Glucose tolerance in the obese surgical patient.

Intraoperative glucose metabolism was studied in seven grossly obese patients during an intestinal bypass surgical procedure. Preoperative fasting plasma glucose levels were in the low normal range. Results of intravenous glucose tolerance studies during the preoperative period suggested that three patients demonstrated a diabetic utilization of glucose. Fasting awake plasma glucose levels were increased after premedication for anesthesia and surgical treatment. Following induction of anesthesia, laryngoscopy and intubation, there was a further increase in glucose concentrations. In five patients, a 25 gram glucose load was given intravenously during the anesthetic period and prior to operation; glucose utilization was severely impaired in all patients. When the glucose load was not administered to two patients, a slow uptake of glucose was suggested. Surgical trauma did not further decrease glucose utilization after anesthesia. In patients with no glucose load, surgical treatment resulted in a gradual rise in glucose levels. These results suggested that intraoperative glucose utilization is impaired in the obese. Although a marked osmotic diuresis leading to hypovolemia is not apparent in the present study, decreased intraoperative glucose utilization demonstrates that cautious intraoperative administration of glucose should be considered in the obese patient.