Study of hypoglycemic patients by the glucose clamp technique using the artificial pancreas.

Using the artificial pancreas, blood glucose levels were maintained at 80 mg/dl in nine hypoglycemic patients (four with histologically proven insulinomas and five with nontumoral hypoglycemia) and in four normal subjects during a 24-h fast. The amount of glucose used, serum insulin levels, and glucose clearance were higher in patients with nontumoral hypoglycemia than in normal subjects and highest in the patients with an insulinoma. Surgical or pharmacological treatment resulted in normalization of all parameters. In contrast to the 72-h fast, the 24-h glucose clamp technique allowed the study of hypoglycemic patients without inducing hazardous hypoglycemia.

Glucose-clamp by artificial pancreas in the study and management of a patient with insulinoma.

Four euglycemic glucose-clamp studies by artificial pancreas (Biostator, Miles) have been performed during prolonged fast before and after pharmacological treatment in a patient with insulinoma. In the basal state a high glucose infusion rate (8.9 g/h) was unable to achieve the preselected blood glucose plateau of 80 mg/100 ml. The plasma insulin levels during this first glucose-clamp were comprised between 18 and 50 microunits/ml. On the first day of diazoxide treatment (300 mg/die),. the glucose infusion rate decreased to 6.4 g/h, without variation in plasma insulin level, thus suggesting a diazoxide effect independent of the inhibition of insulin secretion. After 7 days of diazoxide treatment, a further reduction of glucose infusion (5.8 g/h), together with a lowering of plasma insulin levels (7-18 microunits/ml) was observed. Both in the basal state and during diazoxide treatment a circadian pattern of glucose requirement was noted, with lower glucose need and plasma insulin levels during the night. Surgery was undertaken with glucose-clamp by artificial pancreas; blood glucose level being higher than the preselected value of 80 mg/100 ml, simple monitoring of glycemia was performed. The excision of a single adenoma was followed by a substantial rise in blood glucose 20 min later. An additional glucose-clamp, performed 3 months after surgery showed a dramatic fall of the glucose infusion rate (2.9 g/h) needed to achieve the preselected blood glucose plateau, confirming the completeness of the intervention. This experience shows that glucose-clamp by artificial pancreas may be of great value in the study as well as in the pharmacological and surgical treatment of patients with insulinoma.