Insulin adsorbance to polyvinylchloride surfaces with implications for constant-infusion therapy.
Because of the current interest in constant intravenous infusions of insulin for hyperglycemic conditions, we have re-examined the problem of insulin adsorption to the solid surfaces of commonly used infusion sets. Using both labeled and unlabeled insulin, we have compared solutions with and without albumin through various methods of delivery. An infusion system incorporating a 50-ml. wash-out with a solution of 25 U. regular insulin in 500 ml. normal saline permits delivery of at least 75 per cent of expected insulin for the first 50 ml. of the infusion and 100 per cent thereafter. After the first 20 ml. of the infusion, the per cent insulin recovered from the system is identical to that observed when albumin was added to the infusion solution at a concentration of 1.25 gm. per cent. From these date, we conclude that if an insulin concentration of at least 25 U./500 ml. is used, and if 50 cc. is washed through the infusion apparatus before treatment of a hyperglycemic patient is instituted, no extra protein additives are necessary.