Objective: To evaluate catheter survival and identify mechanisms involved in catheter obstructions during a 109.8 patient-year experience with implanted pumps for peritoneal insulin delivery.
Research design and methods: Fifty-one type I diabetic patients were recruited in feasibility studies of two models of implanted systems for peritoneal insulin delivery. Both systems had a silicone-coated polyethylene catheter and infused Hoechst 21 PH neutral insulin (U400 or U100). Catheter obstruction was suspected each time the increase of insulin flow rate over 50% of usual need was insufficient to correct an impairment of glycemic control in the absence of of intercurrent factors. A laparoscopic examination was then systematically performed under general anesthesia. The disclosed material occluding the catheter was submitted to a pathological analysis. By actuarial analysis, we examined the estimated effects of the potential determinants of the catheters' duration of proper operation on catheter survival.
Results: Over an implantation duration of 25.8 +/- 14.0 months (mean +/- SD), 34 catheter obstructions were diagnosed in 24 patients, resulting in an incidence of 31 events per 100 patient-years. Fifty percent survival rate of the first implanted catheter was 27 months (95% confidence interval [CI]: 19-32) on actuarial analysis. Six catheters were cleared under laparoscopy and 24 were replaced, while 2 systems were definitively explanted and 2 combined replacements of pump and catheter were performed because of an associated pump slowdown. In five cases, an alkaline rinse procedure of the pump was necessary after catheter replacement to restore usual insulin needs, suggesting an associated insulin aggregation in the pump. Twenty obstructions were due to a fibrin clot at the catheter tip, and 14 obstructions were created by a tissue encapsulation around the catheter. A previous experience of peritoneal insulin infusion from portable pumps or a longer duration of diabetes ( > 21 years) both appeared as conditions significantly reducing the time of a catheter's proper operation (P < 0.01 and P < 0.05, respectively) either by tip obstructions or by encapsulations. Pathological analysis of catheter encapsulations showed a collagen fibrosis in all studied patients (n = 11), which was associated with a lymphocytic infiltrate in five patients and also with anti-insulin immunoreactive amyloid deposits in four patients. Catheter tip clots were composed of fibrinlike material, nonreactive to anti-insulin antibodies.
Conclusions: Catheter obstruction is a frequent adverse technical event occurring with implanted insulin pumps. Progress is expected in the biocompatibility of catheter material and more specifically in the stability of insulin preparations to prevent immuno-inflammatory reactions and insulin amyloid deposits that appear to be involved in catheter failures.