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Just as psycho-emotional preoperative preparation of the child should begin before the anesthesiologist meets the child, the anesthesiologist also should have prepared before the meeting. The anesthesiologist should be familiar with the surgery that the child requires, the surgeon's needs, and the anesthetic implications of the surgical procedure. The anesthesiologist should be as familiar as possible with the child's medical background as documented in the medical records. Communication with the pediatrician and surgeon before meeting the child and family will reveal areas of particular interest to the anesthesiologist before the interview.74 An anesthesiologist who is aware of the child's name, age, general background, medical problems, and surgical procedure and who has communicated with the child's pediatrician and surgeon is in a strong position to win the confidence of the child and family. When a child has an extensive previous medical history, it is worthwhile reviewing old records. Specific attention should be directed to the presence of congenital anomalies and pediatric syndromes that may be associated with anomalies that are unrelated to the surgery but that could complicate the anesthetic management. A review of the drug and allergy history may provide information critically important to the anesthetic management.
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Finally, if there were any previous anesthetic procedures, careful review of these records may provide an opportunity to improve anesthetic management. Specifically noting whether premedication was necessary, its effect when given, the response to various anesthetic agents, airway management, and emergence particularly may be useful. There may be information in this record that the anesthesiologist wishes to have before speaking to the parents. If the child, after what appeared to be a minor procedure, was intubated and ventilated in the intensive care unit for 3 days, the parents would be, not surprisingly, somewhat skeptical should the anesthesiologist be unaware of this occurrence. In children who have had several operations, consideration of latex allergy is important. A review of the previous anesthetic records for unexplained hypotension or wheezing should raise the consideration of latex allergy and the need for latex precautions.75
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It may be worthwhile to discuss areas of concern with the surgeon and the child's physicians before meeting the family so the family can have the most complete information possible at the preoperative assessment. When meeting with the family, the anesthesiologist can determine the child's general health, level of activity, interests, favorite toys, background, and mental and medical condition. Knowledge of the parents' nickname for the child might be useful during emergence. Finding out which fingers or thumb the child sucks as a guide to IV placement may make the difference between a calm patient and an inconsolable patient postoperatively.
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A systems review of appropriate depth always is indicated. A history of current and recent drugs and a history of allergies should be completed in all patients. Specific questioning about previous anesthetics and any history of siblings or family members who have had prolonged awakening, canceled surgery while in the operating room, intraoperative cardiorespiratory catastrophes, or unexplained fevers specifically should be sought in each case. Frequently, no one else will have asked questions concerning potential drug allergies, malignant hyperthermia, or adverse anesthetic reactions.
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The examination of the child should begin as soon as the physician enters the room. During the time spent obtaining the history from the parents and, when appropriate, from the child, important observations can be made. This period is invaluable for establishing rapport with the child and family. Constant efforts to gain the child's confidence (eg, by getting down to the child's level [sitting down is necessary], offering a toy, or interacting with the child) are of tremendous help. While discussing the child with the family, attempting to interact with the child and desensitizing the child to the close presence of the anesthesiologist is critical. Briskly walking into the room, interrogating the mother or father, and turning to the child will not yield optimal information from the physical examination. Interacting with, humoring, reassuring, and playing with the child during the interview not only calms the child, but can also provide valuable information regarding the child's general health status, developmental status,76 respiratory condition, level of activity, state of hydration and perfusion, and level of anxiety concerning hospitalization.
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The examination of the child falls into 3 areas: (1) general health and systems examination, (2) areas specifically related to the provision of anesthesia, and (3) areas related to surgery. The physical examination is guided by the findings in the history and interview and the needs of the surgical procedure. As mentioned previously, the examination begins when the anesthesiologist first meets the child. A great deal can be learned about the patient's perfusion, hemodynamic status, and respiratory status by general observation. Determining the child's growth and weight (eg, short stature, failure to thrive) is essential because they guide anesthetic management and may indicate the necessity for closer evaluation (Figs. 20-7, 20-8, 20-9, and 20-10).76
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The airway can be assessed by observing phonation, inspiratory sounds, and respiratory rate; evidence of respiratory distress, such as retractions or tachypnea, are readily noted without interfering with the child. Coughs, runny noses, and upper respiratory tract infections can be detected without hands-on examination of the child. With specific regard to airway evaluation, determining the presence of airway anomalies, such as cleft lip or palate, large tonsils, the state of the child's dentition, loose teeth, or absent teeth is essential. A small jaw or a skeletal anomaly that may indicate a difficult intubation should be noted. It is possible to obtain a fairly comprehensive impression of the child's overall status without actually having to physically examine the child.
