Ann Thorac Surg 2006;82:1574-1575
© 2006 The Society of Thoracic Surgeons
Correspondence
Reply
Heath U. Jones, BS,
Joseph B. Muhlestein, MD,
Kent W. Jones, MD,
Dale G. Renlund, MD,
Tami L. Bair, BS,
Thomas Jared Bunch, MD,
Benjamin D. Horne, PhD, MPH,
Donald L. Lappé, MD,
Jeffrey L. Anderson, MD,
Donald B. Doty, MD
Cardiovascular Department, LDS Hospital and University of Utah, Salt Lake City, UT 84143, Department of Medicine, Mayo Clinic, Mayo Foundation, Rochester, MN 55905
(Email: brent.muhlestein{at}ihc.com).
To the Editor:
We appreciate the interest that Kulik and colleagues [1] have shown in our article describing our observational findings of the hemorrhagic risk associated with postoperative anticoagulation after cardiac surgery [2]. We appreciate their careful critique and have performed further analysis, and we would like to respond to their comments.
In our study, we included all patients who received postoperative anticoagulation any time during the postsurgical hospital stay. Our database does not contain individual postoperative anticoagulation initiation times, but in general our institutional practice has been to initiate anticoagulation 24 to 48 hours after surgery. In most instances, among patients receiving postoperative anticoagulation, return to surgery occurred after the first 24 to 48 hours. Therefore we expect that this is after reinitiation of anticoagulation therapy. Unfortunately our database did not show the exact dose and route of unfractionated heparin administration, nor did it provide specific physician-reported indications for anticoagulation. The proportions of re-do operations among this cohort were 13%, 15%, and 17% in the none, unfractionated heparin, and enoxaparin groups, respectively (p = 0.09), but in the Cox regression adjustment for re-do operation, there is no meaningful confounding effect on the association of postoperative anticoagulants to reoperation. We also performed additional Cox regression adjusting for length of surgical procedure, and it had no meaningful effect on the association either. Adjustment for type of surgery did influence the association with changes in the hazard ratio for unfractionated heparin compared with none, from 2.46 before to 2.42, and for enoxaparin, from 2.31 before to 2.52. These changes did not provide a statistically significant change in the fit of the model. Therefore, after the additional adjustments recommended by Kulik and colleagues [1] we still reach the same conclusion reported in our original article (ie, early postoperative use of anticoagulation therapy [either unfractionated heparin or enoxaparin] is associated with a significant increase in surgical re-exploration for bleeding. However, certainly the presence of this modest but significant increased risk does not preclude the use of postoperative anticoagulation in special circumstances. It merely implies an imperative to perform an appropriate risk-benefit analysis regarding the question.
Our findings do not reveal significant differences in the overall incidence of re-exploration between enoxaparin and unfractionated heparin. Therefore we do not conclude that the higher re-exploration rate is solely attributable to enoxaparin. We merely commented on the interesting finding that patients receiving enoxaparin who required surgical exploration tended to present later than those receiving unfractionated heparin.
Finally, because of the significant limitations associated with any retrospective observational study such as ours, and as we acknowledge in the article, our findings should only be considered as generating hypotheses. We agree that prospective randomized studies are necessary to fully ascertain the relative risks and benefits of different anticoagulation regimens under a variety of clinical circumstances after cardiac surgery. We appreciate the efforts of Kulik and colleagues [1] in providing a systematic review of the available literature regarding early anticoagulation after mechanical valve replacement [3], and we look forward to reading it when it is published in The Annals of Thoracic Surgery.
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References
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- Kulik A, Rubens FD, Mesana TG, Lam B-K. Early postoperative anticoagulation: more questions than answers?(letter) Ann Thorac Surg 2006;82:1573-1574.[Free Full Text]
- Jones HU, Muhlestein JB, Jones KW, et al. Early postoperative use of unfractionated heparin or enoxaparin is associated with increased surgical re-exploration for bleeding Ann Thorac Surg 2005;80:518-522.[Abstract/Free Full Text]
- Kulik A, Rubens FD, Wells PS, et al. Early postoperative anticoagulation after mechanical valve replacement: a systematic review Ann Thorac Surg 2006;81:770-781.[Abstract/Free Full Text]
Related Article
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Early Postoperative Anticoagulation: More Questions Than Answers?
- Alexander Kulik, Fraser D. Rubens, Thierry G. Mesana, and B.-Khanh Lam
Ann. Thorac. Surg. 2006 82: 1573-1574.
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