In a new study, researchers found overall mortality of COVID-19 patients in intensive care units (ICUs) has fallen from almost 60% at the end of March to 42% at the end of May — a relative decrease of one third.
They also found ICU mortality for the disease is similar across the three continents included: Europe, Asia, and North America.
The important message is that as the pandemic has progressed and various factors combine, the survival of patients admitted to ICU has significantly improved.
The research was conducted by a team at the University of Bristol and Royal United Hospitals Bath NHS Trust.
In the study, the researchers reviewed studies reporting ICU mortality for adult patients admitted with COVID-19.
The primary outcome measure was the death in ICU as a proportion of completed ICU admissions, either through discharge from the ICU or death. The definition, therefore, did not include patients still alive in ICU.
A total of 24 observational studies including 10,150 patients were identified from centers across Asia, Europe, and North America.
In patients with completed ICU admissions with COVID-19 infection, combined ICU mortality across all the studies up to the end of May was 41.6%.
This represents a fall of around a third from the 59.5% ICU mortality seen in the studies up to the end of March.
The in-ICU mortality from COVID-19, at around 40%, remains almost twice that seen in ICU admissions with other viral pneumonia, at 22%.
There are several possible explanations for the findings regarding decreasing ICU mortality over time.
The team says it may reflect the rapid learning that has taken place on a global scale due to the prompt publication of clinical reports early in the pandemic.
It may also be that ICU admission criteria have changed over time, for example, with greater pressure on ICUs early in the pandemic surge.
The findings are also likely to reflect the fact that long ICU stays, for example, due to slow weaning from a ventilator, take time to be reflected in the data.
Critical illness linked to COVID-19 can last for long periods, with approximately 20% of UK ICU admissions lasting more than 28 days, and 9% more than 42 days.
One author of the study is Professor Tim Cook, Honorary Professor in Anaesthesia.
The study is published in Anaesthesia.
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