Anesthesia in Pediatric Otolaryngology

Congenital Heart Disease

The presence of congenital (CHD) or acquired heart disease (AHD) poses a unique and serious risk for both elective and emergent surgical procedures. Pediatric patients with heart disease of any type have twofold higher rates of cardiac arrest and death during the perioperative period. The Pediatric Perioperative Cardiac Arrest (POCA) Registry found that children with CHD or AHD were on average sicker than those without heart disease and also had a higher mortality after arrest. For children with CHD or AHD undergoing noncardiac procedures, most cardiac arrests occurred in the intraoperative period and were the result of cardiovascular causes. Of note, otolaryngologic procedures, specifically myringotomy and tubes, bronchoscopy, and tracheostomy, were identified as having higher rates of complications in children with heart disease, as were gastrointestinal procedures.

The care and triaging of children with heart disease is a controversial topic. Proposed high-risk criteria include complex lesions (single-ventricle physiology, aortic stenosis, Eisenmenger syndrome, or cardiomyopathy), poorly compensated physiology (cardiac failure, pulmonary hypertension, arrhythmias, or cyanosis), age younger than 2 years, major surgery, emergency surgery, preprocedural hospital stay of longer than 10 days, and ASA class IV or V ( Box 2.1 ). Low-risk characteristics include compensated or normal physiology, simple lesions, age younger than 2 years, minor surgery, elective surgery, and ASA class I to III.

In general, high-risk patients with CHD in need of surgery should be referred to a specialist center because of the high likelihood of need for specialized care (e.g., pediatric cardiac anesthesiologist, pediatric intensive care, and pediatric cardiology). ^, Intermediate-risk children should be individually evaluated and considered for transfer if options are available. New evidence shows that low-risk children may undergo procedures safely in a local hospital setting.

CHD encompasses a wide spectrum of structural anomalies and, as a group, is considered the most common birth defect found in the pediatric population, with an incidence of 1 in 125 live births. During the latter part of the 20th and early 21th century, improvements in medical innovation and care have led to the survival of 85% to 90% of these patients into adulthood ; consequently, children and adults with CHD are increasingly likely to present for noncardiac surgery. Patients with CHD may have vastly different pathophysiology, and each lesion should be uniquely considered.

Patients with CHD can be classified based on their specific type of circulation: normal “series” circulation, parallel “balanced” circulation, and single-ventricle circulation. Normal or “series” circulation describes normal cardiac flow and physiology, which is typically observed in patients with isolated atrial septal defects (ASD) and ventricular septal defects (VSD). Parallel or “balanced” circulation involves mixing of systemic venous and pulmonary venous blood, often leading to variable degrees of cyanosis. Common lesions of this type include unrepaired atrioventricular septal defects (AVSD), Blalock-Taussig (BT), Glenn, or Sano (right ventricle to pulmonary artery) shunts, and truncus arteriosus. Single-ventricle circulation involves passive blood flow down a pressure gradient to the pulmonary system, usually via a shunt or palliated anatomic pathway, such as with Fontan physiology.

Pulmonary hypertension is defined as a mean pulmonary arterial pressure greater than 25 mm Hg. It is a common sequela of CHD but may also develop because of vascular anomalies, bronchopulmonary hypoplasia, or respiratory disease. Severe pulmonary hypertension is associated with high morbidity and mortality related to perturbations in baseline physiology in the perioperative period. Exacerbating factors include sedation-related hypercarbia and hypoxia, as well as hypothermia resulting from impaired thermoregulation under anesthesia and a cold operating environment. No single anesthetic technique has been shown to be superior in improving patient outcomes, and thus an individualized approach to the patient with pulmonary hypertension is recommended. ^, As with high-risk CHD, patients with pulmonary hypertension should undergo surgical procedures at a center with specialized expertise, including cardiac anesthesiologists, cardiologists, and pediatric intensivists. Inhaled and IV pulmonary vasodilators and postoperative ICU admission should be strongly considered in high-risk cases. ^{, ,} Close monitoring, even after minor, low-risk procedures, is essential, because most perioperative deaths related to pulmonary hypertension occur in the postoperative period. ^,

