Chapter 64. Anesthesia for Children

1. Overall, pediatric anesthesia is extremely safe in the hands of experienced providers. Factors that may increase risk include age younger than 1 year and coexisting disease. Careful attention to maintenance of a patent airway is critical to the safe care of infants and children.

2. One of the challenges of pediatric anesthesia for trainees is selecting appropriately sized equipment and supplies. Endotracheal tubes are generally selected to yield a leak at 15 to 30 cm H2O. Cuffed tubes are gaining wider use in young children as well as those older than 8 years. Straight blades are most commonly used for intubation in infants, with the usual choices being Miller 0 for neonates and Miller 1 for infants. A Wis-Hipple 1.5 blade is often used in toddlers, with progression to Macintosh size 2 for children 3 years and older.

3. The physiologic and psychological contexts must be considered in planning an anesthetic for any child. Premedication and parental presence may be appropriate for children. Induction of anesthesia for elective surgery in young children frequently is accomplished by inhalation of a volatile anesthetic. Sevoflurane is the most common choice in modern practice based on the drug's rapid effect, low degree of airway irritation, and cardiovascular stability.

4. Succinylcholine is no longer used routinely in children because of the potential for hyperkalemia in undiagnosed myopathy. Succinylcholine may still be used when indicated for rapid-sequence induction or treatment of laryngospasm.

5. Regional anesthesia is a useful adjunct to general anesthesia in children for a variety of procedures. Surgery with a regional anesthetic alone is uncommon in young children; one exception is the use of spinal anesthesia in premature infants at risk for postoperative apnea. For common outpatient surgery such as hernia repair or orchidopexy, caudal blockade with a local anesthetic such as ropivacaine provides good intraoperative and postoperative analgesia. Epidural catheters also may be placed in children for more major procedures and generally are placed after induction of general anesthesia in children who are too young to cooperate.

6. Selection of an appropriate plan for postoperative analgesia is important for both inpatient and outpatient situations. Adequate doses of acetaminophen, nonsteroidal anti-inflammatory drugs when not contraindicated, and regional anesthesia may be appropriate in addition to or in place of opioid analgesia, depending on the procedure. Postoperative vomiting is common in children and may occur more frequently during certain procedures, such as strabismus surgery, and in patients with a history of motion sickness or postoperative vomiting. Prophylaxis frequently includes use of a 5-hydroxytryptamine3 (5-HT3) receptor antagonist or a steroid such as dexamethasone. Because of restrictions on the use of droperidol, 5-HT3 receptor antagonists are generally used as first-line treatment of postoperative nausea and vomiting in children.

7. Emergence agitation occurs in a significant number of toddlers and young children, particularly after use of a volatile anesthetic. Appropriate analgesia and possibly supplemental sedation may be helpful. The results in the literature are mixed with regard to links with specific agents (eg, sevoflurane); patient and parental anxiety may contribute to the development of agitation.

8. Many of the procedures performed in children involve concepts similar to those used in parallel adult cases (eg, neurosurgery, thoracic surgery). The concepts related to the surgical subspecialty must be integrated with those specific to the anesthetic care of children. Procedures specific to the pediatric population are discussed.

Perioperative care of infants and children presents a number of special challenges. The anesthesia care team must evaluate and interface with both the child and parents and must consider psychological as well as physiologic factors. In the United States, anesthesia for elective surgery in children is frequently initiated with an inhalation induction, which is significantly different from the intravenous (IV) induction commonly performed in adults. Physiologic differences, such as an increased rate of oxygen consumption, create the potential for rapid arterial blood desaturation with apnea or hemodynamic compromise. Finally, specific technical skills are required in infants and children.

Overall, safety in pediatric anesthesia is excellent. Complications are uncommon, and improvements over the past several decades are attributed to better monitoring (pulse oximetry and capnography), safer anesthetic agents, and better understanding of specific areas of increased risk. Outcome studies dating from the late 1980s1 to the current era2 have identified increased rates of complications and cardiac arrest during anesthesia in children younger than 1 year, although in some studies, the risk appears to be explained by coexisting diseases. American Society of Anesthesiologists (ASA) classification and emergency status also have been predictors of increased risk in pediatric anesthesia outcome studies.

Respiratory Risk

Respiratory complications are common in infants and children. These include laryngospasm, bronchospasm, airway obstruction, and decreased systemic oxygen saturation. Factors that may contribute to respiratory risk include younger age, concurrent disease (syndromes, airway anomalies, or obstructive sleep apnea), recent upper respiratory infection3 (see Chapter 20), and airway procedures (tonsillectomy, airway surgery, cleft palate repair). Screening for potential airway abnormalities, a backup plan for managing airway difficulties, and rapid attention to respiratory changes are critical components of pediatric anesthetic care.

Pulmonary aspiration of gastric contents is reported in pediatric patients in a range similar to that seen in adults (1-10 cases per 10,000 anesthetics).4 Aspiration occurs more frequently in emergency cases and in "full-stomach" situations such as bowel obstruction. The majority of cases of aspiration occur during laryngoscopy, particularly with coughing or unexpected airway difficulties, but some cases occur during maintenance or emergence from anesthesia. Aspiration using a laryngeal mask has generally been related to a predisposing factor such as inadequate depth of anesthesia, gastrointestinal disease or full stomach, lithotomy position, movement of the laryngeal mask airway (LMA), or multiple insertion attempts.5 If clinical signs develop (decreased oxygen saturation, coughing, wheezing), they usually occur in the first 2 hours after aspiration. The long-term outcome is generally good in healthy pediatric patients who aspirate gastric contents, but the acuity of perioperative care may be higher than would otherwise have been planned.

Infants born prematurely have an increased risk of apnea and bradycardia after general anesthesia; apnea risk is inversely proportional to both gestational and postconceptual age and increased by anemia.6 Caffeine administration7 or the use of spinal anesthesia without sedation8 reduces the risk of postoperative apnea. Newer anesthetic agents, such as sevoflurane, are not free of the risk of apnea in infants born prematurely.9 Many hospitals require postoperative overnight admission for monitoring until 50 to 60 weeks' postconceptual age in infants born before 37 weeks; they also may consider anemia, prior apnea, and coexisting disease. Little specific evidence about apnea risk in term infants is available. Some facilities restrict the lower age for day surgery procedures to older than 44 to 46 weeks' postconceptual age in term infants or require a longer observation period (eg, 4 h) before discharge.

Cardiac Risk

An analysis of pediatric cases from the ASA Closed Claims Study found that claims in infants and children were more likely to be related to respiratory events, more often classified as "preventable" (eg, by better monitoring), and resulted in greater injury severity and mortality than adult claims.10 The Pediatric Perioperative Cardiac Arrest (POCA) Registry analyzes anesthetic-related cardiac arrests. POCA data published in the year 2000 showed an overall incidence of anesthetic-related cardiac arrest of 1.4 per 10,000 anesthetics based on more than 1 million anesthetics from 63 institutions.11 Cardiac arrest was most frequent in patients younger than 1 year (55% of cases) and in those with severe underlying disease (ASA classes 3, 4, and 5). Among healthy patients (ASA classes 1 and 2), the most common causes of cardiac arrest were respiratory (related primarily to either laryngospasm or anatomic airway obstruction) and medication related (primarily halothane). In the more recent period, cardiac arrests related to potent inhalational anesthetics have declined,12 presumably related mainly to the use of the safer agent sevoflurane. Cardiac arrest in children with underlying congenital heart disease occurs most frequently in patients with aortic stenosis, cardiomyopathy, and single-ventricle physiology13 and may occur in the setting of the general operating room (OR) as well as during cardiac surgery. Cardiac arrest related to succinylcholine administration was reported in the late 1980s14; the children were found to have unrecognized myopathy with the development of hyperkalemia after succinylcholine administration. Succinylcholine now is used with caution in pediatric patients but is considered an appropriate choice when rapid intubation is required and for treatment of laryngospasm.

