Beginning of the Nervous System

During the third week of fetal development, the ectoderm differentiates into the neuroplate. This neuroplate folds upon itself to form the neural groove. There are two neural folds which form along each side of the neural groove. Neurulation begins at the fourth week of development, when the neural folds fuse dorsally to create the neural tube. The spinal ganglia, cranial nerves, and components of the peripheral and autonomic nervous system are derived from neural crest cells which are located adjacent to the neural folds. The neural tube fuses in a central to caudal and central to cranial direction, creating the neural canal. The small holes remaining at each end of the neural tube fuse at days 25 and 27 days concomitantly with the development of the vascular supply to the neural tube. The ventricular system and central canal of the CNS develops from the neural canal, with the walls of the neural tube forming the brain and spinal cord.

Development of the Spinal Cord

The spinal cord develops from the caudal end of the neural tube, with the neural canal becoming the central canal at about ten weeks’ gestation. The cells of the neural tube differentiate into two different layers; the ependymal layer which becomes neurons, astrocytes, and oligodendrocytes, and the marginal layer which becomes the white matter as axons grow into this area from spinal cord neurons. The sulcus limitans is a longitudinal groove which forms on each side of the fetal spinal cord. This groove forms a separation between the dorsal or afferent portion of the spinal cord from the ventral or efferent portion of the spinal cord. The mesenchymal cells surrounding the protospinal cord differentiate into the dura mater, pia mater, and arachnoid mater. These meninges become fluid filled as cerebrospinal fluid (CSF) is produced during the fifth week of development, which forms the subarachnoid space.

As the spinal cord is developing, the cranial portion of the neural tube undergoes rapid growth and turning, with the neural canal forming the cranial ventricular canal. It is believed by many authors that normal development of the ventricular canal system is dependent of the caudal closure of the neural tube, which causes an increase in intraluminal pressure which stimulates brain growth and ventricular enlargement. This is one possible explanation for the finding that infants with open neural tube defects of the spinal cord, such as meningomyeloceles, very often have associated abnormalities of their brain and ventricular system.

Intracranial Contents

After infancy the cranial vault should be considered a closed space that is normally occupied by three components: the brain and interstitial fluid comprising 80 percent of the volume; the CSF comprising 10 percent of the volume; and the blood comprising 10 percent of the total volume. The Monro-Kellie hypothesis, which states that the sum of all intracranial components are constant, necessitates that an increase in the volume of one component demands a decrease in volume of one or two of the remaining components in children in whom the sutures and fontanelles are closed. Infants with their unfused sutures and open fontanelles can tolerate slow increases in intracranial volumes [1]. Thus a child with an increase in head circumference should be evaluated for a space-occupying brain lesion or hydrocephalus even if there are no signs of increased intracranial pressure. Rapid increases in the volume of CSF or growth of a space-occupying lesion such as a brain tumor even in a young infant will overwhelm the infant’s ability to increase the size of his cranial volume, leading to brain herniation as a result of acute elevations of intracranial pressure (ICP).

Intracranial Pressure

The normal ICP in children is <15 mmHg and < 6mmHg in infants. The normal ICP for premature infants is not known. In infants with open fontanelles, the ICP may remain normal even in the setting of significant intracranial pathology. Careful physical examination should always include an examination of the fontanelles. Full or bulging fontanelles can be a sign of intracranial disease. Often the first sign of intracranial disease in an infant is a normal steady state ICP with occasional ICP pressure waves. These pressure waves should never be considered normal.

Other infants will manifest an elevation of ICP despite open fontanelles. These elevations of ICP can cause either cerebral ischemia and/or brain herniation leading to secondary brain injury. Elevations of the ICP without concomitant elevations of mean arterial pressure (MAP) will result in a decrease in cerebral perfusion pressure (CPP), which can result in cerebral ischemia.

With a decrease in CPP, cerebral blood flow (CBF) decreases. This results in decreased delivery of metabolic substrates and oxygen. Cell damage then occurs, which leads to cell death and an increase in inflammatory mediators, a cascade causing further increases in extracellular water and exacerbating the elevation in ICP. As CPP falls, neuronal dysfunction and ultimately cell death occur [1].

In addition to decreasing cerebral perfusion pressure, elevations of ICP can lead to brain herniation. This occurs when intracranial contents herniate from one compartment into another, leading to further brain ischemia and injury. Transtentorial herniation occurs when the temporal lobe displaces into the infratentorial space. Infants will show signs of hemiparesis, pupillary dilation, and eventual loss of consciousness. This is a medical emergency that will lead to death if the condition is not expeditiously relieved. The clinical signs of elevated ICP are less reliable in infants and children. Infants may exhibit signs of papilledema, hypertension, and bradycardia, but have normal ICP. Or infants with elevated ICP may show no clinical signs at all [2,3]. Classically, young children with chronically elevated ICP will have headaches, irritability, decreased oral intake, and morning emesis without papilledema [4]. Late signs include alterations in the level of consciousness, with children exhibiting abnormal responses to painful stimuli [2]. Depending on the level of obtundation, general anesthesia or sedation may be needed to evaluate these patients. Imaging studies are most commonly done, such as cranial X-rays, computed tomography (CT), and magnetic resonance imaging (MRI). These studies often reveal a decrease or obliteration of the lateral ventricles, hydrocephalus, midline shift, and/or obliteration of the third and fourth ventricles.

Cerebrospinal Fluid

Cerebrospinal fluid is produced by the choroid plexus at the rate of 0.35 ml per minute in both infants and adults [5,6], resulting in approximately 500 ml produced per day in adults [5]. However, the total volume of CSF in the subarachnoid space in adults is only 100–150 ml, meaning that the CSF is replaced several times during the day. The overall volume of CSF in infants and children is much less than in adults because the subarachnoid space is much smaller. Cerebrospinal fluid production is only marginally affected by elevated ICP.

Arachnoid villi within the subarachnoid space absorb the CSF, which enters the venous system via one-way valves between the subarachnoid space and the sagittal sinus. There is also a limited amount of reabsorption that occurs through the ependymal lining of the ventricles. The rate of reabsorption increases with elevation of ICP. Obstruction of the arachnoid villi or obstruction within the ventricular system can lead to decreased absorption. Pathologic processes such as inflammation, infection, intracranial hemorrhage, congenital malformations, and CSF absorption and ICP elevations [2].

Intracranial Compliance

It is important to estimate the amount of intracranial compliance that an infant or child has before administering a general anesthetic. Intracranial compliance is defined as the ratio of change of ICP over change of intracranial volume. In infants who have greater abilities to compensate for increases in cranial volumes because of their open fontanelles, it is difficult to assess the degree of additional compensation available if needed for general anesthesia. Once the ICP is elevated, it is reasonable to assume that compensatory mechanisms have been overridden. But infants with normal ICP may be at high risk for brain injury with even the small increases in cranial volumes/CBF that may occur with certain anesthetic techniques. Assessment of the fontanelles to determine whether the fontanelle is full in infants suspected of having intracranial pathology is essential before administering a general anesthetic. Although infants have higher compliance than adults because of their sutures and open fontanelles, children have lower compliance than adults. This is thought to be due to a higher ratio of brain water content, less CSF volume, and a higher ratio of brain content to intracranial capacity [1]. Infants with fused cranial sutures are at higher risk than normal infants for developing ICP elevations.

Cerebral Blood Volume and Cerebral Blood Flow

The cranial compartment most easily manipulated by anesthesiologists is the cerebral blood volume (CBV), though this compartment only represents 10 percent of the total volume of the cranial contents. Most of the CBF by volume is contained in the low-pressure, high-capacitance venous system. Initially increases in intracranial volume are met with decreases in CBV. Often, venous blood shifts from intracranial to extracranial, as seen in infants with hydrocephalus who develop distended scalp veins [7].

In a normal adult, the CBF is approximately 55 ml per 100 g of brain tissue per minute, which represents approximately 15 percent of the adult cardiac output [8–10]. The CBF is almost double in children, at approximately 100 ml per 100 g of brain tissue per minute, which represents about 25 percent of cardiac output [11,12]. Infants and young children in general have a larger portion of their cardiac output devoted to cerebral perfusion than do adults. Neonates and premature infants appear to have a lower CBF at about 40 ml per 100 g per minute than any other age group. The reasons for this are unclear. There is also greater variability of CBF in neonates and premature infants depending on the physical state of the infant. Cerebral blood flow is decreased during sleep and feeding states [12,13].

Cerebral blood flow in the nonanesthetized state is usually very closely coupled with cerebral metabolic rate for oxygen (CMRO₂), which is known as cerebral autoregulation. In adults, CMRO₂ is approximately 3.5–4.5 ml O₂ per 100 g per minute; in children it is higher, but in premature infants it is lower [11]. Most general anesthetics will depress the CMRO₂ by as much as 50 percent, but in very young premature infants these same general anesthetics can be excitotoxic, leading to an increase in CMRO₂ [14]. Inadequate CBF will lead to conditions that result in acidosis, such as hypoxemia, hypercarbia, and ischemia. These conditions increase the hydrogen ion concentration within the cerebral blood vessels, which will cause cerebral dilation and thereby increase CBF and CBV. When there is a loss of coupling between CMRO₂ and CBF, cerebral autoregulation is impaired. CBF then becomes pressure passive, meaning it varies with the system MAP.

Cerebrovascular Autoregulation

Preoperative Evaluation

It is important to realize that the perioperative period is extremely stressful to both child and family. Parents have concerns about both the immediate risks of general anesthesia as well as the long-term consequences of their infant undergoing a prolonged general anesthetic for a neurosurgical procedure. These issues should be addressed during the preoperative interview in a reassuring manner. A very careful history and review of systems with an emphasis on the neurologic system is essential to obtain from the parents. In addition, it is very important to obtain a history of any coexisting diseases such as pulmonary and cardiac anomalies, prematurity, or evidence of difficult airway issues. Physical examination should focus on the airway, cardiac, pulmonary, and neurologic systems. A thorough history and review of symptoms with particular emphasis on neurological symptoms should be obtained from the parent. A focused physical examination with particular emphasis to the neurological system should be done.

Emergent neurosurgical procedures in infants pose special challenges. In most cases, the infants should be considered as a “full stomach” and airway precautions should be taken to prevent pulmonary aspiration. There may not be resources available to do a complete preoperative evaluation in neonates suspected of having congenital cardiac disease. A transthoracic echocardiogram along with pre- and postductal oxygen saturation on both room air and 100 percent oxygen can discriminate between cardiac and pulmonary disease.

