormality, the fiberoptic bronchoscope can be an effective tool used to place an endotracheal tube even in small infants (see Chapter 10 , Induction of Anesthesia). In experienced hands, a Bullard laryngoscope (see Chapter 10 and Chapter 23 , Anesthesia for Otorhinolaryngology Surgery) is an alternative adjunct for difficult intubation. Rarely, one may need to perform awake intubation or tracheostomy under sedation and local anesthesia. Tracheostomy in infants, and particularly those with an abnormal airway, and without an endotracheal tube in place, is an extremely difficult procedure at best and should be attempted only by a surgical team with experience in performing tracheostomies in infants and children.

Craniofacial reconstructive procedures can be time consuming, lasting many hours; patients should be positioned on the operating room table with great care. Most commonly, the child is supine during the procedure with the head slightly elevated. The neck may be flexed in an extreme position to provide better access to the occiput while keeping the child supine. Eye protection can be provided by placement of scleral shields. Additional protective padding should be used at pressure points and sensitive areas, including eyes, forehead, elbows, genitalia, and knees. In some cases, it may be necessary to place the child in a prone or lateral position. In these instances, the anesthesiologist should take additional caution to ensure that the airway is secure, the eyes are appropriately protected, and the pressure points are well padded. Rolls of bed sheets or other padding are used to distribute the pressure over the shoulders and hips to ensure good excursion of the chest and abdomen. In order to allow maximum surgical access to the head and face for the procedure, the head of the table (and thus the child) often is rotated 90 to 180 degrees away from the anesthesia field. The anesthesia care team has extremely limited access to the child and particularly the airway. A warm-water heating pad under the patient and a forced air warming device to cover the extremities and trunk help maintain body temperature (see Chapter 9, Anesthesia Equipment and Monitoring).

▪ INTRAOPERATIVE MANAGEMENT

Craniofacial reconstruction often involves extensive craniotomies and exposure of large areas of brain encased in the dura (Figs. 20-5 and 20-6 [5] [6]). Direct pressure and trauma on these exposed surfaces during surgery can cause brain swelling and increased intradural pressure, which can further compromise regional cerebral blood flow. The signs of significant increases in intradural pressure include a taut dura and loss of dural pulsation. A lumbar cerebrospinal fluid drain occasionally may be necessary. The drain can be placed after the induction of anesthesia (usually in the L4-5 interspace) and is used to periodically withdraw cerebrospinal fluid during surgery. However, lumbar cerebrospinal fluid drains are contraindicated in patients with preexisting increased intracranial pressure. A commercially available kit for continuous epidural anesthesia can be used to perform a “wet” tap with an 18-gauge Crawford (or Huested) needle. All spinal catheters must be clearly labeled to avoid the accidental injection of drugs into the intrathecal space. Recent body of evidence supports the use of moderate hypothermia to reduce potential neuronal injury. Maintaining the body temperature between 35° to 37°C may be neuroprotective without increasing the risk of cardiovascular or hematologic abnormalities.

 
 

FIGURE 20-5  Presentation and correction of craniofacial abnormalities in a 4-year-old child with Crouzon's syndrome.  (From Welch KJ, Randolph JG, Ravitch MM, et al., editors: Pediatric surgery, vol 1, 4th ed. Chicago, 1986, Year Book Medical Publishers, p 433.)

 

 

 

 
 

FIGURE 20-6  Intraoperative dissection for craniofacial reconstruction. Note the extensive dissection that can be associated with significant blood loss, heat loss, and potential risk to brain. A, Frontal view: anterior skull bones removed in preparation for reconstruction. The underlying dura over the frontal cortex is exposed. B, Frontal view: anterior skull reconstruction using previously removed cranial bones. Note the screw holes in the absorbable plates visible in the midline of skull. C, Lateral view (forehead on right): note the intricate joining of re-formed skull fragments using absorbable plates and screws to reconstruct the forehead. Skin hooks used to retract the covering soft tissues are visible.

