JOHN C PICKUP Guy’s Hospital Medical School, London

A major new approach to the improvements of metabolic control in insulin-dependent diabetic patients is the replacement of insulin by delivery systems which simulate non-diabetic insulin secretory patterns. In the last ten years a number of open-loop, extracorporeal, portable infusion pumps have been used in research trials lasting from a few days to several years. Routine treatment by insulin pumps is now being considered. Most infusers are syringe-drivers, although peristaltic and reciprocating pumps have also been employed. All are based on a slow, basal delivery rate, supplemented by insulin boosts at meal-times. The most popular infusion route is via the subcutaneous tissue. Technological development is concentrating on miniaturisation, alarms (such as low battery state and motor over-run) and more flexible/programmable delivery rates. Attempts are in progress to ‘close the loop ’ using an implanted glucose sensor. Most electrodes are ampero-metric or potentiometric enzyme sensors employing immobilised glucose oxidase. Encouraging in vivo results are being obtained from a novel amperometric biosensor which uses ferrocene to mediate electron transfer. The most likely implantation site is the subcutaneous tissue