Anesthetic Considerations for Pediatric Surgical Conditions

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Anesthetic Considerations for Pediatric Surgical Conditions

Anesthetizing children is an increasingly safe undertaking. When discussing the risks and benefits of a child’s operation with his or her family, surgeons should feel confident that their anesthesiology colleagues can provide an anesthetic that facilitates the procedure while ensuring the child’s safety. Providing optimal perioperative care for children requires close collaboration between the surgeon and anesthesiologist on issues both large and small. This chapter is designed to inform surgeons about the considerations important to anesthesiologists.

Risks of Anesthesia

In an effort to reduce patient complications, anesthesiologists have carefully analyzed anesthetic morbidity and mortality over the past generation. Whereas anesthesia was historically considered a dangerous enterprise, serious anesthesia-related complications are now relatively rare, especially in healthy patients. The reasons for this improvement include advances in pharmacology, improved monitoring technology, increased rigor of subspecialty training, and the ability to target problems using an analysis strategy.

Quantifying the risk of pediatric anesthesia is difficult due to the difficulty in determining whether complications are attributable to the anesthetic, and if so, to what degree. The risk of cardiac arrest for children undergoing anesthesia was estimated in the 1990s to be 1 : 10,000.1,2 However, these studies did not take patient co-morbidity or the surgical condition into consideration. The risk of a healthy child suffering cardiac arrest during myringotomy tube placement is significantly less than the likelihood of a child with complex cardiac disease arresting during a complex cardiac repair.3

A recent review of cardiac arrests in anesthetized children compared 193 events from 1998–2004 to 150 events from 1994–1997.4 A reduction in medication-caused arrests from 37% to 18% was identified, and was attributed to the decline in halothane use (that causes myocardial depression) and the advent of using sevoflurane (that is not associated with myocardial depression). There was also a reduction in unrecognized esophageal intubation as a cause of arrest, due in large part to the advent of end-tidal carbon dioxide (ETCO2) monitoring, pulse oximetry, and an increased awareness of the problem.

Recent large single center reports yield a current estimate of anesthesia-related mortality of 1 : 250,000 in healthy children. To put this into perspective for parents, the risk of a motor vehicle collision on the way to the hospital or surgery center is greater than the risk of death under anesthesia. However, risks of mortality and morbidity are increased in neonates and infants less than one year of age, those who are ASA (American Society of Anesthesiologists) status 3 or greater, and those who require emergency surgery.5

Preoperative Anesthesia Evaluation

All patients presenting for operations under anesthesia benefit greatly from a thorough preanesthetic/preoperative assessment and targeted preparation to optimize any coexisting medical conditions. The ASA physical status (PS) score is a means of communicating the condition of the patient. The PS is not intended to represent operative risk and serves primarily as a common means of communication among care providers (Table 3-1). Any child with an ASA classification of 3 or greater should be seen by an anesthesiologist prior to the day of surgery. This may be modified in cases of hardship due to the distance from the surgical venue or when the patient is well known to the anesthesia service, and the child’s health is unchanged. Finally, outstanding and unresolved medical issues may be significant enough to warrant cancellation of the procedure for optimization of anesthesia and/or further diagnostic workup.

TABLE 3-1

ASA Physical Status Classification

ASA Classification Patient Status
1 A normal healthy patient
2 A patient with mild systemic disease
3 A patient with severe systemic disease
4 A patient with severe systemic disease that is a constant threat to life
5 A moribund patient who is not expected to survive without the operation
6 A declared brain-dead patient whose organs are being removed for donor purposes
E An emergency modifier for any ASA classification when failure to immediately correct a medical condition poses risk to life or organ viability

Criteria for Ambulatory Surgery

Ambulatory surgery comprises 70% or more of the caseload in most pediatric centers. Multiple factors should be considered when evaluating whether a child is suitable for outpatient surgery. Some states regulate the minimum age allowed in an ambulatory surgical center. For example, the minimum age in Pennsylvania is six months. In most cases, the child should be free of severe systemic disease (ASA PS 1 or 2). Other factors that may determine the suitability of a child for outpatient surgery are family and social dynamics. Some institutions utilize a telephone screening evaluation process to determine whether a patient can have their full anesthesia history and physical on the day of surgery rather than being evaluated in a preoperative evaluation clinic prior to surgery.6

Well-controlled systemic illnesses do not necessarily preclude outpatient surgery, but any concerns must be addressed in advance in a cooperative fashion between the surgical and anesthesia services. If a child has a moderate degree of impairment, but the disease is stable and the surgical procedure is of minimal insult, outpatient surgery may be acceptable.

