The lack of effect of a prophylactic dose of enoxaparin on thrombin generation in patients subjected to nephrectomy because of kidney cancer.

It is assumed that major surgery, connected with extensive tissue dissection, brings about the release of tissue factor into circulation and subsequent activation of coagulation system. This activation results in the thrombin generation, which is supposed to be suppressed by the low-molecular-mass heparins (LMMH), administered to the surgical patients as the prophylaxis against postoperative venous thromboembolism. We have estimated the concentration of circulating thrombin-antithrombin (TAT) complex in patients subjected to transperitoneal nephrectomy and randomized into controls and who received 40-mg enoxaparin 12 h before and 12 h after the operation and then once daily for 7 days. We have observed a sharp rise of TAT concentration at the end of surgery and it corresponded to the simultaneous drop of antithrombin (AT) activity. TAT concentration gradually decreased and AT activity increased up to the end of observations on the seventh postoperative day, but there were no differences observed between the groups of patients. We have also observed a biphasic increase of plasmin-plasmin inhibitor (PPI) complex concentration in our patients. Again, there were no differences in PPI between the groups of patients. It is our conclusion that under the conditions of this study, the well-known prophylactic effect of enoxaparin against the venous thromboembolic complications was not mediated by the inhibition of intraoperative thrombin generation. The anti-inflammatory or biophysical influence of LMMH may be rather taken into account in surgical patients receiving prophylactic doses of these heparins.