For elective procedures, infants and neonates are fasted before general anesthesia in order to decrease the risk of pulmonary aspiration. It is important to minimize fasting time to decrease the risk of developing dehydration and hypoglycemia. For routine procedures, fasting times for clear liquids should be no more than two hours and for young infants intraoperative glucose monitoring should occur if the infants are not receiving intravenous glucose solutions intraoperatively.

As part of the preoperative evaluation, the anesthesiologist providing care for the infant should evaluate all neuroimaging studies that have been done on the infant in order to assess the type of lesion, location, the presence of intracranial hypertension, the vascular supply, and the risk of perioperative herniation. Most major neurosurgical procedures in infants are associated with intraoperative blood loss. Accordingly, it is necessary to type and crossmatch blood for intraoperative use. It is also important for the anesthesiologist to confer with the surgeon about special neurophysiologic monitoring that may be done intraoperatively in order to plan the optimal general anesthetic.

Vascular Access and Monitoring

Obtaining adequate intravenous access before incision is essential to conducting a safe general neurosurgical anesthetic. Once the procedure has commenced it is very difficult to place intravenous lines. Two relatively large-bore intravenous lines (larger than 22 gauge) are usually adequate for most procedures. Central venous access can be obtained if peripheral access is difficult. In general, femoral venous access is preferable to internal or external jugular venous access because they are technically easier to place and there is no concern about obstructing cerebral venous drainage. A single lumen central line is preferable to a multilumen central line if rapid transfusion of fluid and blood products is anticipated.

Placement of an intra-arterial catheter for blood sampling and monitoring is also very helpful for procedures in which significant blood loss is anticipated. The most commonly accessed vessel is the radial artery, but dorsalis pedis and posterior tibialis can also be easily accessed. It is important to zero the transducer at the level of the infant’s head in order to get an estimate of the cerebral perfusion pressure (CPP).

Infants undergoing craniotomies, especially in the head-up position, are at increased risk of venous air embolism so precordial Doppler is recommended in addition to standard ASA monitors. During some procedures, electroencephalographic (EEG) and neurophysiologic monitoring are used. Consultation with both the surgeon and neurophysiologist is necessary to coordinate the general anesthetic care.

Keeping the infant warm during neurosurgical procedures can be difficult. Because the head of a neonate is large in comparison with the rest of the body and a larger percentage of cardiac output is directed to the head and upper body, the neonate is at particular risk for significant heat loss during surgery. It is important to use warming lights and forced-air warming blankets, and to keep the operating room temperature high to prevent heat loss. Monitoring core temperature either esophageally or rectally is necessary. Intraoperative hyperthermia should also be scrupulously avoided.

Induction of Anesthesia and Airway Management

The most commonly used inhalational agent for children who are neurologically stable and lack intravenous access is sevoflurane. It lends itself to a rapid and smooth induction without significant myocardial depression and cardiovascular instability. Because inhalational inductions can be accompanied by respiratory depression leading to hypercarbia that could worsen elevated ICP, the anesthesiologist should be prepared to assist in ventilation relatively early during induction. Infants that are cardiovascularly unstable or who have already been accessed intravenously should have an intravenous induction with a rapid-acting hypnotic agent such as etomidate for unstable infants and propofol for stable infants. Although ketamine is a useful medication for infants with cardiovascular instability who are not neurologically compromised, it is not ideal for neurosurgical procedures. It will cause an increase in cerebral metabolism, CBF, and ICP, so it should be used cautiously in this patient population.

For emergency procedures in which the infant is felt to be at risk for pulmonary aspiration, a rapid sequence technique using succinylcholine or a large dose of a nondepolarizing medication such as rocuronium can be used. Care must be taken to ensure there are no contraindications to the use of succinylcholine, such as malignant hyperthermia, myopathies, or denervation diseases.

Elevations of ICP can occur with laryngeal intubation, so it is important to make sure that the anesthetic depth is appropriate before airway manipulation. In infants, a nasal intubation is often more easily secured and less likely to be inadvertently displaced during the surgery, especially when the infant is placed in the prone position.

Maintenance of Anesthesia

Effect of Anesthesia on the Developing Brain

Most general anesthetics have been implicated in animal models in causing long term neurocognitive deficits. In particular, prolonged exposure to agents that are gamma amino butyric acid (GABA) receptor antagonists and those that are NMDA receptor agonists has caused neuroapoptosis and long-term deficits in monkeys, rats, and mice. Although this particular issue is one of the most important in contemporary pediatric anesthesia, a thorough discussion is beyond the scope of this chapter and will be addressed elsewhere in this text.

Blood and Fluid Management

Neurosurgical cases are difficult to manage in young children, in part because fluid management is critical. Over-hydration is very possible in young children with excellent intravenous access, which can lead to excessive cerebral edema. Procedures on the cranium tend to be accompanied by intraoperative hemorrhage that is very difficult to estimate in young children by examination of the suction canisters and drapes. Frequent measured arterial blood gases and hematocrits are an important method to estimate intravascular fluid volume and red blood cell mass. Antifibrinolytics such as tranexamic acid can be administered to ameliorate blood loss in certain patient populations such as children undergoing major orthopedic and craniofacial procedures [21,22].

It should be assumed that the blood–brain barrier is disrupted during neurosurgical procedures. So the choice of intravenous fluids may affect cerebral perfusion, cerebral edema, water and sodium homeostasis, and serum glucose concentration. It is not known whether osmotic or oncotic pressure gradients are more important in preventing cerebral edema, but most investigators lean toward using crystalloid solutions rather than colloid solutions during neurosurgery. Since the goal is to provide a solution that is hypertonic (or at least not hypotonic) to plasma, lactated Ringer’s solution, which has an osmolality of 273 mOsm L^–1 (normal serum osmolality being 285–290 mOsm L^–1) is not ideal for neurosurgery. Normal saline, which is slightly hypertonic with an osmolality of 308 mOsm L^–1, is a better choice for neurosurgical procedures, even though it can lead to a hyperchloremic acidosis if large volumes are infused [23]. Osmotic and loop diuretics can be used to transiently induce dehydration when surgical exposure is difficult or there is a dangerous elevation of ICP. Care must be taken to avoid systemic hypotension due to peripheral vasodilation caused by diuretics, which can diminish cerebral perfusion pressure. Very young patients can benefit from slow glucose administration during neurosurgical procedures. In patients with altered glucose metabolism, such as those treated with hyperalimentation, who are diabetics, or poorly nourished, the addition of glucose intravenously may also be necessary. However, hyperglycemia during procedures has been associated with increasing cerebral infarct size during cerebral ischemia, so avoiding both hyper- and hypoglycemia is important [24].

Hydrocephalus

Hydrocephalus, affecting about 2 in 1000 live births, is a condition in which there is excessive accumulation of CSF around or within the brain. It can be caused by too much CSF production, too little CSF resorption, or a blockage within the cerebral ventricular system that causes a build-up of fluid. Communicating hydrocephalus occurs when the blockage of CSF flow is downstream of the ventricles. Noncommunicating hydrocephalus or obstructive hydrocephalus occurs when the flow of CSF is blocked along one of the passages connecting the ventricles. During infancy, the most common symptoms of hydrocephalus are a rapid increase in head circumference, irritability, sleepiness, vomiting, and downward deviation of the eyes (sunsetting). It is treated by shunting from the ventricles or spinal cord to the abdominal cavity or atria. There is a one-way valve within the shunt that prevents CSF from flowing back into the ventricles. Some infants with hydrocephalus can be treated neuroendoscopically with the creation of a ventriculostomy on the floor of the third ventricle. Complications of ventricular shunts include failures, infections, and disconnections.

Epilepsy

Surgical treatment for epilepsy is being done more commonly in infants. Lesions associated with epilepsy include focal malformations of cortical development, tumors, Sturge–Weber syndrome, epidermal nevus syndrome, and vascular malformations and infarctions. Surgical treatment of focal lesions has a success rate of infants being seizure-free of approximately 60 percent. Infants operated on at a young age and for infantile spasms had the most improvement of developmental quotients [25].

Myelomeningocele

Myelomeningocele occurs when the neural tube fails to fold normally in the third to fourth week of gestation. It occurs in about 1 in 1000 live births in the United States. The infant is at increased risk for infection, so generally closure of the meningomyelocele occurs on the first day of life. It can be associated with other congenital anomalies so a thorough preoperative evaluation is warranted. About 20 percent of cases at birth are associated with hydrocephalus, but eventually 80 percent of patients with meningomyelocele will require ventricular shunting for hydrocephalus. The lesion must be protected prior to closure with sterile warm, wet dressings. Intubation can be accomplished in the lateral position or with the infant supine on foam cushions that shield the meningomyelocele from any pressure. Postoperatively, infants must be in the prone position.

Brain and Spinal Cord Tumors

See Chapter 30 on neonatal and infant tumors.

Laryngeal and Tracheal Issues

Cystic Lesions

Dermoid cysts are structures lined by epithelium which contain various elements derived from epithelium along embryonic fusion plates [9]. They range from 1 to 4 cm in size, are commonly found on the forehead, lateral eye, or neck, and can be fixed or mobile. Most are subcutaneous although there can be extension intracranially or intraorbitally. Treatment is surgical excision so preoperative CT or MR scan to rule out extension is recommended. A tunneled endoscopic approach starting behind the hairline to avoid facial scarring can be utilized.

Thyroglossal duct cysts occur along the tract by which the thyroid descends during embryonic development from the base of the tongue to the normal thyroid position. They are typically noticed as a midline neck mass following an upper respiratory infection, or become primarily infected [10]. These cysts often move when swallowing and can track though the hyoid bone [3]. Preoperative ultrasound is recommended. Treatment is excision to prevent further infection. Recurrence is more likely if the child is under two years of age or has had two or more infections [11].

Branchial cleft cysts are derived from sequestration of first and second branchial cleft elements, resulting in cysts, sinuses, and tags. The incidence is sporadic, although there are reports of autosomal inheritance with equal male to female frequency, and 10 percent are bilateral [9]. These lesions usually present as soft tissue masses along the border of the sternocleidomastoid muscle. First branchial arch cysts are usually high in the neck. The more common second arch cysts are lower in the neck and often communicate with the tonsillar fossa. The less common third arch cysts are low in the neck and can communicate with the pyriform sinus. Branchial cleft cysts usually present after an upper respiratory infection as a tender mass. After treatment of the cysts with antibiotics they are excised in order to prevent reinfection and the possibility of carcinoma [10].

