Activity of intraperitoneal heparin during peritoneal dialysis.

A pharmacokinetic study of intraperitoneal heparin was undertaken in eleven chronic renal failure patients as a guide for its therapeutic use in peritoneal dialysis. The intraperitoneal heparin was assayed as the activated-partial-thromboplastin time (A-PTT) of peritoneal aspirate or outflow dialyzate added to control plasma. This was noted to decay relatively slowly, the mean t 1/2 of heparin in the peritoneal cavity being 10.8 +/- 0.93 hr. The heparin cofactor antithrombin III determined by both immunological and functional methods was found to be present in low concentration in residual peritoneal fluid aspirated prior to commencing dialysis. Generally this was less than one-third of normal plasma values, and with the repeated dilution and outflow sequences of dialysis the cofactor concentrations rapidly fell to negligible levels that were incapable of activating any heparin present. Systemic blood coagulation was unaffected by single 10000 U doses of heparin administered intraperitoneally in that plasma A-PTT values were not lengthened when measured over the ensuing six hours.