When Should Low-Molecular-Weight Heparin Be Stopped Preoperatively?

Patients on warfarin therapy for certain conditions are often switched to bridging therapy with low-molecular-weight heparin before surgery. Researchers measured anti-factor Xa heparin levels just before surgery in 80 patients whose warfarin therapy had been replaced with twice-daily LMWH 3 days earlier; the final dose was given on the eve of surgery.

At a mean of 97 minutes before surgery, 99% of patients had detectable anti-Xa heparin levels, and 68% had levels greater than 0.5 U/mL. Major bleeding occurred in one patient who resumed warfarin and LMWH the morning after a colonoscopy and polypectomy. Another patient, who had atrial fibrillation and a mechanical mitral valve, had an INR of 2.4 when he experienced a stroke 8 days after surger…