Central Nervous System

Disorders of the neuromuscular system only rarely escape notice during the history and review of systems; the purpose of the central nervous system (CNS) examination is primarily to assess the severity of the abnormality and the implications for anesthetic care.

TABLE 9-2 Medical History and Review of Systems: Anesthetic Implications

Trauma is the most common cause of death in children, and most fatal trauma involves injury to the CNS. Head injuries often result in an altered level of consciousness, cerebral edema, and elevated intracranial pressure. Tumors of the brain are the most common solid tumors of childhood and usually occur in the posterior fossa. They generally increase intracranial pressure as a mass effect but also often obstruct cerebrospinal fluid pathways, resulting in hydrocephalus. The anesthetic care of children with elevated intracranial pressure is discussed in Chapter 22, Anesthesia for Neurosurgery.

To ensure both therapeutic levels and the absence of toxic levels, serum levels of certain anticonvulsant drugs should be measured or should have been measured before elective surgery in children with chronic seizure disorders. Most anticonvulsants have a long plasma half-life; therefore, missing one dose in the perioperative period does not significantly diminish the serum level and efficacy. Of the commonly used anticonvulsants, only phenobarbital, phenytoin, or valproate may be given intravenously in the perioperative period. Other commonly administered anticonvulsants, however, such as gabapentin, pregabalin, levatiracetam, or lamotrigene, are available only as oral medications. If a prolonged period without oral intake is anticipated (such as after abdominal surgery), a neurologist should be consulted about possible alternative parenteral drug therapy.

Conditions such as developmental delay and spastic cerebral palsy have important implications for anesthesia. In such children, the response to opioids and anesthetic agents is less predictable than that with healthy children. Many patients with cerebral palsy or intellectual impairment have difficulty managing oral secretions, and gastroesophageal reflux is particularly common in these children. They are at a greater risk of aspirating oral or gastric contents during induction. Cerebral palsy in older children often produces restrictive lung disease as a result of deformities of the spine and thoracic cage and from uncoordinated respiratory muscle function.

Neuromuscular diseases, such as congenital myotonia, muscular dystrophy, and the various forms of myositis, contraindicate the use of succinylcholine even in emergency airway management, although it is rarely used in current pediatric anesthetic practice (see Chapter 36, Systemic Disorders). In myotonia, succinylcholine produces a sustained contracture of skeletal muscle that may impede the ability to maintain a patent airway and ventilate the lungs. In other myopathies, such as clinically active dermatomyositis, succinylcholine produces life-threatening hyperkalemia. Some forms of muscular dystrophy (central core disease) are statistically associated with malignant hyperthermia, whereas others may result in a malignant hyperthermia-like syndrome that is equally life threatening (Guis et al., 2004; Rosenberg et al., 2007; Driessen and Snoeck, 2008; Hayes et al., 2008; Puel et al., 2008; Takagi and Nakase, 2008; Schwartz and Raghunathan, 2009). Although not all children with Duchenne’s or other muscular dystrophies are genetically susceptible, Rosenberg and Heiman-Patterson (1983), as well as Takagi and Nakase (2008), recommend that precautions against malignant hyperthermia be taken in patients with this disorder because of rhabdomyolysis and hypermetabolism that may occur in myopathic children after exposure to triggering agents. For further discussion please refer to Chapter 37, Malignant Hyperthermia.

Cardiovascular System

Evaluation of the cardiovascular system is critical to the delivery of safe anesthesia. The physical examination seldom reveals an unexpected CNS lesion, but a careful history and auscultation of the child’s chest often reveal a congenital cardiac lesion that may be unknown to the parents or the child’s surgeon.

The history-and-systems review yields information regarding known cardiac anomalies of an acquired disease, cyanotic defects, or the presence of congestive heart failure. Symptoms of congestive heart failure may be insidious. In an infant, whose level of activity is not high, the symptoms of congestive heart failure or cyanosis are most likely limited to a few times of physical exertion, such as feeding and crying, and the only symptoms of congestive heart failure may be pallor and diaphoresis, which are subtle findings. Parents should be asked about diaphoresis during nursing or sucking. Resting tachypnea and failure to thrive are also consequences of more advanced degrees of congestive heart failure, which may be the result of ventricular volume overload (most commonly, a ventricular septal defect, patent ductus arteriosus, or anomalous pulmonary venous return), either right- or left-sided outflow obstruction, or pulmonary hypertension.

Preoperative evaluation of a patient with a known or suspected heart defect that is physiologically significant should include a thorough history and physical examination; an electrocardiogram (ECG) and echocardiogram; determination of hematocrit value, a baseline oxygen saturation value (SpO₂); a chest radiograph; and a definitive understanding of the type of cardiac lesion, its degree of severity, and its physiologic effect on cardiac efficiency and oxygen delivery. Such patients should be examined meticulously and should not be accepted for anesthesia until they are in the best possible physical condition. For children with compromising lesions or those requiring cardiac medication, it is advisable to consult the cardiologist shortly before surgery.

