Thromb Haemost 1989; 62(03): 940-944
DOI: 10.1055/s-0038-1651032
Original Article
Schattauer GmbH Stuttgart

The Relationship between Anti-Factor Xa Level and Clinical Outcome in Patients Receiving Enoxaparine Low Molecular Weight Heparin to Prevent Deep Vein Thrombosis after Hip Replacement

M N Levine
*  The Departments of Medicine, Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ont., Canada
,
A Planes
+  The Clinique Radio-Chirurgicale du Mail, La Rochelle, France
,
J Hirsh
*  The Departments of Medicine, Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ont., Canada
,
M Goodyear
*  The Departments of Medicine, Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ont., Canada
,
N Vochelle
+  The Clinique Radio-Chirurgicale du Mail, La Rochelle, France
,
M Gent
*  The Departments of Medicine, Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ont., Canada
› Author Affiliations
Further Information

Publication History

Received: 21 November 1988

Accepted after revision 30 May 1989

Publication Date:
30 June 2018 (online)

Summary

Studies in experimental animals have demonstrated that there is a relationship between levels of low molecular weight (LMW) heparin and both bleeding and inhibition of thrombosis. The relationship between these outcomes and ex vivo anti-factor Xa levels has been examined in 163 patients undergoing total hip replacement who were given prophylaxis once daily with a LMW heparin (enoxaparine). Fifty patients received 60 mg of enoxaparine and 113 received 40 mg, both regimens being administered subcutaneously once daily. Blood samples for anti-factor Xa levels were collected 12 hours after the injection on the day of surgery and on days 1, 3 and 6, postoperatively. The incidence of wound hematoma was 5.3% when the maximum anti-factor Xa level was ≤0.2 units per ml, but increased to 24.5% when the anti-factor Xa level exceeded 0.2 units per ml, P = 0.0008. The incidence of postoperative thrombosis was low (6.3%) if the minimum anti-factor Xa level exceeded 0.1 units per ml, but increased to 14.6% when ≤0.1 units per ml, and to 18.8% if the anti-factor Xa level was ≤0.05 units per ml. Regression analysis revealed that there was a statistically significant relationship between anti-factor Xa level and wound hematoma, P = 0.002 and anti-factor Xa level and thrombosis, P = 0.03. These findings suggest that when enoxaparine is administered as a once daily subcutaneous injection, the 12 hour anti-factor Xa level should not exceed 0.2 units per ml to minimize bleeding and levels >0.05 units per ml should be obtained to optimize efficacy.