 

 

Anesthesia can be maintained using an inhalational anesthetic, intravenous anesthesia, or a combination of both. If a head-up or sitting position is used, nitrous oxide should not be used because of the concern of air embolism (see below). Infusions of remifentanil help provide sufficient anesthesia during prolonged surgery and yet are associated with a rapid emergence at the end of the procedure (Chiaretti et al., 2000 ). Most patients also require supplemental volatile anesthetic, such as isoflurane (commonly 0.25 to 0.5 MAC). Physiologic variables, including body temperature, arterial blood pressure, heart rate, arterial blood gas tensions, pH, PETCO2, SpO2, hematocrit, platelet count, blood glucose levels, and urine output, are monitored through the course of the procedure.

Craniofacial surgery requires attention to fluid homeostasis. The child has a larger body surface area-to-volume ratio compared with the adult. The child's head comprises nearly 18% of the surface area, whereas the adult's comprises only 9%. This larger surface area results in fluid and heat losses that are proportionately greater in the child. If the procedure is extradural, third-space fluid losses may equal 6 to 8 mL/kg per hr or more. If the (fibrous) dura mater is opened, the fluid losses are greater, 10 to 12 mL/kg per hr or more. In addition, these procedures are commonly associated with large intraoperative blood losses (see later). Intravascular volume must be maintained to achieve adequate perfusion of tissue beds and prevent venous air embolism. Fluid restriction and dehydration, common in adult neurosurgical patients, can create a potentially hazardous situation.

Because of the factors confounding intraoperative fluid therapy, the anesthesiologist must rely on various indicators to monitor fluid requirements and therapy. The urine output, along with central venous pressure measurement when available, can help guide intraoperative fluid therapy. A child who has adequate intravascular fluid is expected to have urine output of 1 mL/kg per hr or greater. However, urine output alone may not accurately reflect intravascular volume status and renal perfusion. The presence of diabetes insipidus or glycosuria may be associated with continued “satisfactory” urine output in the presence of reduced intravascular volume. In addition, if mannitol or other diuretics have been administered to reduce intradural pressure, urine output may not reflect intravascular volume status.

Craniofacial reconstruction is often associated with large intraoperative blood losses. The blood loss usually is via venous or bony oozing and generally accumulates in the drapes; estimations of blood loss are often inaccurate. Serial hematocrits, combined with an appreciation of the child's intravascular volume status, should guide transfusion therapy. The decision to transfuse red blood cells is based on the need to maintain the oxygen-carrying capacity of the blood at levels that meet the patient's metabolic demands. This decision is also influenced by the rate of ongoing surgical blood losses. Traditionally, hemoglobin levels less than 8 to 10 g/dL were thought to be insufficient to maintain adequate tissue oxygen delivery ( Fontana et al., 1995 ); a patient was routinely transfused to maintain the hematocrit above 30%. However, with the use of normovolemic hemodilution, it may be possible to maintain adequate tissue substrate delivery with hematocrits as low as 20%. Haberkern and Dangel (1991) found that hemodilution below this value is associated with decreased mixed venous oxygenation, indicating a significant increase in oxygenation extraction, tissue dysoxia, or ischemia ( Dishart et al., 1998 ). Because of the relatively small allowable blood loss in infants and small children, this technique usually does not reduce the exposure risk to a unit of autologous blood ( Brecher and Rosenfeld, 1994 ). Advances in hemostasis have reduced intraoperative blood loss. The use of fibrin glue on the bone margins may substantially decrease ongoing intraoperative blood loss ( Valbonesi et al., 2002 ; Panfilov, 2003 ).

Coagulopathies may occur for several reasons. Coagulation factors may be consumed rapidly because of ongoing blood loss ( Williams et al., 2001 ). Tissue thromboplastin is released by surgical manipulation and inadvertent trauma to the brain and dura. Massive infusion of fluid aimed at keeping up with evaporative losses and transfusion of red cells to replace blood loss can result in dilutional coagulopathies. Any one or a combination of these etiologies can produce the bleeding disorder seen in patients undergoing craniofacial repair. Fresh frozen plasma is reserved for factor-deficient bleeding diatheses documented by a prolongation of the prothrombin time (PT) or activated partial thromboplastin time (aPTT). If coagulation studies can be performed at the point of care or are available in a timely manner, the transfusion of FFP can be based on appropriate laboratory studies. In the absence of such timely results, empiric transfusion of FFP may be necessary. One study in children undergoing craniofacial reconstruction found that the PT is prolonged in up to 19% of cases, lending support to the intraoperative use of FFP transfusion. When necessary, 10 to 20 mL/kg of FFP should correct the prolonged PT ( Williams et al., 2001 ).

