COVID-19 in Norwegian ICUs 2020-2023: Patient characteristics, management, and outcomes-A nationwide prospective observational study.

Background: During the COVID-19 pandemic, Norway experienced successive waves of hospital and intensive care unit (ICU) admissions, each with distinct characteristics, including patient demographics, medical therapies, vaccine coverage, respiratory failure management and mortality rates. The aim of this study was to analyse survival in a national cohort of adult COVID-19 patients admitted to Norwegian ICUs (March 2020-May 2023) and examine how patient characteristics and management strategies were associated with mortality across successive stages of the pandemic.

Methods: Patients admitted to ICUs between 10 March 2020 and 5 May 2023, were identified via the Norwegian Intensive Care and Pandemic Registry. We included all adults (≥18 years) and analysed data on demographics, predefined risk factors, severity, patient management and outcomes. We quantified associations between patient demographics, risk factors and admission period with mortality and ICU length of stay (LOS).

Results: The study included 2655 patients with confirmed COVID-19. Patients admitted from 2022 onwards were significantly older (median age >70) and had more predefined risk factors compared to those admitted during earlier periods (median age < 65 years). Management of respiratory failure shifted towards less frequent use of invasive mechanical ventilation. The crude 90-day mortality rate doubled from 21% (95% CI 14; 24) in the first half of 2020 to 43.5% (95% CI 31.1; 45.7) in the first half of 2023. ICU LOS decreased substantially from a median of 14.1 days (interquartile range [IQR] 6.8; 23.1) to 2.6 days (IQR 1.1; 5.0). The time period of admission, patient age, pre-defined risk factors and Simplified Acute Physiology Score (SAPS II) were significantly associated with mortality. Prolonged ICU LOS was primarily associated with respiratory support mode, age and higher SAPS II scores.

Conclusion: In this nationwide study of the COVID-19 pandemic in Norway, ICU mortality was significantly higher in later compared to earlier admission periods, largely explained by changes in case mix, such as older patients with more co-morbidities. While ICU therapies were modified over the course of the pandemic, their impact on survival cannot be determined from our analyses (NCT04601090).

Editorial comment: In this article, findings from Norway's national Intensive care database are presented for critically ill SARS-CoV-2 cases, including the different pandemic waves throughout the whole period. Characteristics and trends related to illness and ICU care are presented.