Risk of Neurocognitive Impairment

Concern over the possibility that anesthesia could cause impairment of neurodevelopment stems from animal studies showing apoptosis in the brain of immature laboratory animals. There is inadequate evidence to date to decide how relevant this is to clinical practice in human children, but it is an active area of research. Some of the limitations in applying laboratory research include a long duration of exposure, extremely high anesthetic doses, questionable correlation of the age of the experimental animals to human infants, possible species differences, and the anesthetic management in animal studies.15 Adverse neurologic outcomes are more common in research animals when anesthesia is given without a painful stimulus. Certainly, large numbers of children receive anesthetic care without obvious neurologic or cognitive injury, but better epidemiologic evidence is needed in humans. Some preliminary and retrospective work suggests an association between anesthesia and markers of cognitive dysfunction, but others do not. A causal relationship has not been demonstrated, and it is possible that the need for anesthesia is simply a marker for other comorbidities that could contribute to neurocognitive dysfunction. A recent study using the Netherlands Twin Registry was reassuring in that exposed and unexposed co-twins did not differ in cognitive outcomes; the authors concluded that this suggests that anesthesia at an early age is a marker of vulnerability for later learning disabilities rather than a causal factor.16 Several large prospective studies are in process to attempt to obtain more conclusive evidence.17 Until these are available, we should provide parents with available information and reassurance and participate in risk-to-benefit discussions with surgeons and others who request anesthetized procedures.

Facility and Provider Expertise

One of the complex administrative issues in pediatric anesthesia is determining which patients require care by an anesthesiologist who specializes in the care of children. In the United States, pediatric anesthesia fellowship programs are accredited by the Accreditation Council for Graduate Medical Education; subspecialty board certification in pediatric anesthesia is expected to be offered in 2013. Although the link between provider qualifications and outcomes has not been extensively studied, some evidence suggests that children have fewer adverse outcomes when cared for by anesthesiologists with frequent ongoing experience in anesthetizing children.18,19 Several organizations have put forth guidelines for the care of pediatric patients. The American Academy of Pediatrics (AAP) recommends that anesthesiologists caring for children designated by the facility as being at increased risk either should be fellowship trained in pediatric anesthesiology or have equivalent experience.20 The ASA and the Society for Pediatric Anesthesia have made similar recommendations. The AAP guidelines also recommend having airway and monitoring equipment in sizes suitable for pediatric patients, a separate preoperative area for children and their families, and OR and recovery staff with age-specific competencies and resuscitation skills.

Breathing Circuits and Ventilators

Circuits such as the Mapleson D, a modification of a T-piece, were historically recommended for children because they are lightweight and flexible, have minimal resistance to gas flow, and were designed to prevent rebreathing. Potential disadvantages include rebreathing of carbon dioxide (CO2) if fresh gas flow is inadequate to wash out exhaled gas and significant tidal volume lost to expanding the expiratory limb during controlled ventilation. The newer pediatric circle systems, which have a smaller diameter and lower compliance than adult circuits, are primarily used today. The minor resistance of the valves is generally not clinically significant with modern anesthesia machines, but avoidance of prolonged spontaneous respiration by small infants is prudent. Lower fresh gas flows can be used with resultant conservation of volatile anesthetic agents and airway moisture.

Circuit compliance does not significantly affect delivered tidal volume when a peak inspiratory pressure is chosen that provides good chest movement.21 There may be a discrepancy between actual and measured tidal volume unless the machine measures and compensates for circuit compliance. Pressure mode ventilation may be best in infants, particularly if there is a leak around the endotracheal tube, and higher fresh gas flow may be needed in the presence of a leak. With pressure ventilation, changes in pulmonary and chest wall compliance can result in significant changes in delivered tidal volume. In some older anesthesia ventilators, fresh gas flow contributes to tidal volume, so a large increase in gas flow can cause barotrauma. A good understanding of the characteristics of the ventilator and circuit being used is essential to safe ventilation of a child's lungs.

Monitoring

Pulse oximetry has vastly improved the safety of pediatric anesthesia, but capnography, auscultation, movement in the rebreathing bag, and observation of chest motion all contribute to the clinical assessment of airway patency and should detect airway obstruction before desaturation. Electrocardiographic (ECG) monitoring in healthy children is primarily geared toward monitoring heart rate and rhythm. Ischemic changes are extremely rare except in pediatric cardiac surgery; however, if they occur, rapid assessment of the cause must be undertaken with efforts to improve coronary perfusion. Noninvasive blood pressure monitoring can be used on an upper or lower extremity in children. The decision to place arterial or central venous lines is based on the severity of illness or the extent and potential complications of the procedure. Temperature should be monitored for all but the shortest cases. Appropriate warming devices should be chosen to minimize the risk of hypothermia; these are discussed further in Chapter 20.

Developing an anesthetic plan for a pediatric patient involves several decisions. Is the procedure elective or emergent? Does the child have significant coexisting disease, airway concerns, or behavioral challenges? Are there expectations of how the anesthetic will be conducted based on prior experiences of the child or the child's family or friends?

Preparation and Premedication

Many children younger than 6 to 9 months of age will separate from their parents easily if kept engaged. Older children and those who seem anxious or fussy may benefit from premedication before entering the OR. Midazolam is commonly given orally as a premedication; other routes and doses are summarized in Table 64-1. Oral transmucosal fentanyl is infrequently used because of side effects of nausea or vomiting and pruritus, but it may be a reasonable option when other premedication is not well accepted or when an opioid is indicated for analgesia. Oral ketamine may be useful when analgesia is desired. Intramuscular ketamine is administered to patients who are combative or difficult to approach; a sedative dose usually will result in adequate cooperation to obtain IV access or complete induction by administering an inhalation agent. Finally, rectal administration of methohexital is really an induction rather than a premedication. If used, it should be given in a monitored setting with the anesthesiologist present and prepared to move the patient into the OR or procedure area.

Parental presence during induction can be used in addition to or in place of premedication.22 The child's behavior and family dynamics should be considered; transmitted parental anxiety may limit the value of parental presence. Parents who are going to participate in induction should be appropriately instructed. Provider behavior may also have an impact on how the child responds; providing distraction appears to be more effective than reassuring behaviors.23 OR personnel should have an understanding as to who will be interacting with the child so multiple people will not be competing for the child's attention.

Anesthetic Induction

Induction of anesthesia in elective situations for children younger than 8 to 10 years of age frequently occurs by inhalation to avoid venipuncture until the child is asleep. Sevoflurane provides smooth, rapid inhalation induction with good cardiovascular stability; it has largely replaced halothane for inhalation induction. Desflurane and isoflurane should not be used for inhalation induction because both cause airway irritation. In a cooperative child, mask induction can be initiated with 50% to 70% nitrous oxide in oxygen (Fig. 64-1). After 1 to 2 minutes, sevoflurane is introduced either incrementally or at 8%. If the child is agitated initially or becomes combative during the initial stages of induction, a rapid decision must be made either to stop and pursue premedication or to proceed with a high inspired concentration of sevoflurane. As soon as the child's eyes close, the parents (if present) are escorted out, and attention is turned to maintaining a patent airway. Nitrous oxide can be discontinued at this time to improve oxygen reserve. An "excitement phase" is frequently seen with inhalation induction and may include limb movement, rigidity, rapid respirations, and tachycardia, all of which usually resolve over several minutes as the anesthetic deepens. When the child has passed the excitement phase, IV access is established for all but very brief cases.

Children often develop some degree of airway obstruction during inhalation induction. Keeping one hand on the breathing bag to feel gas movement, auscultation by precordial stethoscope, and observation of the end-tidal CO2 tracing and chest movement all provide useful information. Lack of gas exchange during inhalation induction should be assessed rapidly to differentiate central apnea (from high concentration of anesthetic agent) from airway obstruction by attempting a gentle positive-pressure breath. If the patient is easily ventilated, slow manual ventilation using a lower concentration of volatile agent should result in resumption of spontaneous respiration, which may in turn help avoid excessive anesthetic depth. If airway obstruction is present, further evaluation must attempt to distinguish upper airway obstruction from laryngospasm. Upper airway obstruction in a child often can be managed by opening the mouth slightly to displace the tongue from the roof of the mouth and lifting the jaw anteriorly; continuous positive airway pressure (CPAP) of 5 to 10 cm H2O may be helpful. Pressure on the soft tissue beneath the chin may worsen airway obstruction. An oral airway can be inserted if anesthetic depth is sufficient or if the other maneuvers are unsuccessful. If these measures fail to open the airway, an LMA is inserted if upper airway obstruction is believed to be the cause of obstruction or treatment of laryngospasm can be pursued with 100% oxygen, CPAP, and succinylcholine when necessary.24 Succinylcholine 4 mg/kg can be administered intramuscularly or sublingually if IV access has not been established.

