Multisystem inflammatory syndrome in adults with COVID‐19 requiring mechanical ventilation: A retrospective cohort study

AIM: Multisystem inflammatory syndrome in adults (MIS‐A) is a hyperinflammatory multisystem condition associated with coronavirus disease (COVID‐19). Critically ill COVID‐19 patients may develop multiorgan damage and elevated inflammatory responses, thus making it difficult to differentiate between progression to organ damage due to COVID‐19 itself or MIS‐A. This study aimed to explore the characteristics and complications of MIS‐A in critical COVID‐19 patients. METHODS: The Japan Extracorporeal Membrane Oxygenation (ECMO) Network and ICU Collaboration Network developed a web‐based database system called the CRoss Intensive Care Unit Searchable Information System (CRISIS) to monitor critical COVID‐19 patients throughout Japan. We retrospectively identified patients with MIS‐A among critical COVID‐19 patients enrolled from March 2020 to December 2021, using CRISIS. Our MIS‐A definition required patients to be at least 18 years of age, have laboratory evidence of inflammation, severe dysfunction of at least two extrapulmonary organ systems, and no plausible alternative diagnoses. RESULTS: Of the 1052 patients, 26 (2.5%) were diagnosed with MIS‐A. The MIS‐A patients had a higher likelihood of using ECMO (13% vs. 46%, p < 0.001) and lower overall survival (77% vs. 42%, p < 0.001) than non‐MIS‐A patients. More than 80% of the MIS‐A cases occurred 3 weeks after the COVID‐19 onset. CONCLUSION: Multisystem inflammatory syndrome in adults can occur in 2.5% of critically ill COVID‐19 patients, and the mortality rate is high. Multisystem inflammatory syndrome in adults may be considered when there is a re‐elevation of the unexplained inflammatory response and severe dysfunction of at least two extrapulmonary organ systems several weeks after the onset of COVID‐19.