Thrombocytopenia, not factor deficiency, is more commonly the source of the bleeding disorder in the presence of significant blood loss, and serial platelet counts are used to guide transfusion therapy. Platelet transfusion in infants with platelet levels less than 75,000/mm3 should minimize bleeding caused by thrombocytopenia. A new therapy for reducing blood loss during craniofacial surgery is the use of aprotinin, a serine protease inhibitor ( D'Errico et al., 2003) . Aprotinin was administered as a loading dose (240 mg/m2) followed by an infusion (56 mg/m2 per hr) for the duration of the procedure. The patients who received aprotinin experienced significantly less blood loss than did those who were administered a placebo infusion.

The use of deliberate hypotension and patient positioning also may minimize intraoperative blood loss (see Chapter 12 , Blood Conservation). Positioning with the head above the heart (approximately 30 degrees) improves venous drainage, decreases the blood loss, and may optimize the surgical exposure. The addition of deliberate hypotension decreases cerebral perfusion pressure and increases the risk of venous air embolism.

Maintaining body temperature in the desired range can be a significant problem in children in any lengthy procedure involving exposure of a large surface area. Heat loss may be reduced by warming all intravenous fluids, wrapping the nonexposed body parts in plastic sheets, using a forced-air warmer, and placing the child on a heating pad. In addition, heated humidifiers or heat-moisture exchange (HME) devices are used in the airway circuit to minimize evaporative heat loss from the respiratory tree, as well as to prevent dehydration of central airway mucosa. A radiant warmer is often useful when the child first arrives in the operating room and is uncovered during anesthesia induction and monitor placement. The goal of intraoperative temperature maintenance is body temperature of 35° to 37°C, as mentioned earlier.

Craniofacial reconstruction may also present risks specific to the central nervous system, such as air embolism and cerebral trauma. Air embolism can occur when venous structures, which develop subatmospheric intravascular pressure, are exposed to the atmosphere and air is entrained intravascularly ( Souder, 2000 ). Signs of small amounts of venous air embolism can be quite subtle. Mass spectroscopy of end-tidal gases offers the most sensitive indication, with an elevation of the end-tidal nitrogen concentration. More commonly available is PETCO2. A sudden decrease in PETCO2 is nearly as sensitive an indicator of air embolism as is the end-tidal nitrogen concentration. Monitoring for emboli with precordial Doppler stethoscopes has been recommended in adults ( Bedford et al., 1981 ). When positioned properly on the patient's chest, these stethoscopes are extremely sensitive, detecting small venous air embolisms (VAEs) by a characteristic murmur. In infants and small children, however, this technique is extremely cumbersome to use because of the child's small chest and heart size and offers little benefit. Monitoring of blood pressure and oxygenation is relatively insensitive for the detection of VAEs, as is the monitoring of pulmonary artery pressure. If a VAE is suspected or diagnosed, 100% oxygen should be administered to the patient, and the surgical field must be flooded with fluid, so that fluid, and not air, is entrained. Efforts are made to elevate venous pressures by placing the patient in a head-down (Trendelenburg) position and administering intravenous fluids. The central venous catheter may serve a special purpose in the treatment of VAEs. Specifically, in the face of a large VAE, it may be possible to aspirate out air. This effort is most effective if the tip of the catheter is placed within the right atrium at its junction with the superior vena cava ( Bunegin el al., 1981) .

Although these procedures are usually extradural, the brain may be subject to surgical trauma or hypoperfusion. The anesthetic technique should be designed to reduce these risks. Steps include maintaining adequate intravascular volume and systemic perfusion pressure and mild hypothermia.

The pharmacologic maneuvers for brain protection are not clearly delineated because the basic mechanisms of neurologic injury are not completely understood. Central nervous system damage may result from direct cerebral trauma, cerebral edema, or regional hypoxia or hypoperfusion (ischemia). Central nervous system damage induces a common set of reactions, including release of toxic neurotransmitter substances (excitotoxins such as glutamate and aspartate), opening of calcium channels, and influx of calcium into neurons. In turn, these effect detrimental reactions in the neuronal cytosol, such as release of arachidonic acid and other free fatty acids and production of oxygen free radicals that can damage the cell and mitochondrial membranes ( Clausen and Bullock, 2001 ). Despite improved understanding and effort, no current drug or therapeutic modality has been demonstrated to provide clear protection against, nor cure for, such neurologic injury (also see Chapter 18 , Anesthesia for Neurosurgery).

