Association of Medical Burden and Capacity Changes With Clinical Outcomes Among Patients Without COVID-19 During the Pandemic: A Multicenter Retrospective Cohort Study

Abstract

Objectives: The spillover impact of the COVID-19 pandemic on patients without COVID-19 in ICUs should be assessed. We aimed to assess the association of ICUs' medical burden and capacity changes with clinical outcomes in such patients during the COVID-19 pandemic.

Design: Retrospective cohort study.

Setting: Twenty-three ICUs in Japan.

Patients: Patients without COVID-19 in ICUs from January 2019 to February 2023.

Interventions: None.

Measurements and main results: These ICUs completed a web-based questionnaire on medical burden and capacity limitations in November 2023, and they were classified as having a limited capacity if their scores exceeded the median; otherwise, they were categorized as having a maintained capacity. The primary outcome was the standardized mortality ratio (SMR), calculated with the Acute Physiology and Chronic Health Evaluation III-j model, compared with the pre-pandemic level. Using individual-level patient data, a generalized linear Poisson mixed-effects model including an offset-time term was employed to assess the association of capacity limitation, the number of patients with COVID-19, and ICU bed occupancy on the day of admission, with hazard ratios for in-hospital death. Nine and fourteen ICUs had a limited capacity (25,568 patients) and a maintained capacity (45,068 patients), respectively. SMRs increased in four epidemic waves in the ICUs with a limited capacity but in only one wave in those with a maintained capacity. After adjustment, capacity limitation (hazard ratio, 1.19; 95% CI, 1.01-1.41; p = 0.04) and the number of patients with severe COVID-19 (per five patients; hazard ratio, 1.09; 95% CI, 1.03-1.16; p = 0.002) were associated with in-hospital mortality, but ICU bed occupancy was not.

Conclusions: SMRs increased more frequently in ICUs with a limited capacity during the pandemic. Our findings emphasize the need for proactive strategies to mitigate medical burden and capacity limitations for future preparedness.

Keywords: COVID-19; cohort studies; hospital mortality; intensive care units; pandemics.