Variability in the use of thromboprophylaxis and outcomes in critically ill medical patients.

PURPOSE: To describe practices for preventing venous thromboembolism in critically ill medical patients and to identify associations between prophylactic measures and survival.
METHODS: We reviewed the records of all medical admissions to the intensive care units of a university hospital and an affiliated Veterans Affairs hospital over a 1-year period. We recorded patients' demographic characteristics, risk factors for venous thromboembolism, methods of prophylaxis, and in-hospital deaths.
RESULTS: We identified 272 critically ill medical patients who received intensive care for at least 24 hours. Some form of prophylaxis was used in 205 patients (75%), including pharmacologic prophylaxis alone in 55 (20%), mechanical prophylaxis alone in 102 (38%), and both methods in 48 (18%). In-hospital mortality rates were 23% (24/103) for patients who received pharmacologic prophylaxis, and 36% (61/169) for those who received mechanical prophylaxis alone or no prophylaxis (P=.03). After adjusting for demographic characteristics, risk factors for thrombosis and severity of illness, the odds of death were 55% lower in patients who received pharmacologic prophylaxis (odds ratio [OR]=0.45; 95% confidence interval (CI): 0.22 to 0.93; P=.03). Similar results were obtained in propensity-adjusted and propensity-stratified analyses. Use of mechanical prophylaxis was not associated with survival (OR=0.88; 95% CI 0.44 to 1.77; P=.73).
CONCLUSION: In this cohort of critically ill medical patients, pharmacologic but not mechanical thromboprophylaxis was associated with reduced risk of in-hospital death. This hypothesis must be tested in randomized trials.