Secretion of pepsins and hydrogen ions in the stomach of children undergoing cardiac surgery.

Gastric juice was collected from 27 children for 9 to 21 hr following cardiac surgery, from 4 further children during and following cardiac surgery, and from 3 children who had not undergone surgery. Each sample was analyzed for hydrogen ion and pepsin content. The pH of the postoperative secretions from 26 patients was 1.25 to 5.30, and the mean hydrogen ion concentration was 60.1 mmol/liter (range, 21.5 to 119.3 mmol/liter). The mean peptic activity (83.0 units/ml; range, 42.4 to 158.4 units/ml) was not age related and was significantly higher than that of the basal and pentagastrin-stimulated secretion and similar to that of vagally stimulated secretion of adults with peptic ulcer. The pepsin:hydrogen ion and pepsin 1:total pepsin ratios also resembled those of vagally stimulated secretion. During the first 90 min of cardiac surgery, the pH of aspirated gastric juice was 1.40 to 4.90, the hydrogen ion concentration was 15.8 to 72.3 mmol/liter, peptic activity was 39.2 to 164.0 units/ml (mean, 97.2 units/ml). Pepsin 1 was present in all samples. Aspirates from 3 unoperated children had low total peptic activity and only trace amounts of pepsin 1. Children from the age of 5.5 months thus have the capacity to secrete all the major pepsins, including pepsin 1. The findings suggest that vagal stimulation of gastric secretion was occurring during the postoperative period.