Insulin pump proves better than traditional injections
New VA study shows quality of life advantages
For diabetics, a new insulin delivery system shows promising results when compared to the conventional multiple daily insulin (MDI) injections. Called the implantable insulin pump (IIP), the new technology controlled noninsulin-dependent diabetes mellitus on par with or better than the MDI method in a clinical trial conducted at seven Veteran Affairs medical centers throughout the country.1 Also, IIP demonstrated other significant advantages such as reductions in glycemic variability, incidents of clinical hypoglycemia, and weight gain.
IIP vs. MDI
The study comparing the two methods indicated there were reductions in critical blood glucose levels. However, IIP reduced both blood glucose fluctuations and incidence of mild clinical hypoglycemia by 68% in the latter. The findings are significant, says Christopher Saudek, MD, of Johns Hopkins University School of Medicine in Baltimore.
"We have been using implantable insulin pumps for 10 years, but this is the first time we have had formally controlled testing to compare the two systems," says Saudek.
For one year, 121 diabetic patients were studied. All patients were type II diabetics, male, and between 40 and 59 years old. They required intensive therapy or up to four doses of insulin daily. At each site, patients were randomly assigned to either MDI or IIP therapy. Both groups received 20 days of diabetes education and instruction in the use of both therapies. For the 62 patients receiving MDI therapy, multiple doses were prescribed. Patients were provided syringes, insulin vials, and a finger-strike glucose meter, which replaced manual diaries. When required, their doses were adjusted according to glucose levels, food intake, and physical activity.
"We were able to individualize a program [of insulin injection] for each patient," says James W. Anderson, MD, principal investigator at the Omaha (NE) Veteran Affairs Medical Center, one of the participating centers in the study.
The 59 patients on IIP therapy also were equipped with a glucose meter and a pump communicator, a remote control device which signaled the pump to release insulin.
The pump itself is an 8.1 cm-diameter disk, weighing 220 g with a reservoir capable of holding 6,000 units of insulin. It was refilled during follow-up clinic visits every two to three months.
"The pump allowed us to get a higher concentration of insulin in a smaller space," says Anderson. "The pump also released small amounts of insulin consistent with the small levels that the pancreas produces."
Three areas evaluated in study
Throughout the one-year study, researchers charted data in three critical areas: glycemic control, hypoglycemic incidents, and weight gain. Both groups demonstrated a significant decrease in average daily blood glucose levels, hovering at 8.3%. A level of 8% is optimum.
However, members of the IIP group had fewer hypoglycemic events than their MDI counterparts. Definite mild hypoglycemic events were reduced by 68%, suspected mild by 66%, definite severe by 87.5%, and suspected severe hypoglycemic events by 74%.
According to the study, IIP users experienced weight loss, while MDI patients experienced the opposite. On average, IIP patients lost 1 kg throughout the one-year clinical trial, and MDI patients gained 0.36 kg.
However, the most significant distinction was identified as "quality of life" issues, such as the psychological impact of the disease and overall satisfaction with the therapy methods, which was assessed by a patient questionnaire. Researchers originally hypothesized that IIP patients may experience increased worry or negative impacts because the pump was untested and even involved elective surgery. However, in IIP patients, some quality of life indicators such as the "freedom from daily insulin injections and ease of use and predictability" offset those concerns.
"Within the IIP group, the patients had very good control of the disease," said Dianna Dunning, RN, who monitors the 16 study subjects at the Medical Center. "Psychologically, it empowered the patient."
That is not to say there weren’t some flaws in the IIP delivery system. Perhaps, the most frequent difficulty was the catheter which fed insulin into the patient’s peritoneal area. Blockage of the catheter occurred when microprecipitates or crystallized insulin accumulated. There were 26 instances of underdelivery of insulin in 24 individual subjects, or 25% of the study patients, due to the microprecipitates.
Blockage of pump corrected
The blockage was dissolved with a nonsurgical rinse, and patients were managed with subcutaneously delivered insulin until the problem was corrected. Other problems included a communicator alarm malfunction and a correctable loss of telemetry.
When the costs of the two therapies were compared, MDI was superior. For the study, researchers pegged MDI’s cost at $75,000. IIP therapy, which included 51 pumps, insulin, catheters, replacements pumps, service, and all other costs, reached $510,000.
While the study demonstrated the efficacy of IIP therapy, the pump, manufactured by MiniMed Technologies in Sylvan, CA, is not commercially available. However, it may be evaluated by the Rockville, MD-based U.S. Food and Drug Administration in 1997, researchers say.
Reference
1. Saudek, CD, Duckworth WC, et al. Implantable Insulin Pump vs. Multiple-Dose Insulin for Non-Insulin Dependent Diabetes Mellitus. JAMA 1996; 276:1,322-1,327.
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