How to avoid rapid carbon dioxide changes at the start of veno-venous extracorporeal membrane oxygenation: Role of end-tidal CO2 monitoring

Background: Venovenous ECMO is a lifesaving technique for patients with severe respiratory failure. Management of carbon dioxide (CO2) levels at ECMO start is crucial, as recent studies found an association between rapid CO2 shifts and increased incidence of neurological complications. Purpose: To describe the role of end tidal CO2 (etCO2) monitoring at the ECMO start to minimize carbon dioxide shifts. Research design: Retrospective cohort study. Methods: We performed a retrospective analysis of patients who started venovenous ECMO support at our institution between 2011 and 2021. We analysed the minute-by-minute variations of etCO2, ventilatory parameters and arterial blood gas before and after the ECMO start. Results: 36 patients with a complete dataset of parameters were included. After the ECMO start, minute ventilation was progressively reduced from 10.8±;3.3 to 2.9±1.2 L/min (p<0.001). etCO2 did not vary significantly (baseline 37±10 vs 35±9 mmHg 20 minutes after ECMO start, p = 0.36). Despite a stable etCO2 level, a mild drop of arterial CO2 tension (9.5 mmHg, corresponding to a 18% change) was recorded at the first ABG sampled after the ECMO start. No patient developed neurological complications after the ECMO commencement. Conclusion: etCO2 monitoring during ECMO start is feasible and allows to adjust gas flow and ventilator settings to limit changes in arterial CO2 levels.