INSULIN UNDERDELIVERY FROM IMPLANTED PUMPS USING PERITONEAL ROUTE - DETERMINANT ROLE OF INSULIN PUMP COMPATIBILITY

OBJECTIVE - To evaluate the incidence and investigate determinants of insulin underdelivery events occurring with implanted pumps using peri toneal route from a 103 patient-year experiment. RESEARCH DESIGN AND M ETHODS - Of the MiniMed (MIP 2001) pumps implanted in 47 type I diabet ic patients, 70 were refilled quarterly with four successive batches ( A, B, C, D) of U400 Hoechst 21 PH neutral insulin during a 3-year stud y period. Any reduction of insulin flow rate >15% was considered as ab normal insulin delivery. Diagnosis of the cause of underdelivery was e stablished according to the response to the following steps: 1) 0.01 m ol/l NaOH rinse of pump circuits to solubilize insulin aggregates, 2) surgical examination and replacement of blocked catheters, and 3) post surgical 0.01 mol/l NaOH rinse of pump. Step 2 was selected first ii t he increase of insulin requirements or reduction of flow rate were >50 %. Relative contributions of insulin and the implanted system to under delivery events were analyzed. RESULTS - There were 76 episodes of ins ulin underdelivery that occurred during the study, resulting in an inc idence of 74 events per 100 patient-years. Of 52 NaOH pump rinses, 30 restored normal flow rate. Surgery, performed after rinse failure (n = 22) or as the first step (n = 24), disclosed catheter blockages due t o tip obstructions in 28 cases and omental encapsulations in 18 other cases. Five combined severe reductions of pump flow rate requiring pum p replacements were diagnosed during surgery, and additional NaOH rins es had to be performed after catheter change in 12 other cases. Analys is of the incidence of underdelivery events indicated that both pump- and catheter-related problems were significantly increased while impla nted systems infused batches B, C, and D versus batch A (P < 0.01), wh ereas the duration of pump implantation had no significant influence. CONCLUSIONS - Underdelivery events constitute serious limiting obstacl es to prolonged peritoneal insulin infusion from implanted pumps. Prog ress in insulin pump compatibility is expected to reduce their occurre nce and, thus, to improve the feasibility of this treatment.