Another consideration in the CHD population is the need for antibiotic prophylaxis against infective endocarditis (IE). In 2007 the American Heart Association (AHA) published updated guidelines for the prevention of IE in patients with specific cardiac defects who are undergoing procedures disrupting the normal mucosal barrier, including those near the teeth and oropharynx. Antibiotics should be administered to patients with (1) prosthetic cardiac valve/prosthetic material used for valve repair; (2) previous IE; (3) unrepaired cyanotic CHD, including palliative shunts and conduits; (4) CHD completely repaired with prosthetic material or device, whether placed by surgery or catheter intervention, during the first 6 months after the procedure; and (5) repaired CHD with residual defects at or adjacent to the site of prosthetic patch or device. The antibiotic agent should cover streptococcal and staphylococcal species, the most common flora present on mucosal surfaces. Recommended agents include amoxicillin, ampicillin, cefazolin, ceftriaxone, or cephalexin; for those severely allergic to these medications, clindamycin, azithromycin, or clarithromycin are acceptable alternatives.

Neurotoxicity

The effect of anesthetic medications on the developing brain has gained increased attention in the media and is a frequent concern of parents and caregivers whose children are scheduled to undergo surgical procedures. In December 2016, the U.S. Food and Drug Administration (FDA) published a statement regarding anesthetics in young children and pregnant women, specifically warning that “repeated or lengthy use of general anesthetic and sedation medications during surgeries or procedures in children younger than 3 years or in pregnant women during their third trimester may affect the development of children’s brains.” In an effort to better inform the public, the FDA mandated a warning label on all general anesthetic and sedating medications, sparking a controversy as to whether or not parents and caregivers should be warned about “potential neurotoxic effects” of the medications their child may receive during procedures.

Investigation into anesthetic-mediated neurotoxicity began in the early 2000’s when Uemura et al. exposed pregnant rats to low levels of halothane and found decreased measurements of synaptic density and behavioral changes in exposed offspring. In 1999 Ikonomidou et al. published a study demonstrating significant neuronal apoptotic cell death after blockade of N-methyl-D-aspartate (NMDA) receptors in rat pups. In 2003 Jevtovic-Todorovic et al. simulated a relatively common pediatric anesthetic regimen through a 6-hour exposure of midazolam, isoflurane, and nitrous oxide on rat pups, demonstrating widespread apoptotic cell death, deficits in synaptic function, and memory and learning impairments. Although neuronal apoptosis is critical for proper development of the central nervous system, these studies stoked controversy regarding whether or not anesthetic-mediated aberrations in this process could lead to long-term deficits.

Evidence of neuronal and oligodendrocyte cell death has been demonstrated in fetal and neonatal primates exposed to ketamine, propofol, or isoflurane. In addition to rats and primates, multiple subsequent studies have linked anesthetic agents commonly used in clinical practice (e.g., isoflurane, sevoflurane, propofol, phenobarbital, nitrous oxide, midazolam, ketamine) with neurotoxic effects in a variety of other species, including mice, swine, and chickens. Not all studies demonstrate an effect ^{, ,} ; for example, postnatal day 6 cynomolgus monkeys exposed to surgical levels of sevoflurane for 5 hours did not demonstrate deficits in learning and memory (assessed at 7 months of age) or changes in expression of neuron-specific proteins in the hippocampus or cerebral cortex (assessed at 10 months).

The relevance of these studies to human children is controversial. First, the developmental period during which neuronal cells are vulnerable to anesthetic-mediated cell death differs markedly between species. Second, it is difficult to determine any incremental effect of anesthetic exposure on apoptosis beyond physiologically normal programmed cell death. ^, Third, studies vary markedly in terms of duration, quantity, and frequency of anesthetic exposure, as well as age of exposure. Fourth, most study procedures do not incorporate a surgical stress. Lastly, in a significant number of studies, hemodynamic and physiologic parameters, such as mean arterial pressure, end-tidal carbon dioxide (CO ₂ ), and heart rate, were not vigorously controlled or reported.

