Mild hypercapnia versus normocapnia in resuscitated out-of-hospital cardiac arrest patients: a systematic review and meta-analysis

Abstract Introduction After out-of-hospital cardiac arrest (OHCA) resuscitation, current guidelines recommend normocapnia. However, mild hypercapnia may confer several physiological benefits that could enhance post-OHCA outcomes. purpose To assess the effects of moderate hypercapnia versus normocapnia on clinical outcomes after OHCA resuscitation. Methods A systematic review and meta-analysis synthesizing randomized controlled trials (RCTs) and observational studies were retrieved by systematically searching PubMed, Web of Science, SCOPUS, and Cochrane through August 15th, 2023. Dichotomous outcomes were pooled using risk ratio (RR) and continuous data using mean difference (MD), with a 95% confidence interval (CI). Results We included five studies with a total of 42,076 patients. There was no difference between both groups in all-cause mortality (RR: 1.15, 95% CI [0.89 to 1.49], p=0.29), good neurological recovery (RR: 0.95, 95% CI [0.81 to 1.12], p = 0.56), mechanical ventilation duration (MD: 1.00, 95% CI [-5.41 to7.41], p= 0.76), ICU length of stay (MD: 0.01, 95% CI [-0.28 to 0.30], p= 0.96), neuron-specific enolase level (MD: -20.92, 95% CI [-69.53 to 27.69], p= 0.40), and the incidence of any serious adverse events (RR: 1.55, 95% CI [0.06 to 42.92], p= 0.80). However, length of hospitalization was lower in the mild hypercapnia group (MD: 0.99, 95% CI [-1.85 to -0.14], p= 0.02). Conclusion Mild hypercapnia did not decrease all-cause mortality or improve neurological recovery after OHCA resuscitation compared to normocapnia. However, mild hypercapnia significantly reduced the length of hospital stay.Main outcome