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Familiarity with the surgical procedure also is necessary. The anesthesiologist should have a fair idea of how extensive the surgery is, whether it will affect airway management, what sort of blood loss to expect, and if there are any particular factors complicating anesthesia management. Concerns about positioning and duration of surgery should be addressed. The presence of a cystic hygroma, for example, should dictate meticulous examination of the airway, auscultation for upper airway sounds, and determination of whether any airway involvement may have occurred. Discovery of capillary hemangiomas also may indicate the need to rule out airway involvement.
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Much will be apparent about the developmental stage of the child's CNS during the initial contact. Conversely, assessment of anesthetically relevant neurologic conditions will depend on the child's age and developmental status. Familiarity with the development of children gives the anesthesiologist a background by which to assess the child (Fig. 20-11). A wide spectrum of neuromuscular disorders that are important to the anesthesiologist accompanies various childhood conditions. In all children, information concerning mental and developmental stage, gestational age, gross motor function, presence of a seizure disorder, and any preexisting neurologic sensory deficits should be sought.
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Cerebral Palsy and Mental Retardation
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A common problem in children who present for surgery for either multiple congenital anomalies or complications after prematurity is mental retardation or cerebral palsy. It should be stressed that not all children with cerebral palsy, even those with severe neuromuscular involvement, are mentally retarded. Incapacitating hypertonicity and spasticity, which may render a child unable to readily express himself or herself, do not necessarily interfere with the ability of the child to understand or the anesthesiologist's responsibility to inform the child about the course of the perioperative period. The anesthetic implications of mental retardation and cerebral palsy are legion. The response to a host of anesthetic drugs, including muscle relaxants, sedatives, analgesics, and hypnotics, varies and is less predictable in these children compared with healthy children. Older children with mental retardation and cerebral palsy also may have significant pulmonary complications that arise from musculoskeletal anomalies caused by imbalance of muscle groups, resulting in scoliosis and kyphosis and leading to restrictive lung pathology. Pharyngeal discoordination, difficulty with handling secretions, and the not infrequent association of gastroesophageal reflux in children with mental retardation and cerebral palsy can lead to recurrent, chronic, pulmonary parenchymal injury, which may complicate the anesthetic management. The presence of gastroesophageal reflux should be sought because it is frequent in this patient population. This may have particular relevance to NPO precautions and may indicate the need for histamine receptor (H2) antagonism, antacids, agents that hasten gastric emptying, and rapid sequence intubation. Specific questioning about gastroesophageal reflux, recurrent aspiration, recurrent pneumonias, and wheezing should be directed toward the parents, and the anesthetic should be altered accordingly.40
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Children with a history of epilepsy or seizure disorders also are of concern perioperatively. In the past, problems have resulted from a failure to maintain adequate anticonvulsant levels perioperatively. Most oral anticonvulsants can be given on the morning of surgery and have a sufficiently long half-life to ensure adequate levels intraoperatively. Sodium valproate and carbamazepine may be exceptions. The anesthesiologist should ensure that the optimal serum levels of anticonvulsants are achieved preoperatively and that these are maintained perioperatively. If a prolonged NPO status postoperatively is anticipated, alteration of anticonvulsant therapy preoperatively may be indicated to include agents that can be given parenterally. A consultation with the child's pediatrician or pediatric neurologist may be required. Preoperative awareness of the child's epilepsy should lead to avoiding epileptogenic anesthetic agents, such as methohexital and possibly etomidate.
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Intracranial Hypertension
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The management of anesthesia for children with intracranial hypertension requires special care. Recognition of the classic triad of hypertension, bradycardia, and apnea in children who may require neurosurgical procedures, or ventricular peritoneal shunts, or who have suffered acute head injury is crucial in determining the anesthetic management of these children. In younger children with chronically elevated intracranial hypertension, the need for perioperative management of intracranial pressure is indicated by complaints of nausea, vomiting, headache, irritability, lethargy, and finding on physical examination of the sunsetting sign. Careful questioning for an acute change in the child's status may indicate the need preoperatively for measures directed at decreasing intracranial pressure, such as diuresis and osmolar therapy. Intraoperative provision of deep anesthesia and controlled ventilation to maintain normocapnia would be wise.
