In-hospital mortality in patients admitted to Australian intensive care units with COVID-19 between 2020 and 2024

Abstract

Objective

To describe and compare the demographics, management, and outcomes for patients with COVID-19 admitted to intensive care units (ICUs) in Australia across the various waves of the COVID pandemic.

Design, setting, and participants

People aged ≥16 years who were admitted to a participating ICU with confirmed COVID-19 in the Short Period Incidence Study of Severe Acute Respiratory Infection (SPRINT-SARI) Australia study between February 2020 and May 2024.

Main outcome measures

Primary outcome: In-hospital mortality. Secondary outcomes: ICU mortality; ICU and hospital lengths of stay; supportive and disease-specific therapies.

Results

From 27 February 2020 to 18 May 2024, 10171 people were admitted to 72 ICUs with confirmed COVID-19 disease. The Wild Type wave included 518 (5.1%) patients, the Delta wave 2467 (24.3%) patients, and the Omicron wave 7186 (70.7%) patients. The median (IQR) age was 61 (49–70) years, 54 (41–66) years, and 65 (45–75) years, respectively (P < 0.001). The proportion of vaccinated cases increased in successive waves (1% vs 23.9% vs 65.1%) but plateaued in the Omicron subvariant waves (range 60.0%–71.9%). Invasive mechanical ventilation use decreased across successive waves (52.5% vs 43.6% vs 31.7%, P < 0.001). Use of extracorporeal membrane oxygenation was highest during the Delta wave (3.6%, 83 patients, median duration 18 days [IQR 9.8–35]). Multivariable analysis demonstrated an increased risk of in-hospital mortality among patients admitted during the Delta (adjusted HR 1.80, 95% CI: 1.38–2.35, p < 0.001) and Omicron (adjusted HR 1.88, 95% CI: 1.46–2.42, p < 0.001) waves when compared to the Wild Type wave.

Conclusion

COVID-19 continues to manifest significant morbidity and mortality in those requiring ICU admission. Despite a reduced need for ICU level supports, patients admitted during the Omicron wave demonstrated the highest in-hospital mortality.