SummaryExtrinsic coagulation pathway inhibitor may be an important regulator of haemostasis to prevent thrombosis after tissue damage. The functional activity of this inhibitor was determined using a chromogenic substrate assay, and compared to the activities of anti thrombin, heparin cofactor II and protein C during the perioperative period of elective hip replacement (n = 28), cholecystectomy (n = 11), and vascular surgery (n = 5). Peroperatively, all the inhibitors decreased rather similarly and to the same degree as the decrease in albumin concentration. The decreases during hip surgery were about 2-fold the decreases observed during cholecystectomy. A significant peroperative increase in extrinsic pathway inhibitor activity was observed in vascular surgery, probably due to a bolus injection of heparin. Antithrombin, heparin cofactor II and protein C levels normalized on days 3-5 postoperatively in all three patient groups. Sustained low levels of extrinsic pathway inhibitor were observed on postoperative days 1 to 7 in hip surgery patients. Apparently, extrinsic pathway inhibitor is not an acute phase reactant. In uncomplicated surgery, the decreases of the coagulation inhibitor levels are mainly due to hemodilution.
Coagulation testing in the perioperative period
