Insulin responses to selective arterial calcium infusion under hyperinsulinemic euglycemic glucose clamps: case studies in adult nesidioblastosis and childhood insulinoma

Selective arterial calcium stimulation and hepatic venous sampling (ASVS) for insulin secretion is used as a diagnostic procedure in patients with insulinomas or adult nesidioblastosis. In some of those patients, severe hypoglycemia requiring urgent glucose administration occurs during the procedure. Such glucose administration, however, may affect the results and damage the validity of the test. We report two cases of hyperinsulinemic hypoglycemia, in which ASVS tests were successfully performed under hyperinsulinemic euglycemic glucose clamps. A 40-year-old male with nesidioblastosis developed continual severe hypoglycemia several years after a Billroth II-Braun gastrectomy, and continuous glucose infusion could not be stopped even during ASVS tests. A 9-year-old girl with an insulinoma that showed atypical hypovascularity on imaging examinations had ASVS tests under a glucose clamp for safety. Hyperinsulinemic (approximately 100 microU/ml) euglycemic (approximately 90 mg/dl) clamps were achieved by an artificial endocrine pancreas. The insulin analogue lispro was utilized for clamps and endogenous insulin was measured with an assay that does not cross-react with the analogue. Diagnostically significant responses (more than twofold) of insulin secretion were observed under hyperinsulinemic clamps in both cases. The use of the hyperinsulinemic glucose clamp technique during the ASVS test should be considered for maintaining the safety of some hypoglycemic patients.