General Principles

In addition to the physical examination, the essential elements of the preoperative assessment in all patients are listed in Box 3-1. Patients and parents may be anxious about recurrence of adverse perianesthetic events such as those listed, and they should be reassured that efforts will be made to prevent these events.

Patient History

Documentation of allergy status is an essential part of the preoperative evaluation, particularly as prophylactic antibiotics may be administered prior to incision. Allergies to certain antibiotics (especially penicillin, ampicillin and cephalosporins) are the most common medication allergies in children presenting for surgery. Anaphylactic allergic reactions are rare, but can be life threatening if not diagnosed and treated promptly. Latex allergy is the most common etiology for an anaphylactic reaction, and children with spina bifida (myelomeningocele), bladder exstrophy, or those who have undergone multiple operations (such as repeated ventriculoperitoneal shunts) are at greatest risk for such reactions.

In general, parents should be instructed to continue routine administration of anticonvulsant medications, cardiac medications, and pulmonary medications even while the child is fasting.

The family history should be reviewed for pseudocholinesterase deficiency (prolonged paralysis after succinylcholine) or any first-degree relative who experienced malignant hyperthermia (MH). A complete review of systems is important and should focus on those areas in which abnormalities may increase the risk of adverse events in the perioperative period.

Miscellaneous Conditions

Malignant Hyperthermia Susceptibility

MH is an inherited disorder of skeletal muscle calcium channels, triggered in affected individuals by exposure to inhalational anesthetic agents (e.g., isoflurane, desflurane, sevoflurane), succinylcholine, or both in combination, resulting in an elevation of intracellular calcium. The incidence of an MH crisis is 1 : 15,000 general anesthetics in children. Fifty per cent of patients who have an MH episode have undergone a prior general anesthetic without complication. The resulting MH crisis is characterized by hypermetabolism (fever, hypercarbia, acidosis), electrolyte derangement (hyperkalemia), arrhythmias, and skeletal muscle damage (elevated creatine phosphokinase [CPK]). This constellation of events may lead to death if unrecognized and/or untreated. Dantrolene, which reduces the release of calcium from muscle sarcoplasmic reticulum, when given early in the course of an MH crisis, has significantly improved patient outcomes. With early and appropriate treatment, the mortality is now less than 10%. Current suggested therapy can be remembered using the mnemonic ‘Some Hot Dude Better GIve Iced Fluids Fast” and is summarized in Box 3-2.7 It should be noted that dantrolene must be prepared at the time of use by dissolving in sterile water. It is notoriously difficult to get into solution and the surgeon may be asked to help with this process.

Patients traditionally thought to be MH susceptible are those with a spectrum of muscle diseases listed in Box 3-3. However, many patients who develop MH have a normal history and physical examination. In the past, patients with mitochondrial disorders were thought to be at risk. Anesthetic gases appear safe in this population, but succinylcholine should still be avoided as some patients may have rhabdomyolysis (elevated CPK, hyperkalemia, myoglobinuria) with hyperkalemia without having MH.

Trisomy 21

Perioperative complications occur in 10% of patients with trisomy 21 who undergo noncardiac surgery and include severe bradycardia, airway obstruction, difficult intubation, post-intubation croup, and bronchospasm. Patients may have airway obstruction due to a large tongue and mid-face hypoplasia. The incidence of obstructive sleep apnea (OSA) may exceed 50% in these patients, and may worsen after anesthesia and operation. Airway obstruction may persist even after adenotonsillectomy. Many patients with trisomy 21 have a smaller caliber trachea than children of similar age and size; therefore, a smaller endotracheal tube (ETT) may be required.

