Postoperative apnea after pyloromyotomy for infantile hypertrophic pyloric stenosis.

Objective: Infantile hypertrophic pyloric stenosis (IHPS), which causes gastric outlet obstruction and hypochloremic hypokalemic metabolic alkalosis, could pose a risk of postoperative apnea in patients. The aim of this study is to evaluate the incidence of postoperative apnea in babies admitted to a tertiary-level pediatric surgical center in Milano, Italy with diagnosis of IHPS in 2010-2019. The secondary objective is to evaluate the risk factors for postoperative apnea.

Methods: This is a single-center, retrospective, observational cohort study. All patients admitted to our institution with diagnosis of IHPS during the study period were enrolled. Demographic and surgical variables, along with blood gas parameters, were obtained from the population. Postoperative apnea was defined as a respiratory pause longer than 15 s or a respiratory pause lasting less than 15 s, but associated with either bradycardia (heart rate <120 per minute), desaturation (SatO₂ <90%), cyanosis, or hypotonia. Occurrence was obtained from nursing charts and was recorded as a no/yes dichotomous variable.

Results: Of 122 patients, 12 (9.84%) experienced apnea and 110 (90.16%) did not. Using univariate analysis, we found that only postoperative hemoglobin was significantly different between the groups (p=0.03). No significant multivariable model was better than this univariate model for prediction of apnea.

Conclusions: Postoperative anemia, possibly due to hemodilution, increased the risk of postoperative apnea. It could be hypothesized that anemia can be added as another apnea-contributing factor in a population at risk due to metabolic changes.