Background: As part of a study to evaluate the accuracy of the GlucoWatch® G2TM Biographer and the Continuous Glucose Monitoring System (CGMSTM) compared with gold standard blood glucose (BG) measurements in children with T1DM, hypoglycemia was induced with intravenous (IV) insulin. This provided the opportunity to study the physiologic response to IV insulin with regard to the rate of development of hypoglycemia. Objective: To determine the BG pattern of insulin-induced hypoglycemia in children with T1DM and assess its relationship to patient factors. Design/Methods: At five clinical centers, 54 subjects with T1DM [26F, 28M, mean age 12+3 yrs (range 7-17)] received an IV insulin bolus (0.05 units/kg when baseline BG 80-100 mg/dL and 0.1 units/kg when baseline BG >100 mg/dL). After 30-60 min, if needed, a second bolus (0.05-0.10 units/kg) was administered (N=24). Oral or intravenous glucose was given when hypoglycemic levels were reached. Venous blood samples were obtained every 5 minutes for up to 90 minutes and glucose determinations were made at a central laboratory. Results: The BG ranged from 76 to 332 mg/dL at baseline and from 17 to 174 mg/dL at nadir. Among 48 subjects whose baseline BG was >100 mg/dL, BG decreased from baseline by at least 50 mg/dL 92% of the time, and BG decreased by at least 50% of the baseline level 85% of the time. A BG <55 mg/dL was reached by 57% and <70 mg/dL by 80%. Among the 49 subjects reaching a nadir < 60 mg/dL or > 50% drop from baseline, the mean time to the nadir BG was 52+23 min for children 7-<12 yrs (n=20) and 60+24 min for children 12-<18 yrs (n=29; p=0.17). Corresponding values were 55+23 min and 58+25 min for subjects using a pump (n=23) and multiple injections (n=26), respectively (p=0.18). When baseline BG was >100 mg/dL, 94% of pump users had a BG drop >50% compared with 80% of injection-users. There were no serious adverse effects of the protocol. Conclusions:With our protocol, a >50% decrease in BG was achieved by most subjects. The data provide useful information about the physiologic response to intravenous insulin in children with T1DM. In addition, the results will be valuable for the design of future physiological studies which aim to induce hypoglycemia through the administration of intravenous insulin.
The Diabetes Research in Children Network (DirecNet) is an NIH-funded collaborative study group that consists of five clinical centers, a coordinating center, a central laboratory and representatives from NICHD and NIDDK.
DirecNet conducted a study to evaluate the accuracy of the GlucoWatch® G2™ Biographer (Cygnus, Inc., “GW2B”) and Continuous Glucose Monitoring System (“CGMS” Medtronic MiniMed, Northridge CA) compared with reference venous blood glucose (BG) measurements in children with T1DM ages 7-17.