IV induction is generally chosen for older children and adolescents, for children at risk for aspiration of gastric contents, and for any child with IV access already in place unless airway considerations make inhalation induction preferable. Preoxygenation is important in children but may be difficult to accomplish; judicious premedication may be helpful in gaining cooperation. Propofol is frequently used as an induction agent in pediatric anesthesia unless there are hemodynamic contraindications. Burning on injection of propofol into a peripheral IV can be minimized with prior injection of lidocaine, an opioid, or both; thiopental may cause less pain on injection. Ketamine or etomidate is used for induction for specific indications such as hemodynamic instability. Pediatric dosing for induction drugs is summarized in Table 64-2. Intubation can be accomplished with use of a muscle relaxant, with a volatile agent supplemented with propofol or a narcotic or with deep inhalation anesthesia alone. Intubation with a volatile agent alone, particularly sevoflurane, must be accomplished quickly while the patient is at an adequate depth of anesthesia.

Neuromuscular blockade can be used to facilitate endotracheal intubation or may be required to provide optimal surgical conditions. As noted earlier, succinylcholine is indicated in infants and children only when rapid control of the airway is required. Atropine should be given before succinylcholine in infants and young children to minimize the potential for bradycardia. The nondepolarizing muscle relaxants all can be used safely in pediatric practice. Rocuronium is the best alternative for rapid-sequence intubation, but the effective dose of 1 mg/kg has a duration longer than 1 hour. Pediatric doses for muscle relaxants are listed in Table 64-3 and are generally similar to those used in adult practice. Infants appear to have a somewhat increased volume of distribution but also an increased sensitivity to relaxants, so the initial dose remains similar to that used for adults. Rocuronium may have a longer duration of action in infants compared with older children or adults when 0.6 mg/kg is given; a smaller dose (0.45 mg/kg) has been shown to produce good intubating conditions with a shorter duration.25

Reversal of nondepolarizing neuromuscular blockade is advisable unless significant time has elapsed (2 h after a routine intubating dose) or unless the patient clearly exhibits clinical signs of full neuromuscular function. Neostigmine in a dose of 0.05 to 0.075 mg/kg is most commonly administered for reversal. Alternatively, edrophonium can be given at 0.5 to 1.0 mg/kg, although it may be less effective for reversal of profound neuromuscular block. Atropine or glycopyrrolate is administered with reversal agents to prevent bradycardia. Edrophonium has a rapid onset and strong tendency to cause bradycardia; if it is used, atropine should be given first.

Airway Management

Unique anatomic and physiologic aspects of the pediatric airway are discussed in Chapter 20. Because infants and younger children have a large occiput, a roll placed under their shoulders may help to maintain a neutral (and patent) airway (Fig. 64-2). If the mask airway is stable after inhalation induction, maintenance anesthesia can be administered by a face mask, as is commonly done for ear tubes and other minor surgical procedures. An oropharyngeal airway can be inserted when needed to maintain airway patency or if positioning of the mask airway requires frequent manipulation; it should reach from the lips to the angle of the jaw when held next to the child. If access to the face will be limited but intubation is not required, an LMA can be used. LMAs are generally well tolerated in children, but their use is not free from adverse airway events.26,27 Appropriate LMA sizes for various patient weights are listed in Table 64-4. Newer laryngeal mask devices, such as those that afford the ability to vent the stomach, are now being produced in pediatric sizes.

Laryngoscopy in infants and young children has some unique technical aspects related to age-related anatomic changes (see Chapter 20). A child's epiglottis, although rigid, is "slippery" and may be difficult to control with the laryngoscope blade (Fig. 64-3). In the United States, a straight blade is most commonly used in patients younger than 2 years. When performing laryngoscopy with a straight blade, it is important to sweep the tongue to the patient's left; passing the tube down the flange of the blade will obscure the view. If the glottis is not seen after passing under the epiglottis, most likely the blade has already gone too deep and posteriorly; withdrawing the blade slowly with gentle cricoid pressure often brings the glottic opening into view. Choice of laryngoscope blade size by patient age is summarized in Table 64-5.

Traditionally, pediatric endotracheal tubes are selected to allow a small leak at 20 to 25 cm H2O. Because the narrowest portion of a young child's airway is subglottic, the tube must not be forced if any resistance is felt. Approximate endotracheal tube sizes by age are listed in Table 64-5. Tube size can be selected based on age or height or by selecting a tube with an outer diameter similar in size to the child's fifth finger. Tubes are packaged according to internal diameter; specialized endotracheal tubes, such as reinforced tubes, may have a much larger outer diameter than a standard tube of the same internal diameter. Uncuffed endotracheal tubes were traditionally used in children younger than 8 to 10 years of age because of concerns of pressure injury to the tracheal mucosa. Modern tubes are made of less reactive materials and do not cause significant complications when appropriately sized (usually one-half size smaller than uncuffed). Use of a cuffed tube more often results in an appropriate fit28; specific indications include aspiration risk and poor pulmonary compliance. Cuffed tubes allow the use of lower fresh gas flow rates and a decrease in OR pollution from volatile anesthetics. Balloon inflation must be performed carefully, and ideally cuff pressure should be measured, particularly if nitrous oxide is used.

The small distance from vocal cords to carina leaves relatively little margin between correct placement and endobronchial location in small children. For cuffed tubes, the cuff should pass just a short distance below the vocal cords. With uncuffed tubes, options include positioning based on the line markings at the distal end of the tube, deliberate endobronchial intubation and withdrawal until bilateral breath sounds are heard, or use of the common formula

Auscultation of bilateral breath sounds does not guarantee proper TT position.29

A variety of options exist for dealing with the difficult pediatric airway; in contrast to adult practice, inhalation induction with spontaneous respiration is often used because children do not tolerate awake intubation. Insufflation of gas through a nasal airway or endotracheal tube advanced into the nasopharynx may provide a stable airway to allow fiberoptic intubation in an anesthetized child. The LMA can serve as a rescue device or a conduit for fiberoptic intubation. Flexible fiberoptic intubation is a mainstay for difficult intubation; video laryngoscopes and intubating stylets are also available. Skill with these options should be gained first in patients with normal airways. Awake or sedated intubation is possible in infants and children and should be considered when there is no obvious way to ventilate the patient, as in children with congenital abnormalities that preclude achieving a mask seal or when an LMA cannot be inserted. Topical anesthesia can be provided by allowing an infant to suck on a small amount of local anesthetic jelly or by nebulized administration.

Anesthetic Maintenance

A variety of maintenance anesthetic techniques may be appropriate depending on the patient's status and type of surgery. Opinion varies as to whether one volatile agent has a significant advantage over another for pediatric anesthetic use (see Emergence Delirium later). Total IV anesthesia is being used more frequently for a variety of pediatric indications (minor procedures with spontaneous respiration; procedures requiring neurophysiologic monitoring). Metabolic acidosis related to prolonged propofol infusion has been of concern in pediatric intensive care patients.30 Although propofol infusion is widely used in pediatric anesthesia, there is no clear cutoff regarding safe case duration.

Extubation Choices

The endotracheal tube can be removed either when the patient awakens or while the child is deeply anesthetized. The choice depends partly on the preference and experience of the practitioner. Those who advocate "deep extubation" cite smoother emergence with less coughing. Risks include laryngospasm and airway obstruction as the child emerges. Deep extubation requires particular attention to detail and should not be undertaken by individuals inexperienced with the technique; in institutions without proper support for anesthetized pediatric patients in a recovery area; or in patients with full stomachs, oral blood or secretions, or the inability to protect their airway. If deep extubation is chosen, the patient should have a stable pattern of spontaneous respiration and no response to suctioning the oropharynx, stimulation such as jaw thrust, or slight in-and-out movement of the endotracheal tube. Moving the patient while he or she is still deeply anesthetized can prevent the need for stimulation after extubation. Close attention to gas exchange is required after extubation. Evidence supporting or refuting the safety of deep extubation is inconclusive; existing studies are small and cover variable patient populations. Smoother emergence, particularly decreased coughing, has also been suggested when an LMA is removed during deep anesthesia rather than in awake children.

Fluid Therapy

Fluid therapy in pediatric anesthesia is based on calculation and replacement of the fasting deficit, maintenance fluid requirement, insensible and third-space losses, and blood loss. Maintenance fluid and fasting deficits are based on rates of 4 mL/kg/h for the first 10 kg, 2 mL/kg/h for the second 10 kg, and 1 mL/kg/h for weight above 20 kg. Insensible and third-space losses can be high in abdominal surgery, in which the starting replacement volume is 10 mL/kg/h with titration to normal heart rate, blood pressure, urine output, and clinical signs of perfusion. No evidence favors colloid over crystalloid as a generalization, but colloid replacement may have a role in maintaining oncotic pressure when large fluid volumes are given. Fluid boluses for volume-depleted children are given in increments of 10 to 20 mL/kg followed by assessment of clinical parameters. Fluids should be warmed if large volumes are given.

