Prevention of Metabolic Alterations by Insulin Supplements Administered Either Before or After 2-h Nocturnal Interruption of CSII

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 (insulindependent) 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 < .01), resulting in an early and marked fall in blood glucose concentrations between 2300 and 0100 h (−2 .7 ± 0.5 mM, P < .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 < .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 < .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. Thus, an insulin bolus equivalent to the amount of insulin not infused during a 2-h CSII interruption is able to prevent the metabolic alterations resulting from the pump arrest. However, to reduce the risk of hypoglycemia, the insulin bolus should preferably be administered after rather than before the 2-h CSII interruption.