Association between early arterial pH, base excess and lactate and 24-h mortality and neurological outcomes after cardiac arrest and cardiopulmonary resuscitation: a translational study

Aim We aimed to assess the translational relevance of blood gas-derived acid-base parameters measured in rat and pig models of cardiac arrest and cardiopulmonary resuscitation, evaluating their potential as predictors of mortality and poor neurological outcome. Methods Seventy-seven rats, 83 pigs and 61 patients who experienced cardiac arrest of proven or suspected cardiac origin were retrospectively analyzed . Blood gas analyses were performed 4 h after return of spontaneous circulation. Neurological recovery was assessed using Neurological Deficit Score in rats, overall performance category in pigs, and cerebral performance category in patients. Nonlinear associations between blood gas-derived acid-base parameters and outcomes were analyzed using a generalized additive model. Receiver operating characteristics curve analyses were performed. Results In a multivariate regression analysis area under the curve, considering pH, base excess and lactate, for prediction of mortality were respectively: 0.796 (95%CI: 0.635–0.956), 0.980 (95%CI: 0.946–1.000), 0.959 (95%CI: 0.896–1.000) in rats; 0.908 (95%CI: 0.826–0.990), 0.933 (95%CI: 0.863–1.000), 0.798 (95%CI: 0.588–1.000) in pigs; and 0.830 (95%CI: 0.724–0.936), 0.832 (95%CI: 0.731–0.933), 0.839 (95%CI: 0.738–0.940) in patients. Area under the curve, considering pH, base excess and lactate, for prediction of poor neurological outcome were respectively: 0.673 (95%CI: 0.515–0.831), 0.724 (95%CI: 0.576–0.872), 0.900 (95%CI: 0.760–1.000) in pigs; and 0.835 (95%CI: 0.734–0.937), 0.835 (95%CI: 0.735–0.936), 0.884 (95%CI: 0.793–0.945) in patients. Conclusion Arterial pH, base excess and lactate were early independent predictors of both 24-h mortality and neurological outcome following cardiac arrest in animal models and in humans. BE showed the highest predictive value for mortality, while lactate was the strongest predictor for poor neurological outcome.