Internal Methods
Inferior Vena Cava Filtration
Vena Cava Filters are an invasive form of thromboembolic prophylaxis that primarily function to prevent clots from travelling to the heart and lungs while still allowing venous blood flow to flow. Earlier, these cone-shaped filters were placed surgically through the femoral vein; currently, less invasive techniques exist, allowing for filter placement through femoral, internal jugular, or small peripheral veins under fluoroscopic or ultrasound guidance (Jundt, Liem, & Moneta 2014; Tai et al. 2013).
While pharmacological and mechanical methods remain the primary forms of thromboprophylaxis used in acute SCI, the use of vena cava filters is indicated in trauma individuals who are considered to be at high risk for developing DVT, specifically when there are contraindications to using anticoagulation (e.g., bleeding risk) or mechanical prophylaxis (e.g., external fixators or immobilizers are present). The ability to retrieve IVC filters offers the benefit of the filter during periods when PE risk is high, without long-term complications associated with their use (Lo et al. 2013; Rogers et al. 1993; Shackford et al. 2007). Routine implementation of IVC filters is not recommended as prophylaxis in SCI individuals (Maxwell et al. 2002).
Discussion
Several studies have examined the prophylactic effect of IVC filter insertion on the incidence of DVT and/or PE after acute SCI. Roberts and Young (2010) conducted a case series study of individuals who received IVC filters within 72 hours of admission. The authors observed no occurrences of PE or other complications. These findings were supported by two pre-post studies by Wilson et al. (1994) and Rogers et al. (1995). In the latter studies, the authors observed that inferior vena cava filter insertion “as soon as clinically feasible” and on average 4.3 days after admission, respectively, did not result in any occurrences of PE. However, it should be noted that, in the latter study, individuals were not on any other forms of prophylaxis concurrently and as a result, three individuals developed DVT.
Interestingly, a retrospective case control study by Gorman et al. (2009) compared SCI individuals who had received IVC filters during acute hospitalization with SCI individuals who had not received filters. The authors found that the incidence of DVT was significantly higher in individuals with implanted filters (p=0.021).
Three studies have specifically studied the insertion of Greenfield IVC filters. Jarrell et al. (1983) studied 21 individuals with acute SCI who had received a Greenfield filter and reported that one individual 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 individuals with SCI who received this filter and found that 12 of the 13 individuals 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 individuals 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 individuals with SCI; however, this form of prophylaxis is invasive and therefore, should only be considered for high-risk individuals. 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 individuals with active bleeding anticipated to persist for more than 72 hours and begin anticoagulants as soon as feasible” (p. 38).
Conclusion
There is conflicting level 3 evidence (from two case control studies, two case series studies, and one pre-post study: Gorman et al. 2009; Jarrell et al. 1983; Kinney et al. 1996; Roberts & Young 2010; Wilson et al. 1994) that inferior vena cava filters significantly reduce the risk of pulmonary emboli in high-risk individuals with SCI.