Vascular Malformations

Venous Malformations

Venous malformations are the most common vascular malformations. They present as soft, compressible, blue-colored structures. They are found predominantly about the head and neck. A high percentage of larger lesions have associated deep cerebral malformations that should be investigated. Treatment with sclerotherapy is highly successful, especially when surgical excision would be disfiguring or impossible.

Arteriovenous Malformations

Arteriovenous malformations (AVMs) are the most serious vascular lesions. They can cause high-output heart failure or may spontaneously rupture. Dental extraction in the presence of a mandibular AVM has been known to lead to massive bleeding. Treatment of an AVM is sclerotherapy, quickly followed by surgical excision to prevent new arterial channels from opening.

Lymphatic Malformations

Lymphatic malformations are the result of primary lymph sacs that do not coalesce with the rest of the lymphatic system. The resultant cystic structures may be small, microcystic, or large, macrocystic, also termed cystic hygroma. Microcystic lymphangioma are invasive and ill-defined, extending through various tissues and organs. Macrocystic tend to be well circumscribed, although both elements can coexist. Lymphatic malformations present early in life and expand as lymph accumulates within the cysts. Cystic hygromas occur in about 1:12 000 live births, and are located in the posterior triangle of the neck, cephalad to the clavicle [3]. The cyst may extend from the skin internally to the mucosa of the trachea. Lesions can be life-threatening if the trachea becomes compressed [11]. If detected in utero by ultrasonography, the airway may be secured intrapartum while the umbilical vessels are still attached, via an EXIT procedure. Surgical excision is necessary for treatment in most cases. A chest radiograph, ultrasonography, and MR/CT scan are needed to delineate the extent of the lesion. Sclerotherapy may be effective, although for macrocystic lesions a new sclerosing agent, OK432, has been very effective.

Anesthetic Considerations

Airway management is the major anesthetic concern of these patients as they typically are difficult to bag-mask ventilate, difficult to intubate, or both. Patients with midface hypoplasia have high resistance to nasal breathing and are essentially mouth breathers. Standard airway maneuvers, which close the mouth to get a better mask fit, increase the degree of obstruction. Care should be taken to keep the mouth open to allow for air passage. Early insertion of an oral airway is helpful. Topical anesthesia applied to the oral cavity prior to induction anesthesia will minimize the risk of laryngospasm from the early insertion of the oral airway.

Other patients who have mandibular hypoplasia or associated Robin sequence are at high risk of airway obstruction and difficult tracheal intubation. Alternative methods other than direct laryngoscopy to secure the airway include insertion of a laryngeal mask airway (LMA), fiberoptic instrumentation, and surgical instrumentation. Also see ‘Robin sequence’ below.

Cleft Lip and Palate

Cleft lip and palate are the most common congenital anomalies, occurring in 1 in 500 live births [13]. They may occur singly, together, as part of a syndrome, or the result of Robin sequence. The exact causative genetic factors are unknown but there is a strong familial inheritance. The problems associated with cleft lip/palate include difficulties with breathing, feeding, speaking, hearing, and general psychological well-being. The repair of the cleft lip may be staged or done as a primary repair. A dentomaxillary appliance may be inserted prior to repair to align the discontinuous alveolar ridges of the palate. Correction of the cleft palate should be performed before the child starts speaking. Some surgeons will use the Rose positon, resting the patient’s head in their lap, for the palate repair. Similarly, some will use a balsam of Peru-soaked pack sewn on the palate repair to promote wound healing. This dressing effectively obstructs the oral airway and thus patients must breathe nasally postoperatively.

Robin sequence

Robin sequence is defined by the three findings of micrognathia, glossoptosis, and airway obstruction. It was Pierre Robin who first identified the airway obstruction as being the result of glossoptosis as the posteriorly displaced tongue contacts the pharyngeal wall. Cleft palate occurs in 90 percent of Robin sequence patients as the displaced tongue mechanically interferes with closure of the palatal plates. Both the airway obstruction and the cleft palate are the result of micrognathia. Robin sequence may occur by itself or be associated with any syndrome that includes micrognathia.

These patients may have failure to thrive as the result of chronic hypoxia, increased work of breathing, and poor feeding. Treatment is directed at relieving the airway obstruction. Nonsurgical modalities include using the prone position with or without a nasopharygeal airway. Surgical therapies include tongue–lip adhesion, mandibular distraction, and tracheostomy. Additional alimentation may be provided via a feeding tube or a gastrostomy tube. If the Robin sequence is not associated with a syndrome, the mandible eventually will grow to near normal size, alleviating the airway obstruction. However, if associated with a syndrome, the mandible may remain hypoplastic.

Cholesteatoma

A cholesteatoma is squamous epithelium and its accumulated debris within the middle ear and pneumatized temporal bone. It may be characterized as congenital or acquired, with or without an infection. Acquired cholesteatoma is the most common etiology as the result of middle ear disease and is seen in older children. Congenital cholesteatoma is usually diagnosed by a pediatrician and is differentiated from the acquired form by being diagnosed in infancy or early childhood, in patients with no history of prior ruptured eardrums. Treatment is surgical excision either by a tympanoplasty or can be more extensive with a mastoidectomy. A general anesthetic with a secure airway and IV access are required for the surgery.

The patient is positioned supine with the head rotated laterally for exposure of the affected side. Care should be used for patients with limited neck range of motion or those at risk for cervical instability (e.g., patients with trisomy 21). For these patients, consideration for lateral decubitus positioning may be warranted. The facial nerve is usually monitored, necessitating avoidance of long-acting neuromuscular blocking agents. Sevoflorane and/or isoflurane are generally used, but nitrous oxide should be avoided. Tympanometry has shown increased fluctuations in middle ear pressure when nitrous is added to other inhaled anesthetics [15]. Diffusion of nitrous oxide into the middle ear will increase the pressure, causing outward movement of the tympanic membrane. Once the nitrous oxide is turned off, the rapid absorption of gas will create negative pressure, resulting in backward displacement of the tympanic membrane and disrupting the surgical repair. The movement may also be significant enough to cause disarticulation of the ossicles, leading to conductive hearing loss than can persist for several weeks postoperatively. The incidence of postoperative nausea and vomiting (PONV) after tympanoplasty is greater than 50 percent in some studies, although rarely occurs in infants, and the use of nitrous oxide may be contributory. Both dexamethasone and ondansetron have been shown to be efficacious as prophylactic agents for the treatment of PONV [16] in older children. If possible, a deep extubation is desirable to facilitate a smooth wake-up without excessive coughing or head movement.

Cochlear Implants

Cochlear implants are a popular and effective treatment for children with severe to profound sensorineural hearing loss. Unlike hearing aids which simply amplify sounds, the cochlear implants transform acoustic energy into electrical energy and stimulate the remaining inner ear neurons, partially restoring the child’s hearing. The surgical procedure involves attaching an internal processor to the mastoid process and connecting the electrodes to the cochlear neurons. There has been a trend toward earlier placement, with the procedure being performed on children as young as six months of age. The procedure is best completed in tertiary care centers where experienced pediatric surgeons, anesthesiologists, and perioperative care teams can take care of these young children [17].

The procedure requires a general anesthetic with a secure airway for children, though sedation with regional techniques has been used in adults. Use of muscle relaxation for optimal surgical conditions should be discussed with the surgeon as intraoperative facial nerve monitoring may be used. After insertion into the cochlear nerve, the implant is calibrated by two electrically evoked potentials, the evoked stapedius reflex threshold (ESRT) and the evoked compound action potential (ECAP). The ESRT is the loudest stimulus than can be tolerated without pain, while the ECAP is the smallest stimulus that can be perceived as sound. Volatile anesthetics suppress the ESRT in a dose-dependent fashion, resulting in inaccurate calibration, and a stimulus which may be painful when awake. Propofol does not cause this decrement and can be safely used, making it prudent to switch to a total intravenous anesthesia (TIVA) for the calibration portion of the procedure [18]. If volatile anesthetics are used early in the procedure it is important to communicate with the surgeon about the concentration and timing of the inhaled agent in relation to the actual implantation. Alternatively, the device can be calibrated when awake postoperatively, though this is very difficult in an infant. As with tympanoplasty, the PONV rate can be quite high and prophylactic antiemetic agents should be utilized in children older than one year.

Sinus Development in Children

At birth, neonates have pea-sized ethmoid and maxillary sinuses. During the second year of life, the sphenoid sinuses begin to develop, and after age eight the frontal sinuses develop. All reach adult size by adolescence. The paranasal sinuses are very commonly infected in young children, with about 10 percent of upper respiratory infections being complicated by paranasal sinusitis. Diagnosis is usually made in children with a cold lasting longer than 10–14 days, often with a low fever. Sinusitis symptoms are uncommon in infants and should lead to suspicion of immunologic deficiencies, congenital abnormalities, and the possibility of foreign bodies in the nasal cavity. Endoscopic sinus surgery is rarely done in infants. Occasionally adenoidectomies are done in infants to alleviate chronic sinus congestion.

Tracheal Stenosis

Tracheal stenosis may be congenital in etiology, but is more commonly an unfortunate consequence of prolonged intubation in a neonate, even if the endotracheal tube is appropriately sized. The stenosis may be glottic or subglottic, with the latter being much more serious and difficult to intervene upon surgically. Flexible or rigid bronchoscopy is often performed to visualize the site of the lesion and the surrounding anatomy. In combination with CT imaging and bronchoscopy, intubation with the largest endotracheal tube (ETT) that allows an audible leak provides information regarding the diameter of the stenosed portion.

If the stenosis is mild, a simple dilation or laser tracheoplasty may be the only needed intervention. With more severe lesions, invasive reconstructive procedures are indicated. One approach is the anterior cricoid split procedure. This is essentially a cricoid incision that uses an endotracheal tube as a stent. The incision begins just inferior to the thyroid cartilage and traverses the cricoid, continuing into the second tracheal ring. Sutures are then placed through the incision, allowing it to heal over the ETT tube with a slightly larger diameter. The ETT may be left in place for 1–2 weeks while the incision heals.

A more invasive larynogotracheoplasty involves a longer midline incision of the trachea from the inferior portion of the thyroid cartilage to the third or fourth tracheal ring. Following the incision, cartilage grafts are sewn in place to increase the diameter of the lumen. A stent is sometimes needed for mechanical support as the healing takes place. Revisions, excisions of scar tissue, and further procedures are often needed after tracheal surgery.