▪ POSTOPERATIVE MANAGEMENT

After surgery, these patients usually are allowed to emerge from anesthesia and resume spontaneous ventilation. Most patients meet extubation criteria soon after surgery is completed and the trachea is extubated. The child then can be transported to the pediatric intensive care unit (PICU) directly or alternatively taken to the postanesthetic care unit (PACU) for immediate postoperative care and then transported to the PICU. During transport, the child's respiratory and hemodynamic status should be continuously monitored. Occasionally, patients may need to remain intubated for ventilatory support in the immediate postoperative period because of the possibility of hypoventilation, resulting from prolonged anesthesia, hypothermia, or brain edema from trauma or fluid shifts. In addition, the surgical procedure may include manipulation of the mandible, maxilla, or another part of the airway, which can result in mucosal swelling or hematoma that can compromise the airway. All of these children require close observation in the PICU for at least 24 to 48 hours postoperatively. The patient's neurologic status should be assessed frequently for the development of somnolence, confusion, irritability, or other signs of altered mental status. Deterioration may be caused by hypoxia, hypercapnia, cerebral edema, acute or subacute shifts of intracranial contents, intracranial bleeding, hypoglycemia, or electrolyte imbalances, which must be appropriately and quickly treated to prevent further complications.

Postoperative bleeding or fluid losses because of ongoing fluid shifts (from intravascular to interstitial) may compromise systemic and brain perfusion. Transfusion of blood products or isotonic fluid therapy may be necessary to treat decreased peripheral perfusion and systemic hypotension. Additional doses of FFP or platelets may be needed to correct ongoing coagulopathy. The patient's skin perfusion, temperature, arterial blood pressure, blood gas levels, serial hematocrit, coagulation profiles, and urine output must be continually monitored.

Advances in technology have resulted in improved materials for surgical repair of the cranial defect. Absorbable plates and screws were first used in orthopedic surgery and now are commonly used in craniofacial repair. The materials are made from polyglycolic and polylactic acid. The screw and plates dissolve in 1 to 1.5 years, leaving no hardware remaining in the child's skull. The process may reduce the number of repeat operations the patient requires ( Turvey et al., 2002 ).

▪ EXTERNAL FIXATION AND OSSEOUS DISTRACTION DEVICES

Improvements in technology have permitted staged repairs of midfacial, maxillary, and mandibular defects. Osseous distraction is a technique that has been developed over the past 10 to 15 years. Ilizarov (1990) first reported the use of distraction osteogenesis induced by placement of an external fixator to permit proper growth and alignment in long bones. The technique applies tension to distract bone and stimulate new bone formation in a slow progressive nature. The goal is to stimulate soft tissue and bony changes in the craniofacial skeleton. This technique can be applied to the mandible, the maxilla, or the frontal region of the skull. The surgeon performs an osteotomy, usually through one cortex of a bony area that needs to be expanded. Pins are then set on both sides of the osteotomy and a distraction device is applied to the pins. Slow (1 mm/day) distraction tension is applied to stimulate bony formation in the region of the osteotomy. Because the slow tension is also applied to the soft tissues, this facilitates soft tissue mobilization as well. The method is particularly useful in children who have hypoplastic mandibles or hypoplastic midfaces.

After the desirable distraction has been obtained over weeks or months, the device is left in position for several months to allow the bone, which has been formed, to consolidate and create a solid union across the osteotomy site. Once consolidation is completed, the patient is brought back to the operating room (or, for older patients, the office) and the distraction device is removed under anesthesia or intravenous sedation. Devices can be placed externally, like an external fixator ( Fig 20-7 ), or internally, buried under the skin. Some of these devices can be very cumbersome, consisting of a head frame with bars extending in front of the patient's face.

 
 

FIGURE 20-7  A, Infant with Pierre Robin sequence. B, External fixation of the midface following surgery for repair in a patient with Pierre Robin sequence.

 

 

The larger head frame devices pose a real challenge for the anesthesiologist as airway management, including intubation, can be quite difficult. After the procedure, swelling around the osteotomy sites may be present but resolves over 24 to 48 hours.

