A Systematic Review of Warfarin Use in Post-Bariatric Surgery Patients: Cases Compiled From a Literature Review

Objective The objective of this review was to provide dosing recommendations for percentage change in weekly warfarin dose and rates of thrombotic and bleeding events in patients requiring long-term warfarin therapy after bariatric surgery. Data Sources: A comprehensive literature search of PubMed (through April 5, 2021), Cochrane Library, and Google Scholar (through April 5, 2021) databases was completed using the keywords warfarin OR vitamin k antagonist AND bariatric surgery. Study selection and data extraction: Retrospective studies and matched-cohort studies evaluating preoperative and postoperative use of warfarin after bariatric surgery for obesity were considered. Weekly dose defined as sum of daily doses of warfarin for 7 consecutive days was a required outcome to be considered in this review. Patients were excluded from review if post-operative dosage change was not reported. Data synthesis Six studies were included with a total of 160 patients who met the criteria. A decrease in average warfarin dose was seen in all studies, with the largest decrease occurring at 1 month postsurgery followed by an upward trend toward baseline about 90 days postsurgery. While thrombotic events were observed in none of the patients, there was an increased risk of bleeding in patients, particularly in those who underwent roux-en-y gastric bypass (RYGB) surgery. Relevance to patient care and clinical practice The study provides a specific warfarin dosing titration regimen, as well as embolic and bleed risk in post-bariatric surgery population. Conclusions Clinicians may consider lowering warfarin weekly dose by about 25% immediately postsurgery, with doses approaching closer to baseline about 90 days postsurgery.