Despite active investigation recent clinical studies of potential anesthetic neurotoxicity remain mostly retrospective and observational in nature. A matched cohort study of children undergoing anesthesia before the age of 2 years found an association between two or more anesthetic exposures and increased risk of learning disabilities. A retrospective cohort study of 10-year-old children who underwent a single surgical procedure before the age of 3 years demonstrated deficits in language and abstract reasoning. However, a sibling-matched cohort study found that an anesthetic exposure before the age of 36 months did not affect intelligence quotient (IQ) when assessed at 10 years of age. Furthermore, a large retrospective study of 18,056 children showed no difference in Kindergarten Early Developmental Instrument scores between those exposed to a single versus multiple general anesthetics; however, a significant deficit was noted in children aged 2 to 4 years with a single exposure to general anesthesia. In an observational study investigating neurodevelopmental outcome measures, such as IQ, neuropsychological testing, and parental reporting, no association was found between IQ and general anesthesia exposure before age 3 years. However, a decrease in processing speed and fine motor skills, as well as an increase in parental reports of problems with reading, behavior, and executive function were demonstrated in children with multiple anesthetic exposures. Parents of children with a single anesthetic exposure were more likely to report problems with reading and executive function, although neuropsychological testing did not demonstrate an effect.

The General Anesthesia compared to Spinal anaesthesia (GAS) trial is the first international, randomized-controlled trial of infants younger than 60 weeks undergoing inguinal hernia repair, comparing awake regional anesthesia with sevoflurane-based general anesthesia. A report of prespecified secondary outcome measures demonstrated no difference in composite cognitive scores assessed at age 2 years as measured by the Bayley Scales of Infant and Toddler Development III instrument. ^, In addition, the primary outcome measure, full-scale intelligence quotient (FSIQ), on the Wechsler Preschool and Primary Scale of Intelligence, third edition (WPPSI-III) at 5 years of age also demonstrated no difference between the awake regional to general anesthesia groups. The results of the GAS trial are the strongest evidence to date that brief (less than 1 hour) exposure to general anesthesia does not impair gross neurodevelopment.

A definitive consensus on clinically significant anesthetic-related neurotoxicity remains elusive. The variability in study results highlights the limitations in performing observational and retrospective analyses. In addition, determining the significance of specific differences in neuropsychological outcomes is difficult. Thus until conclusive evidence is available, the conversation with concerned parents and caregivers should focus on discussion of the necessity of the surgical intervention, the possibility of alternatives to general anesthesia, the appropriate titration of anesthetic medications, and the acknowledgment of the uncertainty in both human and animal data. Providers should give reassurance that a single, brief anesthetic exposure has demonstrated no identifiable outcome differences.

Prematurity

Prematurity affects virtually every organ system. The cardiovascular system has immature calcium homeostasis and relatively noncompliant cardiac fibers, which result in impaired contractility and limited ability to augment cardiac output. Ex-premature infants have a higher incidence of respiratory complications after surgery, including postanesthetic apnea. Postanesthetic apnea is defined as cessation of breathing for at least 15 seconds or any pause in breathing associated with a heart rate of less than 80 beats/min. Apnea may be central (e.g., because of an underdeveloped brainstem), obstructive (e.g., because of upper or lower airway obstruction), or mixed. It may also be influenced by pharmacologic and metabolic factors (i.e., metabolic alkalosis). The incidence of apnea after anesthesia is highest in the first 4 to 6 hours after the procedure but can persist as long as 12 hours after an anesthetic, often requiring overnight observation. ^, The additional cost associated with a prolonged stay in a PACU and often an overnight hospital stay must be considered versus the risk of postponing elective surgical procedures until the chance of apnea is minimal. This risk decreases with increasing gestational age (GA) and age at the time of surgical intervention, with a risk reduction to 1% at approximately 56 weeks postconceptual age (PCA; Fig. 2.1 ). A conservative approach is to admit all premature infants with PCA less than 60 weeks for at least 12 hours; however, policies will vary across institutions. Fig. 2.2 describes an algorithm for former preterm infants undergoing surgery.

