Outcomes for people admitted to Australian and New Zealand intensive care units with primary, exacerbating, or incidental SARS-CoV-2 infections, 2022–23: a retrospective analysis of ANZICS data

Objectives: To compare in-hospital mortality and intensive care unit (ICU) length of stay for people admitted to Australian and New Zealand ICUs during 2022–23 with coronavirus disease 2019 (COVID-19) pneumonitis, incidental or exacerbating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, or without SAR-CoV-2 infections. 

Study design: Retrospective cohort study; analysis of Australian and New Zealand Intensive Care Society (ANZICS) Adult Patient Database data. 

Setting, participants: Adults (16 years or older) admitted to participating ICUs in Australia or New Zealand, 1 January 2022 – 30 June 2023. 

Major outcome measures: The primary outcome was in-hospital mortality, the secondary outcome ICU length of stay, each by SARS-CoV-2 infection attribution classification: primary COVID-19; exacerbating SARS-CoV-2 infection (SARS-CoV-2 infection was a contributing factor to the primary cause of ICU admission); incidental SARS-CoV-2 infections (SARS-CoV-2 infection detected during ICU admission but did not contribute to admission diagnosis); no SARS-CoV-2 infection. 

Results: A total of 207 684 adults were admitted to 195 Australian and New Zealand ICUs during 2022–23; 2674 people (1.3%) had incidental SARS-CoV-2 infections, 4923 (2.4%) exacerbating infections, and 3620 (1.7%) primary COVID-19. Unadjusted in-hospital mortality for people with incidental SARS-CoV-2 infections (288 deaths, 10.8%) was lower than for those with exacerbating infections (928 deaths, 18.8%) or primary COVID-19 (830 deaths, 22.9%), but higher than for patients without SARS-CoV-2 infections (15 486 deaths, 7.9%). After adjusting for illness severity, frailty, geographic region, and type of hospital, mortality was higher for patients with incidental SARS-CoV-2 infections (adjusted odds ratio [aOR], 1.28; 95% confidence interval [CI], 1.10–1.50), exacerbating infections (aOR, 1.35; 95% CI, 1.22–1.48), or primary COVID-19 (aOR, 2.54; 95% CI, 2.30–2.81) than for patients without SARS-CoV-2 infections. After adjusting for diagnosis and illness severity, ICU stays were longer for people with incidental (mean difference, 3.3 hours; 95% CI, 2.4–4.2 hours) or exacerbating infections (0.8 hours; 95% CI, 0.2–1.5 hours) than for those without SARS-CoV-2 infections. 

Conclusion: Risk-adjusted in-hospital mortality and ICU length of stay are higher for people admitted to intensive care who have concomitant SARS-CoV-2 infections than for people who do not.