Tracheoesophageal Fistula Anomaly

A tracheoesophageal fistula anomaly has five or more configurations, most of which are manifested as an inability to swallow because of esophageal atresia (ending of the esophagus in a blind pouch). The characteristic diagnostic test is the inability to pass a suction catheter into the stomach. Neonates may have aspiration pneumonitis from a distal fistula connecting the stomach to the trachea through the esophagus or from a proximal connection of the esophagus with the trachea. Additionally, this anomaly may be a part of a larger constellation of anomalies known as the VATER association (V, vertebral; A, anal; TE, tracheoesophageal; R, renal) or the VACTERL association (VATER + C, cardiac, and L, limb).^{[339] [340]} Any patient with a tracheoesophageal fistula or esophageal atresia should be suspected of having the other anomalies just described. An echocardiogram to detect a right-sided aortic arch and the presence of congenital heart disease should be performed before anesthesia.

The major issues for management of safe anesthesia include evaluation for aspiration pneumonia; overdistention of the stomach because of entry of air directly into the stomach through the fistula; inability to ventilate the patient because of the large size of the fistula; problems associated with other anomalies, particularly a patent ductus arteriosus (shunting) and other forms of congenital heart disease; and postoperative intensive care.

For management of anesthesia, the child's feedings are withheld, a catheter is placed in the esophagus to drain saliva, and the child is placed prone in a head-up position. If the child has pneumonia, treatment should be initiated; surgery may be postponed until the pneumonitis improves or clears. The child may be a candidate for gastrostomy to provide a means of nutrition during recovery from pneumonitis. Anesthesia evaluation centers on the pulmonary and cardiovascular systems. Generally, an awake intubation is performed, and the endotracheal tube is intentionally passed into the right main stem bronchus; the tube is then slowly withdrawn until breath sounds are heard on the left. Often, this technique ensures that the tip of the endotracheal tube is placed beyond the origin of the fistula, thus avoiding massive distention of the stomach. Care must be taken to avoid rupturing the stomach; therefore, spontaneous and gently assisted ventilation may be appropriate until the gastrostomy is completed. A change in the distance of insertion of the endotracheal tube of as little as 1 to 2 mm may determine whether the anesthesiologist is ventilating both lungs, one lung, or the fistula. Therefore, because a change in oxygen saturation may be the first indication that all is not well, the pulse oximeter is one of the most useful monitors in managing these patients. Taping the stethoscope to the left side of the chest in the axilla also decreases the possibility of unrecognized endobronchial intubation.

Diaphragmatic Hernia

Diaphragmatic hernia is usually manifested on the first day of life as respiratory distress and a scaphoid abdomen. The abnormality is herniation of the abdominal viscera through a defect in the diaphragm, most commonly the foramen of Bochdalek on the left side. Almost all the abdominal viscera, including the liver and spleen, may be above the diaphragm. The gestational age at which herniation occurs may determine the degree of lung hypoplasia.

Anesthesia concerns include hypoxemia and hypotension caused by overdistention of the stomach and herniation across the midline—hypoxemia because of primary pulmonary hypoplasia, pulmonary hypertension, or pneumothorax of the contralateral lung during attempts at high-pressure ventilation; systemic hypotension as a result of kinking of major blood vessels, particularly those of the liver. In general, the anesthesiologist's ability to control arterial carbon dioxide tension (PaCO₂ ) reflects the severity of lung pathology and therefore survival. An inability to reduce PaCO₂ is associated with a poor prognosis.^[341] Extracorporeal membrane oxygenation and the use of nitric oxide have reduced the mortality associated with this condition. In addition, the urgency for surgical intervention has diminished and given way to a desire to stabilize the infant and minimize stress.^[342] It is common practice to postpone surgery on infants with a diaphragmatic hernia until their condition has been stabilized for several days. In some centers, closure is accomplished at the bedside in the neonatal intensive care unit.