Vocal Cord Paralysis

Vocal cord paralysis is a common diagnosis in both adults and pediatric patients. While birth trauma, postoperative nerve dysfunction, and cardiac malformations are some potential etiologies, most patients carry a diagnosis of idiopathic vocal cord paralysis. Inspiratory stridor with hoarseness or a weak abnormal cry is frequently the presenting symptom in unilateral paralysis. Bilateral paralysis results in significant airway obstruction, stridor with a normal cry, aspiration, and difficulty with phonation. Bilateral paralysis is frequently comorbid with posterior fossa lesions and Arnold–Chiari malformation as stretching of the vagus nerve over the jugular foramen leaves it open to injury and paralysis. A tracheostomy may be required for severe obstructive symptoms and aspiration until an underlying cause can be diagnosed and surgical correction performed.

When inducing anesthesia, continuous positive pressure should be gently applied, abolishing the stridor, and stenting the airway open for easy ventilation. A direct laryngoscopy often provides very little information other than seeing if the vocal cord is paramedian and immobile. A fiberoptic intubation in the appropriate candidate provides better visualization, and allows a view of the glottis as well. The paralyzed vocal cord will not narrow the airway so a normal-sized ETT can be used.

Postoperative swelling and edema can make a well-compensated infant with a vocal cord lesion more stridulous and increase the work of breathing. Care should be taken to complete an atraumatic intubation with an appropriately sized ETT. The cuff pressure should not be above 20–25 mmHg. If there is concern about airway swelling, consider leaving the infant intubated or administer steroids.

Adenoids and Tonsils

The tonsillectomy, often performed with an adenoidectomy, is one of the most common pediatric procedures in the United States, but is rarely done in children less than one year. However, there is a recent trend to consider adenotonsillectomy in infants as a primary treatment for obstructive sleep apnea [21]. The efficacy of this treatment is unclear, with several studies showing good benefit from adenotonsillectomy in infants but others showing a greater persistence of OSA after adenotonsillectomy and a higher incidence of postoperative complications despite an improved apnea hypopnea index (AHI) [22,23]. Because of the possibility of worsening OSA in the immediate postoperative period, most institutions will admit infants to the intensive care unit postoperatively.

Laser Procedures and Suspension Laryngoscopy

The most common application for lasers in pediatrics involves airway surgery for recurrent papillomatosis. These benign tumors are the result of a human papilloma virus and may occur anywhere on the laryngeal tissues, including the true vocal cords. To facilitate visualization and access to the glottic region, the infant is often placed in suspension laryngoscopy after the induction of general anesthesia. Depending on the size, location, and characteristics of the lesions, they may cause varying degrees of obstruction. Thus, inhalational induction with spontaneous ventilation is the preferred anesthetic technique. As the anesthesiologist slowly takes over the child’s breathing, an IV is placed and airway management addressed.

Visualization of the larynx is accomplished using suspension laryngoscopy. Prior to suspension, propofol (2–3 mg kg^–1) should be given as this is quite stimulating. Glycopyrolate and/or atropine should be available to treat bradycardia caused by pressure on the larynx. Once in suspension laryngoscopy, the airway can be managed via several techniques including: (1) conventional ETT intubation, (2) intermittent apnea, (3) jet ventilation, and (4) tubeless spontaneous ventilation. The plan for the airway should be discussed with the surgeon prior to induction of anesthesia. The decision to secure the airway is based on the size and location of the tumor, as well as the surgeon’s need for space while applying the laser to the lesions. Anterior laryngeal lesions are generally not obstructed by the ETT, while posterior lesions will be blocked by the ETT lying directly over the posterior vocal cords and laryngeal structures.

Intermittent apnea is a technique that involves repeated intubations and extubations, which are facilitated by suspension laryngoscopy. During intubation periods, the patient can be hyperventilated and well-oxygenated. The tube can be removed, giving unrestricted access to the glottis. Periods of up to two minutes are generally tolerated quite well. This technique works well for shorter cases where anterior lesions require the absence of an ETT. Due to the apnea, a TIVA is preferable for maintenance of anesthesia.

Jet ventilation is a technique that allows ventilation while maintaining an unrestricted view of the glottis and a quiescent operating field. It requires a special jet ventilator to insufflate the lungs by altering the driving pressure, FiO₂, and frequency. A CO₂ monitor can be attached to a side port of the suspension laryngoscopy device to monitor the presence of exhaled CO₂. Chest rise and SpO₂ are used to judge the adequacy of the ventilation. Obese children and those with stiffened chest walls may not show much of a rise in the chest. When in doubt, an arterial blood gas (ABG) can be sent to assess the adequacy of ventilation and other ventilation strategies may need to be considered. In addition to inadequate ventilation, other risks of jet ventilation include gastric insufflation with potential aspiration, pneumothorax, and pneumomediastinum.

Lasers are the second most common cause of operating room fires. The gas mixture and route of delivery are important considerations for laser procedures. Aside from the standard PVC tubes, which are flammable, there are a variety of ETTs available to help reduce the risk of airway fires. These include red rubber tubes that can be wrapped in metallic tape, non-latex tubes, and several ETTs manufactured specifically for laser procedures (see table 3 from [28]). Though routinely used uneventfully in adults, these special ETTs have a large outer diameter and may not be appropriate for infants or children with a partially obstructed airway. It is important to note that the metallic tape-wrapped ETTs are safer than unwrapped tubes, but the cuff remains vulnerable to the laser. Any time lasers are being used, the FiO₂ should be less than 0.3, the eyes and face should be covered with wet sponges, and constant communication should be maintained between the surgeon and anesthesiologist. If possible, jet ventilation or tubeless techniques should be used to reduce the risk of fires [28]. Dexamethasone is typically given, 0.5 mg kg^–1, to reduce airway swelling as all airway procedures produce varying degrees of controlled injury and inflammation.

Classification

Cleft lip is categorized as unilateral or bilateral and designated as incomplete when the skin of the upper lip is not fully separated or complete when the defect involves the nasal floor and alveolus (Figure 22.1).

Figure 22.1 Types of cleft lip: (a) unilateral incomplete; (b) unilateral complete; (c) bilateral complete.

Adapted and reprinted with permission from Dr. John B. Mulliken [1]. Used with permission from the People’s Medical Publishing House, USA.

Cleft of the palate occurs in two major forms: soft palate only, which may extend into the posterior hard palate; and complete defect of the soft/hard palate, which is either unilateral or bilateral. The type and extent of palatal clefting is categorized by the Veau classification (Figure 22.2). Submucous CP is a minor form characterized by bifid uvula, thin soft palate due to incomplete muscular formation and a notch in the posterior edge of the hard palate. There is also an occult submucous CP that appears to be intact but can cause hypernasal speech.

Figure 22.2 Veau classification: soft palate only (Veau I); soft/hard palate (Veau II); unilateral complete cleft lip/palate (Veau III); bilateral complete cleft lip/palate (Veau IV).

Adapted and reprinted with permission from Dr. John B. Mulliken [1]. Used with permission from the People’s Medical Publishing House, USA.

Surgical Procedures and Timing

Many cleft lip and palate centers use some form of preoperative dentofacial orthopedic manipulation of the maxillary segments for the infant with unilateral and bilateral complete CL/P. A surgical alternative is a preliminary lip adhesion (labial closure) if the cleft is especially wide or if dentofacial orthopedics is not available.

Surgical closure of a cleft lip is usually performed at 4–5 months of age, when the infant is gaining satisfactory weight, and is free of any oral, respiratory, or systemic infection. The most commonly used technique for a unilateral CL is the rotation-advancement method of Millard. Repair of a bilateral CL is often accomplished synchronously with nasal and alveolar closure. Some surgeons stage the correction of the bilateral deformity. Most surgeons repair a CL while standing.

Cleft palate should be repaired at 8–10 months of age, because the incidence of velopharyngeal insufficiency increases after this age. Normal speech becomes increasingly unlikely if palatal repair is delayed beyond one year of age. Closure involves elevating mucoperiosteal flaps from the underlying palatal shelves and approximating these flaps in the midline, including dissection and retro-positioning of the levator muscles. Some centers employ a z-plasty palatal closure (Furlow technique). Most surgeons sit while undertaking repair of the CP.

Usually the infants are discharged on the second postoperative day after CL repair and after CP on postoperative day 2–4.

Associated Conditions

Every infant with CL/P or CP should be assessed for other associated anomalies. There is a long list of syndromes associated with CL/P and CP. Cleft lip/palate centers report that up to 30 percent of affected infants have other anomalies [2]. These congenital anomalies tend to be under-diagnosed at birth and early infancy, especially in those infants with a less severe expression of a genetic disorder. Associated anomalies include malformations of the upper and lower limbs or the vertebral column, the cardiovascular system, and gastrointestinal tract. Bilateral CL/P is a common finding in various trisomies, particularly involving chromosome 13. Nevertheless, most cases of CL/P occur as isolated (sporadic) anomalies, they are not syndromic. Cardiac anomalies occur in approximately 8 percent of CP infants. The most common associated disorder with CP is the Robin sequence, which can be nonsyndromic or syndromic.

Robin Sequence

Robin sequence is a diagnostic term that denotes mandibular micrognathia/retrognathia, glossoptosis (posterior displacement of the tongue), anterior larynx, and respiratory and feeding problems (Figure 22.3). Many infants with Robin sequence have ankyloglossia (tongue tie) which should not be severed until the infant is older and the airway is secure. Usually there is a CP but this is not an obligatory finding for Robin sequence. Most infants are either micro- or retrognathic, but not both. There are over 40 syndromes associated with Robin sequence. Stickler syndrome is the most common cause of Robin sequence (30–40 percent), followed by velocardiofacial syndrome (17 percent) (Table 22.1). In infants with nonsyndromic Robin sequence the mandible may grow to approximately normal size and a nearly normal upper/lower jaw relationship is expected so that the patients “grow out” of the airway obstruction. In infants with a syndromic Robin sequence mandibular growth potential differs depending on the particular syndrome. For example, in Stickler syndrome, mandibular growth is nearly normal. In contrast, in infants with Treacher Collins syndrome or bilateral hemifacial microsomia the mandible will remain hypoplastic and proportionally smaller and the airway problems will persist. (Figure 22.5)

Figure 22.3 (a) Infant with Robin sequence. (b) Intraoral view of U-shaped cleft palate.