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If the child has an existing decompressive shunt, the anesthesiologist should be aware of it. If it contains a valve and pump mechanism, its function should be evaluated. Perioperative fluid shifts may alter cerebrospinal fluid (CSF) function and upset the balance of CSF production and drainage, leading to elevated intracranial pressure and perioperative catastrophe, especially in the anesthetized child. Assurance of shunt patency and functional history is necessary.
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Congenital neuromuscular disease, such as muscular dystrophy, myotonic dystrophy, and acquired diseases, such as myositis, dermatomyositis, and collagen vascular diseases, raise questions concerning the use of muscle relaxants. In patients with myotonic dystrophy, the use of succinylcholine should be avoided.77 Although this is less clear in patients with some of the muscular dystrophies, the occurrence of rhabdomyolysis and the suspicion of an increased incidence of malignant hyperthermia in patients with Duchenne muscular dystrophy suggests caution in the use of depolarizing muscle relaxants and inhalational anesthetics.78 The use of nondepolarizing muscle relaxants in children who have muscle weakness and neuromuscular impairment should be guided by meticulous perioperative monitoring and perhaps are best avoided when possible (Box 20-5).
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The majority of neurologic deficits and impairments will be obvious from a review of the patient's records, the parents' interview, and observation of the child. If detailed neurologic examination and documentation are required, or if the presence of serious CNS disease is suspected, a pediatric neurologist should be consulted. With the increasing use of regional anesthesia, it is wise for the anesthesiologist to search for and document existing neurologic deficits before performing nerve blocks.
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A host of illnesses and congenital abnormalities affect respiratory function in children. Many congenital anomalies are associated with small, difficult-to-visualize airways, upper airway obstruction, and difficult intubation. All of these conditions should specifically be sought and investigated whenever the suspicion arises (Table 20-7). The relatively small diameter of a child's airway, a child's different anatomic makeup, and high oxygen consumption relative to FRC put children at increased risk for developing hypoxia, decreasing the margin for error.
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Specific questioning about airway obstruction (eg, snoring), recurring episodes of croup, tonsil or adenoid hypertrophy, and any history of apnea is part of routine history taking in pediatric anesthesia. Noticing characteristic facies, such as those associated with Treacher Collins syndrome, Pierre Robin syndrome, or Hunter and Hurler mucopolysaccharidosis, is an essential skill of the pediatric anesthesiologist in detecting the potential for difficulty with intubation and upper airway obstruction perioperatively. Careful examination of the nares, of the oropharynx for loose teeth, and for the presence of respiratory distress indicating airway obstruction should be part of every examination. Routine attention to these airway issues may prevent potentially lethal complications in the operating room.
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Assessment of children with chronic respiratory disease also is necessary. The high frequency of chronic lung disease (bronchopulmonary dysplasia [BPD]) in former premature infants who required ventilatory support in the neonatal period should be remembered.79 Evidence should be sought for this in the patient's record and by questioning the parents. BPD may range from mild recurrent wheezing to a chronic oxygen requirement—even mechanical ventilation at home. In children with BPD and asthma, the anesthesiologist should be completely familiar with the child's respiratory status and ensure that therapy has been optimized preoperatively. The child's exact therapy should be ascertained, and when possible, an effort should be made to ensure that appropriate doses of bronchodilator therapy have been achieved. A history of recent steroid use should be sought, and consideration should be given to initiating steroid therapy preoperatively.
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Particular attention should be directed to the history of exercise tolerance in children with or suspected of having chronic lung disease. In patients with musculoskeletal disease, especially kyphosis or scoliosis, one should seek evidence of restrictive lung abnormalities. Preoperative investigations in children with chronic lung disease may include determination of blood gases and pulmonary function tests. A cardiac examination with electrocardiography and possibly echocardiography may be necessary to discover and define the severity of pulmonary hypertension and cor pulmonale.
