365 Incidence of Venous Thromboembolism in Critical Care Air Transport Team-Evacuated Casualties Transported to Landstuhl Regional Medical Center

Abstract

Critically injured combat casualties are transported to Landstuhl Regional Medical Center (6-9 hour flights) via Critical Care Air Transport Teams (CCATTs). Immobility and prolonged air travel following traumatic injury may increase the risk of venous thromboembolism (VTE), yet studies on the incidence of VTE following traumatic injury and prolonged air transport are limited. Our objective was to determine factors associated with the incidence of VTE in patients evacuated from theater by CCATTs. We performed a retrospective record review of trauma patients evacuated from the combat setting by CCATT between March 2007 and December 2011. From CCATT records and Department of Defense Trauma Registry query we collected demographics, injury description, vital signs, labs, thromboprophylaxis, adverse events, and disposition up to 30 days. Data elements abstracted from theater medical records included VTE diagnostic information and relevant procedures with timestamps as available. Patients with at least one documented incidence of DVT or pulmonary embolism were grouped into VTE and compared to patients with no deep venous thrombosis or PE (No VTE). Continuous data were analyzed and reported as median (Interquartile Range), while categorical data were reported as frequencies and percentages. Regression models were performed to identify factors associated with the development of VTE. Of the 1351 CCATT records reviewed, 205 records had diagnoses of DVT (n=114), PE (n=69), or both (n=22). Thirty-five records had more than one occurrence of VTE documented. Subjects were male (98%) with median age of 24 (21-29) years. Comparing VTE versus No VTE there was no difference in age, sex, or injury severity. The VTE group was more likely to have sustained injuries related to a fall (5% versus 2%, p=0.015) or blast (75% versus 67%, p=0.027) compared to No VTE group. The VTE group was more likely to receive blood products pre-flight (p<0.001), during flight (p<0.001), and post-flight (p<0.001). The VTE and No VTE group received procoagulants, anticoagulants, and thromboprophylaxis pre-flight at similar rates. From regression models, a low pre-flight hemoglobin level (<8 g/dL), a pH of ≥7.4, and the administration of platelets were associated with VTE (p<0.001). Other pre-flight labs were similar between groups. There was no difference in proportion of patients who required ventilator support during transport (70% versus 65%, p=0.120), but after flight, the VTE group was more likely to be intubated (72% versus 65%, p=0.029). The VTE group compared to No VTE group was more likely to have an adverse event (such as aspiration pneumonia or cardiac arrest) post-flight (95% versus 90%, p=0.037). Mortality rates did not differ between groups (3.8% versus 4.1%, p=0.859). Of the survivors, the VTE group had more hospital days (p=0.047). The proportion of patients who continued to receive medical care (2.9% versus 2.8%) at 30 days post injury did not differ. The VTE group was more likely to receive blood products before, during, and after flight. Factors associated with VTE included a low hemoglobin level, pH of 7.4 or greater, and platelet administration in spite of the administration of anticoagulants. Further research is needed to determine whether this is related to low red cell to platelet ratios, continued bleeding, or other dysfunctional physiologic response in the coagulation system.