Devices and methods for long-term intravenous (i.v.) insulin infusion in ambulatory patients have recently been developed. However, to date optimal waveforms for open-loop insulin administration in severely insulin deficient patients have not been defined.
We studied 7 nonobese uncomplicated type 1 diabetics aged 16.5 ± 0.2 yr who received insulin continuously for 14–23 days by central venous infusion. A pattern of i.v. insulin administration was developed and eventually refined to include a constant basal infusion rate augmented at meal time by a series of 3 pulses. The first pulse lasted 10–15 min with an infusion rate 1.5–2 times the basal rate. The second pulse was 60–100 min in duration with a rate 4–6 times the basal infusion rate. The third pulse lasted 40–100 min with an infusion rate 1.5–3 times the basal rate. Accompanying the evolution of this waveform, the mean fasting plasma glucose fell from 262 ± 40 mg/dl on conventional therapy to 92 ± 9 mg/dl during infusion with normal meal excusions (mean a.c. glucose 80 ± 3 mg/dl with a rise of 35 ± 3 mg/dl at 41 ± 3 min). Mean urinary glucose excretion decreased from 55 before to 1.9 g/day during the infusion period. Fasting serum cholesterol and triglycerides dropped from 220 ± 28 and 281 ± 94 to 138 ± 13 and 115 ± 24 mg/dl, respectively.Mean HbA, declined from 14.8% before to 10.7% at the conclusion of the infusion period. All indices of control showed improvement significant at P < 0.05. There were no catheter-related complications and the system was well accepted by all subjects.
These studies confirm that continuous central venous insulin infusion with a relatively simple waveform is feasible for the prolonged normalization of glycemia and other indices of metabolic control in ambulatory adolescent diabetics.