Trauma patients are at high risk for VTE due to endothelial damage, hypercoagulability from activation of acute-phase proteins, and prolonged immobility because these components fulfill Virchow's triad. PE is the cause of death in 20% of severely injured patients, making it the third most common cause of death in trauma patients who survive the initial 24 hours.53,54,55
VTE risk is 32% to 58%, depending on the extent of injury and use of prophylaxis.56,57
Those at highest risk include (1) severe head injury and coma, (2) spinal cord injuries with neurological deficit, and (3) pelvic and long bone fractures.58
Furthermore, these high-risk patients often carry contraindications to anticoagulation and/or mechanical compression devices.
Prophylactic placement of an IVC filter is increasing utilized in the trauma patient population. A retrospective review by Carlin et al documented an increase in prophylactic filter placement in trauma patients from 3% (1991 to 1996) to 57% (1996 to 2001).59
Several factors underlie this increased use; namely, the high rate of VTE in trauma patients, the ineffectiveness of low-dose heparin or compression devices, and concern among trauma specialists about bleeding complications associated with more potent pharmacoprophylactic methods.60
The development of retrievable filters further spurred utilization because the risk of PE in the trauma population is usually time limited. In other words, retrievable IVC filters offer protection from PE during the posttraumatic period of greatest risk, and subsequent removal of the filter presumably eliminates the chance of long-term filter-related complications. Karmy-Jones et al further expounded on this concept in a multicenter study on practice patterns and outcomes of retrievable IVC filters in trauma patients.61
Specifically, three assumptions lead to increased retrievable filter placement in the trauma patients: (1) retrievable filters are as effective as permanent filters in preventing PE, (2) retrievable filters may be removed, and (3) long-term stability of retrievable filters, if left in situ, are equivalent to permanent filters. This study found that only 22% of retrievable filters were successfully removed, with loss to follow-up (31%) as the most common reason these devices were left in situ. However, if the service placing the filter had the primary responsibility for tracking it, loss to follow-up occurred in only 6% of patients.61
Greenfield et al examined the effectiveness of prophylactic IVC filter placement in trauma patients.62
In this prospective study, 249 patients had prophylactic filters placed. The rate of new PE was 1.5%, and the caval occlusion rate was 3.5%. The authors concluded that prophylactic filter placement is associated with a low incidence of adverse outcomes while providing protection from fatal PE. In an earlier publication, prophylactic filter placement in trauma patients decreased PE-related mortality and overall mortality.63
Another study by Wojcik et al reported a series of 105 trauma victims who received permanent IVC filters in the setting of known VTE or VTE prophylaxis.64
There were no documented PEs in patients with filters, but ~44% of the prophylactic patient cohort developed DVT after filter placement. Hoff et al reported on the use of a retrievable filter, the Günther Tulip filter (Cook), in the trauma population.65
The device was considered for patients at high clinical risk for VTE with a contraindication to anticoagulation and/or pneumatic compression. There was no technical complication of filter placement and no documented in-hospital PE after initiation of IVC filtration. The decision to retrieve the filter was based on the change in VTE risk status (i.e., ambulatory), safety of anticoagulation, and the ability to use pneumatic compression devices. A total of 51% of filters were removed with no procedural complication. The authors concluded that retrievable filters are safe and effective without the potential long-term complications of permanent filters.
The Eastern Association for the Surgery of Trauma states that no level I studies exist to support insertion of IVC filters in trauma patients without a diagnosis of DVT or PE.66
Still, they recommend consideration of prophylactic IVC filter insertion in patients who meet high-risk criteria and cannot be anticoagulated.
To address this lack of level I data, SIR convened a multidisciplinary research consensus panel to develop an agenda for IVC filter research.10
The consensus priority was a randomized controlled trial of prophylactic vena cava filters in trauma patients. Several advantages of this topic were explained including prevention of clinically important PE in a high-risk population that currently receives a large proportion of filters.