High Altitude Is an Independent Risk Factor for Developing a Pulmonary Embolism, but Not a Deep Vein Thrombosis Following a 1- to 2-Level Lumbar Fusion.

ABSTRACT

STUDY DESIGN: Retrospective study. OBJECTIVE: To identify if a 1- to 2-level posterior lumbar fusion at higher altitude is an independent risk factor for postoperative deep vein thrombosis (DVT) and pulmonary embolism (PE). METHODS: A national Medicare database was queried for all patients undergoing 1- to 2-level lumbar fusions from 2005 to 2014. Those with a prior history of DVT, PE, coagulopathy, or peripheral vascular complications were excluded to better isolate altitude as the dependent variable. The groups were matched 11 based on age, gender, and comorbidities to limit potential cofounders. Using ZIP codes of the hospitals where the procedure occurred, we separated our patients into high (>4000 feet) and low (<100 feet) altitudes to investigate postoperative rates of DVTs and PEs at 90 days. RESULTS: Compared with lumbar fusions performed at low-altitude centers, patients undergoing the same procedure at high altitude had significantly higher PE rates (P = .010) at 90 days postoperatively, and similar rates of 90-day postoperative DVTs (P = .078). There were no significant differences in age or comorbidities between these cohorts due to our strict matching process (P = 1.00). CONCLUSION: Spinal fusions performed at altitudes >4000 feet incurred higher PE rates in the first 90 days compared with patients receiving the same surgery at <100 feet but did not incur higher rates of postoperative DVTs.