Bronchopulmonary dysplasia (BPD) is a chronic lung disease commonly associated with prematurity. However, BPD can also occur in full-term infants with a history of prolonged mechanical ventilator support, chorioamnionitis, or persistent patent ductus arteriosus (PDA). BPD is caused by an arrest in lung development and is characterized by formation of fewer, larger alveoli with smaller capillary beds and associated interstitial fibrosis. ^, These abnormalities lead to hypoxemia, bronchial hyperreactivity, ventilation/perfusion mismatch, pulmonary hypertension, and a propensity for tracheobronchomalacia secondary to inadequate cartilaginous support. Management strategies include using optimal peak end-expiratory pressure (PEEP) to prevent large airway collapse and atelectasis, diuresis, avoiding increases in pulmonary vascular resistance (PVR), using smaller tidal volumes to prevent volu- and baro-trauma, and close monitoring of electrolyte abnormalities. ^, Although controversial, several studies advocate maintaining lower oxygen saturation to prevent the sequelae of hyperoxia. Most studies support a goal oxygen saturation of 91% to 95% because of the potential for increased mortality with saturations lower than 90%. ^,

Immature thermoregulatory centers and increased surface-area-to-volume ratio predispose premature infants to hypothermia. In addition, premature, as well as term, infants rely on nonshivering thermogenesis via brown fat cells for heat generation, although this capability is not fully developed until 26 to 30 weeks’ GA. As a result, premature patients require aggressive maneuvers to prevent cooling, including increasing the temperature in the operating suite, convective warmers, infrared lights, humidified anesthetic gases, and warmed intravenous (IV) and irrigation fluids.

Development of electrolyte abnormalities, such as hypoglycemia, hypocalcemia, and hyponatremia, is common in premature infants. Hypoglycemia results from a combination of increased glucose requirements and decreased glycogen stores; therefore premature infants undergoing surgical procedures will generally require glucose-containing fluids. Hypocalcemia is often a result of parathyroid hormone resistance or insufficiency, decreased maternal transfer of calcium, renal losses, and increased calcitonin production. Premature infants have an immature renal tubular collecting system that can lead to the development of hyponatremia. Pharmacokinetic differences with regard to anesthetic medications must also be considered because of a larger volume of distribution (increased total body water) and immature renal and hepatic function.

Children born prematurely continue to be at risk for sedation- and anesthesia-related adverse events, usually related to the airway and pulmonary system. One study demonstrated that preterm patients are nearly twice as likely to experience sedation- or anesthesia-related adverse events compared with term-born children, with adverse consequences extending into adulthood as well.

Cerebral Palsy

Cerebral palsy is defined as a disorder of movement, muscle, and/or posture, characterized by nonprogressive injury to or abnormal development of the immature brain. Children with cerebral palsy may have normal intellect and age-adjusted emotional perioperative concerns, even if they have difficulty articulating them. Impaired oromotor function can lead to excessive secretions with poor clearance, chronic aspiration, and malnutrition; furthermore, decreased pharyngeal tone may result in upper airway obstruction and sedation-related hypoxia. Uncontrolled gastroesophageal reflux disease (GERD) should prompt the anesthesiologist to consider a rapid sequence induction. Succinylcholine is not contraindicated in patients with cerebral palsy; although they may have proliferation of extrajunctional acetylcholine receptors, potassium levels after administration of succinylcholine were not significantly different compared with patients without cerebral palsy. In addition to reactive airway and chronic lung disease, many patients also have coexisting seizure disorders. Chronic antiepileptic therapy may alter the pharmacokinetics of commonly administered anesthetic medications, including antibiotics and neuromuscular-blocking drugs. Temperature management may be challenging as a result of hypothalamic dysfunction and lack of insulating adipose tissue. Some affected children have severe contractures and require careful positioning during surgical procedures. Management of postoperative pain may be difficult because of an inability to adequately verbalize needs; thus having a caregiver present in the recovery room who can recognize and interpret specific behaviors and expressions is useful and recommended.

Autism

Diagnostic criteria for autism spectrum disorders are based on deficits in multiple domains, including interpersonal relationships, nonverbal communication, and social-emotional reciprocity. The perioperative period is often an extremely stressful time for patients with autism, as they are exquisitely sensitive to light, sound, and touch. Wait times should be minimized if possible, and a dim, quiet preoperative room may be helpful in reducing undesirable stimulation. The preoperative interview requires both finesse and flexibility to accommodate behavioral needs. Limiting the number of providers in the area should be considered, and it may be prudent to have a single provider for the patient during induction.

