Patients who take warfarin are at higher risk of death if they sustain trauma than are those not on warfarin, regardless of type of injury, indication for anticoagulation, or comorbidities, according to a report published online Jan. 17 in Archives of Surgery.
This finding is particularly troubling because warfarin use is quite common, particularly among people over age 65, and is steadily increasing, said Dr. Lesly A. Dossett of Vanderbilt University, Nashville, Tenn., and her associates.
Noting that "no large multicenter trial has previously documented the prevalence of warfarin use among injured patients or its impact on mortality," the researchers assessed its use by analyzing data from the American College of Surgeons’ National Trauma Data Bank, a registry that compiles medical records from more than 770 participating trauma centers across the United States and Puerto Rico.
Dr. Dossett and her colleagues assessed 1,230,422 patients treated for injuries at 402 trauma centers between 2002 and 2007. Overall, 3% of patients in this cohort were taking warfarin when they were injured.
The use of warfarin doubled from a 2% prevalence in 2002 to a 4% prevalence by the end of the study.
For the subgroup of patients over age 65, 9% were taking warfarin when they were injured, and the prevalence of warfarin use rose from 7% in 2002 to 13% by the end of the study.
A total of 9.3% of warfarin users died from their injuries, compared with only 4.8% of nonusers. When mortality data were broken down by patient age, the unadjusted odds ratio for death was 1.51 in warfarin users younger than 65 and 1.41 in users older than 65.
"These unadjusted mortality odds suggest that whether or not warfarin use has a mechanistic link to increased trauma mortality, its use indicates a constellation of demographic and clinical characteristics that collectively increases the odds of death in all patients taking warfarin," the investigators said (Arch. Surg. 2011 Jan. 17 [doi:10.1001/archsurg.2010.313]).
Among the nearly 35,000 study subjects who sustained head injuries with intracranial hemorrhage, warfarin users had significantly higher mortality (22%) than did nonusers (18%). However, when the data were assessed by patient age, only the patients younger than age 65 were at increased risk. Their mortality was 50% higher if they were taking warfarin than if they were not.
Even after the data were adjusted to account for injury pattern and patient comorbidities, warfarin use remained "a significant independent risk factor for death from injury," Dr. Dossett and her associates said.
This study was not designed to determine whether warfarin plays a causal role in mortality or simply serves as a marker for other factors that lead to worse outcomes, they added.
The study was limited in that it was unable to account for the use of other anticoagulant and antiplatelet agents. "Since the presumed mechanistic impact of warfarin on trauma outcome is coagulopathy, patients not classified as warfarin users may use antiplatelet agents that introduce this same mechanism, thereby underestimating the effect of warfarin," the researchers said.
They were unable to assess the degree of anticoagulation achieved with warfarin therapy, or even the degree of patient compliance with recommended treatment. However, they said, "For trauma centers treating patients who present as warfarin users, these data should highlight the importance of seeking an accurate history of warfarin use and its indication, as well as the immediate initiation of its reversal."
No financial conflicts of interest were reported.