Prevention of metabolic alterations by insulin supplements administered either before or after 2-h nocturnal...

To evaluate the efficacy of a bolus insulin injection to prevent the metabolic alterations induced by a 2-h nocturnal interruption of a continuous subcutaneous insulin infusion (CSII), nine type I (insulin-dependent) C-peptide-negative diabetic patients were studied from 2200 to 0800 h during two randomized tests. An insulin bolus (2.1 +/- 0.2 U) was administered via the pump either at 2300 h, just before CSII interruption, or at 0100 h, after reactivating the pump at its usual basal rate (1.05 +/- 0.11 U/h). The insulin bolus at 2300 h induced a significant rise in plasma free-insulin levels at 2400 h (+6.9 +/- 1.8 mU/L, P less than .01), resulting in an early and marked fall in blood glucose concentrations between 2300 and 0100 h (-2.7 +/- 0.5 mM, P less than .001), with hypoglycemic values in five patients. The insulin bolus at 0100 h counteracted the fall in plasma free-insulin levels observed between 2300 and 0100 h and significantly increased plasma insulin at 0200 h (+3.2 +/- 0.8 mU/L, P less than .01). Blood glucose concentrations that remained stable during the 2-h arrest of the pump fell significantly between 0100 and 0400 h (-2.1 +/- 0.5 mM, P less than .005). This fall rate was significantly lower than that measured within the 3 h after the insulin bolus given before CSII interruption but significantly higher than that observed in a reference control group of patients whose pump was functioning normally throughout the night.(ABSTRACT TRUNCATED AT 250 WORDS)