Discontinuing wear of the insulin pump for short periods enhances the feasibility of continuous subcutaneous insulin infusion (CSII) therapy. Because insulin requirements differ during pump and injection therapy, we studied the optimal substitution dose arid injection site in seven type I diabetic patients to compensate for the overnight (2100–0730 h) interruption of CSII. The missed basal continuous infusion dose was replaced by injecting intermediate-acting insulin subcutaneously in three different ways: 1) 1.5 times the dose in the abdomen, 2) twice the dose in the abdomen, and 3) twice the dose in the buttock.

During CSII, glycemia remained unchanged throughout the night. Both 1.5 times and twice the replacement doses injected in the abdomen resulted in an initial decline in blood glucose with hypoglycemia in two patients followed by a rebound rise. When the replacement dose of 1.5 times was used, blood glucose rose by 4.9 ± 1.2 mM overnight (P < .02). These changes after abdominal injection were associated with a rapid early absorption of injected insulin with hypoinsulinemia in the morning. With twice the replacement dose injected in the buttock, insulin absorption was slower, fluctuations in nocturnal glycemia were minor, and the blood glucose level at 0730 h was similar to that of the previous night. There was a significant inverse correlation between blood glucose and serum free-insulinlevels in the early morning (r = −.60, P < .01). In conclusion, a substitution dose of 1.5 times to twice the missed basal infusion rate injected in the buttock compensates for the overnight interruption of CSII without risk of major fluctuations in blood glucose levels or nocturnal hypoglycemia.

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