Clinical Twisters: Surgery when INR=2.8

An ambulatory 70-year-old man, F.H., has been admitted to your hospital with a hip fracture that will require surgery. Although F.H. has a history of atrial fibrillation (AF) episodes and transient ischemic attacks (TIA), his heart is currently in normal sinus rhythm. Medications on admission included verapamil 120 mg and warfarin 5 mg daily; fracture pain is being treated with morphine intramuscular (IM) injections at present. F.H.'s INR (International Normalized Ratio) on admission is 2.8; blood pressure is 135/75; lab tests were within normal limits. F.H.'s physician requests an anticoagulation consult to aid him in determining the timing of surgery and venothromboembolism (VTE) prophylaxis. What do you suggest?

Additionally, IM injections are not recommended in anticoagulated patients due to bleeding risk. An intravenous (IV) site should be established to deliver morphine if pain is not controlled with oral medication.

Ideally the surgeon will want INR <1.5 prior to surgery (considering bleeding and anesthesia options) and will want that within one to two days. I would recommend holding warfarin until after surgery and giving oral vitamin K 2.5 mg with the expectation that INR will correct within 24 hours, or if surgery will take place sooner, give fresh frozen plasma to reverse INR. The risk of VTE is high after hip fracture surgery, as is the risk of further arterial events, given AF and TIA history. Reinitiation of full anticoagulation postsurgery would be preferred.

For ease of dosing and administration, I would use full treatment doses of enoxaparin 1 mg/kg every 12 hours (or if necessary, for CrCl <30 ml/min 1 mg/ kg/day) until the INR is therapeutic. This should be initiated six to 12 hours postsurgery as long as hemostasis has been achieved. I'd choose enoxaparin over IV UFH. With regard to warfarin, because we know the currently stable regimen, we could restart 5 mg at bedtime the night of surgery or the next day, or consider giving 7.5 mg for two days, then continue with 5 mg at bedtime to help achieve therapeutic INR quicker and minimize the number of days giving LMWH.

Nancy L. Shapiro, Pharm.D., BCPSClinical Pharmacist, Ambulatory CareClinical Assistant Professor, Dept. of Pharmacy Practice, University of Illinois at Chicago