Brief Communication: Preoperative Anticoagulant Activity after Bridging Low-Molecular-Weight Heparin for Temporary Interruption of Warfarin

6 February 2007 | Volume 146 Issue 3 | Pages 184-187

Background: Preoperative low-molecular-weight heparin (LMWH) is often used when warfarin therapy is interrupted for surgery.

Objective: To determine the preoperative anticoagulant activity of LMWH following a standardized "bridging" regimen.

Design: Prospective cohort study.

Setting: Single university hospital.

Patients: Consecutive patients who had warfarin therapy interrupted before an invasive procedure.

Intervention: Enoxaparin, 1 mg/kg of body weight, twice daily. The last dose was administered the evening before surgery.

Measurements: Blood anti–factor Xa heparin levels measured shortly before surgery.

Results: Preoperative anti-Xa heparin levels were obtained in 80 patients at an average of 14 hours after the last dose of enoxaparin was administered. The average anti-Xa heparin level was 0.6 U/mL. The anti-Xa heparin level, measured shortly before surgery, was 0.5 U/mL or greater in 54 (68%) patients and 1.0 U/mL or greater in 13 (16%) patients. A shorter interval since the last dose (P < 0.001) and a higher body mass index (P = 0.001) were associated with higher preoperative anti-Xa heparin levels.

Limitations: The small sample size limits accurate estimates of the frequency of the clinical outcomes. A single regimen of LMWH was evaluated.

Conclusions: Anti-Xa heparin levels often remain high at the time of surgery if a last dose of a twice-daily regimen of LMWH is given the evening before surgery.

Editors' Notes Context Twice-daily low-molecular-weight heparin (LMWH) is commonly used as bridging therapy when warfarin anticoagulation is interrupted before surgery. Usual practice is to give the last dose of LMWH 12 to 24 hours before surgery. Contribution These investigators found that two thirds of 80 patients who received their last dose of enoxaparin at a mean 14 hours before surgery had markedly elevated anti-Xa heparin levels shortly before surgery was scheduled to begin. Caution Administering the final dose of a twice-daily regimen of enoxaparin on the evening before surgery does not allow adequate time for elimination of the anticoagulant activity. Implications Potential risks for hemorrhage or thromboembolism could not be evaluated in this small group. Results may differ for other LMWH preparations. —The Editors

 

Author and Article Information

From McMaster University and Hamilton Health Sciences Foundation, Hamilton, Ontario, Canada.

Grant Support: This project was funded by an unrestricted grant from the Hamilton Health Sciences Foundation, Hamilton, Ontario, Canada. Drs. Kearon and O'Donnell are supported by the Canadian Institutes of Health Research.

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: Martin J. O'Donnell, MB, Henderson Research Centre, McMaster University, 70 Wing, Room 220, 711 Concession Street, Hamilton, Ontario L8V 1C3, Canada; e-mail, odonnm{at}mcmaster.ca.

Current Author Addresses: Dr. O'Donnell: Henderson Research Centre, 70 Wing, Room 220, 711 Concession Street, Hamilton, Ontario L8V 1C3, Canada.

Dr. Kearon: Henderson General Hospital, 70 Wing, Room 39, 711 Concession Street, Hamilton, Ontario L8V 1C3, Canada.

Dr. A.G. Turpie, Ms. Zondag, Ms. Robinson, and Ms. Johnson: Thrombosis Clinic, McMaster Clinic Building, 6th Floor, Hamilton General Hospital, 237 Barton Street East, Hamilton, Ontario L8L 2X2, Canada.

Dr. I. Turpie: St. Joseph's Centre for Ambulatory Health Services, 2757 King Street East, Hamilton, Ontario L8G 5E4, Canada.

Author Contributions: Conception and design: M.J. O'Donnell, C. Kearon, I. Turpie, A.G. Turpie.

Analysis and interpretation of the data: M.J. O'Donnell, C. Kearon.

Drafting of the article: M.J. O'Donnell, C. Kearon, I. Turpie, A.G. Turpie.

Critical revision of the article for important intellectual content: M.J. O'Donnell, C. Kearon, A.G. Turpie.

Final approval of the article: M.J. O'Donnell, J. Johnson, C. Kearon, M. Robinson, I. Turpie, A.G. Turpie, M. Zondag.

Collection and assembly of data: J. Johnson, M. Robinson, M. Zondag.

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