Congenital heart disease (CHD) is encountered in 40–50% of patients with trisomy 21. The most common defects are atrial and ventricular septal defects, tetralogy of Fallot, and atrioventricular (AV) canal defects. Children with a cardiac history should have records from their most recent cardiology consultation and echocardiogram available for preoperative evaluation. Recent clinical changes in their condition may warrant an assessment by their cardiologist prior to operation.

Cervical spine instability can lead to spinal cord injury in the perianesthetic period. Patients with trisomy 21 have laxity of the ligament holding the odontoid process of C2 against the posterior arch of C1. This can lead to atlanto-axial instability that occurs in about 15% of these patients. The need for preoperative screening for this condition is controversial. However, even if the radiographic examination is normal, care should be taken perioperatively to keep the neck in as neutral a position as possible, avoiding extreme flexion, extension or rotation, especially during tracheal intubation. Any patient with trisomy 21 who has neurologic symptoms such as sensory or motor changes, or loss of bladder or bowel control, should have preoperative neurosurgical consultation to exclude cervical cord compression.

Preoperative Fasting Guidelines

Violation of fasting guidelines is one of the most common causes for cancellation or delay of surgeries. Preoperative fasting is required to minimize the risk of vomiting and aspiration of particulate matter and gastric acid during anesthesia induction. While the risk of aspiration is generally small, it is a real risk that may be associated with severe morbidity or death.

Research performed at our institution has demonstrated that intake of clear liquids (i.e., liquids that print can be read through, such as clear apple juice or Pedialyte) up until two hours prior to the induction of anesthesia does not increase the volume or acidity of gastric contents.8 Our policy is to recommend clear liquids until two hours prior to the patient’s scheduled arrival time. Breast milk is allowed up to three hours before arrival for infants up to 12 months of age. Infant formula is allowed until four hours before arrival in infants less than 6 months old, and until six hours before arrival in babies 6–12 months old. All other liquids (including milk), solid food, candy, and gum are not allowed less than eight hours before induction of anesthesia. Although these are the guidelines for our institution, the surgeon should be aware that NPO (nil per os) guidelines are variable and institutionally dependent.

Mitigating circumstances for NPO rules are limited to emergency operations, in which steps are taken to protect the airway from aspiration through the use of rapid sequence intubation. Nonemergent patients at particular risk for dehydration should be scheduled as the first case of the day when possible, and administration of clear liquids by mouth until two hours prior to arrival at the surgical facility should be encouraged. Insulin-dependent diabetics, infants, and patients with cyanotic or single ventricle cardiac disease are among those requiring careful planning so that fasting times are not prolonged.

Laboratory Testing

At the time of consultation, selected laboratory studies may be ordered, but routine laboratory work is usually not indicated. Policies vary among institutions regarding the need for preoperative hemoglobin testing. In general, any patient undergoing a procedure with the potential for significant blood loss and need for transfusion should have a complete blood count (CBC) performed in the preoperative period. Certain medications, particularly anticonvulsants (tegretol, depakote), may be associated with abnormalities in blood components (white blood cells, red blood cells, platelets), making a preoperative CBC desirable.

Although serum electrolytes are not routinely screened, electrolytes may be helpful in patients on diuretics. Preoperative glucose should be monitored in insulin-dependent diabetic patients, and also in any patient who has been receiving parenteral nutrition or intravenous (IV) fluids with a dextrose concentration greater than 5% prior to surgery.

Routine screening for pregnancy in all females who have passed menarche is strongly recommended. An age-based guideline (at our institution, any female 11 years of age or older) may be preferable. Although it is easiest to perform a urine test for human chorionic gonadotropin (hCG), if a patient cannot provide a urine sample, blood can be drawn for serum hCG testing. Institutional policy may allow the attending anesthesiologist to waive pregnancy testing at their discretion.

Certain medications, particularly anticonvulsants, should be individually assessed regarding the need for preoperative blood levels. The nature of the planned operation may also require additional studies.

