The impact of hyperoxia on outcomes after cardiac surgery: a systematic review and narrative synthesis.

PURPOSE: Historically, cardiac surgery patients have often been managed with supraphysiologic intraoperative oxygen levels to protect against the risks of cellular hypoxia inherent in the un-physiologic nature of surgery and cardiopulmonary bypass. This may result in excessive reactive oxygen species generation and exacerbation of ischemia-reperfusion injury. In this review, we synthesize all available data from randomized controlled trials (RCTs) to investigate the impact that hyperoxia has on postoperative organ dysfunction, length of stay, and mortality during adult cardiac surgery.

SOURCE: We searched Medline, Embase, Scopus, and Cochrane Central Register of Controlled Trials databases using a high-sensitivity strategy for RCTs that compared oxygenation strategies for adult cardiac surgery. Our primary outcome was postoperative organ dysfunction defined by postoperative increases in myocardial enzymes, acute kidney injury, and neurologic dysfunction. Secondary outcomes were mortality, ventilator days, and length of stay in the hospital and intensive care unit.

PRINCIPAL FINDINGS: We identified 12 RCTs that met our inclusion criteria. Risk of bias was unclear to high in all but one trial. Significant heterogeneity in timing of the treatment period and the oxygenation levels targeted was evident and precluded meta-analysis. The large majority of trials found no difference between hyperoxia and normoxia for any outcome. Two trials reported reduced postoperative myocardial enzymes and one trial reported reduced mechanical ventilation time in the normoxia group.

CONCLUSIONS: Hyperoxia had minimal impact on organ dysfunction, length of stay, and mortality in adult cardiac surgery. The current evidence base is small, heterogeneous, and at risk of bias.

TRIAL REGISTRATION: International Prospective Register of Systematic Reviews (PROSPERO) (CRD42017074712). Registered 17 August 2017.