Plasma tissue factor pathway inhibitor levels as a marker for postoperative bleeding after enoxaparin use in deep vein thrombosis prophylaxis in orthopedics and general surgery

Low-molecular-weight heparins (LMWH) are widely used as antithrombotic prop hylactic pharmaceutical agents in orthopedic and general surgery. Their ant ithrombotic characteristics are expressed by plasma mediators such as anti- Xa, anti-IIa, and increased release of tissue factor pathway inhibitor (TFP I) from vascular endothelium. The purpose of this clinical research is to s tudy the relation between plasma levels of these mediators and postoperativ e bleeding. Forty-one consecutive patients undergoing hip or knee arthroplasty (n = 36) and colectomy (n = 5) received the standard enoxaparin (a LMWH) dose preop eratively (general surgery) or immediately postoperatively (orthopedic surg ery). Major bleeding was defined as a postoperative drop of greater than or equal to 5 g/dL) of hemoglobin. The authors observed that there was a line ar relationship between an increase in free/total TFPI ratio levels and pos toperative bleeding. When that ratio increased by >60%, the hemoglobin drop ped to >5 g/dL (n = 17). This relationship between free/total TFPI ratio increase and postoperative bleeding was statistically significant (P < 0.001). Those who did not bleed (hemoglobin drop was less than 5 g/dL) (n = 24) had a ratio increase (if a ny) of less than 50%. However, the authors did not observe any statistical relationship between anti-Xa, anti-IIa, or prothrombin time and postoperati ve bleeding in patients receiving LMWH for deep vein thrombosis prophylaxis in orthopedic and general surgery patients. The authors recommend a pre- a nd postoperative ratio level measurement whenever major bleeding is anticip ated, as adjustments of LMWH dose or frequency might be necessary.