Most healthy children do not need supplemental dextrose to maintain plasma glucose levels unless they have undergone prolonged fasting,31 and liberalization of fasting guidelines may have further reduced any risk of hypoglycemia in healthy children. Patients in whom IV dextrose administration should be strongly considered include neonates, critically ill children with limited metabolic reserve or hepatic failure, children who receive concentrated tube feedings or IV hyperalimentation, and children with inborn errors of metabolism characterized by hypoglycemia. If given, dextrose is preferably administered at a maintenance rate after replacement of the deficit or as a separate infusion. For neonates and high-risk patients, concentrated dextrose solutions may be appropriate; for healthy older children, 1% to 2.5% dextrose solutions are preferred to prevent hyperglycemia.

Blood and Blood Products

Calculation of circulating blood volume and allowable blood loss is covered in depth in Chapter 20. As a useful quick estimate, children who start at a relatively normal hematocrit can lose at least 20% of their blood volume before requiring transfusion if they are kept normovolemic. The patient's clinical condition as well as the rapidity of blood loss and expected further loss should be considered in deciding when to begin transfusion. If crystalloid is used for replacement, it should be given in a 3:1 ratio. Packed cells 10 mL/kg will raise the hematocrit by approximately 6 to 10 percentage points. The amount required to replace the estimated blood loss also can be calculated based on a hematocrit of 70% contained in packed cells:

where Hct is hematocrit and PRBCs is packed red blood cells.

When total transfused volumes of packed cells approach the patient's blood volume, both thrombocytopenia and depletion of clotting factors may occur. Ideally, these parameters are measured to guide replacement therapy, but rapidly changing clinical circumstances may dictate empirical blood component therapy. Platelets are administered in a volume of 5 to 10 mL/kg; 10 mL/kg can be expected to raise the platelet concentration by 100,000/mm3. Thawed fresh-frozen plasma when indicated is also started at 10 mL/kg. Infused packed cells or plasma may cause hypocalcemia if given too rapidly as a result of binding of ionized calcium by citrate. In the setting of large-volume transfusions, potassium release from banked blood may be significant; requesting fresh units or washing the cells may prevent hyperkalemia.

Overview and Safety

Regional anesthesia can provide a useful adjunct for a variety of procedures in pediatric patients, either as a single injection or with postoperative infusion of local anesthetic or other adjuncts. Advantages of regional anesthesia, such as postoperative analgesia, avoidance of narcotic therapy with decreased nausea and vomiting, and early discharge from the recovery area, apply to pediatric patients. This chapter presents particular applications in pediatric anesthesia; further details on standard regional techniques are found in Chapters 46 to 49.

Performing a regional anesthetic in children who are too young to cooperate may require that the block be done during general anesthesia. Using a nerve stimulator to perform "surface mapping" before placing the needle may improve accuracy and decrease the number of attempts required.32 Ultrasound imaging is becoming more common for both neuraxial and peripheral blocks in children. Potential complications of regional techniques in anesthetized patients include intraneural injection, direct needle damage, and local anesthetic toxicity, although these complications are rare. Venous air embolism with hemodynamic consequences has been described during caudal or epidural placement in small children as has neurologic injury been believed to be caused by cerebrovascular air embolism or ischemic injury33; loss of resistance to air is not recommended in pediatric patients. The pediatric anesthesia community has endorsed epidural placement under anesthesia as appropriate practice when it is perceived that the patient will benefit from having the regional anesthetic and there is a risk that the patient might otherwise move during the block.34 The risks and benefits must be weighed in each individual pediatric patient, especially if the procedure is technically difficult.

Local anesthetic toxicity may result from intravascular injection, rapid absorption of an inappropriately large dose, or intravascular accumulation of drug over time. If combinations of local anesthetic agents are used, the toxicity of the agents should be considered to be additive. Local anesthetic blood levels after caudal and peripheral blocks in pediatric patients are generally within acceptable limits. Several cases of toxicity caused by accumulation of high levels in blood occurred in the early 1990s in the setting of postoperative infusion of local anesthetics; these resulted in revision of the recommendations of doses for pediatric infusion, with a maximum dose of 0.4 to 0.5 mg/kg/h for bupivacaine.35 Infants may be at higher risk for toxicity because of lower levels of plasma-binding proteins, diminished clearance, or both, particularly with redosing or catheter infusion techniques. The maximum recommended infusion rates of bupivacaine for patients 6 months and younger is 0.25 to 0.3 mg/kg/h.

Local anesthetic toxicity may not be obvious in the anesthetized patient; aspiration of blood may not reliably occur, and central nervous system signs are difficult to detect. The use of a test dose is recommended to detect inadvertent intravascular injection. Heart rate changes may be less sensitive in the pediatric population, particularly with volatile anesthetics; changes in T-wave morphology on the ECG are a useful indicator. Criteria for a positive test dose in an anesthetized child are heart rate increase greater than 10 beats/min, systolic blood pressure increase greater than 15 mm Hg, and change in T-wave amplitude greater than 25% in lead II. The recommended test dose in children is 0.5 mcg/kg epinephrine (0.1 mL/kg of local anesthetic containing 1:200,000 epinephrine),36 up to the 15-mcg adult test dose. Use of a short-beveled needle or Angiocath may minimize the risk of intravascular injection. In addition, slow incremental injection of local anesthetic is recommended (after test dose, administer a total dose over 1-2 min). Because small veins may easily collapse, observing for passive blood return may be useful in addition to aspiration.

Specific Techniques for Pediatric Regional Anesthesia

Caudal Blocks and Alternatives

The caudal approach to the epidural space is simple in young children, easy to learn, and has a good safety record (Fig. 64-4). Potential complications in anesthetized patients include intravascular injection of local anesthetic, which occurs in approximately 4 in 10,000 patients, and intrathecal injection with total spinal, with a reported incidence of 2.6 in 10,000 cases.37 Children may not develop hypotension or bradycardia even in the presence of a total spinal, but apnea may still occur because of medullary blockade.

Caudal blocks provide excellent analgesia for lower extremity, lower abdominal, and penoscrotal surgery. A short-beveled needle is placed through the sacral hiatus until a typical "pop" is felt, and the needle is anchored in the sacrococcygeal ligament (Fig. 64-5). Aspiration and free drainage should be negative for blood and cerebrospinal fluid (CSF). With correct placement, injection will be easy and will not result in swelling of the subcutaneous tissue. After an epinephrine-containing test dose, the full dose is injected incrementally. Clinical signs of correct placement are generally adequate, but use of a nerve stimulator to confirm caudal needle placement has been described. Laxity of the anal sphincter after placement of a caudal block has been shown to predict success of the block.38 If there is doubt as to efficacy, this sign may assist with the decision to provide additional analgesia. Although the time to first urination may be longer than that without a caudal block, urinary retention is generally not a significant clinical problem. Hemodynamic changes after a caudal block usually are minimal in normovolemic patients.

