Abstract
We originally developed an artificial endocrine pancreas by combining a glucose infusion system with the artificial beta cell. This system was adapted to assist in the intravenous tolbutamide test and in the intraoperative localization of an occult insulinoma in a 45-year-old patient who suffered from hypoglycemic attacks several times within a year.
In this patient, the fasting plasma glucose concentrations were between 23 and 61mg/100ml, corresponding with insulin values of from 13 to 31μU/ml. In a 100g oral glucose tolerance test and a glucagon 1mg iv injection test, insulin secretion was markedly exaggerated. An intravenous tolbutamide injection test was performed under blood glucose control with the artificial endocrine pancreas since severe hypoglycemia was anticipated. With computer-operated glucose infusion, the blood glucose was maintained at levels of between 60 and 80mg/100ml, and then tolbutamideinduced hyperinsulinemia was proven by immunoassay.
Selective angiography of the celiac and superior mesenteric artery failed to demonstrate any tumor shadows. Percutaneous transhepatic portal and pancreatic venous catheterization revealed that the plasma concentrations of insulin were not unequivocally elevated in any sampling location.
Even though preoperative localization of the insulinoma was not successful, laparotomy was performed. During the operation, glycemia was monitored in continuously withdrawn whole blood, and glucose was infused to maintain the blood glucose concentration at a level of 80mg/100ml using an artificial endocrine pancreas with a closed loop that excluded its usual insulin delivery capability.
Inspection and palpation failed to reveal any tumors in the pancreas. Massage on the tail of the pancreas was then performed. After 10min, the blood glucose tended to decrease and the glucose infusion rate progressively increased. Massage of the head of the pancreas failed to increase the glucose infusion rate. The location of the insulinoma was thus decided to be the pancreatic tail. Eighty-five percent of the pancreas including the tail was removed, and the blood glucose then increased rapidly. Subsequently, this was confirmed directly by determination of the increment of insulin after pancreatic tail massage and reduction of insulin after pancreatic resection.
A single tiny (3mm) insulinoma was found in the resected portion of the pancreas. Following the operation, the hypoglycemic symptoms vanished completely.
The artificial endocrine pancreas thus facilitated not only the blood glucose control during insulin secretion stimulation tests and pancreatic resection, but also the intraoperative localization of an occult insulinoma.
