In their interim guidelines, the World Health Organization (WHO) stated that SARS-CoV-2-related acute respiratory distress syndrome (ARDS) could be treated by ECMO intervention in expert centers.1 According to the international registry, more than 2,000 cases of SARS-CoV-2 ARDS have been treated by ECMO, more than 90% of which were in the VV mode.2 Aside from critical issues related to limited numbers of devices and human resources in the recent COVID-19 pandemic, the role of ECMO appeared to be favored as a vital tool for bridging the patient to recovery from severe ARDS. However, indications for its use have to be carefully assessed, and long-term outcomes need to be monitored. Once ECMO is deemed indicated, timely introduction is preferable to allow injured lungs to rest and recover as much as possible, because of its ability to confer lung protection from mechanical ventilator-associated injury.3
Among the contraindications for ECMO administration, obesity (BMI of 35.6 in Case 1) and underlying lung disease (emphysema in Case 2) require extra care over the course of treatment. Bilateral diaphragmatic elevation by the obese abdomen makes it difficult to maintain efficient ventilatory volume. Prone positioning, proven to be effective for ARDS,4 was not undertaken for Case 1 because it could not be performed safely with ECMO cannulas in place in this severely obese patient. In Case 2, we performed early tracheostomy so that the patient could be awake and mobilized for rehabilitation on a ventilator. The patient fortunately recovered with preserved lung function requiring no oxygen therapy. Frequent bronchoscopic drainage to maintain the airway was required in both cases with maximal precautions regarding the use of personal protective equipment by the medical staff.
Among extrapulmonary injuries of severe SARS-CoV-2 infection, renal impairment was observed in both cases presented here, consistent with plausible mechanisms already described, such as direct viral infection by engaging angiotensin-converting enzyme 2 receptors with co-expressed transmembrane serine proteases triggering renal endothelial damage.5 Multiple antibiotics, extracorporeal circulation, and transient perfusion imbalance might also have contributed to causing decreased renal function. Great care was taken to maintain end-organ perfusion with appropriate oxygen delivery, management of which might minimize the duration of temporary hemodiafiltration. Coagulopathy, most likely a consequence of a profound inflammatory response, can cause massive thrombosis in critically ill SARS-CoV-2 cases.6 In a French multicenter study with a propensity-score matching analyses, comparison with non-SARS-CoV-2 ARDS revealed that significantly more thromboembolic events (mainly pulmonary embolisms) were seen in patients with SARS-CoV-2-related ARDS (4.8% versus 11.7%).7 In the current cases, clinically evident thromboembolic events were not seen, perhaps because of the early introduction of anticoagulation therapy along with nafamostat mesylate (a serine protease inhibitor) treatment which might also contribute to reducing thromboinflammation.8,9
In summary, SARS-CoV-2 ARDS could be treated successfully by timely introduction of organ replacement therapy using VV-ECMO and hemodiafiltration. Long-term follow-up of patients who survive SARS-CoV-2 ARDS is warranted, because sequelae of severe SARS-CoV-2 infection remain unclear.