Clinical Scenarios and High Risk Populations

Upper Respiratory Tract Infection

One of the most common questions confronting an anesthesiologist is whether to cancel a procedure because of an upper respiratory infection (URI). It is not uncommon for some patients to spend much of their childhood catching, suffering from, or recovering from a URI, with the highest frequency occurring in children under age 6 who attend day care or preschool.9 Patients with a current or recent URI undergoing general anesthesia are theoretically at increased risk for perioperative respiratory complications, including laryngospasm, bronchospasm, and hypoxia, with the youngest patients (<2 years of age) being at greatest risk.10,11 However, anesthetic management may also be tailored to reduce stimulation of a potentially hyper-reactive airway. In addition, cancellation of a procedure imposes an emotional and/or economic burden on patients and families, physicians, and operating rooms. Unless the patient is acutely ill, it is often acceptable to proceed with the anesthetic. Patients with high fever, wheezing, or productive cough may actually have a lower respiratory tract infection and the planned procedure is more likely to be cancelled. Our approach is to discuss the urgency of the scheduled operation with the surgeon, and then to review the risks and benefits of proceeding versus rescheduling with the parents, taking into consideration the possibility that the child may have another URI at the time of the rescheduled procedure. Allowing the parents to participate in the decision-making process (when appropriate) usually leads to mutual satisfaction among all involved parties.

The decision to cancel or postpone a procedure (usually a delay of four to six weeks because of concern for prolonged hyperreactivity of the bronchi) should not be made lightly. Families have often sacrificed time away from work, taken children out of school, arranged child care for other children, or have planned a vacation around the scheduled surgery. These economic and social considerations deserve respectful attention. Symptoms that would tip the scales toward cancellation include the severity of illness, as measured by an intractable or productive cough, bronchospasm, malaise, fever, or hypoxia on pulse oximetry. In contrast, clear rhinorrhea with a simple cough is usually not sufficient grounds for cancellation, provided the family understands the very small chance of needing postoperative supplemental oxygen and bronchodilator therapy.

The Former Preterm Infant

Infants born prematurely (<37 weeks gestation) may exhibit sequelae such as bronchopulmonary dysplasia (BPD), gastroesophageal reflux, intraventricular hemorrhage/hypoxic–ischemic encephalopathy (IVH/HIE), or laryngo/tracheomalacia or stenosis. Preterm infants are also at increased risk for postoperative apnea after exposure to anesthetic and analgesic agents.

Respiratory and Airway Considerations

Although the incidence of BPD has fallen over the past two decades as the use of surfactant and new ventilation strategies have been introduced, it remains the most common form of chronic lung disease in infants, and significantly complicates the perioperative management of ex-premature infants. BPD is associated with airway hyper-reactivity, bronchoconstriction, airway inflammation, pulmonary edema, and chronic lung injury.

Several effects of anesthesia, together or separately, may have life-threatening consequences. After anesthetic induction, pulmonary vasoconstriction can aggravate ventilation-perfusion mismatch and lead to profound hypoxemia. Anesthetic effects on myocardial contractility can result in impaired right ventricular function, reduced cardiac output, decreased pulmonary blood flow, and profound cardiovascular compromise with hypoxemia. Increased airway reactivity during anesthetic induction or emergence from anesthesia can result in severe exacerbation of bronchoconstriction, impairing ventilation and pulmonary blood flow. Increased oral and bronchial secretions induced by the anesthetic can compromise airflow and lead to airway or endotracheal tube plugging. Because of diminished respiratory reserves in these patients, such plugging can quickly cause profound hypoxia and acute right-sided heart strain, arrhythmias, and possibly death.

Preoperative measurement of electrolytes is warranted in children taking diuretics such as furosemide and spironolactone on a chronic basis, In addition, 48–72 hours of steroid administration may provide anti-inflammatory coverage which may reduce the risk of perioperative bronchospasm. If the child has received large doses of or continuous treatment with steroids, perioperative stress doses may be necessary.

Postanesthetic Apnea

The risk of apnea is increased in ex-premature infants because of immaturity of the central and peripheral chemoreceptors with blunted responses to hypoxia and hypercapnia, even without the additional burden of anesthetic/opioid-induced respiratory depression. In addition, anesthetic agents decrease muscle tone in the upper airway, chest wall, and diaphragm, thereby further depressing the ventilatory response to hypoxia and hypercapnia. In the immediate neonatal period, immaturity of the diaphragmatic musculature causes early fatigability, which may also contribute to apnea.12 Although postanesthetic apnea may be brief and resolve either spontaneously or with minor stimulation, in ex-premature infants even brief apnea may result in significant hypoxia. Although most apneic episodes occur within the first two hours after anesthesia, apnea can be seen up to 18 hours postoperatively.