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Acute lung disease is an indication for canceling elective surgery. Pneumonia, croup, and acute asthma pose serious perioperative threats, both acutely as well as after apparent resolution. Airway reactivity is increased for several weeks after an acute asthmatic attack.80,81 Deteriorating pulmonary status caused by viral or bacterial infection, superimposed on BPD, cystic fibrosis, or asthma may cause serious intraoperative hypoxia, increased secretions with the risk of endotracheal tube obstruction, and difficulty in maintaining airway patency. Postoperative atelectasis and pneumonia can be serious complications after surgery. Specific questioning about episodes of apnea should be included because these may be associated with fatal postoperative respiratory difficulties.82
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Frequently, the problem of the child with a runny nose arises. Rhinorrhea can be caused by an acute viral or bacterial upper respiratory tract infection (URI), allergic rhinitis, or foreign object. There is evidence that recent URIs increase airway hyperreactivity for 6 to 8 weeks after infection.80 Anecdotally, most anesthesiologists believe that URIs are associated with increased secretions, incidence of laryngospasm and bronchospasm, endotracheal tube obstruction, and intraoperative respiratory difficulties.83 An increased incidence of postintubation stridor and other postoperative respiratory complications also has been reported.84 Experience in recent years has failed to substantiate an increased risk of complications in patients with simple URIs.
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When is it appropriate to cancel elective surgery on the basis of rhinorrhea? The patient should be in optimal condition before induction of anesthesia. The recent onset of mucopurulent rhinorrhea, especially if accompanied by pharyngitis and fever, is an indication for cancellation of elective surgery. The child who always has clear rhinorrhea on the basis of allergic rhinitis probably is at no increased anesthetic risk. Multiple considerations, such as the inconvenience to the family because of long travel or arranged time off work, the potential of complications from delaying surgery, and the risks of proceeding, need to be weighed when deciding whether to proceed. With healthy children who are afebrile and have clear rhinorrhea, we proceed with elective surgery. Anesthesia caregivers are more cautious with other respiratory diseases, especially asthma and BPD.80,81 Although this topic remains controversial, whenever possible, surgery and anesthesia should be delayed for at least 2 weeks.85
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Cardiovascular System
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Because of the multiple cardiovascular effects of anesthetics in children and the frequency with which cardiac anomalies accompany other congenital malformations, particular attention to the cardiovascular system is necessary (Table 20-8). Recognition of the setting in which congenital heart disease may occur, coupled with careful attention to the previous history and questioning of the family, help define the type and severity of the defect. Examination of the child may lead to discovery of hitherto undiagnosed cardiac defects or to the presence of a cardiac murmur and demonstrate the need to alter the anesthetic plan and perhaps to seek further pediatric cardiology consultation. The cardiovascular system undergoes significant developmental changes, and reference to normal age-related values is essential in assessing children (see Figs. 20-4, 20-5, and 20-6).86,87
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Poor exercise tolerance, as in adults, is a hallmark of inadequate cardiovascular function. Children who tire easily, become tachypneic, have dyspnea on exertion, or have orthopnea must be evaluated carefully. In infants, the major exercise is feeding. An irritable child with a history of poor feeding accompanied by diaphoresis and tachypnea may have borderline cardiac function. Failure to thrive may indicate compromised cardiac function. In younger infants, clubbing is never present, and cyanosis may be difficult to detect. Palpation and auscultation remain the cornerstones of the cardiology examination. Particular attention should be paid to the presence of a brachial–femoral delay, indicating coarctation, and for left and right ventricular heaves. Detection of a new murmur frequently raises the question of whether it is benign or significant. Differentiating between a venous hum or ventricular outflow murmur and more serious murmurs requires specific examination (Table 20-9). When in doubt, consultation with a pediatric cardiologist is indicated. The child with a murmur who is asymptomatic, acyanotic, healthy, and gaining weight along appropriate percentiles and who has a normal S1 and S2 almost certainly will tolerate routine anesthesia without serious complications. Questions arise regarding the need for further cardiology follow-up, evaluation- and infective endocarditis (IE) prophylaxis (Table 20-10 and Box 20-6). When the history and physical examination indicate possible serious cardiac disease, a hematocrit, electrocardiogram (ECG), chest radiograph, and oxygen saturation (pulse oximetry) form the basis of the laboratory workup. In patients with known serious heart disease, the anesthesiologist should understand the anatomy and physiology of the defect. A hemodynamically inconsequential atrial septal defect, ventricular septal defect, mitral valve prolapse, or the presence of a bicuspid aortic valve may predispose the child to an untoward intraoperative event, and consultation with a pediatric cardiologist may be indicated. For most children with heart disease, it is prudent to obtain a recent consultation with the child's pediatric cardiologist.
