Bariatric surgery affects postoperative warfarin dosing

A small study of patients undergoing bariatric surgery suggests that weekly warfarin doses can change by as much as 20% postoperatively.

The study included 27 patients who were matched, by age and date of surgery, with patients who underwent other abdominal surgeries. The main end point of the study was change in warfarin dose from baseline, measured at weekly postoperative intervals from weeks one to eight and again at months three and six.

After surgery, patients in the bariatric surgery group had statistically significant decreases in weekly warfarin doses compared to preoperative dose, at all postoperative time points except at six months. No statistically significant decreases in warfarin dose were detected at any postoperative time points in the control group. Twenty patients (74.1%) in the bariatric surgery group experienced a decrease of 20% or more in weekly warfarin dose compared with 19 patients (32.2%) in the control group. No significant differences in warfarin-related adverse events were noted between groups.

Source: Irwin AN, McCool KH, Delate T, Witt, DM. Assessment of warfarin dosing requirements after bariatric surgery in patients requiring long-term warfarin therapy. Pharmacotherapy. June 6, 2013; DOI:10.1002/phar.1307.

CHA₂DS₂-VASc score gives better prediction of stroke risk in AF

Further data have just been presented in Europe confirming that the CHA₂DS₂-VASc score is preferable to the CHA₂DS₂ score in identifying patients with atrial fibrillation (AF) at very low risk for stroke.

In the AFNET (German Competence Network on Atrial Fibrillation) registry, which included 8,847 patients with nonvalvular AF, more than one-third of the strokes or other thromboembolic events that occurred in the mean follow-up period of five years were in patients assigned a CHA₂DS₂ score of 0 or 1. The CHA₂DS₂ score assigns point values of 1 for age >75, CHF, diabetes, and hypertension, and a point value of 2 for previous stroke or TIA. Anticoagulation is indicated for scores of 2 or above, but is not definitively recommended for scores of 0 or 1.

In contrast, use of the CHA₂DS₂-VASc score, which adds points for age 65 to 74 years, vascular disease, and female sex as stroke risk factors to the CHADS₂ score, led to the reclassification of more than half of the patients with CHADS₂ scores 0 or 1 to a CHA₂DS₂-VASc score of 2 and higher, for whom oral anticoagulation is the recommended treatment. Only eight strokes and other thromboembolic events were observed in patients classified as CHA₂DSv-VASc 0 at baseline (excluding strokes occurring in association with cardioversion or ablation).

Pharmacists who manage anticoagulation on an inpatient or outpatient basis can play an important role with their patients by continually updating risk factors as patients age or develop new medical problems. They can also help create more awareness of the utility of the CHA₂DS₂-VASc scoring system. Monitoring of these clinical changes during follow-up and recommendation of anticoagulation and other therapies as needed may save lives.

Source: Hughes S. CHA₂DS₂-VASc Score Best for Stroke Risk Assessment in AF. European Society of Cardiology (ESC) Congress 2013. Abstract 4381. Presented September 3, 2013. http://www.medscape.com/viewarticle/811332. Accessed September 29, 2013.

Edoxaban noninferior to warfarin; bleeding risks lower

According to results of a recently reported trial, edoxaban, a new factor Xa inhibitor, is noninferior to standard warfarin therapy for the prevention of venous thromboembolism (VTE).

The study (Hokusai-VTE) enrolled over 8,000 patients with both provoked (following surgery or immobilization) and unprovoked VTE, with a broad spectrum of VTE manifestations. Participants received initial subcutaneous LMWH before randomization to 60-mg edoxaban daily (reduced to 30 mg for those considered at higher risk of bleeding or with low body weight), or warfarin (target INR 2-3) for three to 12 months.

Results showed that the primary (noninferior) end point of recurrent symptomatic VTE occurred in 3.2% of patients taking edoxaban and 3.5% taking warfarin. In the subgroup with pulmonary embolism, however, recurrent events occurred in 3.3% taking edoxaban and 6.2% taking warfarin.

The rate of clinically relevant bleeding events was 8.5% for edoxaban compared to 10.3% for warfarin. This included zero fatal and five nonfatal intracranial bleeds with edoxaban, compared to six fatal and 12 nonfatal intracranial bleeds with warfarin.

Source: Hokusai VTE investigators. Edoxaban vs. warfarin for the treatment of symptomatic venous thromboembolism. N Engl J Med. 369:1406-1415; October 10, 2013; DOI: 10.1056/NEJMoa1306638.http://bit.ly/hokusaiVTE. Accessed September 28, 2013.