The approach to induction of anesthesia should be individualized for each child. Some autistic patients will cooperate with preoperative IV placement, whereas others may need oral premedication or an intramuscular injection prior to entry into the operative suite. Because primary caregivers are often aware of behavioral triggers and techniques to calm these patients, their presence at induction may be helpful. Child life specialists are also an invaluable resource. Postoperatively, actions should be taken to reduce emotional volatility on emergence from anesthesia, including keeping only essential monitors in place, early parental presence in the recovery room, and possible early IV removal.

Upper Respiratory Tract Infection

A child with an upper respiratory tract infection (URI) presents a common dilemma encountered by pediatric otolaryngologists and anesthesiologists. Children have, on average, 6 to 8 URIs per year, with the typical duration of each illness lasting between 7 and 15 days. In addition, airway hyperreactivity may persist for as long as 8 weeks after resolution of initial symptoms and can be exaggerated in patients with asthma or preexisting lung disease. ^, Other perioperative respiratory complications include increased postoperative oxygen requirements, increased risk of breath-holding, and oxygen desaturations to less than 90%.

A prospective case control study found a two- to sevenfold increase in respiratory complications in children with a URI who underwent anesthesia and surgery. Another study by Schreiner et al. demonstrated that children with URIs were more than twice as likely to experience laryngospasm intraoperatively. A prospective study identified independent risk factors for respiratory complications in the perioperative period, namely use of an endotracheal tube (ETT), history of prematurity, presence of reactive airway disease (RAD), parental smoking or smoke exposure, airway surgery, and nasal congestion with copious secretions. Younger age and airway procedures were associated with additive risk.

The decision to go ahead with a procedure in the pediatric patient with a recent or active URI is dependent on multiple factors, including urgency of the procedure, presence of high-risk symptoms such as fever, wheezing, cough, or congestion, consideration of patient and procedural risk factors, and discussion of risk with caregivers. Further workup may be warranted in certain clinical situations, including but not limited to chest radiographs, viral panel, and laboratory studies. In all cases, multidisciplinary discussion between the anesthesiologist and otolaryngologist is highly recommended, and rescheduling elective procedures requiring airway manipulation after 4 weeks in patients with active URI symptoms should be strongly considered. ^{, ,}

Reactive Airway Disease

A history of RAD or asthma may greatly affect the perioperative management of the pediatric patient. The preoperative evaluation should define the severity of the illness by focusing on symptoms, number of recent exacerbations, escalation of treatment and steroid use, emergency center visits, hospitalizations, intubations, and admissions to the ICU. A thorough physical examination by the anesthesia provider in the preoperative bay or preanesthesia clinic should also be performed to evaluate for wheezing or rhonchi. Studies have shown that a history of three or more instances of bronchospastic respiratory symptoms in 1 year was associated with higher risk of adverse perioperative respiratory events. It may be necessary to postpone elective surgery for 4 to 6 weeks to allow for medical optimization in patients with active or recent bronchospasm or exacerbation of their airway disease.

Cystic Fibrosis

Cystic fibrosis (CF) is a congenital multisystem disease characterized by impaired mucociliary clearance. It is inherited as an autosomal recessive trait and results from mutations in the gene encoding the chloride channel CFTR protein. ^, CF primarily affects the respiratory tract, sweat glands, liver, pancreas, intestines, and reproductive tract. Patients with CF are at risk for adverse perioperative respiratory events because of limited respiratory reserve, which is compromised further by anesthesia-induced impairment of mucociliary clearance.

Perioperative considerations for patients with CF include a thorough history and physical examination, specifically assessing baseline pulmonary function, and pertinent imaging studies to evaluate for bronchiectasis. Bronchiectasis is indicative of a fixed lower airway obstruction with an increase in bronchial secretions, which may result in an increased risk of mucus plugging, airway closure, atelectasis, and hypoxemia. In patients older than 6 years, pulmonary function tests and spirometry can be useful to identify airway obstruction. Elective procedures should proceed only after optimization and administration of baseline respiratory medications prior to induction of anesthesia. Patients with CF may display increased airway hyperreactivity secondary to chronic infection, and thus bronchodilators may be useful in the perioperative period. Multidisciplinary communication with the patient’s pulmonologist, institution of therapy for postoperative airway clearance, and the potential need for postoperative ICU level care should also be considered.

