Prehospital End Tidal Carbon Dioxide is Predictive of Death and Massive Transfusion in Injured Patients: An EAST Multicenter Trial.

Prehospital identification of the injured patient likely to require emergent care remains a challenge. End tidal carbon dioxide(ETCO2) has been utilized in the prehospital setting to monitor respiratory physiology and confirmation of endotracheal tube placement. Low levels of ETCO2 have been demonstrated to correlate with injury severity and mortality in a number of in-hospital studies. We hypothesized that prehospital ETCO2 values would be predictive of mortality and need for massive transfusion(MT) in intubated patients. METHODS This was a retrospective multicenter trial with 24 participating centers. Prehospital, emergency department, and hospital values were collected. Receiver operator characteristic(ROC) curves were created and compared. MT defined as >10 units of blood in 6 hours or death in 6 hours with at least 1 unit of blood transfused. RESULTS 1324 patients were enrolled. ETCO2(AUROC of 0.67 CI 0.63-0.71) was better in predicting mortality than shock index(SI)(AUROC 0.55 CI 0.50-0.60) and systolic blood pressure(SBP)(AUROC 0.58 CI 0.53-0.62)p < 0.0005. Prehospital lowest ETCO2(AUROC 0.69 CI 0.64-0.75), SBP(AUROC 0.75 CI 0.70-0.81), and SI(AUROC 0.74 CI 0.68-0.79) were all predictive of MT. Analysis of patients with normotension demonstrated lowest prehospital ETCO2(AUROC 0.66 CI 0.61-0.71) which was more predictive of mortality than SBP (AUROC 0.52 CI 0.47-0.58) or SI (AUROC of 0.56 CI 0.50-0.62) p < 0.001. Lowest prehospital ETCO2 (AUROC 0.75 CI 0.65-0.84), SBP (AUROC of 0.63 CI 0.54-0.74) and SI (AUROC of 0.64 CI 0.54-0.75) were predictive of MT in normotensive patients. ETCO2 cutoff for MT was 26 mmHg. The positive predictive value was 16.1% and negative predictive value was high at 98.1%. CONCLUSIONS Prehospital ETCO2 is predictive of mortality and MT. ETCO2 outperformed traditional measures such as SBP and SI in the prediction of mortality. ETCO2 may outperform traditional measures in predicting need for transfusion in occult shock.Level of Evidence: III diagnostic test.