Background: The trauma literature is inconsistent in its conclusions and recommendations concerning the influence of oral anticoagulation on outcomes after injury. Some report worse outcomes, whereas others showed no effect. We approached this problem by using the patients' admission international normalized ratio (INR) values to document anticoagulation and hypothesized that warfarin anticoagulation is associated with increased mortality after trauma in the elderly. We further questioned the cost-effectiveness of admission INR testing.
Methods: We conducted a retrospective review of 3,242 trauma patients aged 50 and older. INR data were used as a surrogate for warfarin anticoagulation and was related to age, sex, and Injury Severity Scale score (ISS) to analyze effects on mortality. Logistic regression was used to perform multivariate analyses. INR costs were summed from all laboratory department costs.
Results: Of the 3,242 elderly injured patients, admission INR was obtained in 1,251 patients. One hundred and two patients had an "elevated" INR of >1.5. Mortality for those with an INR >1.5 was 22.6%, versus 8.2% for those with an INR <1.5 (p < 0.0001). The logistic regression gave an age and ISS adjusted odds of death of 30% for a one unit increase in INR (OR 1.3, 95% CI 1.1-1.5; p value 0.002). This correlates to an age and injury score adjusted odds of death of 2.5 for an INR >1.5 (95% CI 1.2-4.2; p value 0.014). INR cost was estimated at $5 per blood draw.
Conclusion: After adjusting for age, gender, and ISS, anticoagulation was associated with increased overall mortality. Elderly patients are commonly anticoagulated and anticoagulation is a therapeutically reversible risk factor. Considering the increasing number of indications for and prevalence of anticoagulation, the low cost of an INR and the potential reduction in costs associated with traumatic brain injury, these data support the recommendation to assess a coagulation profile in elderly trauma patients to identify earlier those in need of closer monitoring and a more aggressive reversal of their anticoagulation.