Musculoskeletal Diseases

Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy. Patients with DMD lack the dystrophin protein. DMD is characterized by a painless degeneration of muscle fibers and subsequent fatty hypertrophy of muscle tissue. Progressive respiratory weakness, difficulty with handling secretions, and ineffective cough and airway clearance may lead to recurrent pneumonias, and most patients generally suffer respiratory-related morbidity and mortality. Severe scoliosis may lead to development of restrictive lung disease. Cardiac disease may manifest as conduction defects or progressive cardiomyopathy. Patients may suffer from gastric hypomotility and delayed gastric emptying, which increase the risk for aspiration during induction.

There is no standardized anesthetic technique for patients with muscular dystrophies, although some specific considerations apply to each of the various types. Pulmonary function testing should be considered for symptomatic patients, and perioperative optimization of patients with muscular dystrophy may warrant initiation of noninvasive positive-pressure ventilation. Preoperative echocardiogram should be considered to assess for cardiac dysfunction. Long-term steroid usage may necessitate “stress doses” in the perioperative period. Succinylcholine has been implicated in several cases of hyperkalemic cardiac arrest in previously healthy children who were subsequently found to have an underlying myopathy; as a result, the FDA placed a black box warning on the use of succinylcholine in pediatric patients, recommending its use for emergency situations only.

Muscular dystrophy is not independently associated with an increased risk of malignant hyperthermia (MH) unless the patient is known to have a mutation of the ryanodine receptor 1 gene (RYR1). Despite this lack of evidence, use of volatile anesthetics in patients with muscular dystrophy remains controversial. Volatile anesthetics are considered relatively contraindicated as a result of reports of rhabdomyolysis attributed to muscle membrane fragility. ^, Most anesthesiologists favor performing a total IV anesthetic when feasible.

Mitochondrial Myopathies

Mitochondrial myopathies describe a group of disorders of variable genetic penetrance, which affect tissues with high-energy consumption, most notably neurologic and musculoskeletal systems. Common symptoms at presentation include hypotonia, respiratory muscle weakness, seizures, and encephalopathy. Patients with mitochondrial myopathies may be exquisitely sensitive to hypoglycemia and metabolic stress, and many have the propensity to develop lactic acidosis. Therefore fasting periods should be minimized, IV glucose supplementation should be provided when indicated, and avoiding exogenous lactate-containing fluids may be necessary. The risk of lactic acidosis may be mitigated by preventing shivering, maintaining normothermia, and optimizing perioperative analgesia. All general anesthetic medications depress mitochondrial function to some degree; thus careful anesthetic titration is of utmost importance. ^,

Obesity

According to the Centers for Disease Control and Prevention, childhood obesity affects more than 18% of the U.S. population between ages 2 and 19 years. Comorbidities related to obesity include impaired glucose tolerance, diabetes, hypertension, cardiovascular disease, asthma, and sleep-disordered breathing (SDB). Obesity affects all aspects of anesthetic care. Monitoring of vital signs, such as blood pressure and electrocardiogram (ECG), as well as neuromuscular blockade, may be difficult because of body habitus and soft tissue impedance. Obtaining IV access, performing mask ventilation and intubation, patient positioning, and determining correct medication dosing in obese patients pose a serious challenge for the anesthesiologist. ^,

Diabetes Mellitus

Successful management of patients with diabetes mellitus requires interdisciplinary communication between the perioperative team and the patient’s endocrinologist to optimize oral medication and insulin dosing. Near-normoglycemia is the goal, and dose reduction of intermediate- and long-acting insulin formulations is often required to avoid hypoglycemia. Metformin should be held for 24 hours preoperatively to decrease the risk of lactic acidosis. Diabetic patients should also be scheduled as the first case of the day to limit nil per os (NPO) times and facilitate optimal perioperative glucose values. Typically, preoperative correction of hyperglycemia is not necessary unless glucose values are greater than 250 mg/dL. Intraoperatively, frequent blood glucose monitoring is recommended, and in major procedures of 2 hours or more in which operative stress can lead to an increase in blood glucose levels, an insulin infusion is preferred versus subcutaneous correction. Postoperatively, diabetic patients should resume their home medication regimen as soon as they are able to tolerate a normal diet.