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Asymptomatic renal disease, apart from bacteriuria, is rare in children. The likelihood of discovering a new renal lesion during routine physical examination done for the preanesthetic evaluation is almost nonexistent. The presence of hypertension (see Table 20-3) should indicate the need for urinalysis and electrolyte analysis.35 The unexpected presence of anemia also may indicate chronic renal disease. The anesthetic implications of renal disease in the presence of normal electrolytes, normal growth and development, and normotension are minimal. In infants, there may be the inability to concentrate urine or to handle a large fluid load, both of which dictate cautious fluid management perioperatively.
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In the presence of serious preexisting renal disease, careful attention should be paid to the child's preoperative preparation. If the child requires dialysis (peritoneal dialysis or hemodialysis) to maintain optimal electrolyte levels and growth, consideration of dialysis on the day before surgery is indicated. Antihypertensive therapy, if required, should be optimized. Electrolytes should be monitored carefully. Particular attention is necessary concerning the serum potassium concentration. Serum potassium greater than 5.5 mEq/L is worrisome in children with renal disease. The propensity of succinylcholine to induce hyperkalemia in patients who may have a concurrent metabolic acidosis puts these patients at particular risk. Elective surgery should be canceled in the presence of a potassium level higher than the acceptable upper level of normal for the individual hospital's laboratory (5.5 mEq/L, generally). Regarding hematocrit in patients with chronic renal failure, there is some controversy. It is usual practice to accept a lower hematocrit (20%) in these children than would be normally tolerated. This is based on the assumption of chronic adaptation, which includes increased blood volume and increased cardiac output. These may be compromised during anesthesia. Although the child may be chronically adapted, it should be remembered that the reserve necessary to tolerate the stresses that may accompany anesthesia and surgery is markedly decreased. Preoperative erythropoietin therapy and transfusion before surgery may be administered if time allows.
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Gastrointestinal System
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The major anesthetic issues concerning the GI system center on a predisposition to aspiration pneumonitis. Children with increased gastric residual volumes and gastroesophageal reflux should be identified preoperatively. Those children who have a history of tracheoesophageal fistula, mental retardation, cerebral palsy, apnea, and recurrent aspiration pneumonia always should be suspected of having gastroesophageal reflux (Box 20-7).40,88 Careful scrutiny of medical records and questioning of the parents may indicate that gastroesophageal reflux has been evaluated in the past. If not, consultation with pediatricians might prove worthwhile. The history of recurrent aspiration pneumonia in a child with a predisposing condition raises the likelihood of aspiration during anesthesia, and a rapid sequence induction is indicated. The treatment of children with gastroesophageal reflux includes administration of antacids, histamine (H2) receptor antagonists, agents that encourage gastric emptying (metoclopramide), and the Sellick maneuver during induction and intubation.89 Consider awake intubation in young infants.
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Halothane hepatitis developing de novo in children appears to be exceedingly rare, occurring in perhaps less than 1 in 50|000 to 250|000 anesthetic inductions.90 The relationship between the occurrence of halothane toxicity in patients with previous liver damage and resulting hepatitis is unclear. Many premature infants have abnormal liver function tests and elevated bilirubins. Some children also may have hyperbilirubinemia and elevated transaminases. Although the advisability of using halothane under these circumstances is not clear, it probably is best avoided because suitable alternatives are available. Currently, sevoflurane has almost entirely replaced halothane in practice, and reports of hepatitis after sevoflurane are extremely rare.
