To the Editor:—
Kawabata et al. 1reported a case of unanticipated vomiting and pulmonary aspiration after induction of anesthesia in a formula-fed 4-month-old female infant who weighed 6.26 kg scheduled for elective cheiloplasty. Anesthesia was induced with sevoflurane and nitrous oxide in 33% oxygen. The anesthesiologist tried to maintain spontaneous respirations but, abruptly, mask ventilation could not be performed. Arterial oxygen saturation decreased to 28% and formula was found in the patient's mouth. The authors argue that despite surveys and the American Society of Anesthesiologists practice guidelines' recommended 4-h fasting time,2–4the risk of aspiration remains and suggested that further studies and discussions are needed for a consensus on fasting time for formula-fed infants. Several comments related to the case appear warranted.
First, this case demonstrates that despite more than 4 h of fasting, residual formula can still be present in some infants. Not surprisingly, studies have shown that a completely empty stomach is often not achieved after the recommended fasting time.5,6
Second, although the authors claim that their patient vomited, it appears from their own description that the action was regurgitation rather than vomiting. Various factors can play a role in inducing regurgitation in infants.7Airway obstruction during spontaneous breathing during anesthetic induction may cause regurgitation by increasing pleuroperitoneal pressure differences (thus increasing the intragastric-esophageal pressure difference) and by raising the intragastric pressure as a result of the “over action” of the diaphragm.7,8Positive airway pressure (in excess of 20 cm H2O) may result in intermittent opening of the cricopharyngeal sphincter and the gastroesophageal junction with a subsequent increase in intragastric pressure.7,8The resting intragastric pressure can be higher in infants9(as compared with adults) because of the relatively small size of the stomach, encroachment of some abdominal organs, previous air swallowing during crying, and strenuous diaphragmatic breathing.7,9In addition, a mild from of relaxation of the gastroesophageal junction may exist in the first 6 months of age. Once gastric contents are forced up into the esophagus, they may readily find their way into the pharynx because of the short esophagus in the infant.7,9,10
Third, although inhalation induction using 30–35% oxygen is commonly practiced in infants and children, it is time to seriously consider “preoxygenation” to increase oxygen reserves and thereby delay the onset of arterial oxygen desaturation in case airway obstruction occurs.11–14Infants are at an increased risk of hypoxemia because of their small functional residual capacity and increased oxygen consumption.15The value of preoxygenation in pediatric patients has been recently discussed in a number of reports15–17and certainly can be easily achieved.11–17
In conclusion, despite what appears to be an adequate preoperative fasting, the anesthesiologist should proceed with the assumption that the stomach is not completely empty. It behooves the anesthesiologist to take into consideration the factors that may induce regurgitation during induction and specifically avoiding and immediately correcting airway obstruction. Finally, preoxygenation before induction should be practiced.
* Advocate Illinois Masonic Medical Center and University of Illinois College of Medicine, Chicago, Illinois. firstname.lastname@example.org