ECMO in COVID-19-prolonged therapy needed? A retrospective analysis of outcome and prognostic factors

Abstract

Background: The role of venovenous extracorporeal membrane oxygenation (VV ECMO) in patients with COVID-19-induced acute respiratory distress syndrome (ARDS) still remains unclear. Our aim was to investigate the clinical course and outcome of those patients and to identify factors associated with the need for prolonged ECMO therapy.

Methods: A retrospective single-center study on patients with VV ECMO for COVID-19-associated ARDS was performed. Baseline characteristics, ventilatory and ECMO parameters, and laboratory and virological results were evaluated over time. Six months follow-up was assessed.

Results: Eleven of 16 patients (68.8%) survived to 6 months follow-up with four patients requiring short-term (<28 days) and seven requiring prolonged (⩾28 days) ECMO support. Lung compliance before ECMO was higher in the prolonged than in the short-term group (28.1 (28.8-32.1) ml/cmH₂O vs 18.7 (17.7-25.0) ml/cmH₂O, p = 0.030). Mechanical ventilation before ECMO was longer (19 (16-23) days vs 5 (5-9) days, p = 0.002) and SOFA score was higher (12.0 (10.5-17.0) vs 10.0 (9.0-10.0), p = 0.002) in non-survivors compared to survivors. Low viral load during the first days on ECMO tended to indicate worse outcomes. Seroconversion against SARS-CoV-2 occurred in all patients, but did not affect outcome.

Conclusions: VV ECMO support for COVID-19-induced ARDS is justified if initiated early and at an experienced ECMO center. Prolonged ECMO therapy might be required in those patients. Although no relevant predictive factors for the duration of ECMO support were found, the decision to stop therapy should not be made dependent of the length of ECMO treatment.

Keywords: ARDS; COVID-19; ECMO; SARS-CoV-2; extracorporeal membrane oxygenation; prolonged.

Figure 1.

Levels of respiratory rate, positive end expiratory pressure (PEEP), driving pressure (∆P), compliance, PaO₂/FiO₂ ratio, tidal volume (V_T), ECMO blood flow, and sweep gas flow over time. Days on ECMO except 2 hours = values 2 hours after ECMO implantation. A p-value < 0.05 was considered statistically significant for short-term group versus non-survivors (†), prolonged group versus non-survivors (◊), and short-term versus prolonged group (*). Data are shown as median and their interquartile range, and only for patients still on VV ECMO.

Figure 2.

Levels of ferritin, interleukin 6 (IL-6), platelets, C-reactive protein (CRP), white blood cells (WBC), and D-dimers over time. Days on ECMO except 2 hours = values 2 hours after ECMO implantation. A p-value < 0.05 was considered statistically significant for short-term group versus non-survivors (†), prolonged group versus non-survivors (◊), and short-term versus prolonged group (*). Data are shown as median and their interquartile range, and only for patients tested at the respective time point.

Figure 3.

Timeline of the viral load of SARS-CoV-2 in respiratory samples for survivors on ECMO <28 days (n = 4), survivors on ECMO ⩾28 days (n = 7), and non-survivors (n = 5).

Figure 4.

Levels of anti-SARS-CoV-2 IgG, presented as signal-to-cutoff ratio, in serum over time. Values ⩾1.0 were considered positive. Data are shown as median, and only for patients tested at the respective time point.