Intra-arrest partial carbon dioxide level and favorable neurological outcome after out-of-hospital cardiac arrest: a nationwide multicenter observational study in Japan (the JAAM-OHCA registry)

Aims Little is known about whether guideline-recommended ventilation during cardiopulmonary resuscitation results in optimal partial carbon dioxide (pCO(2)) levels or favorable outcomes. This study aimed to evaluate the association between intra-arrest pCO(2) level and the outcome after out-of-hospital cardiac arrest (OHCA). Methods and results We performed a secondary analysis of a multicenter observational study, including adult patients with OHCA who did not achieve a return of spontaneous circulation (ROSC) upon hospital arrival and whose blood gas analysis was performed before the ROSC between June 2014 and December 2017. The patients were categorized into four quartiles based on their intra-arrest carbon dioxide levels: Quartile 1 (<66.0 mmHg), Quartile 2 (66.1-87.2 mmHg), Quartile 3 (87.3-113.5 mmHg), and Quartile 4 (>= 113.6 mmHg). The primary outcome was 1-month survival with favorable neurological outcomes defined as cerebral performance Category 1 or 2. Multivariate logistic regression analysis was used to evaluate the association between pCO(2) and favorable neurological outcomes. During the study period, 20 913 patients were eligible for the analysis. The proportion of favorable neurological outcomes was 1.8% (90/5133), 0.7% (35/5232), 0.4% (19/5263), and 0.2% (9/5285) in Quartiles 1-4, respectively. Multivariable logistic regression analysis demonstrated that the probability of favorable neurological outcome decreased with increased intra-arrest carbon dioxide levels (i.e. Q1 vs. Q4, adjusted odds ratio 0.25, 95% confidence interval 0.16-0.55, P for trend <0.001). Conclusion Lower intra-arrest pCO(2) levels were associated with a favorable neurological outcome.