Association between arterial carbon dioxide tension and poor outcomes after cardiac arrest: A meta-analysis

Abnormal arterial carbon dioxide tension (PaCO₂) is a common finding after cardiac arrest (CA). Inconsistent results regarding the association between abnormal PaCO₂ and poor outcomes have been reported previously. We performed a meta-analysis to evaluate whether hypocapnia or hypercapnia is associated with an increased risk of hospital mortality and poor neurological outcomes in adult patients with CA.

PubMed, Embase, and the Cochrane Library databases were searched through October 2024 to determine studies investigating the association between PaCO₂ and the risk of hospital mortality and/or poor neurological outcomes in adult patients with CA. A random-effects model was used to calculate the pooled odds ratio (OR) with 95% confidence intervals (CIs) for cohort studies and relative risks (RRs) with 95% CIs for randomized controlled trials (RCTs).

A total of 14 cohort studies and 3 RCTs comprising 72344 patients were included. Pooled analysis indicated that hypocapnia was associated with an increased risk of hospital mortality (nine cohort studies, OR 1.37; 95% CI, 1.18-1.59; P < 0.0001) and poor neurological outcomes (five cohort studies, OR, 1.75; 95% CI, 1.04-2.96; P = 0.035). Within cohort studies, hypercapnia was associated with increased risk of hospital mortality (10 trials, OR 1.40; 95% CI, 1.13-1.73; P = 0.002), but not associated with poor neurological outcomes (six cohort studies, OR, 1.57; 95% CI, 0.87-2.83; P = 0.130). Within RCTs, mild hypercapnia was not associated with an increased risk of poor neurological outcomes after CA.

Current evidence indicated that hypocapnia was associated with an increased risk of hospital mortality and poor neurological outcomes after CA; however, hypercapnia was associated with an increased risk of hospital mortality but did not appear to be associated with increased poor neurological outcomes after CA.

INPLASY 2024100120. Registered 28 October 2024.