Inappropriate preinjury warfarin use in trauma patients: A call for a safety initiative

INTRODUCTION: Warfarin continues to be widely prescribed for a variety of conditions. It has been shown that preinjury warfarin may worsen outcomes in trauma patients. We hypothesized that a substantial proportion of injured patients seen at our institution were receiving preinjury warfarin for inappropriate indications and that a significant number of such patients had subtherapeutic or supratherapeutic international normalized ratios as well as increased mortality. MATERIALS AND METHODS: A retrospective review of registry data from a Level I trauma center was conducted for the period from January 2004 to July 2013. Included were patients aged ≥22 years (based on the youngest recorded patient on warfarin in this study). Abstracted variables included patient age, Injury Severity Score (ISS), Maximum Abbreviated Injury Score for Head (MAISH), mortality, hospital length of stay (HLOS), indication(s) for anticoagulant therapy, admission Glasgow Coma Scale (GCS), and admission international normalized ratio (INR). Suitability of warfarin indication(s) was determined using the most recent American College of Chest Physicians (ACCP) Guidelines. Inappropriate warfarin administration was defined as use inconsistent with these guidelines. For outcome comparisons, a case-control design with 1:1 ratio was used, matching patients taking preinjury warfarin to a random sample of trauma patients who were not taking warfarin. Severe traumatic brain injury (sTBI) was defined as MAISH ≥4. RESULTS: A total of 700 out of 14,583 patients aged ≥22 years were receiving preinjury warfarin (4.8% incidence, WG). This group was age- and ISS-matched with 700 patients (4.8% total sample) who were not taking warfarin (NWG) in a total case-control sample of 1,400. The two groups were similar in age, gender, ISS, and initial GCS. According to the ACCP guidelines, 115/700 (16.4%) patients in the warfarin group were receiving anticoagulation for inappropriate indications. Nearly 65% of the patients were outside of their intended INR therapeutic window (43.4% subtherapeutic, 21.6% supratherapeutic). Overall, median HLOS was greater among patients taking preinjury warfarin (4 days vs 2 days, P < 0.010). Mortality was higher in the WG (7.4% or 52/700) than in the NWG (1.9% or 13/700, P < 0.010). Patients with sTBI in the WG had significantly greater mortality (12.8% or 34/266) than those with sTBI in the NWG (5.3% or 9/169, P < 0.013). CONCLUSION: A significant proportion of trauma patients admitted to our institution were noted to take warfarin for inappropriate indications. Moreover, many patients taking warfarin had either subtherapeutic or supratherapeutic INR. Although warfarin use did not independently predict mortality, preinjury warfarin use was associated with greater mortality and HLOS in the subset of patients with sTBI. Safety initiatives directed at better initiation and management of warfarin are needed.