Adapted and reprinted with permission from Dr. John B. Mulliken [1]. Used with permission from the People’s Medical Publishing House, USA).

A few days after birth, the severity of Robin sequence can be clinically graded: eats and breathes well with supine positioning (grade I); breathes well but obstructs when fed by mouth (grade II); cannot breathe or eat without obstruction and desaturation (grade III). Infants in the grade III group present with periods of cyanosis, usually with substernal and intercostal retractions. Feeding through a nasogastric tube might be a short-term solution; some infants need a gastrostomy. Initially the airway may be controlled by placing the infant in a lateral position with the head of the bed slightly raised and using a nasopharyngeal airway or a pacifier to keep the tongue forward. Prone position facilitates drainage of oral secretion and helps posture the tongue forward. Respiratory obstruction may occur combined with central and obstructive sleep apnea which can lead to cor pulmonale. If the infant desaturates despite all attempts of positioning or cannot be fed orally (many grade II and all grade III), operative intervention may include tongue–lip adhesion, mandibular distraction, and, as a last resort, tracheotomy if the tongue–lip adhesion fails (Figure 22.4) [3,4]. Airway management can be complex, with very difficult intubation, so awake techniques may be considered. In skilled hands fiberoptic intubation under general anesthesia may be used. For postoperative extubation infants should be fully awake [5].

Figure 22.4 Left lateral, frontal and right lateral view of former 33-week premature infant with Robin sequence (syndromic) and right predominant hemifacial microsomia. A tracheostomy was placed at age one month because of airway obstruction and apnea along with a gastrostomy for feeding difficulties. Note right micro-ophthalmia, right-sided soft tissue hypoplasia, bilateral mandibular deformity, retrognathia, right macrostomia (transverse oral cleft) and right microtia. He also has cervical vertebral and renal anomalies.

Courtesy Dr. John B. Mulliken.

Figure 22.5 Infant with bilateral hemifacial microsomia, predominant on left side, presented with noisy breathing and feeding difficulties requiring gastrostomy. Associated anomalies include bilateral eyelid colobomas, left limbal lipodermoid, facial asymmetry with midfacial hypoplasia, slightly elevated and rotated left nostril, small nasal airways with left-sided choanal atresia, minor bilateral macrostomia, restricted oral opening, micro-retrognathia, ankyloglossia (tongue-tie) glossoptosis, intact palate, bilateral low-set and posteriorly rotated ears with complex pretragal chondro-cutaneous remnants, and cardiac defects. During inhalational induction he did poorly with mask ventilation; two anesthesiologists were required to hold the mask, unable to pass a nasal trumpet but able to insert an oral airway. Direct laryngoscopy and intubation was difficult but possible using a video laryngoscope.

Courtesy Dr. John B. Mulliken.

Preoperative Evaluation and Anesthetic Considerations

Careful preoperative assessment, especially of heart, lungs, and airway, is mandatory to reveal associated conditions and abnormalities related to syndromes (Table 22.1). Infants with a large cleft and acute respiratory infection tend to have a higher intra- and postoperative complication rate which should initiate a discussion with the surgeon to postpone the operation [6]. Cleft lip repair involves minimal blood loss. Cleft palate repair has more blood loss but usually does not require blood transfusion in otherwise healthy infants with hematocrit values greater than 30 percent.

In our experience, tracheal intubation is not particularly difficult in most infants with CL/P, unless concomitant defects are present. The incidence of a difficult airway in infants with CL/P ranges between 5 and 10 percent [7–9]. The incidence of difficult laryngoscopy is 7 percent in the age group of 1–6 months old infants and is greatest for infants with bilateral CL/P [8]. Midfacial anomalies, mandibular hypoplasia (retro- or micrognathia, e.g., in Robin sequence, hemifacial microsomia, Treacher Collins syndrome) or restricted cervical movement are indicators of serious airway problems. If micrognathia is present, the incidence of difficult laryngoscopy is approximately 50 percent whereas without micrognathia it is about 4 percent [8]. Intubation difficulty decreases with increasing age in infants with nonsyndromic Robin sequence; however, in syndromic Robin sequence it differs depending on the particular syndrome (Table 22.1). Given the difficulty of recognizing micrognathia and retrognathia in young infants and that the ear and mandible develop from the first and second pharyngeal arches and first branchial cleft, abnormalities of the ear should prompt a closer examination of the mandible for hypoplasia. The presence of isolated microtia is also an indicator for difficult intubation with an incidence of difficult laryngeal view of 42 percent in patients with bilateral microtia, and 2 percent in those with unilateral microtia [10]. A careful review of previous anesthetic records may forewarn of a difficult airway.

Induction of anesthesia is usually performed in a spontaneously breathing infant with a non-irritating inhalational agent and is expected to be uncomplicated in an infant presenting for closure of simple CL/P with a history of airway patency during natural sleep (no snoring or sleep apnea). In the presence of a wide cleft palate the tongue can fall into the cleft and may obstruct the nasal airway. With increased relaxation of the oropharyngeal muscles the tongue will fall further posteriorly and may obstruct the oropharynx completely, which can be prevented by placing an oropharyngeal airway. Spraying the mouth with a topical anesthetic prior to induction will allow placement of an oral airway at light depths of anesthesia. If the anesthesiologist is comfortable ventilating the infant with a mask, a nondepolarizing muscle relaxant can be administered. Intubation of a patient with unilateral right-sided cleft is usually straightforward. Infants with left-sided complete cleft are more difficult because the laryngoscope blade will tend to fall into the cleft as the tongue gets swept to the left side and alters the line of vision. In bilateral CL/P, the premaxilla is angled anteriorly, altering the anesthesiologist’s line of sight onto the entrance of the larynx and hampering the insertion of the laryngoscope blade. To prevent traumatic laryngoscopy and intubation, the wide or bilateral cleft can be packed with moist sterile gauze. Sometimes external laryngeal manipulation of the larynx is useful during direct laryngoscopy if the mandible is hypoplastic. Infants with Robin sequence and associated craniofacial syndromes have a small oral cavity because of a hypoplastic mandible (Table 22.1); the larynx is positioned cephalad and anterior under the base of the tongue, and airway management requires more planning. If the patient has a history of lack of airway patency during sleep, successful ventilation by mask might be very difficult or unlikely. Consequently, alternative techniques for securing the airway need to be considered such as sedated/awake techniques, fiberoptic intubation, intubation through a laryngeal mask airway, and in severe cases tracheostomy [11]. In severe cases an otorhinolaryngologist should be available to help with the airway management and assessment for other causes of obstruction such as anomalies of the epiglottis and laryngomalacia.

For orotracheal intubation a variety of tubes are available. The Ring–Adair–Elwyn (RAE) or the microcuff Kimberly Clark preformed tracheal tube are frequently used and can be fixed on the chin, placed over the midline of the lower lip to facilitate optimal surgical access and visualize lip and palate. In infants with micro- and retrognathia the preformed tubes can be too long, which results in one-sided intubation. The advantage of the microcuff tube is the slimmer cuff which is positioned further distal (no Murphy eye) compared to the RAE tube, which facilitates appropriate midtracheal placement. The tube and the tubing system need to be carefully arranged when the operating room table is turned 90 or 180 degrees away from the anesthesia provider to prevent inadvertent extubation. Care must be taken that bilateral ventilation of the lungs is present during all repositioning maneuvers by the surgical team and after the mouth gag and throat pack is positioned. Insertion of the gag and repositioning of the neck tends to advance the tip of the tube in the trachea, with the risk of one-sided ventilation. The eyes need to be carefully protected before incision. Monitoring should include the standard ASA monitors and ventilation parameters (compliance, ventilation pressures, tidal volume) to recognize compression of the tube caused by surgical maneuvers or obstruction (e.g., secretion).

Maintenance of anesthesia is achieved with low doses of inhalational agents combined with short-acting opioids (e.g., 1–2 μg kg^–1 fentanyl for induction as well as for incision and repeated doses during each consecutive surgical hour) or medium-acting opioids (e.g., 30 μg kg^–1 morphine for induction, as well as for incision and 30–40 minutes before emergence). Very short-acting opioids, like remifentanyl, are avoided in our practice because of the risk of developing hyperalgesia during the immediate postoperative period. Local infiltration with local anesthetic (e.g., lidocaine 0.5 percent or bupivacaine 0.25 percent with epinephrine 1:200 000) and bilateral infraorbital blocks during CL repair may reduce the amount of opioids and risk of postoperative respiratory depression [12–15]. In neonates, Boesenberg et al. prefer a percutaneous technique instead of a perioral one, with bupivacaine 0.5 percent 0.5–0.75 ml with epinephrine 1:200 000 [16]. Communication with the surgeon and parents is recommended because even small amounts of local anesthetic can cause edema and small hematomas in the cheeks.

Extubation, Acute Airway Obstruction and Postoperative Care

At the end of the procedure infants should wake up in an unagitated state, as hypertension and undue crying may cause bleeding or place excessive tension on the repair. After cleft repair, the minimal to moderate amount of blood in the oropharynx needs to be carefully suctioned. Extubation should be performed after airway reflexes have returned in an infant that is awake, opens the eyes, and presents with regular breathing and good muscle tonus. There may be some respiratory difficulties on emergence, including acute upper airway obstruction as a result of upper airway narrowing due to the surgical reduction of the pharyngeal space, edema, and residual anesthetic effects. All infants with a nonsyndromic or syndromic Robin sequence who presented with a difficult airway management during induction should be observed in the NICU/ICU post CP repair. Rare cases are reported of massive lingual swelling in infants with Robin sequence as well as in otherwise healthy infants follow CP closure. The reasons might be prolonged procedures, head-down position, and prolonged lingual retraction [17,18]. In selected cases surgeons provide a tongue suture for traction which often proves helpful in restoring the infant’s airway. In some institutions after CL repair, surgeons like to use a Logan bow to protect the operative site combined with a saline-soaked gauze over the wound (Figure 22.6). In these cases awake extubation with good airway reflexes is of special importance because mask placement and ventilation is impossible with the bow in place. The saline-soaked gauze is used for the first 24 hours to prevent crusting and the bow is temporary. Arm restraints are used in many centers to prevent trauma to the labial repair. During the postoperative course vigilance and monitoring is required for upper airway obstruction (48 hours), late postoperative edema, subcutaneous emphysema and negative pulmonary pressure edema. Any signs of airway obstruction and stridor require careful attention and treatment with corticosteroid and racemic epinephrine to prevent reintubation. Postoperative bleeding is difficult to detect because the blood is usually swallowed. Postoperative analgesics should be titrated to avoid causing sedation and airway obstruction. Pain is managed with acetaminophen and IV opioids can be titrated in the PACU with conversion to oral opioids as soon as oral intake permits. Feeding is usually initiated as soon as the infant is awake.

