J Thorac Cardiovasc Surg 2004;128:327-328
© 2004 The American Association for Thoracic Surgery
Use of enoxaparin in cardiac surgery
Marco Pocar, MD, PhDa,
Alessio Assaghi, MDa,
Francesco Donatelli, MDa
a Cattedra di Cardiochirurgia, Università degli Studi di Milano, Policlinico MultiMedica, Milan, Italy
To the Editor:
We congratulate Dr Medalion and coworkers1 for the results reported in their study recently published in the Journal that focused on the effects of enoxaparin in patients undergoing coronary operations. The optimal administration of low-molecular-weight heparin in cardiac surgery is a controversial issue.2,3 The use of enoxaparin in patients with prosthetic valves has also been recently described.4,5 Because we have routinely used enoxaparin both preoperatively and postoperatively in nonemergency cardiac patients at our institution during the last 5 years, we would like to outline some aspects of our experience.
When we started using enoxaparin in 1998, we had some concerns related to the potential bleeding hazards. Although we never measured anti-factor Xa activity, we did not experience any major bleeding complications that could primarily be related to the use of enoxaparin itself, and we gradually developed a simplified protocol (Table 1), which is, however, significantly different from the one described. Doses of preoperative enoxaparin are much lower, and antiplatelet therapy is stopped on admission. On the other hand, a low dose of enoxaparin is given to all patients awaiting surgical intervention once daily (twice daily if the dose exceeds 4000 U/d). Also, patients who could potentially be stabilized with higher doses of enoxaparin and treated on an urgent basis, typically patients with coexistent left main disease and unstable angina, are instead treated as emergency cases and, as such, receive unfractionated heparin infusion until transfer to the operating room. Enoxaparin is also used after surgical intervention to minimize thromboembolic complications until a satisfactory international normalized ratio is attained in patients receiving oral anticoagulation and to prevent deep venous thrombosis.
In the study cited above,1 although it is clear that patients classified as emergency cases receive heparin infusion, the authors do not specify when to administer subcutaneous enoxaparin versus intravenous heparin in urgent cases. The level of anticoagulation and the laboratory tests used (eg, partial thromboplastin time and activated clotting time) in patients receiving intravenous heparin are also not reported, and this might influence the measurements of anti-factor Xa activity at skin incision. Although results might be biased by a special accuracy in surgical hemostasis in patients enrolled in the study, bleeding rates were low in all subgroups despite high doses of enoxaparin (1 mg/kg twice daily), administration of enoxaparin late until surgical intervention (8.7 ± 0.75 hours preoperatively), and nonwithdrawal of aspirin.
In conclusion, we agree with the authors that the use of enoxaparin before routine cardiac operations appears safe as far as major bleeding complications are concerned. Probably this consideration also applies to the early postoperative period; in this respect administration of high-dose enoxaparin (1 mg/kg twice daily) has recently been reported after mechanical valve implantation as a bridge to satisfactory oral anticoagulation.5 Finally, higher doses might be justified in some subsets of critically ill patients undergoing coronary operations, although a clear cutoff indication between subcutanous enoxaparin versus heparin infusion remains to be elucidated. In our opinion caution is advised because the benefits of high-dose enoxaparin might be outweighed by the risks related to a less aggressive attitude toward unstable patients awaiting coronary bypass surgery.
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References
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- Medalion B, Frenkel G, Patachenko P, Hauptman E, Sasson L, Schachner A. Preoperative use of enoxaparin is not a risk factor for postoperative bleeding after coronary artery bypass surgery. J Thorac Cardiovasc Surg. 2003;126:1875–1879[Abstract/Free Full Text]
- Kincaid EH, Monroe ML, Saliba DL, Kon ND, Byerly WG, Reichert MG. Effects of preoperative enoxaparin versus unfractionated heparin on bleeding indices in patients undergoing coronary artery bypass grafting. Ann Thorac Surg. 2003;76:124–128[Abstract/Free Full Text]
- Jones HU, Muhlestein JB, Jones KW, Bair TL, Lavasani F, Sohrevardi M, et al. Preoperative use of enoxaparin compared with unfractionated heparin increases the incidence of re-exploration for postoperative bleeding after open-heart surgery in patients who present with an acute coronary syndrome: clinical investigation and reports. Circulation. 2002;106(suppl I):I19–22
- Ferreira I, Dos L, Tornos P, Nicolau I, Permanyer-Miralda G, Soler-Soler J. Experience with enoxaparin in patients with mechanical heart valves who must withhold acenocumarol. Heart. 2003;89:527–530[Abstract/Free Full Text]
- Fanikos J, Tsilimingras K, Kucher N, Rosen AB, Hieblinger MD, Goldhaber SZ. Comparison of efficacy, safety, and cost of low-molecular-weight heparin with continuous-infusion unfractionated heparin for initiation of anticoagulation after mechanical prosthetic valve implantation. Am J Cardiol. 2004;93:247–250[Medline]
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References