This increased risk of apnea affects the postanesthetic care of infants born prematurely, mandating that those at risk be admitted for cardiorespiratory monitoring. Despite numerous studies on this issue, the postnatal age at which this increased risk of apnea disappears is still being debated. The results of a meta-analysis of pertinent studies indicated that a significant reduction occurred in the incidence of apnea at 52 to 54 weeks’ postconceptual age.13 A hematocrit less than 30% was identified as an independent risk factor, and it was recommended that ex-premature infants with this degree of anemia be hospitalized postoperatively for observation regardless of the postconceptual age. However, conclusions drawn from this meta-analysis have been challenged. Moreover, the sample size of this study may not have been large enough to draw valid conclusions.14

Until more patients are systematically studied, the choice of when a former preterm infant can undergo an outpatient operation is up to the discretion and personal bias of the anesthesiologist and surgeon. Institutional policies most commonly mention ages of 44 weeks for infants born at term (>37 weeks), and from 52 weeks to 60 weeks postconceptual age for infants born at <37weeks. Legal issues direct these practices in many institutions, but regardless of the postconceptual age at the time of surgery, an infant should be hospitalized if any safety concerns arise during the operative or recovery period.

Although the risk of apnea can be decreased with regional anesthesia and/or caffeine, our practice is to admit all at-risk patients (those with a postconceptual age of younger than 60 weeks), regardless of the anesthetic technique used, to monitored, high-surveillance inpatient units for 23 hours after anesthesia and operation. Similarly, infants born at term must be at least 1 month of age to be candidates for outpatient surgery because postanesthetic apnea has been reported in full-term infants up to 44 weeks postconceptual age.13 Figure 3-1 shows an algorithm useful for decision making regarding eligibility for day surgery in young infants.

Anterior Mediastinal Mass

It has long been recognized that the anesthetic management of the child with an anterior mediastinal mass is very challenging and fraught with the risk of sudden airway and cardiovascular collapse. Signs and symptoms of positional airway compression and cardiovascular dysfunction may, or may not, be present. However, the absence of signs and symptoms does not preclude the possibility of life-threatening collapse of the airway or cardiovascular obstruction upon induction of anesthesia. Patients presenting with anterior mediastinal masses (e.g., lymphoma) are at particularly high risk of airway compromise and cardiovascular collapse with the induction of general anesthesia due to compression of the trachea or great vessels when intrinsic muscle tone is lost and spontaneous respiration ceases.15–17 When this occurs, there may not be airway compromise, but rather obstruction of vascular inflow to the right atrium and/or outflow tract obstruction from the right or left ventricle.

Preoperative evaluation should begin with a careful history to elicit any respiratory symptoms. Common symptoms of tracheal compression and tracheomalacia include cough, dyspnea, wheezing, chest pain, dysphagia, orthopnea, and recurrent pulmonary infections. Cardiovascular symptoms may result from infiltration of the pericardium and myocardium or compression of the pulmonary artery or superior vena cava. The diagnostic evaluation includes chest radiographs and/or computed tomography (CT) scans. Echocardiography may be useful to assess the pericardial status, myocardial contractility, and compression of the cardiac chambers and major vessels. Flow-volume loops and fluoroscopy can provide a dynamic assessment of airway compression that other tests cannot assess. Chest CT is helpful in planning the anesthetic technique and in evaluating the potential for airway compromise during anesthesia. Tumor-associated superior vena cava syndrome develops rapidly and is poorly tolerated.

Premedication is inadvisable in most patients with an anterior mediastinal mass as any loss of airway muscle tone may upset the balance between negative intrathoracic pressure and gravity, resulting in airway collapse. Once the decision is made to sedate or anesthetize the child, maintenance of spontaneous respiration, regardless of induction technique, is paramount. It is essential to avoid the use of muscle relaxants because the subsequent airway collapse can be fatal.

