INTRAOPERATIVE INSULIN MEASUREMENT DURING SURGICAL-MANAGEMENT OF INSULINOMAS

Intraoperative hormonal measurements have been used successfully to gu ide the surgical treatment df various endocrine diseases. In this stud y, we report the results of intraoperative insulin measurement (IIM) i n patients with organic hypoglycemia. rms were performed during 52 ope rations in 51 patients. Hyperinsulinism was secondary to a sporadic in sulinoma (M = 40), a type I multiple endocrine neoplasia (MEN-I) (M = 8), an insulin-secreting carcinoma (M = I), or pancreatic nesidioblast osis (M = 2). The insulin was measured with a radioimmunologic assay i n blood samples simultaneously drawn from a peripheral vein and the po rtal vein at the beginning of the operation (T1) and 20 minutes after tumor removal (T2). Normoglycemia was achieved after surgery in 50 cas es (96%). Systemic and portal insulin Levels were normal at T1 in eigh t patients, precluding any further interpretation of the test. Complet eness of surgery was confirmed by normalization of both systemic and p ortal insulin levels at T2 in 36 patients. In seven cases the systemic or portal insulin levels (or both) remained elevated at T2 despite a favorable outcome after surgery. Failure of the surgical procedure was predicted in two patients by the persistence of high levels of insuli n at T2. In patients with initially elevated serum insulin levels, the positive predictive value and the specificity of intraoperative insul in measurement for completeness of surgery were both 100%. The sensiti vity was 84%, the negative predictive value 22%, and the accuracy of t he test 84%. We concluded that IIM is a simple, highly reliable tool f or predicting the completeness of surgery in patients with organic hyp oglycemia. IIM appears to be a valuable addendum to the surgical armam entarium against insulinoma especially for patients with atypical caus es, such as MEN, insulin-secreting carcinoma, or pancreatic nesidiobla stosis.