PCO2 on arrival as a predictive biomarker in patients with out-of-hospital cardiac arrest

Treating patients with out-of-hospital cardiac arrest (OHCA) requires early prediction of outcome, ideally on hospital arrival, as it can inform the clinical decisions involved. This study evaluated whether partial pressure of carbon dioxide (PCO2) on arrival is associated with outcome at one month OHCA patients. This was a single-center retrospective study of adult OHCA patients treated between January 2016 and December 2020. Outcomes were defined along the Cerebral Performance Category (CPC) scale. Primary outcome was mortality (CPC 5) at one month. Secondary outcomes were death or unfavorable neurological outcome (CPC 3–5) and unfavorable neurological outcome (CPC 3–4) at one month. Multivariable analysis was adjusted for age, sex, witnessed cardiac arrest, bystander cardiopulmonary resuscitation, initial shockable rhythm, and time from call to emergency medical services to hospital arrival. Out of 977 OHCA patients in the study period, 19 were excluded because they were aged under 18 years, 79 because they underwent extracorporeal cardiopulmonary resuscitation, and 101 due to lack of PCO2 data. This study included 778 patients total; mortality (CPC 5) at one month was observed in 706 (90.7%), death or unfavorable neurological outcome (CPC 3–5) in 743 (95.5%), and unfavorable neurological outcome (CPC 3–4) in 37 (4.8%). In multivariable analysis, high PCO2 levels showed significant association with mortality (CPC 5) at one month (odds ratio [OR] [per 5 mmHg], 1.14; 95% confidence interval [CI], 1.08–1.21), death or unfavorable neurological outcome (CPC 3–5) (OR [per 5 mmHg], 1.29; 95% CI, 1.17–1.42), and unfavorable neurological outcome (CPC 3–4) (OR [per 5 mmHg], 1.21; 95% CI, 1.04–1.41). High PCO2 on arrival was significantly associated with mortality and unfavorable neurological outcome in OHCA patients.