Bupivacaine in concentrations of 0.125% to 0.25% traditionally has been used for caudal blocks in children in a dose of 1 mL/kg. Freshly added epinephrine to a concentration of 1:200,000 (5 mcg/mL) may improve the duration of analgesia. Because the block will begin to regress after several hours, the more concentrated solution or redosing the block at the end of the case is appropriate for longer procedures. Duration of analgesia from a single-shot caudal injection ranges from 4 to 12 hours. Use of a larger volume of local anesthetic to achieve a higher level may block stimulation from traction during procedures such as orchidopexy.39 The newer local anesthetics ropivacaine and levobupivacaine offer the advantages of decreased cardiac toxicity40 and reduced motor block. Ropivacaine and levobupivacaine have equivalent efficacy at either 0.2% or 0.25% compared with bupivacaine 0.25% (all given at 1 mL/kg); ropivacaine produced the least motor blockade.41

Caudally administered clonidine has shown good efficacy for augmenting and prolonging the analgesia produced by local anesthetics in a variety of procedures.42 A few studies question the benefit.43,44 Single doses of 1 to 2 mcg/kg provide analgesia with a lower incidence of nausea and vomiting than produced by opioids. Some sedation is seen at the higher dose of 5 mcg/kg. Most studies have not shown respiratory depression with epidural or caudal clonidine, although 2 case reports suggest apnea risk in premature infants. Use of epidural or caudal clonidine is fairly common in children in the United States, although a Food and Drug Administration (FDA) "black box" label warns of hypotension in adult patients after epidural clonidine administration. Ketamine has been shown to have good efficacy by the caudal route, but appropriate preparations of preservative-free S-ketamine are not available in the United States.45

Ilioinguinal or iliohypogastric nerve blocks can be performed preoperatively by the anesthesiologist or intraoperatively by the surgeon for procedures such as hernia repair and orchidopexy in children. Some surgeons believe that the injected local anesthetic distorts the surgical dissection planes and prefer to perform the block at the end of surgery. In this situation, a caudal block might be preferable to allow a contribution of the block during surgery. Ilioinguinal blocks generally have equivalent efficacy to caudal blocks, but this may be operator dependent. Cadaver dissection has shown that the optimal insertion site is more lateral than is generally taught and is located approximately 2.5 mm medial to the anterior superior iliac spine on both sides of a line drawn between the anterior superior iliac spine and the umbilicus.46 Ultrasound guidance may improve success and allow use of a lower volume of local anesthetic.47 Although quite safe, complications such as puncture of the bowel wall with hematoma formation have been reported after ilioinguinal block. Other techniques, such as paravertebral or lumbar plexus blockade, have been used in pediatric patients in select settings. Further experience with these techniques is needed before their use can be recommended outside of centers performing them frequently.

Penile block is commonly performed for circumcision and sometimes for simple hypospadias repair. Epinephrine should never be injected in a penile block because of the risk of vascular compromise. As with ilioinguinal blocks, many studies have compared caudal and penile blocks with variable results; most suggest that they are approximately equal. In the traditional dorsal penile block, the needle is passed from the base of the penis until the symphysis pubis is contacted and then withdrawn slightly and redirected to each side of the midline before local anesthetic is deposited. Because of the small risk of hematoma or damage to the dorsal penile vessels, some advocate a "ring block" or subcutaneous injection around the base of the penis. A combination of dorsal and ring blocks may provide the best analgesia. Simple application of topical anesthetic cream (eutectic mixture of local anesthetics [EMLA]) provided equivalent analgesia to dorsal penile block, but the duration of blockade was significantly longer with the injected nerve block.48

Spinal Anesthesia

The primary use of spinal anesthesia in the pediatric population is for hernia repair or other relatively minor surgery in infants considered to be at risk for postoperative apnea. The dose requirement on a weight basis is significantly higher than in adults, and the duration is relatively shorter: 1 mg/kg hyperbaric bupivacaine has a duration of 1 to 2 hours. Levobupivacaine and ropivacaine also have been used. The decision to administer spinal anesthesia should depend on the patient's medical condition and the extent of the procedure. The perceived benefit of a reduced apnea frequency compared with general anesthesia in premature or former premature infants is valid only if no sedation is given. Spinal anesthesia may not be a good choice for a large or incarcerated hernia because of the limited duration and the fact that unsedated babies may fuss and strain.

Epidural Analgesia

Either thoracic or lumbar epidural catheters can be placed in children. Postoperative epidural analgesia may be of benefit to pediatric patients after major thoracic, abdominal, urologic, and lower extremity surgery. For patients weighing between 10 and 25 kg, the approximate depth of the epidural space in millimeters will be predicted by the weight in kilograms. Postoperative infusions should be prescribed to optimize analgesia and minimize side effects. Patient-controlled epidural analgesia can be given to children as young as 5 years of age and may decrease total drug administration.49 The pediatric orthopedic community has expressed concern that epidural analgesia may "mask" development of a compartment syndrome, but in the reported cases, pain was out of proportion to what was expected and was unrelieved by the epidural analgesia.50 Nevertheless, complications other than inadequate epidural analgesia must always be considered and evaluated promptly.

An epidural catheter can be threaded via the caudal route either to allow redosing for longer infraumbilical surgery or for the purpose of threading the tip of the catheter to a higher thoracic or lumbar level.51 In general, the ability to thread the catheter cephalad is best in infants because the epidural fat is not as dense as in older patients. The type of catheter may affect the success rate, and some recommend using a styletted catheter. Radiographic confirmation of tip placement52 or stimulation of the trunk musculature53 may be helpful in positioning the catheter.

Extremity Blocks

Regional anesthesia of the upper extremity can be used in children for procedures performed on the arm and hand. Performing the entire surgical procedure under a regional technique is less common in children than in adults. In conjunction with general anesthesia, even distal blocks can provide excellent analgesia for hand procedures. Axillary blockade is the most common brachial plexus approach in children, although various infraclavicular approaches have been reported. Because of case reports of syrinx formation in adults after interscalene blocks placed under general anesthesia or deep sedation,54 this approach has not been recommended unless the patient can cooperate with block placement with minimal sedation. Some consider that ultrasonography may improve the safety adequately to permit this block under anesthesia.

A number of regional techniques can be performed in children for lower extremity surgery. A psoas compartment approach to the lumbar plexus has been described in children using a nerve stimulator and can be used for unilateral surgery on the hip, thigh, or knee.55 This block may require significant experience for the anesthesiologist to develop mastery,56 and there is some potential for vascular puncture. Femoral nerve blocks are useful in managing pain from a femur fracture even preoperatively. The "fascia iliaca" block has a high rate of success in children when anesthesia of the obturator and lateral femoral cutaneous nerves is needed in addition to the femoral nerve. The sciatic nerve can be blocked by the traditional posterior approach, at the midthigh, or in the popliteal fossa.

The anesthetic plan should include management of pain both in the immediate postoperative period and during later recovery, whether the patient is admitted to the hospital or sent home after surgery. Managing pain in children is a special challenge because our ability to evaluate their pain and their ability to communicate their needs may be limited. Pain scales based on behavior and facial expressions are available for younger children. The analgesic plan may include opioid or nonopioid analgesics, regional or local anesthesia, or a multimodal approach. When a regional anesthetic is used in the early postoperative period, the patient and parent should be told what to expect in terms of duration of effect, and plans for a transition to other types of analgesia should be formulated. Particularly for outpatients, parents should be instructed to begin administering oral analgesics before the child is in severe pain.

Acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs) can provide significant postoperative pain relief and may have an opioid-sparing effect. A rectal loading dose of acetaminophen may be given intraoperatively, but onset is slow with peak plasma concentration at approximately 200 minutes. A rectal loading dose of 40 mg/kg of acetaminophen followed by 20 mg/kg every 6 hours does not appear to result in drug accumulation in the first 24 hours.57 An oral loading dose has faster onset; 40 mg/kg (compared with the traditional dose of 15 mg/kg) resulted in plasma levels at 30 and 60 minutes in an effective range to treat pain (after tonsillectomy) and below levels considered to be toxic.58 Although these higher doses are considered safe and effective in healthy children, parents of outpatients must understand the instructions regarding the concentration and amount to be administered postoperatively. Smaller doses may be appropriate in critically ill patients and those with impaired drug clearance. Injectable forms of acetaminophen may offer an advantage in eliminating the variability of onset time.

Nonsteroidal anti-inflammatory drugs have been used in a wide variety of pediatric procedures with good safety and efficacy; the usual contraindications are concern for bleeding and renal function. As with many drugs, detailed data are not available for infants, but in limited studies, ketorolac appears to be a safe and effective analgesic for infants. NSAIDs appear to be effective in treating pain after tonsillectomy, but studies are mixed as to whether this causes an increased bleeding risk because of inhibition of platelet aggregation.

Opioid analgesics are needed after many pediatric procedures. Side effects include somnolence, vomiting, pruritus, and a risk of respiratory depression. Codeine, which has commonly been prescribed to children after surgery, is dependent on conversion to morphine for its effect; genetic variability in metabolism makes dosing relatively unreliable.59 Fentanyl is given IV at a dose of 1 to 2 mcg/kg for short procedures. For more major procedures, a loading dose of 5 mcg/kg is followed by hourly dosing of 1 to 3 mcg/kg as needed. Morphine can be administered as a sole analgesic in a total dose of 0.1 mg/kg or titrated in smaller increments (0.02 mg/kg) after the initial use of fentanyl or another opioid intraoperatively. Nasal administration of fentanyl is useful for minor procedures when IV access is not established, such as myringotomy with tubes.60 Remifentanil can be infused as a component of a general anesthetic technique, allowing intraoperative titration and rapid emergence, but it provides no residual postoperative analgesia. Regardless of the drugs or technique chosen, frequent assessment of analgesic efficacy and side effects, as well as access to appropriate breakthrough pain medication, is important to providing postoperative pain relief for children.