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Laboratory Investigations
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It may seem surprising that the American Society of Anesthesiologists, the American College of Surgeons, and the American Academy of Pediatrics do not make any specific recommendations for preoperative testing in children.91 Specific laboratory testing that is indicated by information obtained from the chart review, history, and examination of the child is straightforward. Routine testing for healthy children remains controversial. In the past, guidelines that had been developed for adults were applied to children. These tests included a complete blood count, urinalysis, and chest radiograph. With the streamlining influence prevalent in health care systems today, critical appraisal of the need for these examinations has been undertaken. All aspects of the preoperative laboratory investigation have been questioned. The standard that required a routine chest radiograph in healthy children without symptoms or signs was abandoned.92 Recent experience with large numbers of outpatient anesthetics has raised serious questions about the need for routine performance of other laboratory tests. In general, preoperative laboratory testing should be dictated by the child's condition and status, rather than merely by the need for an anesthetic.66
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It generally is accepted that a preoperative hematocrit is unnecessary in most healthy children for operations in which significant blood loss is not expected. The value of a complete blood count and whether there is a role for determination of platelets and coagulation studies are also unclear. These decisions should be guided by patient considerations. There are developmental differences in the standard level of hematocrit (Table 20-11).93 For years, "normal" hematocrits were required for elective surgery. Later, the lower limit of normal (ie, hematocrit of 30% or a hemoglobin of >10 g/dL) became the requirement. Elective surgery probably should await attaining this level, short of transfusion. Iron and nutritional support are indicated. In the emergent situation, transfusion therapy may be indicated as directed by patient need, such as anticipated blood loss and cardiorespiratory status. Transfusion should not rely on arbitrary and unsupported boundary of "normal" hemoglobin.94
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What are the essential considerations? In a healthy child with normal cardiorespiratory function, a fully saturated hemoglobin of 10 g/dL would require a cardiac index of 3.4 L/min/m2 to provide an oxygen delivery 3 times the average oxygen consumption. If the child's hemoglobin were 7 g/dL (hematocrit approximately 20%), a cardiac index of 4.8 L/min/m2 is required to maintain the same level of oxygen delivery. This is well within a healthy child's cardiac reserve and should represent no major difficulty. The assumptions underlying this are that the child remains 100% saturated, receives no cardiac-depressant drugs, and loses little blood. These circumstances frequently cannot be guaranteed during surgery and anesthesia, and this lack of guarantee is the key issue. The major concern is not for healthy children having minor surgery, but when surgery will result in blood loss and lower this margin of reserve further. A child whose hemoglobin drops to 5 g/dL from 10 g/dL should double cardiac output to around 6.6 L/min/m2 to maintain oxygen delivery. This remains well within the average child's cardiac reserve. If a child's hemoglobin drops to 2 g/dL from 7 g/dL intraoperatively, the child requires a cardiac index of nearly 17 L/min/m2 to maintain a marginal oxygen delivery, which is beyond the ability of even the healthy child's cardiovascular system to compensate for, especially when anesthetized.
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A third issue that frequently is raised is adaptation. The classic teaching is that children with renal disease tolerate lower hematocrits because they have had time to adapt. There is little evidence to demonstrate this is so; 2,3-diphosphoglyceric acid may not be increased in children with renal disease, and there is no reason to suggest that they have a shift in the oxyhemoglobin dissociation curve. The concept that they can adapt to lower levels of oxygen delivery or consumption is unsupported. If serious blood loss is expected perioperatively, the margin of safety is considerably less in patients who begin with low hematocrit.
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As mentioned previously, there are no absolute guidelines for preoperative hematocrit, and at present, each anesthesiologist should decide on a standard for each child. Motoyama95 found that a hemoglobin of 7.5 to 8.5 g/dL will deliver oxygen to the tissues of children equivalent to what a hemoglobin of 10 g/dL will in adults. In neonates, 12 to 13 g/dL is necessary. This is largely related to shifts in the P50 (partial pressure of oxygen at which hemoglobin is 50% saturated).95 It seems reasonable that a hemoglobin of 8 g/dL in an ASA PS P1 child may be acceptable if no major perioperative blood loss is expected. A child who has chronic restrictive lung disease and is about to undergo scoliosis repair probably should have a hemoglobin higher than 10 g/dL (at least initially).
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Many abnormalities can be discovered during preoperative laboratory screening.96 These abnormalities fall into 2 categories: those that are relevant to the anesthetic management of the child and those that are relevant to the child's general health. The degree to which a preanesthesia screening clinic wishes to be responsible for the general health care of children needs to be determined by each facility. There is a responsibility to ensure follow-up evaluation for abnormal laboratory tests that may be discovered coincidentally with preoperative assessment. O'Connor and Drasner97 reported that 17% of children who had a complete blood count (CBC) were anemic or had a microcytosis. Only 2 of these children had surgery canceled because of anemia (hemoglobins <10 g/dL).97 A mechanism to arrange follow-up evaluation with the pediatric clinic should be available, and communication should be assured.
