Intensive insulin treatment improves forearm blood flow in critically ill patients: a randomized parallel design clinical trial

INTRODUCTION: Intensive insulin treatment of critically ill patients was seen as a promising method of treatment, though recent studies showed that reducing the blood glucose level below 6 mmol/l had a detrimental outcome. The mechanisms of the effects of insulin in the critically ill are not completely understood. The purpose of the study was to test the hypothesis that intensive insulin treatment may influence forearm blood flow independently of global hemodynamic indicators. METHODS: The study encompassed 29 patients of both sexes who were admitted to the intensive care unit due to sepsis and required artificial ventilation as the result of acute respiratory failure. 14 patients were randomly selected for intensive insulin treatment (Group 1; blood glucose concentration 4.4-6.1 mmol/l), and 15 were selected for conventional insulin treatment (Group 2; blood glucose level 7.0 mmol/l-11.0 mmol/l). At the start of the study (t(0), beginning up to 48 hours after admittance and the commencement of artificial ventilation), at 2 hours (t(1)), 24 hours (t(2)), and 72 hours (t(3)) flow in the forearm was measured for 60 minutes using the strain-gauge plethysmography method. Student's t-test of independent samples was used for comparisons between the two groups, and Mann-Whitney's U-test where appropriate. Linear regression analysis and the Pearson correlation coefficient were used to determine the levels of correlation. RESULTS: The difference in 60-minute forearm flow at the start of the study (t(0)) was not statistically significant between groups, while at t(2 )and t(3 )significantly higher values were recorded in Group 1 (t(2); Group 1: 420.6 ± 188.8 ml/100 ml tissue; Group 2: 266.1 ± 122.2 ml/100 ml tissue (95% CI 30.9-278.0, P = 0.02); t(3); Group 1: 369.9 ± 150.3 ml/100 ml tissue; Group 2: 272.6 ± 85.7 ml/100 ml tissue (95% CI 5.4-190.0, P = 0.04). At t(1 )a trend towards significantly higher values in Group 1 was noted (P = 0.05). The level of forearm flow was related to the amount of insulin infusion (r = 0.40). CONCLUSIONS: Compared to standard treatment, intensive insulin treatment of critically ill patients increases forearm flow. Flow increase was weakly related to the insulin dose, though not to blood glucose concentration. TRIAL REGISTRATION: Trial number: ISRCTN39026810.