Prehospital End-tidal Carbon Dioxide Predicts Mortality in Trauma Patients.

BACKGROUND: End-tidal carbon dioxide (EtCO2) measurement has been shown to have prognostic value in acute trauma. OBJECTIVE: Evaluate the association of prehospital EtCO2 and in-hospital mortality in trauma patients and to assess its prognostic value when compared to traditional vital signs. METHODS: Retrospective, cross-sectional study of patients transported by a single EMS agency to a level one trauma center. We evaluated initial out-of-hospital vital signs documented by EMS personnel including EtCO2, respiratory rate (RR), systolic BP (SBP), diastolic BP (DBP), pulse (P), and oxygen saturation (O2) and hospital data. The main outcome measure was mortality. RESULTS: 135 trauma patients were included; 9 (7%) did not survive. The mean age of patients was 40 (SD17) [Range 16-89], 97 (72%) were male, 76 (56%) were admitted to the hospital and 15 (11%) went to the ICU. The mean EtCO2 level was 18 mmHg (95%CI 9-28) [Range 5-41] in non-survivors compared to 34 mmHg (95%CI 32-35) [Range 11-51] in survivors. The area under the ROC curve (AUC) for EtCO2 in predicting mortality was 0.84 (0.67-1.00) (p = 0.001), RR was 0.82 (0.63-1.00), SBP was 0.72 (0.49-0.96), DBP was 0.72 (0.47-0.97), pulse was 0.51 (0.26-0.76), and O2 was 0.64 (0.37-0.91). Cut-off values at 30 mmHg yielded sensitivity = 89% (51-99), specificity = 68% (59-76), PPV = 13% (6-24) and NPV = 99% (93-100) for predicting mortality. There was no correlation between RR and EtCO2 (correlation 0.16; p = 0.06). CONCLUSION: We found an inverse association between prehospital EtCO2 and mortality. This has implications for improving triage and assisting EMS in directing patients to an appropriate trauma center.