The presence of polycythemia is uncommon in modern clinical practice but still should be ruled out in children with cyanotic heart disease; a hematocrit value of greater than 65% may be reduced by red blood cell pheresis or isovolemic hemodilution. Dehydration must be avoided, preferably through the use of controlled intravenous hydration beginning the night before surgery or by following the nil per os (NPO) guidelines and ensuring adequate oral intake of clear liquids up until 2 hours before surgery.

Particular care must be taken to rule out the existence of any infection, especially in the throat, ears, skin, or genitourinary tract. Bacteremia and infections of the teeth or gums should be controlled with appropriate antibiotics. The preoperative occurrence of fever or rhinitis or a significant preoperative exposure to a source of infection should be considered a possible indication for postponement of the operation.

Asymptomatic cardiac murmurs occasionally have implications for anesthesia. If they represent small ventricular septal defects or mild valvular disease, prophylaxis against bacterial endocarditis is indicated for procedures that may result in bacteremia, such as dental surgery, gastrointestinal or urogenital endoscopy, and nasotracheal intubation (Wilson et al., 2007). Atrial septal defects contraindicate the use of the sitting position for suboccipital craniotomies in order to minimize the risk of paradoxical air embolism (Fischler, 1992). The defects may also make intraoperative transesophageal echocardiography desirable in certain cases that have been associated with venous air embolism (e.g., posterior spine fusions or liver transplantation), so the movement of air from the pulmonary to the systemic circulation may be detected. If the anesthesiologist detects a previously undescribed murmur in these circumstances, a consultation with the cardiologist is indicated to further delineate the nature of the lesion (Fig. 9-3). Many congenital anomalies and syndromes are associated with cardiac defects or other cardiovascular problems; Box 9-1 provides an outline of these conditions.

FIGURE 9-3 Sites for auscultation where murmurs are heard best.

(From Beerman LB, Kreutzer J, Park SC: Cardiology. In Zitelli J, Davis HW, editors: Atlas of pediatric physical diagnosis, ed 5, St Louis, 2007, Mosby.)

Respiratory System

Chapter 3, Respiratory Physiology in Infants and Children, describes the anatomic and physiologic differences between the pediatric and adult respiratory systems. The differences in dimension and function predispose the child to perioperative airway obstruction, which mandates a critical preoperative evaluation of the airway. The upper airway of the child may be further compromised by many entities, including: tonsillar or adenoidal hypertrophy or both; craniofacial anomalies such as Crouzon’s disease, Apert’s syndrome, hemifacial microsomia, Goldenhar’s syndrome, Treacher Collins syndrome (or Pierre Robin syndrome); lingular hypertrophy (common in trisomy 21); Beckwith’s syndrome and the various forms of mucopolysaccharidosis (Hurler’s syndrome and Hunter’s syndrome being the most common); isolated airway anomalies, such as cleft palate, laryngeal web or cleft, laryngomalacia, or subglottic stenosis; or tumors, such as hemangiomas and lymphangiomas, which may occur anywhere along the airway. Cutaneous cervicofacial hemangiomas along a beard distribution are suggestive of an association with upper airway or subglottic hemangiomas (Orlo et al., 1997).

Acute upper respiratory tract infections provide a common dilemma for the anesthesiologist. The mere volume of publications that evaluate the risk of adverse events of anesthesia in children with upper airway infections speaks to the ongoing controversy (Tait and Malviya, 2005). In the best of all worlds, no child would be anesthetized electively during an acute respiratory illness. Although not all studies have identified acute respiratory illness as a cause of perioperative complications in children, there is compelling evidence that the occurrence of both intraoperative and postoperative hypoxemia and other airway complications are increased in children with upper respiratory tract infections (DeSoto et al., 1988; Cohen and Cameron, 1991; Kinouchi et al., 1992; Levy et al., 1992; Rolf and Coté, 1992; Parnis et al., 2001; Bordet et al., 2002; Elwood et al., 2003; Tait, 2005). There is also evidence that the incidence of bronchospasm is increased in the presence of upper respiratory infections in children who are intubated (Rolf and Coté, 1992; Rachel Homer et al., 2007; von Ungern-Sternberg et al., 2007). In a prospective study, Tait and colleagues (2001) noted that endotracheal intubation, a history of prematurity, reactive airways disease, parental smoking, airway surgery, and nasal congestion are all risk factors associated with respiratory complications in infants and children who have upper respiratory infections and who are undergoing anesthesia. Furthermore, the child with an acute respiratory disease exposes other patients and health care workers to their contagion, which may not be a trivial concern when these individuals are immunocompromised.

