Conservative or liberal oxygen therapy in adults after cardiac arrest: An individual-level patient data meta-analysis of randomised controlled trials

Abstract

AimThe effect of conservative versus liberal oxygen therapy on mortality rates in post cardiac arrest patients is uncertain. MethodsWe undertook an individual patient data meta-analysis of patients randomised in clinical trials to conservative or liberal oxygen therapy after a cardiac arrest. The primary end point was mortality at last follow-up. ResultsIndividual level patient data were obtained from seven randomised clinical trials with a total of 429 trial participants included. Four trials enrolled patients in the pre-hospital period. Of these, two provided protocol-directed oxygen therapy for 60 min, one provided it until the patient was handed over to the emergency department staff, and one provided it for a total of 72 h or until the patient was extubated. Three trials enrolled patients after intensive care unit (ICU) admission and generally continued protocolised oxygen therapy for a longer period, often until ICU discharge. A total of 90 of 221 patients (40.7%) assigned to conservative oxygen therapy and 103 of 206 patients (50%) assigned to liberal oxygen therapy had died by this last point of follow-up; absolute difference; odds ratio (OR) adjusted for study only; 0.67; 95% CI 0.45 to 0.99; P = 0.045; adjusted OR, 0.58; 95% CI 0.35 to 0.96; P = 0.04. ConclusionConservative oxygen therapy was associated with a statistically significant reduction in mortality at last follow-up compared to liberal oxygen therapy but the certainty of available evidence was low or very low due to bias, imprecision, and indirectness. PROSPERO registration numberCRD42019138931.