To the Editor:—  Anesthesiologists have been focusing their attention on preanesthetic fasting time to prevent pulmonary aspiration. To establish a standard for preanesthetic fasting time, large surveys have been conducted in the United Kingdom and Ireland 1and the United States. 2By these efforts, a consensus was reached and was presented in the form of practice guidelines. 3However, some disagreement about fasting time for formula-fed infants remains, and the topic is still controversial. We experienced unanticipated vomiting and pulmonary aspiration at the time of anesthesia induction in a formula-fed infant with 4 h of preanesthetic fasting.

A female patient was born at full term; cheiloschisis was diagnosed without any other anomaly. An elective cheiloplasty was planned at 4 months of age. The patient’s body weight and height were 6,260 g and 60 cm, respectively.

Infant formula was allowed up to 4 h before anesthesia, and clear liquids were permitted up to 2 h before. However, the patient actually drank 160 ml formula 5.5 h before anesthesia and an additional 100 ml 4.5 h before anesthesia. This formula was a product of cow milk that contained 9.7 g whey protein, 6.4 g casein protein, 34 g fat, and 76 g carbohydrates per liter. No premedication was administered.

Anesthesia was induced by inhalation of sevoflurane and nitrous oxide with 33% oxygen. During the induction, the anesthesiologist in charge tried to maintain the patient’s spontaneous respiration. However, abruptly, mask ventilation could not be performed, and then arterial oxygen saturation decreased to 28%. Immediately, the anesthesiologist checked the patient’s mouth and found infant formula in it. It was excluded with suction of the oral cavity, and tracheal intubation was performed. Arterial oxygen saturation recovered to 100%. A coarse crackle on chest auscultation and a shadow on the chest radiograph suggested atelectasis at the right upper lung field. Transendotracheal suction and physiotherapy for 1 h improved the atelectasis; finally, the patient was extubated.

The recommended preoperative fasting time for formula-fed infants varies from 4 to 8 h. The American Society of Anesthesiologists (ASA) recommends 6 h for formula-fed infants in their guidelines. 3However, the ASA recommends 4 h for formula-fed infants younger than 6 months in their ASA refresher course lecture. 4Therefore, disagreement is present in this matter. Our institution adopted the latter fasting time.

Some reports have suggested that the half-life of formula is 1 h; 5–7therefore, the gastric residue of formula for a 4-h fasting time and that for 6 h are expected to be 6 and 1.5%, respectively. Furthermore, it has been reported that 9% of formula-fed infants who fasted for 4 h had undigested traces of formula in their gastric content. 8 

In our case, the patient vomited undigested formula and aspirated it under the condition of a 4.5-h fasting time. We think that our case should be considered an extreme case, but the importance is that the risk of vomiting still remained following the ASA refresher course’s recommendation. Therefore, more studies and discussions are needed for a consensus on fasting time for infant formula.

University of the Ryukyus, Okinawa, Japan.

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