Background
Most data on intensive care unit (ICU) patients with COVID-19 originate in selected populations from stressed healthcare systems with shorter term follow-up. We present characteristics, interventions and longer term outcomes of the entire, unselected cohort of all ICU patients with COVID-19 in Denmark where the ICU capacity was not exceeded.

Methods
We identified all patients with SARS-CoV-2 admitted to any Danish ICU from 10 March to 19 May 2020 and registered demographics, chronic comorbidities, use of organ support, length of stay, and vital status from patient files. Risk factors for death were analyzed using adjusted Cox regression analysis.

Results
There were 323 ICU patients with confirmed COVID-19. Median age was 68 years, 74% were men, 50% had hypertension, 21% diabetes, and 20% chronic pulmonary disease; 29% had no chronic comorbidity. Invasive mechanical ventilation was used in 82%, vasopressors in 83%, renal replacement therapy in 26%, and extra corporeal membrane oxygenation in 8%. ICU stay was median 13 days (IQR 6-22) and hospital stay 19 days (11-30). Median follow-up was 79 days. At end of follow-up, 118 had died (37%), 15 (4%) were still in hospital hereof 4 in ICU as of 16 June 2020. Risk factors for mortality included male gender, age, chronic pulmonary disease, active cancer, and number of co-morbidities.

Conclusions
In this nationwide, population-based cohort of ICU patients with COVID-19, longer term survival was high despite high age and substantial use of organ support. Male gender, age, and chronic co-morbidities, in particular chronic pulmonary disease, were associated with increased risk of death.