The notion that it would be beneficial to provide insulin in a more physiologic manner by continuous infusion began to receive serious attention in the 1970s. Early studies used intravenous delivery of insulin to achieve near-normal plasma glucose levels (1-3). Promising reports of subcutaneous delivery of insulin using portable pumps soon followed (4,5) and the concept of continuous subcutaneous insulin infusion (CSII) or 'insulin pump therapy' was born.
The early portable pumps were large and quite complicated to use. They offered a single basal rate, plus a stepped up rate of infusion to cover increased insulin requirement after meals. Insulin (diluted with saline) was delivered through a nylon cannula implanted in the abdominal wall (4).
It was soon demonstrated that CSII could offer an alternative means of improving glycaemic control (6,7) and the feasibility of using insulin pump therapy to obtain near-normoglycaemia during pregnancy was also recognised (8,9).
Whilst it was acknowledged that near-normoglycaemia could be achieved with the use of an insulin pump, there remained the possibility that the same improvement in glycaemic control could be achieved by using multiple daily injection regimens (10-12).
In one crossover study, it was reported that pump therapy and multiple injection regimens were both equally effective during the initial 2 - 4 day period of inpatient management. However, pump therapy was found to be more effective in achieving blood glucose control in the outpatient setting. Importantly, patients also found pump therapy preferable to multiple daily injections (13).
Longer studies were conducted in order to evaluate the long-term efficacy of insulin pump therapy. Mecklenburg and co-workers demonstrated significantly improved glycaemic control over a three year period in patients using CSII (14).
Early reports of patient satisfaction with insulin pump therapy confirmed that greater flexibility in diet and insulin delivery were appreciated (15) and many patients reported an improved quality of life associated with using an insulin pump (16).
The success of insulin pump therapy is highly dependent upon motivation of patients (15) and confidence in their own ability to self-manage diabetes (17). These factors are of importance in selecting suitable candidates for insulin pump therapy.
During the 1980s much attention was focussed on the importance of glycaemic control in relation to the development of the late complications of diabetes. CSII was widely used as a means of achieving near-normoglycaemia in such studies. The results of the Diabetes Control and Complications Trial (DCCT) (18) subsequently provided the most compelling proof that intensive treatment, aimed at achieving near-normal blood glucose levels, could prevent or delay the onset of microvascular complications. Such as retinopathy (eye disease), nephropathy (kidnbey disease) and neuropathy (damage to nerves). By the end of the study, 42 % of participants in the intensive treatment group were using insulin pump therapy (19).
Enthusiasm for CSII was tempered as potential complications specific to insulin pump therapy were realised. In particular, reports of infusion site infection (20) and accelerated ketoacidosis (21) caused concern. However, the risk of these problems is considerably reduced if patients are properly supervised, and perform frequent self-monitoring of blood glucose (SMBG) (22). Indeed, it was noted that factors such as insufficient blood glucose monitoring, failure to detect mechanical problems, failure to adhere to sick day management guidelines and delay in seeking medical assistance contribute to the risk of ketoacidosis (23). All of these factors can be minimised with careful patient selection, and thorough education and training.
The recently introduced insulin analogue insulin lispro is stable in subcutaneous insulin infusion systems (24) and has been reported to improve glycaemic control without increasing the risk of hypoglycaemia (25). Whilst there remains the possibility that metabolic deterioration may be accelerated on interruption of insulin delivery when using insulin lispro, its rapid action more effectively help correct this state (26).
Insulin pump therapy today
In recent years, insulin pump technology has improved considerably. Today's pumps such as the DANA R from Sooil are smaller and less complicated to use and have advanced safety features and alarms. In addition developments in infusion technology have reduced the potential for blockage of the tube and hence the risk of ketoacidosis. The potential complications of ketoacidosis and infusion site problems can be minimized through careful selection of patients, proper education, adequate self-care skills and appropriate hygiene precautions. The American Diabetes Association recognize that CSII is as safe as multiple injection therapy, when recommended procedures are followed (27).
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27. American Diabetes Association. Continuous Subcutaneous Insulin Infusion. Position Statement. Diabetes Care 2000;23(Suppl 1):S90.