Postoperative Nausea and Vomiting

Postoperative vomiting is distressing to children and their parents and may delay or prevent discharge of postsurgical patients from the recovery room. Because nausea may be difficult to quantify in children, most studies focus on the incidence of vomiting. Overall, the incidence of vomiting is higher in children than in adults; the incidence appears to increase with age up to puberty and then decrease.61 Procedures with a high incidence of postoperative vomiting in children include strabismus surgery, adenotonsillectomy, orchidopexy, and laparoscopic surgery. Gender differences are not believed to be a major factor until puberty. Even in small doses, opioids may increase the incidence of postoperative vomiting in children. Adult risk scores for postoperative nausea and vomiting do not apply well to children.62 A 4-component pediatric risk score has been proposed using: surgery 30 minutes or longer; age 3 years or older; strabismus surgery; and positive history of postoperative vomiting in the patient, parents, or siblings.63 Value was demonstrated in giving prophylactic antiemetics to patients with 2 or more risk factors. For patients at risk for postoperative vomiting, tailoring the anesthetic technique may be of benefit, as well as using propofol rather than volatile anesthetics64 and regional anesthesia, NSAIDs, and acetaminophen rather than opioids. The impact of nitrous oxide in pediatric patients is as controversial as in adults, but one comparison of sevoflurane-anesthetized children did not show an increase in postoperative vomiting when nitrous oxide was used.65 Adequate hydration intraoperatively and avoiding early oral intake may help reduce postoperative vomiting.

Pediatric dosing for antiemetic agents is summarized in Table 64-6.

Ondansetron and the newer 5-hydroxytryptamine3 (5-HT3) receptor antagonists dolasetron and granisetron have excellent efficacy for prophylaxis and treatment of postoperative vomiting in children.66 Some dose-related improvement in antiemetic efficacy is seen, but for most patients, the lack of a significantly important effect does not justify the added expense of a larger dose. Administering ondansetron early in a case appears to be of no "preemptive" value; effect duration relates to the half-life of the drug. Dexamethasone used in tonsillectomy to prevent edema also reduces postoperative vomiting and improves pain scores. Although frequently given at 0.5 mg/kg, the antiemetic effect appears not to have a significant dose–response relationship,67 and doses as small as 0.05 mg/kg have been shown to be effective.68 A combination of dexamethasone and ondansetron is frequently given for antiemetic prophylaxis and may be more effective than ondansetron alone.69

Droperidol has largely disappeared from routine use because of the FDA "black box" drug label warning related to case reports of torsades de pointes in adults. It may be used for refractory nausea and vomiting if administered with ECG monitoring. A meta-analysis suggested that droperidol was as effective as ondansetron in adults but not in children,70 but several individual pediatric studies found equal efficacy at higher doses of droperidol. Side effects of sedation and dysphoria may be troubling. Metoclopramide, which has commonly been given for postoperative emesis, is no more effective than placebo.71 Finally, there is interest in nonpharmacologic antiemetic therapy in children; acupuncture or electrostimulation may be as effective as the available medications.72

Emergence Delirium

Postanesthetic agitation is a common problem in toddlers and young children; the risk factors and mechanism remain incompletely understood. Pain is a contributing factor in postanesthetic agitation, but emergence agitation also is exhibited after anesthesia for nonpainful procedures, such as magnetic resonance imaging, in children.73 Agents that provide analgesia as well as sedation have shown efficacy in reducing agitation; these include fentanyl, ketamine, clonidine, and dexmedetomidine. Results have been mixed as to whether residual postoperative sedation with benzodiazepines or propofol reduces agitation. One study found a higher incidence of emergence delirium in children who had received midazolam premedication.74

Agitation occurs with variable frequency after use of all volatile agents.75 It occurs less frequently after propofol, and crossover studies between sevoflurane and propofol show a lower incidence with propofol in individual patients, but a small percentage of children receiving frequent anesthetics exhibit severe agitation after propofol use. The perceived prominence of agitation after sevoflurane may be attributed to a higher incidence in the very early postoperative period, but the overall postanesthesia care unit incidence may be similar among the inhalation agents.76 The actual rate of emergence does not appear to be the cause of postanesthetic delirium; children emerging at the same rate from propofol or sevoflurane showed a significantly higher agitation rate in the sevoflurane group.77 Delaying emergence by continuing the volatile anesthetic into the postoperative period does not appear to decrease the incidence of agitation,78 although using nitrous oxide during the washout period may reduce the incidence.79

In addition to acute postoperative agitation, children may develop postoperative maladaptive behavioral changes, such as changes in sleep or eating patterns, separation anxiety, and withdrawn or aggressive behavior. No clear association has been established with a specific anesthetic agent.80,81 Kain et al82 identified an association between preoperative anxiety in both the child and the parent, emergence delirium, and maladaptive behaviors after discharge. They suggest that some children, based on their own personality traits and those of their parents, may be more susceptible to developing these changes after the experience of anesthesia and surgery. Negative behavioral changes are more common in younger children.

The remainder of this chapter is devoted to specific clinical scenarios that are unique to pediatric anesthesia; the basic concepts are discussed more thoroughly in other subspecialty chapters. Other cases in pediatric anesthesia are presented within specialty chapters in this text (eg, spine surgery in Chapter 65; tonsillectomy and pediatric airway surgery in Chapter 67)

Pediatric General Surgery and Urology

Elective surgery in healthy children typically involves inhalation induction; maintenance can be with a mask or LMA for shorter or simpler procedures. General anesthesia may be supplemented with a regional technique. Hernia surgery is common in infants and children. Surgical practice varies with regard to indications for exploration of the contralateral side if no clinical evidence of a hernia is seen; this also can be done laparoscopically. For boys with undescended testes, orchidopexy is performed through a groin incision when the patient has a palpable testis or may be combined with laparoscopy when the testis cannot be felt. Although orchidopexy is performed through a groin incision similar to herniorrhaphy, orchidopexy patients tend to have more severe pain of longer duration; multimodal analgesia, including a regional technique, may be helpful. During both of these procedures, the occurrence of sudden intraoperative stimulation because of traction on the spermatic cord should be anticipated.

Hypospadias repair may require from 30 minutes to several hours and can require skin grafting or staged repair, depending on the complexity of the lesion. A caudal or penile block is frequently performed; a urethral stent may be left in at the end of surgery. Ureteral reimplantation for vesicoureteral reflux is performed through a low transverse abdominal incision. Children are hospitalized for 2 to 3 days and may have a urinary catheter in place overnight. Advances in the operative management of ureteral reimplantation (eg, minimizing use of catheters) have shortened the postoperative course. Bladder spasm may occur and can be treated with ketorolac.83 Caudal and epidural analgesia also are frequently used for this surgery. Congenital anomalies of the kidney and ureters may lead to infection; these usually are repaired either through a flank incision or by laparoscopy.

Laparoscopy in Children

Laparoscopic operations performed in children include transperitoneal procedures such as cholecystectomy, fundoplication, appendectomy, and exploration for undescended testes; retroperitoneal approaches to the kidney and urinary tract; and use of the laparoscope to visualize the contralateral side in inguinal hernia repair. Before or during laparoscopy, producing a pneumoperitoneum with CO2 may cause systemic hypercarbia, and a higher peak airway pressure may be needed for adequate ventilation and oxygenation.84 Hemodynamic compromise from impairment of venous return or from gas embolism during insufflation is possible. Another potential source of gas embolization is use of argon beam coagulation during laparoscopic procedures such as partial nephrectomy.85 Although early studies suggested a decrease in aortic blood flow and stroke volume with a compensatory increase in systemic vascular resistance, other studies in healthy children having low-pressure insufflation for laparoscopic procedures showed that the cardiac index is preserved or minimally affected.86 Transient oliguria or anuria may occur during laparoscopy, particularly in younger children. This appears to be a reversible phenomenon in brief procedures.87

Laparoscopy in children usually is performed with general anesthesia. Endotracheal intubation is usually used to control respiratory changes, although an LMA may be acceptable if low intra-abdominal inflation pressures are used. Analgesia is provided by some combination of local anesthetic infiltration, acetaminophen, and NSAIDs. Caudal or epidural analgesia can be used as a supplement but may not provide any benefit over simple local infiltration for uncomplicated laparoscopy.

