Control of Cardiac Output with Ivabradine or Beta-Blockers for Refractory Hypoxemia under Veno-Venous ECMO for Severe ARDS

Purpose: Hypoxemia is a risk factor for mortality and long-term neuropsychological impairment during severe acute respiratory distress syndrome (ARDS). Veno-venous extracorporeal membrane oxygenation (VV-ECMO) is a potential treatment for such cases but may not suffice. We aimed to evaluate the effects of pharmacological interventions for cardiac output (CO) control using ivabradine or beta-blockers for refractory hypoxemia during VV-ECMO.

Methods: The study involved retrospective analysis of consecutive patients with severe ARDS who underwent VV-ECMO at a tertiary university hospital between March 2020 and May 2022. Patients with refractory hypoxemia under VV-ECMO were included. Pharmacological interventions included ivabradine and/or short half-life beta-blockers. The primary endpoint was the change in ECMO flow/CO ratio and secondary endpoints were changes in macrocirculation (mean arterial pressure), oxygenation [arterial saturation (SaO₂) and oxygen transport (DO₂)] and tissue hypoxia (lactate levels).

Results: Out of 70 patients on VV-ECMO, ten had refractory hypoxemia under VV-ECMO and received pharmacological interventions to control CO. The ECMO flow/CO ratio significantly increased with pharmacological intervention overall (from 60% [50-66] to 69% [61-81], p = 0.02), as well as with beta-blockers or ivabradine individually. However, DO₂ decreased, especially with beta-blockers and to some extent with ivabradine. There were no reported immediate adverse events, and lactate levels remained below the anaerobic threshold.

Conclusion: Ivabradine and beta-blockers were clinically well-tolerated and improved the ECMO flow/CO ratio in patients with refractory hypoxemia during VV-ECMO. However, the improvement of arterial oxygenation was associated with decreased DO₂.