Epidural placement does not result in an increased incidence of venous thromboembolism in combat-wounded patients

Background: Patient-controlled epidural analgesia (PCEA) decreases the amount of systemic opioid required for adequate analgesia and decreases the rate of opioid-induced adverse effects. Given the location of catheters required to deliver analgesics and the potential for epidural hematoma, the American Society of Regional Anesthesia and Pain Medicine recommends modification of the standard trauma venous thromboembolism (VTE) prophylaxis regimen of enoxaparin 30 mg twice daily to 40 mg daily. The objective of this retrospective study was to determine if 40-mg daily dosing would increase the incidence of VTE. Methods: With institutional review board approval, records of all combat casualties admitted to our institution between November 2010 and November 2012 were reviewed for demographics, VTE prophylaxis regimen, PCEA days, and incidence of VTE. Patients who arrived without VTE were the study cohort. Rates of VTE were compared between PCEA and no-PCEA groups. Variables were analyzed with Mann-Whitney U-test, Pearson's χ test, and Fisher's exact test. A p ≤ 0.05 was considered significant. Data are expressed as median (interquartile range). Results: A total of 565 records were reviewed; 484 met inclusion criteria; and 181 patients (37.4%) had PCEA for 13 days (6-25 days). Age and sex were similar between the groups. PCEA patients were more often injured by dismounted improvised explosive devices (75.1% vs. 39.3%, p < 0.001), had longer hospital stays (38 days vs. 17 days, p < 0.001), had higher Injury Severity Score (ISS) (14 vs. 12, p = 0.033), and were more likely to have an amputation (66.1% vs. 20.4%, p < 0.001). Twenty-three PCEA patients (12.7%) developed VTE versus 32 no-PCEA patients (10.6%) (p = 0.464). Eleven VTE events (47.8%) occurred with the catheter in place, while 12 VTE events (52.2%) occurred 6 days (2-15 days) after removal. Conclusion: Although PCEA catheters were more often placed in patients prone to VTE, there was no difference in incidence of VTE with their use. These data suggest that enoxaparin 40 mg daily in patients with PCEA is not inferior to 30 mg twice daily for VTE prophylaxis in combat-wounded patients.