Thoracotomy and Thoracoscopy

Children present for thoracic procedures for primary lung processes, tumor, or drainage of empyema, as well as for access to tracheal structures or vascular anomalies. Systemic hypoxia may be a problem in small children because of their nonrigid rib cages and the potential for compression of the dependent lung.88 Video-assisted thoracoscopic surgery (VATS) is used in pediatric patients for biopsy or limited resection of a tumor or infectious lesions and for drainage and decortication of empyema. Empyema may develop as a complication of community-acquired pneumonia even in otherwise healthy patients, and early VATS results in fewer postoperative complications and a shorter overall hospital stay compared with tube thoracostomy.89

Traditionally, thoracotomy in children was performed with the surgeon packing 1 lung out of the surgical field. However, thoracoscopy and advances in equipment and anesthetic techniques (bronchial blockers, fiberoptic bronchoscopes) have led to broader use of 1-lung ventilation in children. Double-lumen tubes, when available in appropriate sizes, allow suctioning of each lung and provision of oxygen and CPAP to the deflated lung. The outer diameter of available tubes must be compared with the expected tracheal and bronchial sizes.90 The smallest available double-lumen tube is 26 Fr, which is slightly larger than a 6.5-mm ID endotracheal tube suitable for children as young as 8 years. The Univent tube is a single-lumen tube with a built-in bronchial blocker; a 3.5-mm ID Univent tube has an external diameter similar to a standard 6.0 endotracheal tube. In children younger than 6 years of age, options for 1-lung ventilation include use of a bronchial blocker (placed using a fiberoptic bronchoscope) or intentional mainstem bronchial intubation (blindly or with fiberoptic guidance). If mainstem intubation is planned, a smaller endotracheal tube must be used than would be chosen for tracheal placement; a small cuffed tube allows lung reinflation after the tube is withdrawn into the trachea. Options for 1-lung ventilation in children are summarized in Table 64-7.

Other considerations for pediatric thoracic surgery include adequate venous access and appropriate monitoring. Use of an arterial catheter depends on the extent of the procedure and the underlying lung function. Most children can be extubated after a thoracotomy or VATS unless respiratory function is severely impaired. Appropriate analgesia is helpful in speeding recovery; for open procedures, this may include administration of a local anesthetic with or without an opioid through a thoracic epidural catheter or via a caudal catheter threaded to the thoracic region in small children.

Pectus Excavatum and the Nuss Procedure

Pectus excavatum is the most common congenital chest wall deformity of children. Left uncorrected, it can result in respiratory and cardiac compromise. Traditionally, pectus excavatum was corrected during the teenage years by an open approach. More recently, a convex steel bar is inserted ("Nuss procedure") to mechanically raise the sternum. Cartilage remodels over time, and the bar is removed several years later. After bar removal, patients have a subjective improvement in functional status and a small but significant improvement in pulmonary function studies.91 Preoperatively, most patients have some mild degree of exercise limitation, but significant dyspnea should prompt further evaluation. The mechanism of exercise limitation in pectus excavatum may reflect a combination of restrictive lung disease and impaired right ventricular function. Pulmonary function testing and echocardiography are frequently performed but probably are not essential except for patients with significant symptoms.

Early studies of the Nuss procedure reported a moderate intraoperative complication rate, including cardiac compression, disruption of great vessels with significant hemorrhage, and tension pneumothorax. A very low rate of complications occurs now because of improved surgeon experience and refinement of the surgical technique, particularly the use of thoracoscopy to guide bar placement.92 Postoperative complications include dislodgement of the bar (which has been minimized through use of lateral stabilizers), pneumothorax, pneumonia, and significant pain. Outcomes appear better in younger patients, and the trend is toward correcting these deformities in the preteen years.

The Nuss procedure is performed with general anesthesia, often in conjunction with a thoracic epidural. Arterial lines (frequently placed in the early days of this procedure because of concern for hemodynamic compromise and blood loss) are rarely required. The duration of surgery is approximately 2 hours; patients can be extubated at the end of the procedure unless they experienced intraoperative difficulties. Although pectus bar placement is considered a minimally invasive procedure, the initial postoperative period can involve significant pain caused by the pressure of the bar. Thoracic epidural infusion of local anesthetic and opioid is commonly used for the first 2 to 3 days.

Cancer-Related Procedures in Children

Abdominal Tumors

Neuroblastoma, the most common extracranial solid tumor of childhood, arises from neural crest cells. Risk varies depending on clinical stage and biologic features of the individual tumor. Children with neuroblastoma require biopsy for diagnosis and multiple imaging studies during treatment. Treatment may include limited or aggressive surgical resection, chemotherapy, and radiation therapy. High-risk patients may receive a bone marrow transplant. Considerations for resection include adequate venous access, arterial monitoring if extensive blood loss is expected, and a complete blood count if chemotherapy has been given before surgery. A subset of these tumors may produce significant catecholamine secretion, causing perioperative hemodynamic lability.

Wilms tumor (nephroblastoma) most commonly occurs in young children. If diagnosed in its early stages, it can be approached by laparoscopic nephrectomy. However, the tumor may remain asymptomatic until the mass is quite large, and resection may involve a more extensive procedure. If vascular and intracardiac extensions have occurred, then cardiopulmonary bypass may be required for resection. Renin production or renovascular compression may result in hypertension. Treatment and prognosis are stratified by surgical stage and histologic type.

Mediastinal Mass

Tumors, particularly lymphoma, may develop rapidly and present with respiratory symptoms related to mediastinal involvement. Inducing general anesthesia may lead to compression of the airway or vascular structures when thoracic muscle tone is reduced, with catastrophic results. Exercise tolerance and tolerance of the supine position may give some idea of the severity of disease, but absence of symptoms does not eliminate the possibility of difficulties during anesthetic induction. Respiratory flow–volume loops can be helpful in delineating the extent of airway compression. Unless the possibility of airway and vascular compression can be ruled out with preoperative tests, serious consideration should be given to performing a minimal procedure with local anesthesia to obtain the diagnosis and deferring major interventions until initial treatment has reduced the tumor mass. If general anesthesia is required, maintenance of spontaneous respiration is preferred and can be accomplished with volatile or IV agents (propofol, opioids, ketamine). A head-up or lateral induction position may prove helpful. Emergency backup plans should be formulated before induction and may include rigid bronchoscopy and cardiopulmonary bypass.93

Even in the absence of overt signs or symptoms of increased intracranial pressure (ICP), children presenting for ventriculoperitoneal shunt revision, resection of a brain tumor, or posterior fossa decompression may be near the point of decompensation and should be managed so that ICP does not increase. The history should address recent nausea and vomiting and the potential for volume depletion as well as aspiration risk. Preoperatively, oversedation should be avoided because of the risk for hypercarbia, but individual patients may benefit from judicious premedication in a monitored setting to minimize agitation. Intraoperatively, the various inhalational agents may cause a slight increase of ICP; maintenance of mean arterial pressure is critical to maintain the cerebral perfusion pressure.94 Steroids, anticonvulsant medications, or both are usually continued perioperatively. If treatment of increased ICP is needed, hyperventilation, mannitol infusion (0.5-1 g/kg), increasing anesthetic depth, and drainage of CSF all may be appropriate.

Ventriculoperitoneal Shunt

Ventriculoperitoneal shunts in infants are discussed in detail in Chapter 63. Older children may require replacement or revision of shunts because of malfunction or growth, or they may require new shunts after tumor resection or discovery of other intracranial pathology. In some cases of cysts or other obstruction to CSF outflow, endoscopic ventriculostomy may restore normal flow patterns and obviate the need for shunting. Patients with multiple shunts may have an acquired latex allergy or may be receiving treatment in a latex-free environment to prevent sensitization.

Craniotomy for Tumor

A higher percentage of brain tumors are infratentorial in pediatric patients than in adults, with medulloblastoma and astrocytoma being the common posterior fossa lesions. Other common tumors include the supratentorial counterparts of medulloblastoma (pineoblastoma and primitive neuroectodermal tumor), glioma, and ependymoma. Anesthetic management for craniotomy is discussed in more depth in Chapter 51. In general for a pediatric craniotomy, adequate peripheral venous access and an arterial line are needed. Central lines are of limited use for aspirating air in the pediatric population and usually are not placed for this purpose in smaller children. If the anatomy and positioning suggest a risk of venous air embolus, then precordial Doppler monitoring should be used. Depending on the location of the tumor and the course of surgery, development of diabetes insipidus or other endocrine abnormalities may occur during or after surgery.