Although helpful in improving surgical results and reducing the risk of repeat major operations, these devices pose potential and real postoperative risks to the patient, as well as nursing challenges. Admission to the intensive care unit (ICU) should be planned ahead of time and postoperative management discussed with the ICU staff. Often, the surgical repair involves wire fixation of the maxilla and mandible, producing a “locked jaw with clenched teeth” that cannot be opened easily. The patient's airway may or may not be patent via the nasal route. Children often mouth breath through teeth clenched in place. Emergent care and access to the airway may require cutting the wires to open the mouth. In these children, wire cutters should be readily available (taped to the bedside). However, this maneuver poses its own risks because of an unstable midface or mandible. Furthermore, if disturbed during routine or emergent care, the metal parts may cause bleeding from areas that are difficult to see and control. Initial postoperative care must be provided in the pediatric ICU. In addition, the anesthesiologist or intensivist should be available and be familiar with the use of equipment to secure a patent airway (e.g., transtracheal jet ventilation, cricothyrotomy, and management of the difficult airway).

Complications that can occur with the distraction devices include infections along pin sites and mobilization of the pins prior to the completion of the distraction, making it necessary to remove them prematurely. In addition, patients must live with these devices for weeks to months, creating possible psychological problems for them at home and school. Osseous distraction of the facial skeleton has been a very popular and successful technique. It is most often useful in children who have a hypoplastic mandible, midface, or both.

▪ SPECIAL CONSIDERATIONS FOR PIERRE ROBIN SEQUENCE

The syndrome of micrognathia and glossoptosis and cleft palate is known as the Pierre Robin sequence ( Robin, 1934 ). Because of the anatomic anomalies, infants often present with respiratory distress shortly after birth. Because of the small mouth cavity and relatively large tongue, the infant can experience partial or profound airway obstruction. In most infants, airway patency can be achieved through changes in the position of the head and neck in relation to the body. Often, placement in the prone position relieves the barrier to airflow. The placement of a nasopharyngeal airway may permit the child to breath relatively normally and provides a temporizing intervention. The airway problems are less likely to be life threatening with age and usually, after 6 months of age, are not a cause of significant concern ( Benjamin and Walker, 1991 ). On occasion, the obstruction is severe enough to require urgent intubation and, possibly, surgical intervention. Airway management may be extremely difficult in these children because of the distorted anatomy related to the small jaw, the large tongue, and cleft palate.

Children with Pierre Robin sequence may present in the neonatal period for tracheostomy if the mandibular hypoplasia is severe. More commonly, these patients present later in infancy or toddlerhood for corrective surgery of the cleft palate and for mandibular reconstruction. Anesthetic considerations in these children are similar to those undergoing cleft palate repair (see later). Children with Pierre Robin sequence who undergo mandibular reconstruction with an osseous distraction device are susceptible to the same perioperative issues discussed earlier.

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

Copyright © 2005 Mosby, An Imprint of Elsevier

▪ CLEFT LIP AND CLEFT PALATE REPAIR

Cleft lip and cleft palate may occur together or separately ( Westmore and Willging, 1996 ). Cleft lip with or without cleft palate occurs in 1:1000 births; cleft palate alone occurs in approximately 1:2500 births. The syndrome of cleft lip (with or without cleft palate) is more common in males, whereas isolated cleft palate is more common in females. In addition to the lip and palate abnormalities, these patients have a higher incidence of other congenital malformations ( Table 20-1 ). Middle ear disease is extremely common in patients with cleft palate ( Stool and Randall, 1967 ). Siblings and offspring of persons who have cleft palate or cleft lip are also at greater risk of having one or the other.

