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Brief Communication: Preoperative Anticoagulant Activity after Bridging Low-Molecular-Weight Heparin for Temporary Interruption of Warfarin
- Martin J. O'Donnell, MB;
- Clive Kearon, MB, PhD;
- Judy Johnson, RN;
- Marlene Robinson, RN, BScN;
- Michelle Zondag, RN;
- Irene Turpie, MB, MSc; and
- Alexander G. Turpie, MB
Abstract
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.
Article and Author Information
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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.
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Potential Financial Conflicts of Interest: None disclosed.
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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.
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Current Author Addresses: Dr. O'Donnell: Henderson Research Centre, 70 Wing, Room 220, 711 Concession Street, Hamilton, Ontario L8V 1C3, Canada.
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Dr. Kearon: Henderson General Hospital, 70 Wing, Room 39, 711 Concession Street, Hamilton, Ontario L8V 1C3, Canada.
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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.
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Dr. I. Turpie: St. Joseph's Centre for Ambulatory Health Services, 2757 King Street East, Hamilton, Ontario L8G 5E4, Canada.
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Author Contributions: Conception and design: M.J. O'Donnell, C. Kearon, I. Turpie, A.G. Turpie.
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Analysis and interpretation of the data: M.J. O'Donnell, C. Kearon.
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Drafting of the article: M.J. O'Donnell, C. Kearon, I. Turpie, A.G. Turpie.
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Critical revision of the article for important intellectual content: M.J. O'Donnell, C. Kearon, A.G. Turpie.
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Final approval of the article: M.J. O'Donnell, J. Johnson, C. Kearon, M. Robinson, I. Turpie, A.G. Turpie, M. Zondag.
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Collection and assembly of data: J. Johnson, M. Robinson, M. Zondag.
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