Positioning the child is an important part of the anesthetic plan for these patients. The sitting position favors gravitational pull of the tumor toward the abdomen rather than allowing the tumor to fall posteriorly onto the airway and major vessels as occurs in the supine position. However, the sitting position makes intubation challenging. Thus, positioning the symptomatic child in the lateral decubitus position is recommended. Turning the child lateral or prone, or lifting the sternum, have been shown to alleviate acute deterioration in ventilation or cardiovascular collapse secondary to tumor compression.18,19 In any patient with an increased potential for such obstruction, provision should be made for the availability of a rigid bronchoscope, the ability to move the operating room table to effect position changes, and the ability to institute cardiopulmonary bypass or extracorporeal membrane oxygenation (ECMO). Compression of greater than 50% of the cross-sectional area of the trachea on CT imaging has been suggested to identify a population at risk of airway collapse during induction of general anesthesia.20

When possible, percutaneous biopsy of the mass using local anesthesia with or without judicious doses of sedative medication is often ideal and poses the least risk to the patient. In patients who have additional tissue sites from which a biopsy can be obtained (e.g., cervical, axillary, or inguinal lymph nodes), it may be safer to proceed with the patient in a semi-sitting position using local anesthesia and carefully titrating sedation so that spontaneous ventilation is preserved. Recently, ketamine and dexmedetomidine have been shown to provide good sedation with preservation of airway patency and spontaneous respiration in this setting.21 If progression to general anesthesia is required and airway and/or vascular compression exists, standby ECMO capability is strongly recommended.

The inherent conflict between the need to obtain an accurate and timely tissue diagnosis and the very real concern regarding the safe conduct of the anesthetic requires an open dialogue between the anesthesiologist, surgeon, and oncologist to reach an agreement on strategies to achieve these goals. Many experts recommend the development and utilization of an algorithm for anesthetic management of the child with an anterior mediastinal mass (Fig. 3-2). The algorithm addresses assessment of signs and symptoms, evaluation of cardiopulmonary compromise, and treatment options.18,22,23

Patients with Congenital Heart Disease

Each year in the U.S., nearly 32,000 children are born with CHD. Extracardiac anomalies are seen in up to 30% of infants with CHD,24,25 and may necessitate operative intervention in the neonatal period prior to repair or palliation of the cardiac lesion. Although physiologically well-compensated patients may undergo noncardiac surgery with minimal risk, certain patient groups have been identified as high risk: children less than 1 year of age, especially premature infants; patients with severe cyanosis, poorly compensated congestive failure or pulmonary hypertension; patients requiring emergency surgery and patients with multiple coexisting diseases.26

Preoperative Preparation and Evaluation

The spectrum of congenital and acquired cardiac lesions is so varied that formulating one set of rules for evaluation and perioperative care is nearly impossible. Children with unrepaired or palliated heart disease, children requiring operation as a result of their cardiac disease, and children undergoing emergency surgery tend to be more critically ill and require more intensive preoperative preparation and assessment.

Patients with CHD may be receiving antithrombotic therapy for a variety of reasons, including the presence of systemic-to-pulmonary shunts, mechanical or biological prosthetic heart valves, a history of thrombosis involving a conduit or a shunt, recent transcatheter interventions or device placement, treatment of Kawasaki disease, and the presence of risk factors for thromboembolic events including Fontan physiology. No specific pediatric guidelines exist for the discontinuation of antithrombotic medications prior to an elective operation, and management strategies ideally should be coordinated between the child’s cardiologist, surgeon, and anesthesiologist.

An emergency operation presents additional management issues and often adds risk in several areas. There may be little time preoperatively to optimize the patient’s cardiac condition, along with difficulty in quickly obtaining complete cardiology and surgical records. In these cases, the anesthetic preoperative evaluation is distilled into the most important factors, including the nature and duration of the present illness, the child’s underlying cardiac disease, baseline status, and medications. Patients with cyanosis, or those who depend on shunts for pulmonary blood flow (PBF), or those with single ventricle physiology who have undergone total cavopulmonary anastomosis (Fontan procedure) require intravenous hydration prior to induction of anesthesia if they are hypovolemic. Based on the child’s condition and the nature of the emergency, a decision can be made as to whether to proceed with the case with no further workup or a review of available old records, or whether new consultations and studies should be obtained prior to surgery.