TABLE 20-1   -- Congenital anomalies associated with cleft lip with or without cleft palate

Frequent

Occasional

Fetal hydantoin syndrome

Cri du chat syndrome

Mohr syndrome

Larsen's syndrome

Fetal trimethadione syndrome

Facioauriculovertebral anomalad

Orofaciodigital syndrome

Meckel-Gruber syndrome

Roberts' syndrome

Oculodentodigital syndrome

Trisomy 18 syndrome

Trisomy 18 syndrome

4 p-syndrome

Waardenburg's syndrome

 

 

The cleft lip deformity may be as mild as a small defect in the vermilion border or may manifest as much as a complete separation that involves the nasal floor. The clefts may be unilateral or bilateral and may involve the alveolar ridge ( Fig 20-8 ). In addition, associated dental abnormalities may also be seen. Cleft palate may occur as an isolated deformity or in association with cleft lip. Isolated cleft palate is commonly a midline defect involving simply the uvula or may manifest more extensively as a defect of the soft and hard palates. If cleft lip is associated, the cleft palate defect may expose either one or both of the nasal cavities to the oral cavity. Such obvious defects of the upper airway predispose the child to difficulties in swallowing and repeated aspiration and pulmonary infection.

 
 

FIGURE 20-8  Infants with single or unilateral (A) and double bilateral cleft lip (B). Presence of the clefts, especially with the free premaxilla and double cleft, makes intubation difficult.

 

 

Before surgery, the clinical management is aimed at reducing the chance of aspiration and pulmonary compromise by feeding these infants in an upright position with either an infant or a “premie” nipple. The Haberman nipple is the most successful for feeding these children because the child does not have to generate suction to get the fluid from the nipple. In some situations, it may be appropriate to feed the child through a nasogastric tube. However, this is less than ideal. The anesthesiologist should know if there is or has been pulmonary compromise. In addition, any associated congenital anomalies should be noted.

Anesthesia may be induced via mask or intravenous techniques. In general, the more severe the cleft palate, the less chance there is for airway obstruction; in patients with hypoplastic mandibles or cleft palates wide enough that the tongue can prolapse into the nasopharynx, airway obstruction can occur and pose a significant problem during the induction of anesthesia. With adequate preparation and experience in caring for these children, induction of anesthesia and endotracheal intubation can be performed quite safely. After induction, endotracheal intubation can proceed with the placement of an appropriately sized oral RAE endotracheal tube. After proper intratracheal positioning is confirmed, the tube may be secured with benzoin and taped to the middle chin. Ventilation during the procedure may be assisted or mechanically controlled. Before surgery begins, the eyes should be securely taped shut to prevent trauma or other damage.

Maintenance of anesthesia may be accomplished using inhalation agents alone or in combination with opioids. Nondepolarizing muscle relaxants may decrease the total amount of volatile anesthetics needed ( Fogdall and Miller, 1975 ). The duration of the repair is usually 60 to 120 minutes.

Before beginning the repair, the surgeon places a throat pack in the posterior portion of the pharynx. In addition, a Dingman gag is used in cleft palate repair to hold the mouth open during surgery ( Fig 20-9). This apparatus contains a groove in which the endotracheal tube should sit without being occluded. Malposition of the gag in relation to the endotracheal tube, however, can lead to partial or complete obstruction of the tube. The anesthesiologist must be particularly aware of the breath sounds and chest compliance during placement and manipulation of the gag. Cleft lip repair is associated with only modest amounts of blood loss. The repair of cleft palate, however, may be associated with moderate bleeding, but rarely is there a need for blood transfusion.

 
 

FIGURE 20-9  Management of cleft palate repair. Tongue blade of Dingman gag holds endotracheal tube in place and provides exposure for the surgeon. Eyes are covered with scleral shields for protection.

 

 

After the repair is complete, the inhalation anesthetics are discontinued and the child is allowed to emerge from anesthesia. If muscle relaxants have been used, appropriate reversal is accomplished with neostigmine (0.07 mg/kg) or edrophonium (1.0 mg/kg), and atropine (0.02 to 0.03 mg/kg) or glycopyrrolate (0.01 mg/kg). When the child exhibits good spontaneous ventilation, a negative inspiratory force of -30 cm H2O or greater, and a good leg or head lift, he or she can be safely extubated. Any posterior pharynx throat pack must be removed and an oropharyngeal airway may be inserted before extubation. In addition, the oropharynx should be suctioned to remove pooled blood or secretions. The patient should be fully awake before extubation, because partial or complete upper airway obstruction with soft tissue is common after repair of cleft palate. After the child has been extubated, he or she is placed in the lateral position to optimize air movement and to minimize the chance of aspiration. Usually, nasal passages are blocked postoperatively, and the infant may experience difficulty breathing through the mouth before readjusting to oral breathing.

