Covid Scotland: Most ICU 'Covid' patients since Omicron in hospital for other reasons

A total of 296 patients with a positive PCR test for Covid were admitted into ICUs across Scotland between January 1 and March 13 this year.

However, the report by the Scottish Intensive Care Society Audit Group (SICSAG) found that only 26 per cent of these Covid positive patients “had Covid-19 as the primary reason for admission to critical care”.

For a further 14% of patients, their Covid infection was not the main cause of illness but “may have contributed to the reason for admission”.

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In the remaining 60%, however, Covid was “coincidental” - signalling that patients had tested positive on, or after, admission for other ailments.

The turnaround in intensive care trends since Omicron has been particularly dramatic.

During the first and second Covid waves in Spring 2020 and winter 2020/21, when the Alpha variant took off, more than 80% of Covid positive patients in ICU were there as a result of being critically ill with the infection.

Covid positive admissions where infection was primary cause of admission (dark blue) or where other diagnosis was main reason for admission (purple) during various Covid waves

Even in the latter stages of the Delta wave in October and November last year, around 60% of Covid positive patients were there because of the infection, compared to just 26% now in the Omicron wave.

It is unclear how much of this change is driven by the Omicron variant specifically, and how much reflects the impact of substantial increases in booster uptake which occurred during December.

However, the effect in intensive care is much more pronounced compared to overall hospital Covid admissions, covering all departments and wards.

Between March and August 2021, when Delta was dominant, around 68% of all the Covid positive patients in hospital were there because of the infection, with this falling only slightly to around 50-60% with Omicron.

The SICSAG report said using PCR tests to identify Covid ICU cases "no longer identifies patients admitted with Covid-19 disease with sufficient accuracy", but that a revised method - based on patients' "reason for admission" code - was also problematic as it misses cases where Covid was a contributory factor for admission and also fails to "reflect the resource implications associated with isolating patients with a positive SARS-CoV-2 test from other patients".

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The report also outlines how demand for the highest level of intensive care has fluctuated during the pandemic.

NHS Scotland has a baseline capacity of 173 ICU beds at 'Level Three', for the sickest patients. These are individuals requiring mechanical ventilation and organ support, and who should be cared for on a ratio of one nurse per patient.

At the start of the pandemic, health boards rapidly expanded this capacity by re-purposing areas of the hospital - such as operating theatres - as makeshift ICUs, with separate units for Covid and non-Covid patients.

Total demand for ICU beds with ventilation from Covid (dark blue) and non-Covid (light blue) patients (periods when baseline capacity exceeded highlighted in red)

In total, this 'surge capacity' meant that the NHS could care for a maximum of 585 patients with invasive mechanical ventilation.

This maximum capacity was not required, but demand for Level Three care did peak in April 2020 when around 250 patients were being ventilated in ICU beds - around 190 of them Covid patients.

By the end of February this year, however, demand for Level Three beds was the lowest since late summer 2020, with only around 50% of the baseline capacity of 173 beds being used.

Of these, around one in five were filled with Covid positive patients.

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This does not mean that Level Three beds were lying empty, however, as intensive care beds can be downgraded or converted into high-dependency beds instead for patients who require critical care without ventilation.

Since February this year, the total number of ICU admissions - for Covid and non-Covid illnesses combined - has been in line with pre-pandemic averages, of around 250-300 per week.

Number of weekly elective (planned) admissions to intensive care, 2019 (dark blue) to 2022 (red)

However, the report notes that planned ICU admissions - for example, for patients undergoing complex cancer, heart, or brain surgery - remain well below pre-pandemic levels.

This suggests that a substantial portion of the ICU admissions are unplanned emergency and urgent cases, caused by non-Covid illness.

The SICSAG report states: "Despite the demand on ICUs, some elective activity continued throughout the pandemic, albeit complicated by the requirement to maintain separate non-Covid ICUs.

"At the time of maximum bed use across Scotland, there was a 64% reduction in elective activity compared to 2019.

"At the time of [this] report, elective activity remains 36% less than the equivalent week in 2019.

"Since the start of the pandemic, elective admissions have remained below that seen in 2019."