Other considerations, however, must be taken into account before making the decision to postpone surgery. For example, the relatively small risk to the child must be weighed against the expense and effort the family has made to come to the hospital, often from a distant locale and at the cost of lost income. Some children, particularly those seen for otolaryngologic surgery, appear to never be free from respiratory infections during much of the year. Postponement of surgery may not be practical in these circumstances. Indeed, one study indicates that myringotomy is therapeutic in these children and is not associated with an increased incidence of postoperative pulmonary complications (Tait and Knight, 1987).

The presence of acute disease of the lower airways, however, should generally delay elective surgery. The presence of fever, cough, and an abnormal auscultatory examination is reason for radiographic evaluation and possibly cancellation of scheduled surgery. Patients with a viral lower respiratory tract infection such as influenza may develop airway hyperreactivity that is indistinguishable from bronchial asthma and can last as long as 6 or 7 weeks from onset.

Chronic diseases of the lower respiratory tract occur in both children and adults. Asthma and cystic fibrosis are the most common chronic pulmonary diseases of childhood. A careful history and physical examination usually suffice in the preoperative evaluation of these diseases. If preoperative impairment is severe, however, or if the planned surgery is extensive, formal pulmonology consultation and pulmonary function testing may provide the anesthesiologist with information that can be used to provide optimal postoperative care. Children with asthma are commonly medicated with β₂-adrenergic agents and inhaled corticosteroids. Other first-line drugs include cromolyn sodium and leukotriene receptor antagonists; rarely are theophylline preparations administered at this time. However, when theophylline is a part of the patient’s treatment, serum concentration of theophylline should be measured preoperatively to ensure blood levels in a therapeutic range (10-20 mcg/mL), and the anesthesiologist should be aware of potential interactions among theophylline, β₂-adrenergic drugs, and halothane (although it is not often used). Asthmatic children who receive corticosteroids should also be considered for perioperative therapy with stress doses of corticosteroids if steroid therapy has been recent, although as previously stated, the evidence to support this convention is lacking. For those children who have required systemic steroids in the past, a short course of steroids beginning 1 to 2 days before the day of surgery may be beneficial (see Chapter 36, Systemic Disorders).

Severe kyphoscoliosis typically leads to significant restrictive lung disease. This is particularly true in cases of kyphoscoliosis that occur before the teenage years. Particularly in this age group, the cause of the kyphoscoliosis should be assessed, because it typically results from neuromuscular diseases such as cerebral palsy or muscular dystrophy or from anatomic anomalies such as hemivertebrae, which may be part of a syndrome that is associated with other congenital anomalies of importance to the anesthesiologist (e.g., VATER association). Preoperative testing of pulmonary function may be useful in predicting which children will require admission to an intensive care unit with or without mechanical ventilation postoperatively, but usually the decision to mechanically ventilate patients after spinal surgery is based on general preoperative condition, duration and difficulty of surgery, blood loss, and other surgical factors, rather than on the test of pulmonary function itself (see Chapter 26, Anesthesia for Orthopedic Surgery).

An infant who was born prematurely is often left with a residual chronic obstructive pulmonary disease called bronchopulmonary dysplasia, the consequence of both oxygen toxicity and ventilator-induced lung injury to immature lungs. The incidence and severity of this disabling condition have been dramatically reduced by the use of surfactant in neonatal intensive care units. Children with bronchopulmonary dysplasia exhibit a combination of fibrotic and cystic changes in the lung parenchyma with reactive small airways disease, with or without wheezing and air trapping. These children may respond to steroids and bronchodilators in varying degrees. More advanced bronchopulmonary dysplasia is associated with chronic hypoxia, carbon dioxide retention, pulmonary hypertension, and ultimately cor pulmonale (Berman et al., 1982).

As in the adult with chronic pulmonary disease, elective surgery is best delayed until preoperative cardiopulmonary function has been optimized. Children with severe bronchopulmonary dysplasia are usually treated with diuretics to reduce extravascular lung water; consequently, abnormal serum electrolyte levels are common preoperatively (e.g., hypokalemia, hypochloremia, or metabolic alkylosis). Arterial saturation should be maximized at all times to reduce pulmonary hypertension, and perioperative bronchodilator therapy should be considered. Alterations in anesthetic care include: judicious, if any, use of nitrous oxide to avoid exacerbation of pulmonary gas trapping and pulmonary vascular resistance; very conservative fluid therapy and restriction of sodium; and continuation of bronchodilator therapy. Postoperative mechanical ventilation may be required in this population.

