Mortality among people admitted to Australian intensive care units for reasons other than COVID-19 during the COVID-19 pandemic: a retrospective cohort study

Abstract

Objective: To investigate in-hospital mortality among people admitted to Australian intensive care units (ICUs) with conditions other than coronavirus disease 2019 (COVID-19) during the COVID-19 pandemic. Design: National, multicentre, retrospective cohort study; analysis of data in the Australian and New Zealand Intensive Care Society Centre for Outcome and Resource Evaluation (ANZICS CORE) Adult Patient Database. Setting, participants: Adults (16 years or older) without COVID-19 admitted to Australian ICUs, 1 January 2016 – 30 June 2022. Main outcome measures: All-cause in-hospital mortality, unadjusted and relative to the January 2016 value, adjusted for illness severity (Australian and New Zealand Risk of Death [ANZROD] and hospital type), with ICU as a random effect. Points of change in mortality trends (breakpoints) were identified by segmental regression analysis. Results: Data for 950 489 eligible admissions to 186 ICUs were available. In-hospital mortality declined steadily from January 2016 to March 2021 by 0.3% per month (P < 0.001; March 2021 v January 2016: adjusted odds ratio [aOR], 0.70; 95% confidence interval [CI], 0.62–0.80), but rose by 1.4% per month during March 2021 – June 2022 (P < 0.001; June 2022 v January 2016: aOR, 1.03; 95% CI, 0.90–1.17). The rise in mortality continued after the number of COVID-19-related ICU admissions had declined; mortality increased in jurisdictions with lower as well as in those with higher numbers of COVID-19-related ICU admissions. Conclusion: The rise in in-hospital mortality among people admitted to Australian ICUs with conditions other than COVID-19 from March 2021 reversed the improvement of the preceding five years. Changes to health service delivery during the pandemic and their consequences should be investigated further.