Overall mortality of COVID-19 patients admitted in ICUs has reduced considerably, shows study

A systematic review and meta-analysis of published studies from three continents shows overall mortality of COVID-19 patients in intensive care units (ICUs) has fallen from almost 60 per cent at the end of March to 42 per cent at the end of May — a relative decrease of one third.

The review, led by the University of Bristol and Royal United Hospitals Bath NHS Trust and published today in Anaesthesia, a journal of the Association of Anaesthetists, also shows 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, survival of patients admitted to ICU has significantly improved. There were no significant effects of geographical location, but reported ICU mortality fell over time.

Optimistically, as the pandemic progresses, we may be coping better with COVID-19," said lead author Professor Tim Cook, Honorary Professor in Anaesthesia at the University of Bristol and Consultant in Anaesthesia and Intensive Care Medicine at Royal United Hospitals Bath NHS Foundation Trust.

The researchers searched the MEDLINE, EMBASE, PubMed and Cochrane databases up to 31 May 2020 for studies reporting ICU mortality for adult patients admitted with COVID-19. The primary outcome measure was 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 on ICU.

A total of 24 observational studies including 10,150 patients were identified from centres 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 per cent. This represents a fall of around a third from the 59.5 per cent ICU mortality seen in the studies up to the end of March.

Professor Cook said: "The in-ICU mortality from COVID-19, at around 40 per cent, remains almost twice that seen in ICU admissions with other viral pneumonias, at 22 per cent."

There are several possible explanations for the findings regarding decreasing ICU mortality over time.

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."

Tim Cook, Study Lead Author and Honorary Professor,  Anaesthesia, University of Bristol

The findings are also likely to reflect the fact that long ICU stays, for example, due slow weaning from a ventilator, take time to be reflected in the data. Critical illness associated with COVID-19 can last for long periods, with approximately 20 per cent of UK ICU admissions lasting more than 28 days, and nine per cent more than 42 days.

The ICU mortality did not differ significantly across continents despite some evidence of variations in admission criteria, treatments delivered and the thresholds for their application. This is consistent with research findings up until the end of May suggesting that no specific therapy reduces ICU mortality. In the last few weeks dexamethasone has been found to have significant benefit and there is hope this will improve survival further.