Meal challenge during a hyperinsulinemic euglycemic clamp – new protocol for a proven technique

Abstract

To optimize meal-related insulin doses in diabetic patients, 3 variables need to be assessed: pre-meal blood glucose (BG), insulin to carbohydrate ratio (I:CHO) and basal insulin. When any of these variables are miscalculated, postprandial glucose is affected. We are presenting preliminary data for a novel use of the hyperinsulinemic euglycemic clamp (HEC) technique in patients with type 1 diabetes which minimizes the impact of these variables. Six subjects (3 men, 3 women) treated with continuous subcutaneous insulin infusion pumps were recruited for this study (24–65 yrs; BMI 26.4±15.8 kg/m2; A1c 7.0 ±1.4%). Subjects started the HEC after an overnight fast. A cannula was inserted for infusions and another cannula was inserted in the warmed contralateral arm for sampling of arterialized venous blood. To achieve euglycemia an insulin (Humulin R; Eli Lilly) infusion was started at t=0 using a primed continuous intravenous infusion of 40mU/m2/min. Whole BG was measured every 5 mins and a variable infusion of 20% glucose was used to maintain BG at 90mg/dl. When subjects were in a euglycemic steady state (SS) for 50 mins a standardized meal (40% of total calories/day − 30% carbohydrate, 30% protein, 40% fat) was consumed. Subjects gave the insulin bolus with their insulin pump and used their usual I:CHO ratio. No changes were made in the glucose and insulin infusion rates. The BG excursion was observed, and, using the peak excursion from SS, the correct I:CHO was isolated. Mean BG at SS was 83.3±4.7 and at peak was 117.3±16.3 mg/dl. This novel use of the HEC can be used to determine the I:CHO ratio and obliterate any interfering factors. (The study is supported by NIDDK 1R01DK068663)