Restoration and maintenance of intravenous insulin infusion in the vapor-pressure powered implantable infusion device.

Of the reasons to discontinue continuous implantable insulin pump therapy, flow rate reduction is the most common, occurring in 27 of 42 pumps in the University of Minnesota series. Thrombosis at the catheter tip appears to be a major reason for flow reduction. Six different procedures to restore flow in pumps were performed. Two of the procedures involve the infusion of an alkaline solution through the device, replacing the insulin/glycerol solution normally infused; the other four procedures are surgical ones involving manipulation of the catheter. In restoring flow the non-operative procedures achieved a success rate of 50%, having taken as long as 3 months to restore flow, and having allowed up to 1 year of further insulin pump therapy; flow in all the pumps so treated eventually decreased again. The operative procedures were nearly 100% successful, restored flow immediately, and allowed longer periods of adequate flow, but flow rate did again decrease. When flow rate reduction occurs further flow improvement procedures may be attempted without difficulty and are well tolerated. In implantable pumps the biocompatibility of the blood-catheter tip interface needs to be improved to deal with the recurrent problems of insulin infusion device flow rate decrease.