Posterior Fossa Decompression

Chiari type I malformation, a caudal displacement of the cerebellar tonsils through the foramen magnum into the spinal canal, may result in a variety of symptoms, including headache or other pain, weakness, ataxia, and sensory loss. Patients may have brainstem and spinal cord dysfunction, the latter often as a result of syrinx formation. Surgical management consists of suboccipital craniectomy with posterior fossa decompression. Extreme flexion should be avoided to minimize the risk of brainstem compression. Postoperatively, these patients may have respiratory abnormalities, perhaps related to ischemia or edema of the brainstem respiratory centers.

Craniosynostosis

Craniosynostosis represents premature closure of 1 or more cranial sutures. The incidence is approximately 1 in 2000 births, with more boys than girls affected. Uncorrected, craniosynostosis may lead to increased ICP. Correction may be performed for cosmetic reasons. Simple craniosynostoses usually are corrected between 3 and 6 months of age, with more complex craniofacial reconstruction after 9 months of age. Significant blood loss and venous air embolism are risks of the procedure; overall, morbidity and mortality are low. Adverse events are significantly associated with secondary versus primary operation and in patients with craniofacial syndromes.

Craniosynostosis may be an isolated defect or part of a craniofacial syndrome, such as Crouzon or Apert syndrome, which can include a difficult airway, cleft palate, syndactyly, and cardiac or other abnormalities. Children with uncorrected complex craniosynostosis may have increased ICP; decreased cerebral perfusion pressure; and obstructive respiratory symptoms, particularly during sleep.95

Preparation for the case includes consideration of positioning, access to the patient and lines, and avoidance of soft tissue or ischemic injury. Surgeons may request elevation of the head to enhance venous drainage; however, this advantage must be weighed against the risk of venous air entrainment. Goals of anesthetic management include minimizing severe increases in ICP. Hyperventilation, administration of mannitol, or both may be indicated if the craniectomy is technically difficult. Monitoring must include evaluation of circulating blood volume status, blood loss and associated metabolic changes, and maintenance of temperature. Adequate venous access and availability of blood and blood products are critical to safe management.

Craniosynostosis repair requires transfusion in almost 95% of patients; however, newer surgical techniques may result in reduced blood loss.96 Techniques that have been used to minimize allogeneic blood transfusion include preoperative administration of erythropoietin, selection of an optimal age to achieve a favorable balance between fetal and adult hemoglobin, preoperative preparation of an autologous blood supply, and intraoperative and postoperative blood salvage and reinfusion. When massive transfusion is required, coagulopathy may develop.97

Several studies suggest that venous air embolism occurs frequently during craniosynostosis repair, although the majority of episodes are not hemodynamically significant.98 Maintenance of adequate vascular volume, positive-pressure ventilation, and precordial Doppler or end-tidal nitrogen monitoring for early detection may all help to minimize the incidence and consequences. Management of venous air embolism includes putting the head down, flooding the field with saline, and using bone wax to attempt to limit the amount of entrained air. Compression of the jugular veins may increase venous pressure and prevent further air entrainment. Aspiration of air is technically difficult to achieve in small children.

After routine craniosynostosis repair, most patients with a normal airway can be extubated. Ideally, an anesthetic technique is chosen so that surgery is completed with adequate analgesia and a calm patient but with the ability to evaluate neurologic status. Ongoing blood loss from drains may require further transfusions during the next 24 hours. If the procedure was extensive or blood loss was very large, hemodynamic stability or swelling may suggest the need to leave the patient intubated and perhaps mechanically ventilated in the early postoperative period.

Pediatric Ambulatory Surgery

Many pediatric procedures can be performed on an outpatient basis; this is frequently done in a mixed adult and pediatric setting, but facilities, equipment, and staff competencies must be suitable for children. The general concepts of ambulatory anesthesia discussed in Chapter 68 apply to children: the anesthetic should be tailored to rapid recovery with attention to pain management and control of postoperative vomiting. A qualified caregiver should be present at home for the remainder of the day and night, and parents must be given careful instructions about postoperative medications and any signs or symptoms that should prompt contact with or return to the hospital.

Out‐of-Operating Room Procedures in Children

Children frequently require anesthesia for even nonpainful procedures simply because they are unable to hold still. Teaching about the procedure and distraction may help some older children to cooperate. Planning an appropriate anesthetic requires evaluation of the patient as well as understanding the logistics of the procedure. General considerations about safety in offsite anesthesia locations are presented in Chapter 69.

Magnetic resonance imaging scans can range from 15 minutes to several hours in length; some sequences are noisy, and some are associated with significant vibration of the table. Simple scans are often done with the child breathing spontaneously with a propofol infusion and supplemental oxygen. Certain abdominal and cardiac scans may require breath-holding to optimize the image; this as well as scan length may prompt a general anesthetic with controlled ventilation. Equipment safety in the magnetic environment is a prime concern; the child is monitored either directly or through a window with remote monitors.

Radiation therapy is often done with a similar propofol technique. For radiation of the head and neck area, the child is immobilized in a rigid face mask; ensuring an adequate area during construction of the mask is extremely important. If at all possible, airway instrumentation is avoided because children will come for sequential treatment over a prolonged period.

Endoscopy is performed frequently in pediatric patients for a variety of indications (eg, evaluation of bleeding, inflammatory bowel disease, esophagitis from a variety of etiologies, malabsorption or failure to thrive). Knowing the proceduralist and what to expect are key; these cases are often done with spontaneous respiration using propofol with or without an opioid.

Finally, brief diagnostic and therapeutic procedures such as lumbar puncture and bone marrow aspiration are often performed in oncology clinics and sedation rooms. Because these children usually have indwelling venous access, propofol with or without an opioid is again a frequent choice. Use of topical local anesthetic cream over the site can be useful in minimizing anesthetic requirements.

The practice of pediatric anesthesia encompasses a broad spectrum of surgery and patients and creates many challenges in terms of patient and family dynamics, technical skills, and anatomic and physiologic factors. Meticulous attention to detail and anticipation of common perioperative problems are essential, as are training and ongoing experience in the care of children.

• Birmingham PK, Tobin MJ, Fisher DM, et al. Initial and subsequent dosing of rectal acetaminophen in children: a 24-hour pharmacokinetic study of new dose recommendations. Anesthesiology. 2001;94:385.
• Cote CJ, Zaslavsky A, Downes JJ, et al. Postoperative apnea in former preterm infants after inguinal herniorrhaphy. Anesthesiology. 1995;82:809.
• Giaufre E, Dalens B, Gombert A. Epidemiology and morbidity of regional anesthesia in children: a one-year prospective survey of the French-Language Society of Pediatric Anesthesiologists. Anesth Analg. 1996;83:904.
• Hackel A, Badgwell JM, Binding RR, et al. Guidelines for the pediatric perioperative anesthesia environment. Pediatrics. 1999;103:512.
• Kain ZN, Caldwell-Andrews AA, Weinberg ME, et al. Sevoflurane versus halothane: postoperative maladaptive behavioral changes: a randomized, controlled trial. Anesthesiology. 2005;102:720.
• Kain ZN, Mayes LC, Wang SM, et al. Parental presence and a sedative premedicant for children undergoing surgery: a hierarchical study. Anesthesiology. 2000;92:939.
• Krane E, Dalens B, Murat I, et al. Epidural catheters in anesthetized patients. Reg AnesthPain Med. 1998;23:433.
• Mamie C, Habre W, Delhumeau C, et al. Incidence and risk factors of perioperative respiratory adverse events in children undergoing elective surgery. Paediatr Anaesth. 2004;14:218.
• Morray JP, Geiduschek JM, Caplan RA, et al. A comparison of pediatric and adult anesthesia closed malpractice claims. Anesthesiology. 1993;78:461.
• Murat I, Constant I, Maud'huy H. Perioperative anaesthetic morbidity in children: a database of 24,165 anaesthetics over a 30-month period. Paediatr Anaesth. 2004;14:158.
• Tait AR, Malviya S. Anesthesia for the child with an upper respiratory tract infection: still a dilemma? Anesth Analg. 2005;100:59.