Efficacy of insulin pump therapy: mealtime delivery is the key factor

To investigate, in a clinical setting, the effect of implementation of continuous subcutaneous insulin infusion (CSII) on control of plasma glucose and to identify factors associated with improved glycemic control in patients with type 1 diabetes mellitus.

Nineteen patients (16 women and 3 men) with type 1 diabetes were studied retrospectively. Their mean age was 42.6 years (range, 30 to 58), and the mean duration of diabetes was 21 years. The subjects underwent follow-up for a mean of 14 months after conversion to CSII therapy. With use of paired t tests, pre-CSII and follow-up data were evaluated relative to changes in weight, insulin dosing, and glycosylated hemoglobin (HbA(1c)).

At follow-up, the total daily dose of insulin had decreased by 18%, from a baseline mean value of 45.2 IU to 37.1 IU (P = 0.02). HbA(1c) was reduced from 8.4% to 7.7% (P<0.01). The total daily insulin-to-weight ratio also significantly decreased from 0.66 IU/kg to 0.53 IU/kg (P<0.05). Before insulin pump use, the regular/NPH insulin ratio was 0.5 IU; at follow-up, the pump bolus/basal insulin ratio was 1.0 IU (P = 0.02). No weight gain was observed; the mean weight of the study patients decreased 0.2 kg, from 69.4 kg at baseline to 69.2 kg at follow-up (not significantly different).

In a clinical setting, CSII therapy in patients with type 1 diabetes improves glycemic control and lowers the total daily basal insulin dose without affecting weight. Improved glycemic control was associated with a shift in insulin therapy from a high percentage of intermediate-acting insulin to a greater percentage of insulin administered in a meal-associated bolus form. This study emphasizes the importance of mealtime insulin adjustment for tight glycemic control in patients using CSII therapy. Future studies evaluating the benefits of decreased total insulin and an increased bolus/basal insulin ratio may be important in helping to understand how to avoid long-term complications of diabetes.