Association between the first post-resuscitation partial pressure of arterial carbon dioxide and neurologic outcomes in children with out-of-hospital cardiac arrest: a multicenter retrospective cohort study.

BACKGROUND: The prognostic significance of the first post-ROSC PaCO2 in pediatric out-of-hospital cardiac arrest (OHCA) remains uncertain. We evaluated its association with 30-day outcomes. METHODS: We conducted a multicenter retrospective cohort study using the Japanese OHCA registry (2014-2022). Pediatric patients aged <18 years with return of spontaneous circulation (ROSC) were included, and the primary analysis was restricted to patients with first post-ROSC blood gas sampling within 60 minutes. Patients were categorized as hypocapnia (<35 mmHg), normocapnia (35-45 mmHg), or hypercapnia (>45 mmHg) according to the first post-ROSC PaCO2 measurement. The primary outcome was favorable neurologic outcome at 30 days, defined as a Pediatric Cerebral Performance Category score of 1-3. The secondary outcome was 30-day survival. Associations were evaluated using multiple propensity score-based overlap weighting and hospital-clustered weighted generalized estimating equation models, with normocapnia as the reference. RESULTS: Among 215 patients, 27 had hypocapnia, 39 normocapnia, and 149 hypercapnia. Favorable neurologic outcome at 30 days occurred in 41 (19.1%), and 30-day survival in 92 (42.8%). After adjustment, we found no clear evidence that either hypocapnia or hypercapnia was associated with favorable neurologic outcome (hypocapnia: adjusted odds ratio [aOR], 0.83; 95% confidence interval [CI], 0.13-5.14; hypercapnia: aOR, 1.46; 95% CI, 0.25-8.68) or 30-day survival (hypocapnia: aOR, 1.46; 95% CI, 0.26-8.01; hypercapnia: aOR, 0.36; 95% CI, 0.09-1.46). CONCLUSIONS: In this multicenter study of pediatric OHCA, we found no clear evidence of an independent association between first post-ROSC PaCO2 category and 30-day outcomes, although estimates were imprecise.