The response of gastric secretion and serum gastrin to an insulin infusion test in patients with duodenal ulcer

The intravenous infusion of insulin 0.04 U/kg-hr for 2-1/2 hours was performed in 26 patients with chronic duodenal ulcer. In 15 patients this infusion test was compared with the standard test of a single intravenous injection of insulin 0.2 U/kg. The mean lowest blood glucose level in the infusion group (25.1 mg/100 ml) was significantly higher than in the standard test (17.4 mg/100 ml), and the interval from injection to acid stimulation about twice as long (75versus 45 minutes). The peak acid output and mean rise in acidity were comparable in the two procedures. Serum gastrin responded reciprocally to insulin-induced hypoglycemia with a significant inverse correlation between blood glucose and gastrin. In 13 patients tested after vagotomy, there was no significant difference in the rise in acidities in the two groups, and the Hollander status was the same in all but one patient. The mean basal, peak, and absolute rise of serum gastrin in unoperated patients and patients with incomplete vagotomy were almost identical. In patients with complete vagotomy there was no significant rise in serum gastrin after insulin infusion. Unpleasant side effects as assessed by an independent observer were fewer and less severe in patients undergoing infusion tests than in the standard test. The insulin infusion test is recommended as a safer and more acceptable test than the standard insulin test since it avoids severe hypoglycemia and has milder side effects yet achieves comparable acidity and acid outputs. Measurements of serum gastrin after either insulin test provide no additional information helpful in the assessment of the completeness of vagotomy.