Diabetes Care, Vol 15, Issue 7 877-885, Copyright © 1992 by American Diabetes Association
Clinical trial of programmable implantable insulin pump for type I diabetes
JL Selam, P Micossi, FL Dunn and DM Nathan
Department of Medicine, University of California, Irvine.
OBJECTIVE--The first step in the evolution of an artificial pancreas is the
development of a reliable implantable pump for insulin delivery. Despite
recent advances, significant issues remain, including small size of studies
and frequent irreversible catheter obstructions. We report safety,
feasibility, and efficacy results from 56 patients, representing 73
patient-yr of pump experience, entered into a multicenter trial with a new
implantable programmable pump. RESEARCH DESIGN AND METHODS--All patients
had insulin-dependent (type 1) diabetes, were 38 +/- 8 yr old, and were not
prone to severe hypoglycemia. The pump (Infusaid 1000) has a pulsatile
mechanism powered by freon-vapor pressure. Its rate is regulated by
battery-powered valves, operated via a hand-held programmer. The pump is
refilled transcutaneously with 25 ml U100 insulin (Hoechst 21PH) on a
monthly basis and has a second septum (side port) proximal to the catheter,
which allows flushing the catheter or lavaging the pump unit. The pumps
were implanted after 3 mo intensive subcutaneous insulin therapy and
catheters were positioned either in the peritoneum (i.p., n = 38) or the
superior vena cava (i.v., n = 18). RESULTS--All implanted pumps have
functioned safely with no instance of overdelivery or stoppage. The most
frequent complications were flow slow downs, presumably due to insulin
precipitation within the pump, which occurred in 86% of pumps and were
resolved in all but one case by lavaging the pump in situ with alkaline
solution. Flow slow downs due to catheter obstruction occurred in 52% of
the intravenous catheters but only 21% of the intraperitoneal catheters (P
less than 0.05) and were resolved in all but two cases by diluent flushing
through the sideport. Incidence of severe hypoglycemia decreased from 0.47
before implant to 0.05 episodes/patient-yr after pump implantation (P less
than 0.001). Mean HbA1c fell from 7.4 +/- 1.2% after intensive subcutaneous
therapy to 7.1 +/- 1.0% 12 mo after implantation. Only 2 patients withdrew
from study after recurrent catheter problems, and quality-of-life
questionnaires showed improvement in satisfaction with diabetes-specific
quality of life when on implantable pump therapy. CONCLUSIONS--Insulin
therapy with implantable pumps is effective and safe for periods up to 1.7
yr with a decreased risk of severe hypoglycemia than with intensive
subcutaneous insulin therapy.