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The American Academy of Pediatrics recommends that a sickle preparation or other screening test be performed in all children of African descent.98 Is it reasonable for the anesthesiologist to insist on receiving the results of a sickle cell preparation in all children of African descent requiring anesthesia and surgery?99 Is anesthetic management different for those who have sickle trait than for those who do not? Is it necessary to have a sickle cell preparation in nonanemic at-risk children? Anesthetizing a child with sickle cell disease who is anemic and with 95% sickle hemoglobin poses a major threat to that child and should never be undertaken without good reason. The likelihood of a child older than age 2 years with a normal hemoglobin having sickle cell disease is extremely low. If all children with hemoglobins less than 10 g/dL require further investigation, among the factors to be investigated, in addition to iron deficiency, is sickle hemoglobin status in at-risk children. This might not apply to neonates or infants who may have hemoglobin concentration greater than 10 g/dL and have sickle cell disease and high levels of sickle hemoglobin. Unless a sickle hemoglobin preparation is performed, cases might be missed in this population which is at risk for hypoxia and low cardiac output during anesthesia. Common practice is to perform a sickle cell preparation on all children of African descent unless their status is known and to screen for anemia in all other children. In those with positive sickle screen, hemoglobin electrophoresis is required.100,101 It should be noted that infants younger than age 4 months have maternal antibodies that interfere with performing a quick sickle index preparation. These children require hemoglobin electrophoresis to determine their sickle cell disease status.
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Does sickle trait pose a threat to older children who may not be anemic but who have some amount of sickle hemoglobin? Although there are some anecdotal stories of sickling and rare vasoocclusive phenomena in children with sickle cell trait during anesthesia with resulting hypothermia, ischemia, and hypoxia, sickle cell trait generally is associated with less than 40% of hemoglobin S in the circulating blood.101 This is the target level that is obtained with transfusion protocols for sickle cell disease. Prudent avoidance of tourniquets that cause blood stasis and hypoxia in the affected limb probably is wise in patients with sickle cell trait. Anesthetic management will not vary because the routine goals of anesthesia (avoidance of hypoxia, hypothermia, hypovolemia, and hypotension) are as important in routine anesthetic management as they are for patients with sickle cell trait.101,102
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In patients with sickle cell disease, preoperative treatment is directed at reducing sickle hemoglobin to less than 40%. Chronic transfusion, exchange transfusion, and acute blood transfusion are reported to be useful in achieving this goal.98,103
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In one study, leukocyte counts were abnormal only in patients who were ill or otherwise suspected of having an infection.66,93 No occult leukocytosis was discovered in 463 preoperative screening evaluations.97 When indicated by suspicion of sepsis, infection, fever, or respiratory tract infection, a CBC might be useful in arriving at the diagnosis; however, routine leukocyte determination does not appear to be warranted.
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Routine urinalysis is part of preoperative recommendations in children. Apart from providing a possible contribution to routine health screening, the relevance to anesthetic management is unclear.66,104 In children who are febrile, have congenital anomalies of the urinary tract, or have suspected renal function anomalies, urinalysis might be beneficial. In otherwise healthy children in whom urinalysis can be difficult to obtain and unreliable, abnormal results appear to occur in 15% of children and usually are asymptomatic bacteriuria.97 The majority of these are either false-positive results, clinically insignificant, or previously known. In only 2 of 453 cases was surgery canceled, and both of these were canceled because of suspected colonization or asymptomatic bacteriuria, which was of no anesthetic relevance. In afebrile, ASA PS P1 children with no history of renal disease, most centers have abandoned routine urinalysis.
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Screening for pregnancy varies widely from center to center. The evidence that anesthesia, per se, is deleterious to the continued pregnancy or the fetus is extremely sparse. On the other hand, the logistic, behavioral, privacy, and social implications of testing all female children of child-bearing age for pregnancy, with or without consent, are quite complex. Each institution must resolve these issues for itself.
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In children who are receiving therapeutic drugs, it frequently is worthwhile to know whether the therapeutic level has been achieved. The 2 major areas in which this is of concern are in children with epilepsy and asthma. Obtaining routine blood levels of theophylline (although now only rarely used) and anticonvulsants to ensure compliance with therapy and adequate levels for the perioperative management appears to be a wise precaution. It is not so clear what should be done when an abnormal result is found. Does an asymptomatic healthy child with a nontherapeutic drug level require therapy? Should therapeutic levels of indicated drugs be achieved before elective surgery? These decisions may require input from the child's primary care physician and perhaps a pediatric neurologist in children with epilepsy. Frequently, it is worthwhile to inform the primary caregiver that the level is subtherapeutic so that the drug can be discontinued before surgery. There is a caveat. Discontinuing anticonvulsants may lead to withdrawal seizures, which is not a pleasant prospect perioperatively. Asymptomatic children with low theophylline levels may not be wheezing on the day of examination but may develop wheezing on the day of surgery and may have serious underlying bronchial hyperreactivity, which may pose difficulties intraoperatively. Our current practice is if a child requires theophylline to suppress wheezing episodes, the child requires therapeutic theophylline levels perioperatively. If this is not possible, knowing the level will allow the anesthesiologist to specifically direct therapy intraoperatively if required. Further testing is guided by the patient's underlying medical condition.
