Utility of arterial CO2-End-tidal CO2 gap as a mortality indicator in the surgical ICU

Background: End-tidal CO2 (ETCO2) measurements have been an established tool for assessing critically ill pa-tients. We aim to show that PaCO2-ETCO2 gap can be used as a predictor of mortality over a 7-day ICU stay. Methods: A retrospective chart review was performed on intubated surgical/trauma patients with documented ETCO2. We performed a univariate analysis and a receiver operating characteristic (ROC) curve. Results: Thirty-four patients were included. Patients who died were found to have longer days on vasopressors, and higher lactic acid levels on days 2-5, and 7. PaCO2-ETCO2 gap was higher on days 2-4 in those that died. Using ROC, days 2 and 4 PaCO2-ETCO2 gaps had good sensitivities, comparable to lactic acid sensitivity, in predicting mortality. Conclusions: PaCO2-ETCO2 gap was shown to be comparable to lactic acid in predicating mortality. Using this surrogate may aid to predict the clinical course in the ICU.