Unchanged insulin absorption after 4 days' use of subcutaneous indwelling catheters for insulin injections.

Abstract

Since 1985, we have used indwelling catheters (Insuflon, Maersk Medical, Lynge, Denmark; Chronimed, Minnetonka, MN) to lessen pain when injecting insulin. However, some patients experience a rise in blood glucose after using indwelling catheters for a few days. We therefore studied the absorption of 125I-labeled insulin when using indwelling catheters. Five men and five women participated (age 18-25 years, C-peptide negative, HbA1c 9.0 +/- 1.0% [mean +/- SD, DCA-2000 method], diabetes duration 5-21 [median 9.5] years). After thyroid blockage with potassium iodide, we injected 5IU of 125I-labeled short-acting insulin subcutaneously in the abdomen ("ordinary injection") and 5 IU on the contralateral side through an indwelling catheter ("catheter injection"). The injection/insertion area was free of lipohyper- and lipohypotrophies. Disappearance rate was measured for 180 min with a gamma camera. The patients injected all premeal injections of short-acting insulin through the same indwelling catheter in the following 4 days. The investigation procedure was repeated day 3 and 5. We found no statistically or clinically (95% CI) significant difference in residual activity of 125I-insulin after 60 min or in time for 50% of the injected depot to disappear (T-50%) among catheter injections on day 1, 3, and 5; ordinary injections on days 1, 3, and 5; or catheter and ordinary injections on days 1, 3, and 5, respectively. HbA1c correlated both to T-50% (r = 0.73, P = 0.016) and residual activity of 125I-insulin after 60 min (r = 0.69, P = 0.028), indicating that patients with a slower absorption will have a less ideal metabolic control when using premeal bolus injections. We conclude that using indwelling subcutaneous catheters for insulin injections for up to 4 days does not affect the absorption of short-acting insulin.