The effects of operative stress on the coagulation profile.

There is a tendency toward hypercoagulability in the postoperative period. This is manifested by changes in a number of coagulation parameters, and if not offset by some protective mechanism, thrombosis may occur. This protection appears to be mediated more through the fibrinolytic mechanism than through the action of antithrombin 3 (AT-3) because AT-3 activity diminishes in the early postoperative period. The introduction of variables such as invasion of the vascular system, intraoperative heparin administration, administration of whole blood, and insertion of a Dacron prosthesis does not appreciably affect the response of the coagulation profile to operative stress.