Characteristics and outcomes of patients admitted to Swedish intensive care units for COVID-19 during the first 60 days of the 2020 pandemic: a registry-based, multicenter, observational study
Authors: Chew Michelle S , Blixt Patrik , Åhman Rasmus , Engerström Lars , Andersson Henrik , Berggren Ritva Kiiski , Tegnell Anders , McIntyre Sarah 
Published: August 2020

Background

The mortality of patients admitted to the intensive care unit (ICU) with COVID-19 is unclear due to variable censoring and substantial proportions of undischarged patients at follow-up. Nationwide data have not been previously reported. We studied the outcomes of Swedish patients at 30 days after ICU admission.

Methods

We conducted a registry-based cohort study of all adult patients admitted to Swedish ICUs from 6 March-6 May, 2020 with laboratory confirmed COVID-19 disease and complete 30-day follow-up. Data including baseline characteristics, comorbidities, intensive care treatments, organ failures and outcomes were collected. The primary outcome was 30-day all-cause mortality. A multivariable model was used to determine the independent association between potential predictor variables and the primary outcome.

Results

A total of 1563 patients were identified. Median ICU length of stay was 12 (5-21) days, and fifteen patients remained in ICU at the time of follow-up. Median age was 61 (52-69), median Simplified Acute Physiology Score III (SAPS III) was 53 (46-59), and 66·8% had at least one comorbidity. Median PaO2/FiO2on admission was 97·5 (75·0-140·6) mmHg, 74·7% suffered from moderate to severe acute respiratory distress syndrome (ARDS). The 30-day all-cause mortality was 26·7%. The majority of deaths occurred during ICU admission. Age, male sex (adjusted odds ratio [aOR] 1·5 [1·1-2·1]), SAPS III score (aOR 1·3 [1·2-1·4]), severe ARDS (aOR 3·1 [2·0-4·8], specific COVID-19 pharmacotherapy (aOR 1·4 [1·0-1·9]), and CRRT (aOR 2·2 [1·6-3·0]), were associated with increased mortality. With the exception of chronic lung disease, the presence of comorbidities was not independently associated with mortality.

Conclusions

Thirty-day mortality rate in COVID-19 patients admitted to Swedish intensive care units is generally lower than previously reported. Mortality appears to be driven by age, baseline disease severity, the degree of organ failure and ICU treatment, rather than preexisting comorbidities.

Funding

Region Östergötland County Council and Linköping University; number 30320008.

Research in context

Evidence before this study

In previous studies reporting outcomes for COVID-19 patients admitted to intensive care units (ICUs), none reported 30-day mortality rates, many were censored after short observation periods, and most had substantial proportions of undischarged patients at the time of follow-up. Incomplete data may cause bias in reported mortality rates. Further, national data on critically ill patients have not been previously published.

Added value of this study

Our study provides complete 30-day follow up in a nationwide population of 1563 unselected patients admitted to intensive care units in Sweden. All but 15 patients had been discharged from ICU at follow-up thus the study also provides an accurate reflection of ICU mortality. We also provide age-stratified mortality rates and information on ICU treatment and outcomes. This cohort also differs from previous studies in so far as directed antiviral therapy for COVID-19 disease was infrequently used. Adjusted risk estimates for the effect of baseline factors, ICU complications and treatment demonstrate that age, the severity of respiratory failure and need for continuous renal replacement therapy were the most important risk factors for death.

Implications of all the available evidence

Mortality rates of COVID-19 patients in Swedish ICUs are lower than those previously reported, despite the high incidence of comorbidities, an ageing population and a high proportion of patients with severe ARDS. Directed antiviral pharmacotherapy was given only to a minority of patients suggesting that survival from COVID-19 in ICU is achievable with good supportive care. Our analysis also suggests that unaccounted factors eg. process and organizational, may be important in determining the outcome of critically ill patients with COVID-19. Our results may be of interest since Sweden has a very limited number of ICU beds and has adopted a unique response to the pandemic compared to other countries. Despite limited numbers of ICU beds per capita, Sweden was able to increase its ICU capacity during the first 2 months of the COVID-19 pandemic and provide essential care to the critically ill with encouraging results.