Long term open loop intravenous insulin infusion in type I diabetes: feasibility, problems and promise

The response of four Type I diabetic patients to long term (1,4,4, and 8 months) intravenous insulin infusion is reported. As compared to their usual subcutaneous depot insulin treatment, glycosylated hemoglobin (HbAl) decreased from 12.2 +/- 0.7 to 8.8 +/- 0.9 (p less than 0.05). However, only 49 to 76.5% of self blood glucose monitoring results were between 60-179 mg/dl range. Although 6.3 to 15.2% of capillary blood glucose levels were less than 60 mg/dl, severe hypoglycemia occurred only on one occasion. Plasma cholesterol, triglyceride and high density lipoprotein all decreased significantly (p less than 0.005). The major motivating factors for participation in this study were: (1) the hope of preventing diabetic complications; (2) the wish for more knowledge about diabetes; (3) a sense of special purpose and (4) a general interest in science and research. Catheter obstruction as a result of insulin aggregation terminated the study in two subjects. A third subject requested the study be stopped primarily because of imposed travel restrictions. In one subject, the study was stopped because of a disrupted personal life and developing depression. Diabetic ketoacidosis or sepsis from the centrally placed intravenous catheter did not occur. Although long term intravenous insulin infusion is feasible in a clinical research setting, insulin aggregation continues to be a major limiting factor. The widespread clinical use of implantable pumps will have to await the development of a suitable insulin formulation.