Timing of pulmonary emboli after trauma: implications for retrievable vena cava filters.

BACKGROUND: Four recent reports of the retrieval of optional vena cava filters (VCF) in trauma patients had average implant durations of 10, 19, and 19 days (one not specified). Two patients in these studies had pulmonary emboli after VCF removal. No evidence-based guidelines exist on the appropriate time to remove optional VCF. The purpose of this study was to examine the timing of pulmonary emboli (PE) and determine the optimal time to remove optional VCFs.
METHODS: A multicenter retrospective chart review of trauma patients who had a postinjury PE between January 2001 and December 2004 was performed. We examined the demographics, prophylaxis at the time of PE (pharmacologic [unfractionated or low molecular weight heparin] or sequential compression devices [SCD]), diagnostic test used, timing of PE from the date of injury, and survival outcome.
RESULTS: In all, 146 patients were identified, mean age 45.1 (+/- 21.1 SD); Injury Severity Score 18.0 (+/- 12.1 SD). Diagnosis was obtained by spiral computed tomography (N = 93), pulmonary arteriogram (N = 18), V/Q (N = 26), autopsy (N = 6), clinical (N = 6), and unknown (N = 3). Overall mortality was 17.8% (N = 26). Pulmonary embolism was felt to contribute to or was the cause of death in 85% (N = 22) of these patients. Two late PE deaths occurred (days 21 and 43). Sixty (37%) patients had pharmacologic prophylaxis at the time of PE and 83 (50.9%) had SCDs. Average time from injury to PE was 7.9 days (+/- 8.1 SD), the longest being 43 days postinjury. Eleven percent of PE occurred after 21 days, including fatal PE.
CONCLUSIONS: Clinical criteria defining the time to remove optional VCFs without exposing patients to the risk of PE by removing a filter too soon should be determined.