A vena cava filter is a cone shaped medical device that is inserted into the inferior vena cava (IVC), the largest vein in the body, to prevent devastating pulmonary embolisms. The filters are inserted into easily accessible blood vessels (e.g. femoral vein, internal jugular vein) using a catheter and guided fluoroscopically to the inferior vena cava just below the kidneys. The IVC filter is designed to capture blood clots from deep veins (mostly commonly from the leg) that would otherwise travel to the heart and lungs. The device is safe and cost effective if inserted percutaneously in the intensive care unit rather than in the operating room or radiology suite (Dhall et al. 2013).
Six studies have examined the effect of prophylactic IVC filter insertion on the incidence of PE after SCI. Gorman et al. (2009) conducted a retrospective chart review of individuals admitted to SCI rehabilitation receiving IVC filters compared to those that did not. The authors found that individuals with IVC filters had significantly lower DVT incidence rates compared to those without a filter (p=0.021). These results were supported by a case series study by Roberts et al. (2011) and a pre-post study by Wilson et al. (1994) who both demonstrated that retrievable IVC filters were effective in reducing incidence of PE without causing any insertion-related complications.
Three studies have specifically studied the insertion of Greenfield IVC filters. Jarrell et al. (1983) studied 21 acute SCI patients who had received a Greenfield filter and reported that one patient developed a PE. On follow-up, no other PEs were noted although two individuals developed thrombosis of the inferior vena cava. Balshi et al. (1989) reported on patients with SCI who received this filter and found that 12 of the 13 patients had a DVT; distal migration of the filter was a common complication. Kinney et al. (1996) also studied Greenfield filter placement among 27 individuals with SCI and noted that filters migrated frequently in patients with cervical injuries (45.5%). The mean migration distance was significantly higher than individuals with non-cervical injuries (p<0.05). Overall, there was a greater number of PEs sustained in the SCI population compared to the non-SCI control group.
The literature has shown that IVC filters significantly reduce PE in SCI patients; however, this form of prophylaxis is invasive and therefore, should only be considered for high-risk patients. According to the Consortium for Spinal Cord Injury (2008) clinical practise guidelines, it is recommended that health care providers should “consider placing a vena cava filter only in those patients with active bleeding anticipated to persist for more than 72 hours and begin anticoagulants as soon as feasible” (p. 38).
There is level 3 evidence (from two case control studies, two case series studies, and one pre-post study; Roberts et al. 2011; Gorman et al. 2009; Kinny et al. 1996; Wilson et al. 1994; Jarrell et al. 1983) that inferior vena cava filters significantly reduce the risk of pulmonary emboli in high-risk SCI patients.