Anesthesia management of patients with diaphragmatic hernia includes the following: (1) an awake intubation without bag and mask ventilation prevents overdistention of the stomach and herniation across the midline; (2) insertion of an arterial line and close observation of the surgical field are most helpful in diagnosing impairment in venous return or cardiac output; (3) blunting of the stress response is accomplished by providing analgesia with narcotics (usually fentanyl) and by controlling respiration

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In most centers, the approach to these patients has changed to supportive care initially with permissive hypercapnia, extracorporeal membrane oxygenation, high-frequency ventilation, and inhaled nitric oxide. We no longer rush to the operating room soon after birth, and this approach seems to have reduced mortality.^{[343] [344] [345]}

The Former Preterm Infant

Since the early retrospective reports noting the frequent occurrence of postoperative apnea in former preterm infants (gestational age [GA] less than 37 weeks), a number of studies have tried to define the population at risk.^{[282] [346] [347] [348] [349] [350] [351] [352] [353] [354]} Most studies have found the majority of infants in whom postanesthesia apnea develops to be younger than 46 weeks' postconceptual age (PCA); however, apnea has been reported in infants up to 60 weeks' PCA.^[354] The conclusions reached by each of these studies were limited by the relatively small number of patients. I had the opportunity to obtain and analyze the original

Figure 60-16 Predicted probability of apnea for all patients by gestational age and weeks' postconceptual age. Patients with anemia are shown as the horizontal hatched line. Bottom marks indicate the number of data points by postconceptual age. The risk for apnea diminishes for infants born at a later gestational age. The shaded boxes represent the overall rates of apnea for infants within that gestational age range. The probability of apnea was the same regardless of postconceptual age or gestational age for infants with anemia (horizontal hatched line). (Redrawn from Coté CJ, Zaslavsky A, Downes JJ, et al: Postoperative apnea in former preterm infants after inguinal herniorrhaphy. A combined analysis. Anesthesiology 82:809–822, 1995.)

Although the risk of apnea may be less with regional anesthesia, apnea may still occur and may even be increased if regional anesthesia is combined with sedation (ketamine, midazolam).^{[348] [350] [356] [357] [358] [359] [360] [361]} There are insufficient numbers

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Part of the problem of how to treat these children is the fact that we do not know the clinical importance of brief apnea/bradycardia spells that do not require intervention. Because cerebral blood flow is markedly reduced with heart rates below 80 beats/min, even brief apnea associated with bradycardia may have adverse effects.^[362] The problem faced by the clinician is how to manage former preterm infants scheduled for outpatient procedures. Information concerning the true incidence of postoperative apnea is still very limited because the available data have been collected from so many institutions. Nevertheless, one can conclude that the incidence of apnea is inversely related to PCA and GA and anemia is also an independent risk factor.^[283] More prospective studies need to address whether regional techniques are safer than general anesthesia. Pulse oximetry would help define the severity of desaturation, and electrocardiographic monitoring would help define episodes of bradycardia, which may reduce cerebral blood flow. Kurth and colleagues demonstrated that up to 12% of apnea spells are accompanied by desaturation to below 80%.^[354] It would seem reasonable that the combination of desaturation and bradycardia is of more physiologic importance than simple documentation of pauses in respiration.

Because the available data are so confusing, it appears that outpatient anesthesia should be considered only when former preterm infants have had a totally unremarkable neonatal history and are currently healthy. If there is any question, a prudent anesthesiologist will plan on postoperative admission and monitoring. If appropriate facilities are not available, a premature infant who is less than 60 weeks' PCA should be referred to an institution that has such facilities. High-dose caffeine (10 mg/kg) has been recommended.^[352] This therapy may be effective; however, the half-life of caffeine in older former preterm infants is only 6 hours and the first apnea spells after anesthesia may not be manifested until 12 hours.^{[283] [363]} Therefore one cannot administer caffeine, send the infant home, and assume that the problem is treated.

To make the issue even more complex, I have observed a full-term infant who became apneic after general anesthesia. This infant had periodic breathing, which is distinctly unusual in a full-term infant.^[364] We still do not know with certainty which patients are truly anesthetized safely on an outpatient basis and at what PCA and GA. Because most organ systems are still rapidly developing during the first month of life (44 weeks' PCA), it is reasonable to delay elective surgery during the first month of life and consider postoperative admission and apnea monitoring, even in full-term infants. Alternatively, performing the procedure as the first of the day and then observing for an extended period may permit safe discharge in the late afternoon or early evening.