In the postoperative period, arm restraints, which prevent elbow flexion, are routinely used to keep the child's hands away from the child's face. Care should be taken to provide adequate fluid therapy to maintain hydration. In addition, the child may experience further bleeding from the operative site, particularly if a cleft palate has been repaired. More important, partial or complete airway obstruction may occur because of mucosal swelling in the hypopharynx. Use of a mouth gag is the most frequent cause of postoperative tongue swelling, and the degree and frequency of swelling appear to be associated with the duration of tongue compression by the mouth gag blade. Other causes of postoperative airway obstruction include subglottic edema, flap edema, increased oral secretion, posterior displacement of the tongue, and an overlooked throat pack. The child should be closely monitored for at least the first 24 hours.

Children who have undergone cleft palate repair may develop difficulty with speech during the toddler years. Although most children have satisfactory speech patterns, some may manifest velopharyngeal incompetence. These children should be evaluated aggressively with the use of speech recordings, airflow studies, video fluoroscopy, and endoscopy. If velopharyngeal incompetence is diagnosed, surgery may be indicated, as this condition does not resolve with nonsurgical treatment. Velopharyngeal incompetence can be treated by various surgical options, including complete revision or re-repair of the palate deformity, a pharyngeal flap, or a sphincter pharyngoplasty. The superiorly based pharyngeal flap is commonly performed when the lateral wall motion is good to excellent ( Fig 20-10 ). The flap is elevated down to prevertebral fascia and up to the base near the midpoint of the tonsillar fossa. The palate is split and the nasal mucosa dissected into two posterior flaps. Any operation on the palate can cause edema and potential airway obstruction.

 
 

FIGURE 20-10  The superior velopharyngeal flap. The soft palate is divided (A) and the nasal layer flaps are dissected (B). The flap is elevated and attached to the nasal aspect of the soft palate (C). The nasal layer flaps (a) and the pharyngeal flap (b) are approximated (D)and the soft palate is closed (E)F shows the relative positions of the pharyngeal and nasal flaps. The relative position of the pharyngeal flap in the pharynx is shown in G.  (Adapted from Johnson P, Pirruccello FW: Surgical repair of cleft lip and palate. In Pirruccello, editor: Cleft lip and palate plastic surgery: Genetics and the team approach. FW Charles C Thomas, 1987. Courtesy of Charles C Thomas Publisher, Ltd., Springfield, IL.)

 

 

 

The sphincter pharyngoplasty may be performed in patients who have poor lateral pharyngeal wall movement but good motility of the palate ( Hofer et al., 2002) . The procedure involves elevating the posterior faucial pillars with the underlying muscles. In addition, a transverse incision is made. The medial walls of the faucial flaps are sutured to the superior aspect of the posterior wall incisions. Subsequently, the lateral edges of the flap are sutured closed to reduce the velopharyngeal defect. Stumps of the palatal pharyngeous muscles are sutured closed. Such a procedure again involves a posterior oral pharynx and involves extensive soft tissue dissection. The airway patency during the immediate postoperative period is of great concern to the anesthesiologist.

The anesthetic management and the approach to the airway during surgery for velopharyngeal incompetence are similar to those in the child with a primary cleft palate. Postoperative problems specific to the child with a pharyngeal flap and sphincter pharyngoplasty include possible airway obstruction because of swelling of the oropharynx, intraoral bleeding, and obstruction or aspiration of blood. Postoperative coughing on emergence may increase venous pressures and the chance of postoperative bleeding. Great caution should be used to minimize the chance of postoperative coughing and vomiting. The child must be closely monitored, usually overnight, as with primary closure.

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

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

Copyright © 2005 Mosby, An Imprint of Elsevier

▪ SUMMARY

Plastic surgery in infants and children is primarily aimed at repairing anomalies of bony growth—primarily of the head and face. Surgical procedures are aimed at relieving airway obstruction and modeling the bones and soft tissues of the skull and face so that they grow and develop normally. Anesthetic management of these patients is challenging for many reasons, including the presence of airway abnormalities and perioperative airway compromise, massive intraoperative bleeding and coagulopathies, and potentially difficult postoperative course. Proper care of these infants requires a knowledgeable anesthesia care team as part of the whole craniofacial team.

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

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

Copyright © 2005 Mosby, An Imprint of Elsevier

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