A portable system for continuous intravenous insulin delivery: characteristics and results in diabetic patients.

Abstract

A portable insulin delivery system for clinical use has been developed, with the aim of improving glycemic control for prolonged periods for individuals with insulin-dependent diabetes. It weighs 1.5 kg and measures 8 × 11 × 20 cm. A plastic case contains two insulin reservoirs, two peristaltic pumps (flow variability ± 3%), a battery pack, and voltage regulator. Silastic tubes connect the reservoirs to an indwelling intravenous catheter inserted into the arm. The system is carried by a strap over the shoulder. One pump operates continuously, giving insulin at a “basal” rate, and the other is activated during meals to give a preprogrammed waveform of insulin, the latter controlled by a small bedside unit. Twelve insulin-dependent diabetic patients were infused with insulin by this system for 4–60 days (mean 18 days), for a total of 199 patient days. Insulin delivery rates were modified according to data obtained by intermittent glycemic monitoring, and on one and in some cases two days glycemia was continuously monitored (N = 10). With a basal infusion rate of 18 ± 2 mU/min (mean ± SEM), fasting glycemia was 99 ± 7 mg/dl. The mean insulin delivered with meals was 12 ± 2 U for breakfast, 9 ± 2 U for lunch, and 11 ± 2 U for dinner. Mean glycemia before lunch and supper was 102 ± 6 and 121 ± 11 mg/dl, respectively. The lowest mean glycemia occurred after lunch (88 ± 7 mg/dl) and the mean peak postprandial glycemia was 136 ± 8 mg/dl (2 h after supper). The range from lowest to highest observed value was 47–189 mg/dl. This system is capable of maintaining glycemia within the normal range for periods up to 60 days. Further refinement of the waveforms of insulin delivery may allow for total glycemic normalization. The future refinement of such a system will allow for longer-term studies addressing the relationship between glycemic control and complications.