Sickle Cell Disease

Sickle cell disease (SCD) is an inherited group of hemoglobinopathies prevalent in the African American and Hispanic population. The pathophysiology of SCD is extremely complex but can be broadly described as accumulation of sickled erythrocytes in the microvasculature, leading to decreased peripheral perfusion. Children diagnosed with SCD have a higher degree of perioperative morbidity and mortality, with the rate of complications estimated to be 30% to 50% higher than in patients without SCD.

Preoperative evaluation should include a detailed history and physical focusing on prior vasoocclusive crises (e.g., acute chest syndrome, cerebrovascular accidents, and pulmonary hypertension), prior transfusions, current analgesic regimen, neurologic assessment, and oxygen saturation. Important laboratory tests include baseline hematocrit and type and crossmatch. Preoperative methods to decrease the risk of sickling include aggressive IV hydration, bronchodilators, hydroxyurea, and transfusion. The current recommendation is to transfuse to a hemoglobin goal of 10 g/dL in children with SCD to decrease the risk of vasoocclusive crises and cerebrovascular accidents. Exchange transfusion should be used in patients with more severe sickle cell phenotypes who are still experiencing frequent pain crises or other complications related to the disease despite hemoglobin levels greater than 10 g/dL.

Goals of intraoperative anesthetic care should focus on maintaining normal physiology and avoiding factors that may precipitate sickling crises. Postoperative considerations include consultation with a hematology service, monitoring for complications such as acute chest syndrome and cerebrovascular accidents, oxygen supplementation, appropriate antibiotics, adequate hydration status, and early mobilization. Aggressive pain management is essential but achieving adequate pain control may be difficult because of high rates of chronic analgesic use to treat chronic pain. Consultation with an acute pain service is often desirable and effective.

Down Syndrome

Down syndrome, or trisomy 21, is the most common chromosomal disorder found in the pediatric population, with a prevalence of approximately 1 in 600 live births. Children with trisomy 21 are at increased risk of anesthesia-related complications, including but not limited to, severe bradycardia, airway obstruction, difficult intubation, postintubation stridor, and bronchospasm. Higher rates of SDB are present in this population, resulting in higher propensity for airway obstruction. Mask ventilation and intubation may be challenging because of the presence of a hypoplastic midface, relative macroglossia, short neck, and upper and lower airway abnormalities. ^{, ,}

Almost half of children diagnosed with Down syndrome have malformations of the cardiovascular system, with the most common being endocardial cushion defects such as complete atrioventricular canal defects, ASD, and VSD. ^, An increased incidence of pulmonary hypertension is present in children with Down syndrome. ^{, ,} With inhalational induction, multiple studies have demonstrated an exaggerated bradycardic response to sevoflurane. ^,

Hypotonia, obesity, endocrinopathies, blood dyscrasias, seizure disorders, psychiatric conditions, and varying degrees of intellectual disability are other common findings in patients with trisomy 21. ^{, ,} Approximately 8% to 63% of children with Down syndrome have incidental craniocervical instability, with symptomatic disease present in 1% to 2%. Obtaining routine preoperative cervical spine films is not generally advised; rather, the head and neck should be manipulated with caution in all patients with Down syndrome, avoiding hyperextension. Negative cervical spine films do not rule out cervical spine instability, as young children may have incomplete ossification, and ligamentous change can occur spontaneously.

Genetic Syndromes Associated With a Difficult Airway

The potential for difficult airway should be anticipated in children with genetic conditions, including but not limited to Down syndrome, Beckwith-Wiedemann syndrome, Pierre Robin sequence, Treacher Collins syndrome, hemifacial microsomia, Apert syndrome, Klippel-Feil anomaly, muscular dystrophies, and mucopolysaccharidoses. ^, Factors evaluated by anesthesiologists to determine the potential for a difficult airway include Mallampati score, thyromental distance, mouth opening, tongue size, presence of loose teeth, cervical flexibility, and previous intubation history. In 2014 a review of airway management at a tertiary care pediatric hospital demonstrated that patient history identified 98% of patients with difficult airways. The most common etiologies identified were micrognathia, limited neck extension, poor temporomandibular joint mobility, macroglossia, severe glottic or subglottic stenosis, and tracheal anomalies or stenosis. Thus a careful history and physical exam should identify the majority of difficult or potentially difficult airway situations, allowing for thorough planning and care coordination between the anesthesiologist and otolaryngologist for both otolaryngologic and nonotolaryngologic procedures.