The gradient between arterial and end-tidal carbon dioxide predicts in-hospital mortality in post-cardiac arrest patient

PURPOSE We investigated the predictive value of the gradient between arterial carbon dioxide (PaCO 2 ) and end-tidal carbon dioxide (ETCO 2 ) (Pa-ETCO 2 ) in post-cardiac arrest patients for in-hospital mortality.
METHODS This retrospective observational study evaluated cardiac arrest patients admitted to the emergency department of a tertiary university hospital. The PaCO 2 and ETCO 2 values at 6, 12, and 24 h after return of spontaneous circulation (ROSC) were obtained from medical records and Pa-ETCO 2 gap was calculated as the difference between PaCO 2 and ETCO 2 at each time point. Multivariate logistic regression analysis was performed to verify the relationship between Pa-ETCO 2 gap and clinical variables. Receiver operating characteristic (ROC) curve analysis was performed to determine the cutoff value of Pa-ETCO 2 for predicting in-hospital mortality.
RESULTS The final analysis included 58 patients. In univariate analysis, Pa-ETCO 2 gaps were significantly lower in survivors than in non-survivors at 12 h [12.2 (6.5-14.8) vs. 13.9 (12.1-19.6) mmHg, p = 0.040] and 24 h [9.1 (6.3-10.5) vs. 17.1 (13.1-23.2) mmHg, p < 0.001)] after ROSC. In multivariate analysis, Pa-ETCO 2 gap at 24 h after ROSC was related to in-hospital mortality [odds ratio (95% confidence interval): 1.30 (1.07-1.59), p = 0.0101]. In ROC curve analysis, the optimal cut-off value of Pa-ETCO 2 gap at 24 h after ROSC was 10.6 mmHg (area under the curve, 0.843), with 77.8% sensitivity and 85.7% specificity.
CONCLUSION The Pa-ETCO 2 gap at 24 h after ROSC was associated with in-hospital mortality in post-cardiac arrest patients.

as reported in: Am J Emerg Med. 2019 Jan; 37(1): 1-4