Figure 22.6 Five-month-old infant with unilateral left incomplete cleft lip following rotation advancement repair and correction of minor nasal deformity. Xeroform gauze-wrapped tubing inserted in left nostril. Logan bow (left and center picture) holds an iced saline sponge (right picture). The infant was extubated fully awake and recovered in the postanesthesia care unit.

Courtesy Dr. John B. Mulliken.

Classification

Craniosynostosis occurs as either an isolated single fusion (80 percent) or as multiple-sutural fusion (20 percent) that can be syndromic or nonsyndromic. Sagittal craniosynostosis is the most common form (sagittal: 50–60 percent, coronal 20 percent, metopic 10 percent). Increased intracranial pressure can occur in 15–20 percent of infants with single sutural synostosis and in 40–70 percent of those with syndromic craniosynostoses [20]. Surgical intervention is indicated to prevent complications such as cerebral compression, auditory impairment and visual loss [21–24]. The etiology of most cases is sporadic, although there is often a strong genetic component. Genetic mutations that are responsible for the syndromic craniosynostoses include mutations in the fibroblast growth factors (FGFR 1, FGFR2, FGFR3), TWIST, and MSX2 genes.

Progressive postnatal craniosynostosis, a rare presentation, is characterized by a normal cranial shape and normal radiological images at birth. Later in childhood there is slow development of intracranial pressure (ICP), with signs/symptoms such as headaches, vomiting, irritability, papilledema, progressive optic atrophy, seizures, and/or bulging fontanelles [25].

Positional plagiocephaly, also known as deformational plagiocephaly, is extremely common and can be confused with craniosynostosis, particularly lambdoid fusion. There is characteristic unilateral occipital flattening and anterior displacement of the ipsilateral ear. This harmless condition is treated nonsurgically by an orthotic helmet if initiated early enough [26,27].

Craniosynostotic syndromes and implications for preoperative assessment

There are important anesthetic implications in the care of infants with craniosynostoses, which can be associated with numerous syndromes. The most frequent ones are detailed in Table 22.3.

Airway comorbidity. Children, especially those with syndromic craniosynostosis, can present with a compromised airway. Although the incidence of sleep disorder and obstructive sleep apnea syndrome is high, it is often unrecognized [28,29]. Obstructive sleep apnea symptoms occur in almost half of the children during episodes of upper respiratory tract infections. Major upper airway obstruction is found more frequently in patients with Crouzon, Pfeiffer, and Apert syndromes and less often in patients with Muenke and Saethre-Chotzen syndromes [30]. Causes for severe airway obstruction include mid-facial hypoplasia, choanal atresia, and also lower airway anomalies. Tracheal cartilaginous sleeve is a rare congenital cartilage malformation reported only in children with craniosynostosis syndromes and is characterized by fusion of the tracheal arches that may be isolated to a few tracheal arches, involves the entire trachea, or extends beyond the carina into the bronchi [31]. Infants with syndromic craniosynostosis can present with difficult airway management [11,32] but rarely require tracheostomy, unless there is marked facial dysmorphism [33].

It is important to consider the effect of chronic airway obstruction on the cardiovascular system and the central nervous system. Patients who have a history of longstanding airway obstruction may have chronic hypoventilation and hypoxia that can lead to pulmonary hypertension and subsequently cor pulmonale. The chronic respiratory obstruction forms part of a vicious cycle with increased intracranial pressure and a subsequent decrease in cerebral perfusion pressure [34]. Recurrent episodes of intermittent reduction of cerebral perfusion pressure most likely have a negative effect on neurological and cognitive development in the long term.

Cardiac comorbidity. Craniosynostotic syndromes can occasionally be associated with cardiac anomalies (Table 22.3). Congenital heart disease, both repaired and unrepaired, has been shown to increase the risk for anesthesia and any surgery. Infants with patent foramen ovale or ductus arteriosus are at risk for paradoxical air emboli (coronary or cerebral air embolism) through these defects.

Neurological Comorbidity. Several factors contribute to the risk of developing increased ICP, including decreased intracranial volume and increased number and location of sutures involved [35]. Although it is well known that increased ICP is commonly associated with multiple suture craniosynostosis [30], ICP monitoring has demonstrated that 14–24 percent of infants with single-suture craniosynostosis also have raised ICP [24,36]. Positron emission tomography scans have shown reduced cortical blood flow in the vicinity of sagittal synostosis in 70 percent of cases, which can be corrected by early release [37]. Hydrocephalus is seen sometimes in patients with craniosynostosis. It is particularly associated with Crouzon and Pfeiffer syndrome, and Kleeblattschädel (cloverleaf skull syndrome; see Figure 22.9). Multisuture craniosynostoses, particularly with lambdoid involvement, are associated with a higher incidence of acquired Chiari deformation, require multiple operative procedures, and cause more developmental delay than isolated single-suture synostoses [38]. Evidence of jugular foraminal stenosis or atresia and dilated collateral emissary veins in children with syndromic craniosynostosis is associated with venous outflow obstruction and elevated intracranial venous hypertension [39,40]. Disruption of emissary veins during an operation can produce massive hemorrhage. Enlarged basal emissary foramina which transmit enlarged emissary veins result from stenosis or atresia of the jugular foramen. Bilateral basilar venous atresia is most common in patients with the FGFR3 ala391glu mutation (crouzonoid features with acanthosis nigricans) but also may be found in patients with FGFR2 mutations [39]. Preoperative assessment of patients with syndromic craniosynostosis and enlarged emissary foramina should include skull base vascular imaging of the basilar venous drainage [39]. Significant increased intracranial bleeding is expected during craniectomy.

Ophthalmologic Comorbidities. Ophthalmologic examinations may show papilledema and optic atrophy with chronically raised ICP [41]. Syndromic craniosynostoses with shallow, deformed orbits, and exorbitism increases the risk of corneal abrasion and ocular trauma during an operation.

Cervical vertebra anomalies, particularly in Apert, Pfeiffer, and Crouzon syndromes, limit neck motion (flexion and extension) and can increase the difficulty of intubation and positioning for the operation.

Surgical Procedures and Timing

The type and timing of the operative correction for craniosynostosis varies with age, location, and number of sutures involved, and the experience of the surgical team. Indications for repair of craniosynostosis include: increased ICP, cranial deformity, exorbitism, airway obstruction, and psychosocial reasons.

Endoscopic-assisted strip craniectomy (ESC) is considered for infants less than three months of age, usually for single-suture synostosis and in selected cases for multiple sutural synostosis. Endoscopic-assisted strip craniectomy is a short surgical procedure (approximately 30–45 minutes) associated with low incidence of perioperative blood transfusion (0–11 percent) [42–45], VAE (2–8 percent) [44,45], ICU admission (8 percent) [44], and expense [46]. Most infants are discharged on postoperative day one. Postoperative molding helmet therapy for approximately eight months (Figure 22.7) is an integral part of this treatment modality necessary to counteract the tendency of the cranial vault to revert to premorbid shape after strip craniectomy [43].

Figure 22.7 Endoscopic-assisted strip craniectomy (ESC). Upper left and center picture: Infant in prone position for sagittal ESC on a modified prone head holder in sphinx position. It illustrates the extended head position and the significant distance between the highest point of the surgical field to the right atrium, a risk factor for venous or paradoxical air embolism. Upper right picture: Intraoperative picture of sagittal ESC with two skin incisions perpendicular to the fused sagittal suture: one posterior to the coronal sutures and the other at the junction of the lambdoid sutures. After endoscopic suturectomy, the 1–2 cm wide bone strip of the fused sagittal suture is removed. Lower pictures: Postoperative orthosis after ESC. Infant with sagittal synostosis after sagittal ESC wearing the helmet with openings at the side that allows the growing brain to push the skull out which finally results in the desired round head form.

Courtesy Dr. Mark Proctor.

Patient positioning during neuroendoscopic procedures remains one of the paramount concerns in providing optimal surgical access and exposure of the suture for visualization and resection. Sagittal ESC and lambdoid ESC are usually performed in prone position, often using special headrests (e.g., Doro headrest system, PMI, Freiburg im Breisgau, Germany; Figure 22.7) and metopic and coronal ESC in supine position, commonly using the cerebellar headrest. The endotracheal tube has to be carefully placed in midtracheal position to prevent inadvertent extubation or bronchial mainstem intubation, taking into account the resultant displacement related to the head positioning (Figure 22.7).

Cranial burr holes are made through the midline of each scalp incision. An endoscope is used to visualize the fused suture, identify emissary veins, dural attachments, and assure hemostasis. The fused suture is resected as a 1 cm wide bony strip and removed through the burr hole (Figure 22.7). Bone bleeding is controlled using bone wax and thrombin-soaked absorbable gelatin (Gelfoam, Pharmacia and Upjohn, Kalamazoo, MI).

Spring-assisted cranioplasty involves implanted springs in the synostosed sutures that allow gradual correction of the cranial malformation over time. It is used in infants older than three months of age with single sutural craniosynostosis and in selected infants with multiple sutural synostoses [47,48]. Different surgical groups report varying mean surgical times (range 30–170 minutes for insertion and 20–60 minutes for spring removal) and need for blood transfusion ranging from no blood transfusion [49] to blood loss comparable to open strip craniectomy [48,50]. This technique involves an osteotomy and resection of the prematurely closed suture combined with the insertion of 1–3 stainless steel springs across the newly created cranial gap (Figure 22.8). The expansion of a spring is a slow process and is monitored both clinically and radiologically. The springs are surgically removed after adequate cranial expansion (2–7 months).

Figure 22.8 Spring-assisted cranioplasty: After midline sagittal osteotomy, two omega-shaped springs are placed and cause a separation/distraction between the parietal bones. The two skin flaps created by the lazy-S incision are held aside with sutures.

Courtesy Dr. Claes G.K. Lauritzen.

