Increased national critical care demands were associated with a higher mortality of intubated COVID-19 patients in Japan: a retrospective observational study.

Background: There was no study to investigate the association between the national surge of Coronavirus disease 2019 (COVID-19) patients and the mortality of mechanically ventilated COVID-19 patients. The aim of this study was to assess the association between mortality in mechanically ventilated COVID-19 patients and two distinct national COVID-19 surge indices: (1) the daily number of newly confirmed COVID-19 cases, representing overall medical demands and (2) the total number of critically ill COVID-19 patients, reflecting critical care demands.

Methods: We analyzed the patient data registered in a national database of mechanically ventilated COVID-19 patients between February 6, 2020, and May 16, 2023, combined with the data officially published by the Japanese government. Multivariable logistic regression analysis was performed to evaluate the association of these two indices with COVID-19 mortality. A generalized linear mixed effect model was used to examine the relationships between the variation in the impact of critical care demands across hospitals and the variation in baseline risk across hospitals.

Results: The data of 8327 patients from 264 centers in Japan were analyzed. The overall mortality rate was 24% (1990/8327). The critical care demands, but not overall medical demands, were independently associated with the mortality (OR, 1.11; 95% CI 1.07-1.16; p < 0.001). This effect of critical care demands on the mortality was more pronounced in hospitals with higher baseline risk (r = 0.67).

Conclusions: The national critical care demands were independently associated with the mortality of COVID-19 patients requiring mechanical ventilation. This effect was more pronounced in hospitals with higher baseline risk.