Veno-arterial CO2 difference and respiratory quotient after cardiac arrest: An observational cohort study.

Abstract

To characterize venous-arterial CO2 difference (ΔpCO2) and the respiratory quotient (RQ) in post cardiac arrest patients and evaluate the association between these parameters and patient outcome. Data were obtained retrospectively from post cardiac arrest patients admitted between 2007 and 2016 to a medical intensive care unit. Comatose, adult patients in whom arterial and venous blood gas analyses were concomitantly performed in the first 24h were included. Patients were grouped according to the time-point of sampling; 0-6, 6-12 and 12-24h after admission. 308 patients were included; 174 (56%) died before ICU discharge and 212 (69%) had an unfavorable neurologic outcome. RQ was associated with ICU mortality (OR:1.09 (95%CI: 1.04-1.14; p<0.01)), although not with neurological outcome. ΔpCO2 was negatively associated with both ICU mortality (OR: 0.92 (95%CI: 0.86-0.99; p=0.02)) and poor neurologic outcome (adjusted OR: 0.93 (95%CI: 0.87-0.99; p=0.02)). ΔpCO2 predicted an elevated RQ; a ΔpCO2 above 8.5mmHg identified a high RQ with reasonable sensitivity and specificity. RQ was associated with ICU mortality and ΔpCO2 identified elevated RQ in the early phase after cardiac arrest. However, ΔpCO2 were negatively associated with both ICU mortality and neurologic outcome.