(182) Hypercapnia Versus Normocapnia in Post-Cardiac Arrest: An Updated Meta-Analysis and Systemic Review

Introduction: Hypoxic-ischemic encephalopathy is the leading cause of post-cardiac arrest morbidity and mortality. The partial pressure of arterial carbon dioxide (PaCO2) plays a pivotal role in regulating cerebrovascular tone. Guidelines recommend normocapnia, but evidence suggests hypercapnia may improve outcomes. Our meta-analysis compares normocapnia and hypercapnia effects on neurological outcomes and survival post-cardiac arrest, in-hospital and out-of-hospital.

Methods: We did an extensive search using PubMed, EMBASE, and Cochrane Library for studies published prior to May 01, 2024, evaluating normocapnia (Paco2, 35 to 45 mm Hg) or hypercapnia (Paco2, 50 to 55 mm Hg) as a ventilation strategy after cardiac arrest. Data was extracted and analyzed on RevMan v.5.2. Pooled proportions with 95% confidence intervals (95% CIs) were calculated using a random effects model. Odds ratios (ORs) with 95% confidence intervals were used as effect measures for dichotomous variables. Our outcomes of interest were favorable neurologic outcome and survival.

Results: We identified a total of 06 studies, including 28,513 patients. Our inclusion criteria was, hospitalized adults (≥18 years of age) with coma who had been resuscitated after cardiac arrest with a follow up duration of 6 months or more for outcomes of interest. 18,570 patients were in the normocapnia group, and 9,943 patients were in the hypercapnia group. Although not statistically significant, there was a trend suggesting lower odds of achieving a favorable neurological outcome in the hypercapnia group compared to the normocapnia group (OR: 0.86 [0.73, 1.02]; I2=75%; P=0.08). The odds of survival did not significantly differ between the two groups (OR: 0.99 [0.88, 1.10]; I2=83%; P=0.80).

Conclusions: Our study suggests a potential trend towards better neurological outcomes with normocapnia compared to hypercapnia post-cardiac arrest. Survival rates were similar between the two groups. While these findings are intriguing, further research is needed to draw definitive conclusions and guide clinical practice.