Postoperative Hypercoagulability, Detection And Measurement Using A Modified Recalcification Time System, Effects Of Low Dose Heparin And Types Of Surgery

Abstract

The purpose of the study was to demonstrate postoperative hypercoagulability and its possible prevention by low dose heparin (LDH). Healthy volunteers (with LDH), patients undergoing cholecystectomy (with & without LDH) and patients undergoing arterial reconstructive surgery with synthetic grafts (with LDH), were tested. All were tested 1, 3 & 5 hrs after LDH.Overall coagulability was determined by using platelet free plasma and a modified recalcification time system with a nefelometer to detect first fibrin formation. Recalcification times were measured before (T0) and after (TA) plasma activation against glass, in vitro. Heparin levels were determined with the Factor Xa inhibition test using a chromogenic substrate (CoatestR, Kabi).T0 and TA were prolonged after LDH in healthy volunteers. Cholecystectomy caused shortening of T0 and TA. This could be prevented by LDH, raising T0 to level recorded after LDH in normals. Patients receiving synthetic arterial grafts showed no prolongation of T0 and TA after surgery with LDH, but rather a shortening. These patients showed hypercoagulability in spite of LDH.It is concluded that postoperative hypercoagulability can be traced with the presented method and counteracted by LDH in patients undergoing cholecystectomy but not in patients receiving synthetic arterial grafts. All patients on LDH had similar heparin levels, determined with the Factor Xa inhibition test. Vascular surgery with synthetic grafting and Cholecystectomy seem to induce two different kinds of hypercoagulability, where the former is thought to be induced by the foreign surface. Subcutaneous heparin therapy (LDH) results in poor inhibition of surface induced coagulation, in vivo.