Plasma insulin and surgery. II. Later changes and the effect of intravenous carbohydrates.

Long-term hyperinsulinemia and improved glucose tolerance were produced postoperatively by intravenous feeding with glucose or sorbitol. Raised immuno-reactive insulin (IRI) values persisted eight hours after carbohydrate infusions although the basal plasma glucose concentrations had returned to control values. Plasma glucose curves were normal at this time but were associated with an increased IRI response. These findings suggest that insulin secretion is modified by glucose not only in the short term but also by a separate effect acting over many hours. The combination of starvation and low dose glucose infusion to simulate the hyperglycemia of operation also produced high IRI values but these were associated with a rapid fall in the plasma glucose curve. Starvation alone reduced basal values of plasma glucose and IRI, and the IRI response to glucose infusion was also reduced, despite the plasma glucose curve being at a higher level. It is suggested that the high values of IRI reported in the postoperative period are mediated by a long-term effect of the small but sustained rise in basal plasma glucose. This specific role of glucose in the long-term potentiation of insulin secretion make it the carbohydrate of choice for the intravenous feeding in postoperative patients.