Background: COVID-19 has led to increased numbers of patients in need of venovenous extracorporeal membrane oxygenation (ECMO) support, but knowledge on management in comparison to acute respiratory distress syndrome (ARDS) of other etiologies is still lacking. We analyzed venovenous ECMO management and survival outcomes in patients with COVID-19 in comparison to influenza ARDS and pulmonary ARDS of other origin. Results: Retrospective analysis of prospective venovenous ECMO registry-based data collection was performed. One hundred consecutive venovenous ECMO patients with severe ARDS were included (41 COVID-19, 24 influenza A, 35 ARDS of other etiologies). Patients with COVID-19 had higher BMI (body mass index), lower SOFA (Sequential Organ Failure Assessment) and APACHE II (Acute Physiology and Chronic Health Evaluation II) scores, lower C-reactive protein and procalcitonin levels and less vasoactive support at ECMO initiation. Significantly more patients were mechanically ventilated for more than 7 days prior to ECMO initiation in the COVID-19 group, however they were ventilated with lower tidal volumes and more often received additional rescue therapies prior to and on ECMO. COVID-19 patients had significantly more barotrauma and thrombotic events on ECMO. There were no differences in weaning of ECMO, however duration of ECMO runs and ICU length of stay was significantly longer in the COVID-19 group. The leading cause of death in the COVID-19 group was irreversible respiratory failure, while uncontrolled sepsis and multiorgan failure were leading causes in the other 2 groups. All patients who survived ICU treatment were discharged out of hospital, and there were no differences in survival among groups at 180 days. Conclusions: Survival outcomes of venovenous ECMO patients do not differ between COVID-19 and ARDS of other pulmonary etiologies. ARDS guidelines were in greater proportion adhered to in COVID-19 patients, with, however, longer time to ECMO initiation. COVID-19 ARDS seems specific as a more single-organ disease with longer ECMO duration and irreversible respiratory failure as a main cause of ICU mortality.

Background: Necrotizing lung infections (NLI) are rare yet severe complications of lower respiratory tract infections with high mortality. Due to their scarcity and varying severity, there are no specific guidelines on managing these entities. Incidence and outcomes of NLI in patients on VV-ECMO remains largely unknown. Methods: This observational cohort study retrospectively analyzed data from a prospective ECMO registry at University Medical Centre Ljubljana. Consecutive adult VV-ECMO patients hospitalized between 2010 and 2023 were screened. Patients with NLI, defined as computed tomography (CT) documented necrotising pneumonia, lung abscess or necrotizing cavitation were identified and included in the analysis. Results: Out of 125 VV-ECMO patients with severe respiratory failure due to lung infections, 38 (30.4%) had NLI. Majority of patients (71%) initially presented with viral pneumonia with secondary bacterial superinfection and most had multi-lobar involvement (73.7%). There was considerable overlap of all necrotizing entities. Duration of hospitalization prior to ECMO initiation was the only significant factor determining patient outcome (2 days in survivors vs 8 days in non-survivors, p = 0.04), while duration of mechanical ventilation prior to cannulation had no significant effect on patient outcome. Although not statistically significant, survival rates were considerably higher in patients who primarily presented with community-aquired pneumonia compared to those with hospital-aquired pneumonia (38% vs 14%). Patients with additional complications like empyema or bronchopulmonary fistula had poor outcomes, with only 5% survival. Surgical lobectomy was performed in 5 (13%) patients, all patients died. Nine (24%) patients survived to ICU and hospital discharge and were still alive at 1-year follow-up. Conclusions: Incidence of NLI in VV ECMO patients is higher than reported in non-ECMO population. Surgical interventions were not successful in this cohort. Considering the combination of severe respiratory failure and necrotising complications, overall survival rate of respiratory ECMO patients with NLI is still reasonable.

We greatly appreciate the comments of Rakovich and Kurz regarding our recently published article. In our correspondence, we clarify several issues raised by the authors regarding the definition, pathophysiology and management of necrotizing lung infections (NLI) in patients requiring VV-ECMO support for severe respiratory failure. We emphasize that there is currently no universally accepted radiological definition or volumetric cut-off for necrotizing pneumonia. Our study intentionally used a broader CT-based definition encompassing necrotizing pneumonia, lung abscess and necrotizing cavitation to capture the clinically relevant spectrum of destructive pulmonary complications observed in critically ill ECMO patients. Following the authors’ suggestion, we additionally re-analysed our cohort using a proposed threshold of >50% non-enhancing consolidated parenchyma, with 55% of patients still fulfilling these criteria. We further clarify that our cohort consisted primarily of patients with severe ARDS requiring ECMO support in whom NLI developed as a complication of extensive pre-existing lung injury, rather than as the primary cause of refractory hypoxemia. The high proportion of viral pneumonia, particularly COVID-19, concomitant thromboembolic events, corticosteroid exposure and severe ventilation/perfusion abnormalities likely contributed to the high incidence of necrotic complications observed in our cohort. Finally, we agree that surgical intervention should remain a last-resort strategy in these patients and provide additional clinical data regarding surgically treated patients to better illustrate the severity of disease and indications for operative management.