Open cranial procedures are usually performed in infants at ages 6–12 months. The surgical procedures vary in the extent of cranial elements moved, risk of dural tear, sinus injury, and blood loss (simple strip craniectomy, π cranioplasties, cranial vault remodeling). Anterior calvarial procedures and fronto-orbital advancement involve bilateral craniectomy and sometimes require also posterior cranial vault remodeling, with or without barrel stave osteotomies. These techniques are associated with major blood loss, varying between 0.2 and 4 blood volumes, lengthy operative times (3–8 hours), and hospital stay (4–7 days), and require postoperative monitoring in a pediatric intensive care unit [51–53].

Anesthetic Considerations

Anesthetic Considerations

If the infant presents for serial procedures, premedication should be considered. The location and size determine the frequency and anesthetic technique. If the face, neck, and head are involved, airway management needs to be discussed with the surgical team. The tissue expander is implanted under general anesthesia. The expanders are usually inflated in the outpatient setting via percutaneous access using local anesthetics at the puncture site until calculated inflation volume is achieved. Some infants might also require anesthetics/sedation for the tissue expansion process. The location of the tissue expanders and their expansion can make positioning of the infant challenging for airway management and surgical exposure. It can be managed by special head rings and positioning devices (e.g., blankets) to build up the body to the level of the head. The most common complications of tissue expansion are infection, deflation, and exposure of the expander [85]. Other indications for tissue expansion include craniofacial anomalies, aplasia cutis congenital, meningomyelocele, and giant abdominal defects [90,91].

Anesthetic Considerations

Antenatal diagnosis of cervicofacial LM permits planning for delivery and immediate postnatal care (Figure 22.10). If prenatal ultrasonography demonstrates a severely narrowed airway, ex utero intrapartum treatment (EXIT) can be life-saving [93–96]. After Cesarean section, the patency of the neonate’s airway is assessed before clamping the umbilical cord. Intubation may be possible, but if laryngeal LM prevents insertion of the endotracheal tube, tracheostomy can be performed [97]. A cervicofacial LM is soft, allowing the neonate to breath spontaneously, whereas a large teratoma in this location is usually a firm, solid mass and more likely causes a problematic airway.

Figure 22.10 Neonate with left cervicofacial lymphatic malformation, born at 34 weeks’ gestational age. Ex utero intrapartum treatment (EXIT procedure) ensured uteroplacental gas exchange and fetal hemodynamic stability while ENT service established and secured the airway. After intubation using a Parson laryngoscope, the neonate was fully delivered and taken to the warming table and ventilated.

Courtesy Dr. Reza Rahbar.

A newborn with cervicofacial LM can exhibit rapid enlargement of the tongue or floor of the mouth, leading to respiratory obstruction with stridor, dysphagea, and apnea. A complete examination of the airway is necessary, including fiberoptic nasopharyngoscopy and laryngoscopy to assess for potential involvement of the hypopharynx, supraglottis, and larynx. Acute airway obstruction can occur during induction and spontaneous ventilation should be maintained until the airway is secure. Fiberoptic intubation might be possible; however, a large cervicofacial LM usually necessitates tracheostomy due to involvement of the supraglottic airway and the risk of acute swelling secondary to intralesional hemorrhage and sepsis [92,98].

Treatment options for LM include sclerotherapy for macrocystic lesions, preoperative embolization to control lingual bleeding, CO₂ laser and radiofrequency ablation for vesicles, and well-timed staged resection to debulk the mass [99–102]. Resection of a facial LM is difficult because the lesion permeates through the soft tissue. Monitoring of the facial nerve can be helpful and requires withholding of muscle relaxation during that phase of the procedure. Corticosteroid is given intraoperatively to reduce postoperative swelling and tapered over 2–3 postoperative days.

Postoperative complications include: airway obstruction, laryngeal edema, nerve damage, and wound infection or delayed cellulitis. After resection of a LM, a stay in the intensive care unit is required until swelling subsides. An infant undergoing resection of LM in the tongue and oral floor usually has a tracheostomy or requires prolonged postoperative intubation because the tongue has a remarkable capacity to swell and protrude in the immediate postoperative period. A serosanguineous fluid collection may have to be tapped, often repeatedly, by ultrasonographic guidance. Partially resected LM has the potential for regeneration.

Gastrointestinal Duplications

Gastrointestinal duplications are rare congenital lesions that occur in approximately 1 in 4500 live births [14]. Duplications have been described at all points along the gastrointestinal tract as proximally as the mouth and as distal as the anus. The etiology of gastrointestinal duplications is unclear, but they are thought to occur between four and eight weeks during embryonic development. Existing theories to explain their occurrence include errors in recanalization of the primitive intestine, failure of regression of embryonic diverticuli, and errors of notochord splitting [15,16]. Gastrointestinal duplications can either occur as an isolated occurrence or involve multiple locations. Duplications generally do not communicate with adjacent gastrointestinal structures, though this is not universally the case. Similar to the case of many congenital malformations, there are often associated systemic abnormalities that should be identified and evaluated [17,18].

With the advent of and improvements in prenatal imaging, most gastrointestinal duplications are detected in utero and have in only rare instances required fetal intervention. Most pediatric surgeons advocate resection of the duplication, though for asymptomatic patients the optimal timing of surgery remains unclear, and presently there are no concrete data to aid in guiding practice [14]. Patients who develop sequelae of duplications usually do so in the context of secretions that accumulate in noncommunicating and closed space duplications, leading to pain and compression of adjacent structures. Such developments are of particular concern when the compression of adjacent vasculature leads to bowel ischemia. The duplication can also serve as a lead point for the bowel to telescope around surrounding intestinal segments, leading to intussusception. Ulcerations resulting in bleeding can occur in the duplication itself secondary to ectopic gastric tissue or in adjacent tissue [19].

Anesthetic considerations for gastrointestinal duplications include localization of the duplication, identification of any associated abnormalities, and the clinical manifestations of the duplication. Potential for airway obstruction may require the use of rigid bronchoscopy, and bowel obstruction will mandate full stomach precautions.

Pyloric Stenosis

Pyloric stenosis is a relatively common condition requiring surgical intervention in infants and occurring in approximately 2–5 out of 1000 live births [20]. The etiology of pyloric stenosis is not entirely clear, though likely multifactorial. The condition occurs four times more commonly in males than in females and has a higher prevalence in first-born children [21]. Unlike many other gastrointestinal abnormalities, patients with pyloric stenosis are otherwise generally healthy, though a familial genetic predisposition is observed.

The pathological finding in pyloric stenosis is hypertrophy of the muscularis layer of the pyloric sphincter, leading to gastric outlet obstruction. Patients typically present with immediate, nonbilious, nonbloody, postprandial projectile vomiting at the age of 3–12 weeks [22] that often increases with intensity over time. The severity of dehydration and electrolyte abnormalities generally correlates with the degree and duration of symptoms prior to presentation [23]. In general, patients will present with a chloride-sensitive, hypochloremic, hypokalemic, metabolic alkalosis with some degree of hyponatremia secondary to volume depletion and paradoxical aciduria. However, if there is longstanding volume loss without correction, patients can present with metabolic acidosis as a result of both lactic acidosis and renal dysfunction.

Pyloric stenosis can often be diagnosed by history alone, but supporting physical exam findings include an olive-shaped mass in the right upper quadrant. Diagnosis is typically confirmed with an abdominal ultrasound, though barium studies have also been utilized [24].

Pyloric stenosis is not a surgical emergency, though definitive treatment is surgical pyloromyotomy, which can often be performed laparoscopically. Prior to surgical intervention, acid–base status and electrolyte abnormalities should be corrected. Patients with persistent or untreated metabolic alkalosis are at increased risk of postoperative apnea [25]. Metabolic alkalosis is often corrected after hospital admission and preoperatively with saline administration that corrects volume status, replenishes total-body sodium and chloride, and promotes excretion of urine bicarbonate. Secondary to dehydration, patients may present with renal insufficiency, and potassium repletion should be initiated only with the establishment of urine output. Serum chloride concentration can be followed to gauge the adequacy of rehydration and correction of the underlying metabolic alkalosis. Studies by Goh et al. and Shanbhogue et al. demonstrated that a serum chloride concentration greater than 106 meq L^–1 predicts correction of alkalosis in the majority of patients with pyloric stenosis [26,27].

Due to functional gastric outlet obstruction, patients with pyloric stenosis are at high risk for aspiration during induction. The stomach should be emptied with a large-bore orogastric tube, sometimes with several passes, prior to induction. This does not necessarily guarantee an empty stomach. The airway should be secured by means of a (modified or standard) rapid sequence induction or awake intubation. Anesthesia can be maintained with nondepolarizing neuromuscular blockade and volatile anesthetics, though Davis et al. showed decreased postoperative respiratory events with the use of a remifentanil-based anesthetic [28]. For longer cases, a dextrose infusion should be started. Surgeons may ask that an orogastric tube be used to insufflate the stomach to rule-out luminal perforation following repair. Adequate analgesia can generally be obtained with rectal or intravenous acetaminophen combined with local anesthetic via caudal block or local infiltration by the surgeon. Sparing use of intermediate and long-acting opioids is advocated. The patient should be awake and vigorous at the end of the case prior to extubation. In addition to remaining metabolic alkalosis, hypothermia, hypoglycemia, residual neuromuscular blockade, and previous opioid administration can all further increase the risk of postoperative apnea, and every attempt should be made to avoid these conditions [21,29].

Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is characterized by ischemic necrosis of the intestinal mucosa, leading to gut translocation of enteric organisms and to potential local and systemic complications. Necrotizing enterocolitis occurs in approximately 1 out of 1000 live births, is inversely related to birth weight and rarely occurs spontaneously in full-term neonates unless associated with predisposing conditions, such as congenital heart disease, sepsis, or hypotension, that lead to compromise of intestinal blood flow [30,31]. Mortality from NEC is 15–30 percent, and survivors often suffer from long-term sequelae such as short-gut syndrome, parenteral nutrition dependence, and growth and neurodevelopment deficits [30,32].

Necrotizing enterocolitis classically develops in the second to third week of life after the initiation of feeding, though it can develop in patients prior to initiation of feeding and has been rarely observed in patients who have tolerated feeding for a significant length of time. NEC often initially presents with constitutional symptoms such as lethargy, temperature instability, hypotension, and apnea in conjunction with or followed by gastrointestinal symptoms such as feeding intolerance, emesis, abdominal distention, or bloody stool. As the disease progresses, worsening abdominal distention, increased abdominal tympany, palpable bowel loops, and periumbilical abdominal wall erythema and ecchymosis can develop. Imaging studies can help to confirm diagnosis, although NEC is a clinical diagnosis and radiographic findings are not always appreciated. Findings that are highly suspicious for NEC include pneumatosis intestinalis, pneumoperitoneum, and evidence of air within the portal system. Patients may concurrently experience deterioration of other organ systems by avenues such as hematologic abnormalities (disseminated intravascular coagulation, thrombocytopenia, coagulopathy), metabolic acidosis, respiratory failure, and septic shock.