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Preoperative assessment for elective surgery should be done early enough to allow all special investigations to be performed before surgery. Consultation with other services and the performance of other investigative procedures, such as computed tomography (CT) scans, ECGs, and echocardiograms, should be timed so that the results will be available to the anesthesiologist before induction of anesthesia. Deciding that such information is important preoperatively but acting before it is obtained or reported sets the stage for medical or legal misadventures.
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NPO Status and Preoperative Fasting
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Of all the shibboleths of pediatric anesthesia, perhaps the one most time honored and most frequently under attack is the duration of preoperative fasting. The days of NPO after midnight for all children who require surgery is over. For years, we have realized that small infants, with their unique glucose and fluid requirements, do not benefit by being NPO for 12 hours before surgery. Serious hypovolemia with intraoperative hypotension and hypoglycemia is the result.66,105 Concerns have been raised about hypoglycemia occurring in older children after a prolonged fast.105–107 There also are concerns about comfort and the need for the imposition of starvation on children preoperatively. The goal is to reduce gastric volume and minimize the risk of aspiration pneumonia perioperatively. There are many studies looking at factors predisposing to gastric acid aspiration and lung injury and their relationship to gastric residual volumes. The fact remains that perioperative aspiration pneumonia is remarkably rare (a fact that may attest to the success of severe NPO restrictions).
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There is little evidence that in a healthy child prolonged fasts are required to ensure minimal gastric volumes. NPO for solid foods and large meals for 8 hours before surgery should be maintained because gastric volumes may be increased for up to 6 hours. The question becomes less clear with fluids. Several studies demonstrate that ad lib clear liquids up until 2 hours before surgery are associated with lower gastric volumes and higher pHs than those found in fasting patients.108,109 If this is the case, the recommendation ought to be to encourage oral clear fluids preoperatively rather than to limit them. Studies demonstrate that not only is there no major burden of hypoglycemia placed on the healthy child by fasting, but that feeding the child clear liquids is not associated with increased gastric volumes.110
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The final factor that needs to be considered is whether one should change an age-old guideline for a more liberal approach that may be confusing and lead to unintended changes in other requirements. The guideline of NPO after midnight perhaps is draconian, but it is clear to all concerned. No solids after midnight and clear liquids up to 1 hour before surgery ad lib, if the patient is healthy, without gastroesophageal reflux, or other significant GI disease, certainly is less clear. These liberal rules are bound to be applied in inappropriate situations, potentially leading to catastrophe. Some major institutions allow clear liquids until 1 to 2 hours before surgery in their outpatients, and a large series reported from the Children's Hospital of Philadelphia reports no incidence of gastric aspiration after years of this approach.109 ASA guidelines indicate fasting for clear liquids from 2 hours preinduction. Communication, education, monitoring current protocols, and flexibility in approach, based on known facts, should form the guidelines for anesthesia practice. This is no less true regarding preoperative fasting rules. The trend is toward more liberal fasting requirements for clear liquids (Table 20-12).111,112
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One final question: What are clear liquids? Water, glucose water, and commercially available pediatric electrolyte solutions are clear. Some institutions consider breast milk a clear liquid and cow's milk a solid food. Breast milk is not emptied as rapidly as clear liquids from the stomach, and the ASA guidelines state breast milk should not be given within 4 hours of induction. Some institutions encourage gelatin (no additives) and fruit juices, including pulp-free orange juice, as perfectly allowable. It is unlikely that there will be hard scientific data to aid the anesthesiologist in these decisions. The application of common sense and the provision of clear instructions for families are essential. Simplicity is best. Adhering to local protocols is important to avoid confusion and ignoring stated regulations is detrimental to the organized anesthetic care of children.