Life-threatening apnea and bradycardia may occur after general anesthesia, most commonly in the preterm infant who is still younger than 45 weeks’ or as old as 60 weeks’ postconceptional age (the sum of gestational age and postnatal age) (Liu et al., 1980; Kurth et al., 1986; Wellborn et al., 1986). Hospital admission and respiratory monitoring are necessary for infants at risk, even after brief general anesthesia. Risk factors for postoperative apnea in preterm infants include: a history of mechanical ventilation, history of apnea and bradycardia, and anemia at the time of surgery (Kurth and LeBard, 1991; Wellborn et al., 1991; Spear, 1992; Malviya et al., 1993; Coté et al., 1995). In a meta-analysis of eight studies, Coté et al. (1995) reported that the postconceptual age required to reduce the risk of postoperative apnea to 1% was 54 weeks for infants born at 35 weeks’ gestation and 56 weeks for infants born before 32 weeks’ gestation. For further information, see Chapter 17, Neonatology for Anesthesiologists, Figure 17-10.

Congenital diseases of the lungs are usually recognized and surgically corrected in the newborn period. These conditions and their anesthetic management are discussed in Chapters 18 and 23, Anesthesia for General Surgery in the Neonate, and Anesthesia for General Abdominal, Thoracic, Urologic, and Bariatric Surgery.

Gastrointestinal System

The primary concern of the anesthesiologist is to assess the integrity of the gastroesophageal sphincter, the emptiness of the stomach, and, hence, the risk of aspiration on induction of or emergence from anesthesia. Gastroesophageal reflux occurs as an isolated entity in some otherwise healthy infants. Parents describe regular spitting up after meals, and there may be a history of recurrent lower respiratory tract infections, small airways disease, wheezing, or esophagitis that points to the diagnosis. Gastroesophageal reflux is very common in the child with developmental delays. After repair of tracheoesophageal fistulas, abnormalities of esophageal motility and decreased competence of the gastroesophageal sphincter are often present, increasing the risks of vomiting and aspiration on induction of anesthesia. Children who fall into these categories should be considered to have a “full stomach.”

Renal System

Renal failure is uncommon in childhood. Chronic renal failure is typically managed with either peritoneal dialysis or, in the older child, hemodialysis. The evaluation of the child with preoperative renal disease includes serial measurements of blood pressure to assess the adequacy of antihypertensive therapy; careful determination of vascular volume; and measurement of serum levels of electrolytes, urea nitrogen, creatinine, phosphate, calcium, and magnesium, as well as hematocrit value. Electrolyte levels should be within a reasonably normal range; if significant derangement exists, additional electrolyte therapy or dialysis should be performed before elective surgery. The acceptable lower limit of hematocrit is generally considered to be about 20% with chronic renal failure. Such an assumption of adaptation, however, is controversial because the blood levels of 2,3-diphosphoglycerate in these children are not necessarily increased, depending on the chronicity of anemia or recent history of dialysis.

Milder degrees of renal dysfunction may also affect anesthetic care. In small children with mild or moderate underlying renal disease, clinically significant hypervolemia may occur without compensation by augmented urine output, and an excessive sodium or free-water load further deranges the serum electrolyte level. Particular caution is important in the management of fluids in children, and central venous pressure monitoring is required during major surgery in which significant blood loss or fluid shifts are anticipated (see Chapter 5, Regulation of Fluids and Electrolytes).

Hematologic System

Underlying disorders of the hematologic system are not common. The systems review should include an inquiry into unusual bleeding in the family’s or child’s medical history to explore possible genetic coagulopathies. A report of excessive bleeding from a circumcision or tonsillectomy should raise the possibility of thrombocytopenia, von Willebrand’s disease, or one of the inherited factor deficiencies and is a reason to measure platelet count, bleeding time, and coagulation time (see Chapter 36, Systemic Disorders).

Sickle cell disease typically produces no symptoms in early childhood, so a systems review is unlikely to detect its presence. For this reason, children of African heritage should be screened for sickle cell disease before surgery. A positive result should be followed by a hemoglobin electrophoresis to confirm the diagnosis or to define other hemoglobinopathies. The anesthetic plan may then be altered to ensure preoperative and postoperative hydration and to provide a high concentration of inspired oxygen. To prevent ischemia and subsequent sickling in the operated limb, the use of a tourniquet during orthopedic surgery is contraindicated when sickle cell disease or trait is present. This has become controversial, however.

In a report by the Preoperative Transfusion in Sickle Cell Disease Study Group, aggressive treatment (transfusion to a hemoglobin S level of less than 30%) was compared with a more conservative management regimen (hemoglobin maintained at 10 g/dL). The conservative approach was equally as effective as the aggressive approach in preventing serious complications but was associated with half the number of transfusion-associated complications (Vichinsky et al., 1995). A hematologic consultation should be sought or institutional protocols be developed for children with hemoglobinopathies who are undergoing anesthesia (see Chapter 36, Systemic Disorders).