Initial management includes supportive measures such as bowel rest, nasogastric tube decompression, broad-spectrum antibiotics, and hemodynamic and respiratory support if necessary. Medical management is continued with serial monitoring of abdominal exam and radiographic studies. If there is high suspicion or frank evidence of intestinal perforation, surgical intervention is indicated and includes laparotomy with resection of affected bowel segments and/or bedside peritoneal drainage. Between 20 and 40 percent of NEC cases require surgical intervention [31,33], with Guthrie et al. showing a mortality rate of 23 percent for surgical NEC patients compared with 4 percent for medically managed NEC patients [33].

Patients who present requiring surgical treatment will often have multi-organ dysfunction that will complicate perioperative management. Existing hematologic abnormalities may require ongoing treatment with appropriate blood component therapy. Hypotension secondary to intravascular volume depletion and septic vasoplegia is common in the presence of intra-abdominal fluid sequestration and distributive shock. Consequently, the patient may require additional or initiation of vasoactive infusions and continued fluid administration to maintain blood pressure. A primarily narcotic-based anesthetic may be better tolerated from a hemodynamic perspective than one that utilizes higher concentrations of volatile anesthetics. In addition, delivery of volatile agents may be limited if an ICU ventilator is utilized for transport and better control and monitoring of respiratory parameters. If the airway is not already secured, consideration should be given to a rapid sequence induction or to an awake intubation. Venous access should take into account the likely need for administration of large amounts of volume and vasopressor therapy. Obtaining arterial access for hemodynamic monitoring and blood sampling is optimal but should not unduly delay definitive surgical treatment in a clinically deteriorating patient.

Meconium Ileus

Meconium ileus (MI) is characterized by bowel obstruction, generally at the level of the terminal ileum and ileocecal valve secondary to accumulation and failure of passage of thick, desiccated meconium. Patients with cystic fibrosis (CF) in particular have a propensity to develop MI due to secretion of highly viscous meconium that adheres to the intestinal lumen. Twenty percent of CF patients who develop MI represent 80–90 percent of the total MI cases [34,35]. Meconium ileus is categorized as simple or complex. Simple MI presents clinically with abdominal distention, failure to pass meconium and, in some cases, emesis. Roughly 50 percent of cases of MI are classified as complex. Meconium ileus is classified as complex if there is associated gastrointestinal pathology such as perforation, peritonitis, atresia, or volvulus. Volvulus and other ischemic insults that occur in utero may manifest postnatally as bowel atresia. Simple MI is treated with nasogastric decompression, correction of any fluid or electrolyte abnormalities, and administration of serial hyperosmolar enemas [36]. Repeat enema administration is common but increases the risk of perforation and other complications with each additional attempt [37,38]. Simple MI that is refractory to more conservative medical management requires surgical intervention.

Preparation for the operating room should identify and initiate correction of electrolyte abnormalities and volume depletion as a result of potential dehydration, hyperosmolar enema therapy, or fluid shifts associated with bowel injury or obstruction. In CF patients, the lung pathology is generally not a concern until after several years of life [39], unless the clinical presentation is associated with previous aspiration or secondary lung injury due to sepsis or systemic inflammatory response syndrome. Stomach contents should be decompressed with an orogastric tube prior to induction to minimize the risk of aspiration during anesthetic induction. Rapid sequence induction or awake intubation with local anesthetic should be employed to secure the airway. Anesthetic can be maintained with neuromuscular blockade and, depending on hemodynamic status, with volatile versus an opioid-based anesthetic. Vasoactive infusions should be readily available to treat potential hypotension.

Malrotation

Malrotation results from in utero arrest of normal rotation of the embryonic gut, leading to narrowing of the mesenteric base and to a predisposition to mesenteric twisting and consequent volvulus. With malrotation, there can also be abnormal attachments, known as Ladd’s bands, that form in the process of attempting to affix the bowel in the peritoneal cavity and that can lead to duodenal obstruction. Symptomatic malrotation occurs in approximately 1 in 5000 live births [40], and 50–70 percent of cases are associated with other congenital abnormalities. Gastrointestinal anomalies are most common, though cardiac, orthopedic, and central nervous system anomalies also frequently occur [41,42]. Intestinal atresia can be seen in cases in which malrotation occurs in utero during bowel development. In children with malrotation requiring surgery, up to 65 percent present during the first month of life [42].

Patients with malrotation can clinically present with either volvulus or nonischemic intestinal obstruction due to Ladd’s bands or atretic bowel. Patients with volvulus present with bilious emesis, symptoms of bowel obstruction, and potentially an acute abdomen. Grossly bloody stool can also be seen and usually indicates a more severe presentation with significant bowel ischemia. Diagnosis of malrotation in a clinically stable patient can be made radiographically with plain film or fluoroscopic upper gastrointestinal series with small-bowel follow-through or an abdominal ultrasound to determine the relative orientation of mesenteric vessels [43].

A patient with suspected or confirmed volvulus requires prompt surgical treatment to salvage affected bowel segments. Because volvulus is a surgical emergency, every effort should be made to safely proceed as quickly as possible to surgery with the goal of saving any viable bowel. The airway should be secured using full-stomach precautions. Arterial access can be obtained as needed, though doing so should not delay surgery and relief of ischemic bowel. As with many other ischemic abdominal pathologies, patients may present with a combination of intravascular depletion due to intra-abdominal inflammation and swelling along with vasodilation from sepsis. Treatment for hypotension may therefore require both fluid and blood component therapy in addition to vasoactive infusions. In cases in which abdominal compartment syndrome is present, concern should be exercised upon surgical decompression of the peritoneal cavity. With the relief of elevated abdominal pressures, subsequent systemic washout of lactate and products of cell ischemia, such as potassium, can result in rapid clinical deterioration.

Intestinal Atresia

Intestinal atresia is the complete congenital obstruction of the lumen of a hollow viscus. Intestinal atresia can occur at any point of the intestinal tract, with the small intestine being the most common site of pathology. Of the cases of small-bowel atresia, the majority occur within the jejunum and ileum. The atresia can also be present in the large bowel, though these cases constitute only 7–10 percent of all cases of intestinal atresia [44].

Intestinal atresia is classified into types I–IV using the following definitions:

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  Type I: Intact muscularis and serosa, with the lumen obstructed by an intact diaphragm or membrane.

  
  
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  Type II: Obvious gap in bowel with the proximal and distal segments connected by a fibrous band.

  
  
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  Type III:

  
  
  
  
  1. 
     

     a. Obvious gap in bowel with no connection between proximal and distal segments.

     
     
  2. 
     

     b. Proximal small-bowel atresia, absence of mid-small bowel that would normally be supplied by the superior mesenteric artery and a large gap in small-bowel mesentery.

  
  
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  Type IV: Multiple II or IIIA atresias.

In many cases, intestinal atresia can be diagnosed prenatally and is often accompanied by polyhydraminios. Patients with intestinal atresia present with abdominal distention, emesis, and failure to pass meconium. With bowel obstruction, there can be increased enterohepatic circulation of bilirubin and resultant jaundice. Patients with partial obstruction or stenosis will often present later than those with complete intestinal atresia. Diagnosis should exclude other intra-abdominal pathologies, and additional radiographic studies can help to confirm the diagnosis, particularly plain film or fluoroscopy with and without contrast imaging.

Patients with duodenal atresia should be screened for other associated abnormalities, with particular attention to the heart, kidneys, spine, and hepatobiliary system. There are associated chromosomal abnormalities in approximately 30 percent of cases of duodenal atresia, most often trisomy 21 [45]. Though the majority of patients with jejunal and ileal atresia are otherwise healthy, it can be associated with coexisting disease such as CF, gastroschisis, and, less commonly, omphalocele [44]. Patients with CF are predisposed to develop in utero bowel ischemia due to volvulus or perforation; the resultant necrotic bowel is resorbed, leaving behind an atretic segment of gut. Patients with colonic atresia are generally healthy, though they can also be affected with pathology such as gastroschisis and Hirschsprung’s disease (HD) [44].

Initial management of intestinal atresia involves discontinuation of feeding, decompression with a nasogastric tube, and correction of fluid and electrolyte abnormalities. Patients with duodenal atresia should be evaluated for possible comorbidities, while those with jejunal or ileal atresia should be tested for CF.

Emergent surgery for intestinal atresia is generally not indicated, and clinical stability should be established and further evaluation of potential associated abnormalities should be completed prior to bringing the patient to the operating room. Patients with intestinal atresia by definition have a full stomach, and appropriate measures should be taken during anesthetic induction to minimize risk of aspiration. Adequate peripheral intravenous access should be obtained and an arterial line placed if needed in the setting of associated cardiac abnormalities.

Prognosis

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  If performed before 60 days of age, 80 percent of children achieve some bile drainage.

  
  
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  Prognosis is progressively worse the later surgery is done.

  
  
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  Postoperatively, cholangitis and malabsorption are common.

  
  
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  Many children with biliary atresia will require liver transplantation despite the attempted surgical repair.

  
  
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  In type I, atresia is limited to the common bile duct, and the gallbladder and hepatic ducts are patent (i.e., “distal” BA). In type II, atresia affects the hepatic duct, but the proximal intrahepatic ducts are patent (i.e., “proximal” BA). Type II is subgrouped in type IIa, where a patent gallbladder and patent common bile duct are present (sometimes with a cyst in the hilum, i.e., “cystic BA”), and in type IIb, where the gallbladder as well as the cystic duct and common bile duct are also obliterated. In type III, there is discontinuity of not only the right and left intrahepatic hepatic ducts, but also of the entire extrahepatic biliary tree (i.e., “complete” BA). The French classification is similar, but the designation of the above types IIa and IIb as types 2 and 3 results in a total of four types [3].

  
  
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  Most often, BA is complete (Japanese/Anglo-Saxon type III, 73 percent) or subcomplete (type IIb, 18 percent), with “cystic” BA and “distal” BA being infrequent (types IIa and I, 6 percent and 3 percent, respectively) [4].