Exposure to hyperoxemia worsens survival and neurological outcome in patients supported by veno-arterial extracorporeal membrane oxygenation: a meta-analysis

Abstract

Background Veno-arterial Extracorporeal Membrane Oxygenation (VA-ECMO) is a rescue treatment in refractory cardiogenic shock (CS) or refractory cardiac arrest (CA). Exposure to hyperoxemia is common during VA-ECMO, and its impact on patient’s outcome remains unclear. Methods We conducted a systematic review (PubMed and Scopus) and metanalysis investigating the effects of exposure to hyperoxemia on mortality and poor neurological outcome in patients supported by VA-ECMO. Whenever provided, we used the Odds Ratio (OR) adjusted for confounders. Results are reported as OR and 95% confidence interval (CI). Subgroup analyses were conducted according to VA-ECMO indication and hyperoxemia thresholds. Results Data from 11 observational studies were included. Ten studies reported data on mortality (6 on refractory CA and 4 on CS), and 4 on neurological outcome. Hyperoxemia exposure was associated with higher mortality (OR:1.81, 95%CI [1.22–2.71]; p = 0.003; I2 = 81%) and worse neurological outcome (OR:1.97, 95%CI [1.30–2.96]; p = 0.001; I2 = 0%). Magnitude and effect of these findings remained valid in subgroup analyses conducted according to different hyperoxemia thresholds (> 200 or > 300 mmHg) and VA-ECMO indication, although the association with mortality remained uncertain in the refractory CA population (p = 0.07). Analysis restricted only to studies providing data in adjusted OR confirmed the increased mortality (OR:1.72, 95%CI [1.00-2.97]; p = 0.05) and poorer neurological outcome (OR:1.99, 95%CI [1.18–3.37]; p = 0.01) in patients exposed to hyperoxemia. Conclusions Hyperoxemia exposure after initiation of VA-ECMO is associated with an almost doubled increased probability of poor neurological outcome and mortality. Clinical efforts should be made to avoid severe hyperoxemia during VA-ECMO support.