A kinetic model of the circulatory regulation of tissue plasminogen activator during orthotopic liver transplantation

To better understand the regulation of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1) during liver transplantation, we used a computer model of the human circulatory system to simultaneously evaluate the effect of t-PA secretion, t-PA inhibition by PAI-I, hepatic c learance of t-PA, blood loss, transfusion and hemodynamics on t-PA and PAI- 1 levels during liver transplantation in three patients that differed in se verity of liver disease, blood loss and anhepatic changes in t-PA. Higher p reoperative t-PA. levels were primarily related to underlying liver disease and reduced hepatic clearance. During the anhepatic stage, when hepatic t- PA clearance was eliminated: (1) the expected rise in t-PA was modulated by the extent of bleeding, which acted as an alternate t-PA clearance mechani sm; and (2) the ratio of t-PA:PAI-I was increased due both to lower t-PA cl earance and reduced PAI-I secretion. Recirculation of the new liver was ass ociated with renewed clearance of t-PA, an acute phase increase in PAI-1 an d a drop in the t-PA:PAI-1 ratio. Understanding fibrinolytic regulation req uired simultaneous analysis of t-PA secretion, inhibition and clearance. An hepatic t-PA levels could be predicted based on preoperative liver function and surgical blood toss, which acted as an alternate t-PA clearance mechan ism. (C) 2000 Lippincott Williams & Wilkins.