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

ObjectiveTo 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. DesignNational, 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, participantsAdults (16 years or older) without COVID-19 admitted to Australian ICUs, 1 January 2016 - 30 June 2022. Main outcome measuresAll-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. ResultsData 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. ConclusionThe 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.