Clinical Pearls & Morning Reports
The use of vena cava filters has become widespread in many trauma centers as a primary means to prevent pulmonary embolism in patients who are at high risk for bleeding. Most studies evaluating the clinical efficacy of vena cava filters in trauma patients have been observational. Ho et al. conducted a multicenter, randomized, controlled trial that evaluated whether early placement of a retrievable vena cava filter reduced the risk of symptomatic pulmonary embolism or death in severely injured patients in whom prophylactic anticoagulation was contraindicated. Read the Original Article here.
Q: How common is venous thromboembolism in severely injured patients?
A: Venous thromboembolism is common after major trauma. A prospective surveillance study involving 349 consecutive severely injured patients showed that without prophylactic anticoagulation, proximal deep-vein thrombosis occurred in 18% of patients, and pulmonary embolism occurred in 11%. Fatal pulmonary embolism is less common (0.4 to 4.2%); however, it accounts for 12% of all deaths after major trauma, and half of these deaths are considered preventable.
Q: To what extent does a delay of several days in initiating thromboprophylaxis in severely injured patients increase the risk of venous thromboembolism?
A: Observational studies have suggested that a delay of more than 1 to 3 days in initiating thromboprophylaxis in severely injured patients triples the risk of venous thromboembolism and possibly increases mortality. However, prophylactic anticoagulation has also been reported to be associated with an odds ratio of more than 13 for progressive enlargement of hematoma in patients with traumatic brain injury.
A: The incidence of symptomatic pulmonary embolism or death (the primary composite end point) was not significantly lower among those in whom a vena cava filter was placed than in those in whom no filter was placed (13.9% vs. 14.4%; hazard ratio, 0.99; 95% confidence interval, 0.51 to 1.94; P=0.98 by log-rank test).
A: Unnecessary insertion of a vena cava filter has the potential to cause harm. In the trial by Ho et al., an entrapped thrombus was found within the filter in almost 5% of the patients in whom a filter was placed, and the filter had to be surgically removed in one patient. Previous studies have suggested that vena cava filters are associated with an increased risk of deep-vein thrombosis in the legs. This complication was not confirmed in the trial by Ho et al. — perhaps because of the use of intermittent pneumatic compression in the legs, the initiation of prophylactic anticoagulation, and the removal of the filter as early as possible.