The safety of warfarin therapy in the nursing home setting

PURPOSE: We examined the preventability of adverse warfarin-related events and potential adverse warfarin-related events ("near misses") in the nursing home setting. METHODS: We performed a cohort study of all long-term care residents of 25 nursing homes (bed size range, 90-360) in Connecticut during a 12-month observation period. The total number of residents in these facilities ranged from 2946 to 3212 per quarter. There were 490 residents who received warfarin therapy. Possible warfarin-related incidents were detected by quarterly retrospective review of nursing home records by trained nurse abstractors. Each incident was independently classified by 2 physician-reviewers to determine whether it constituted a warfarin-related event, its severity, and its preventability. The primary outcome was an adverse warfarin-related event, defined as an injury associated with the use of warfarin. Potential adverse warfarin-related events were defined as situations in which the international normalized ratio (INR) was noted to be 4.5 or greater, an error in management was noted, but no injury occurred. We also assessed time in specified INR ranges per nursing home resident day on warfarin. RESULTS: Over the 12-month observation period, 720 adverse warfarin-related events and 253 potential adverse warfarin-related events were identified. Of the adverse warfarin-related events, 625 (87%) were characterized as minor, 82 (11%) were deemed serious, and 13 (2%) were life-threatening or fatal. Overall, 29% of the adverse warfarin-related events were judged to be preventable. Serious, life-threatening, or fatal events occurred at a rate of 2.49 per 100 resident-months; 57% of these more severe events were considered preventable. Errors resulting in preventable events occurred most often at the prescribing and monitoring stages of warfarin management. The percentages of time in the less than 2, 2 to 3, and more than 3 INR ranges were 36.5%, 49.6%, and 13.9%, respectively. CONCLUSIONS: The use of warfarin in the nursing home setting presents substantial safety concerns for patients. Adverse events associated with warfarin therapy are common and often preventable in the nursing home setting. Prevention strategies should target the prescribing and monitoring stages of warfarin management. (c) 2007 Elsevier Inc. All rights reserved.