NEW research has cast doubt on the dangers of anaesthetic procedures and the need for tough restrictions that are piling pressure on waiting lists.

A study carried out in NHS operating theatres in Bristol found that surgeons were being exposed to a fraction of the particles they would from a normal cough.

Researchers have called for a re-evaluation, saying that the findings suggest operations carried out under anaesthetic are being wrongly classified as 'aerosol-generating procedures' (AGPs).

Medics and dentists involved in AGPs are required to wear high-grade protective gear, whereas staff looking after patients known to be infected with Covid - even those carrying out nasal and throat swabs on patients with virus symptoms - are only required to wear standard PPE.

It was thought that inserting and removing a tube from a patient's airway during surgery would produce a fine spray, potentially containing virus particles.

The restrictions apply universally, regardless of Covid status. Even if the patient tests negative, they can still be incubating the virus and infectious.

As a result, theatre staff must wear high-grade respirators, a long sleeved gown, gloves and eye protection as a precaution during surgery, with operating rooms deep-cleaned between patients.

This has contributed to severely reduced theatre capacity and turnaround times for operations, exacerbating the backlog on elective waiting lists.

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Despite the presumed risk, the volume of aerosols released by intubation and extubation had never been measured.

Researchers carried out environmental monitoring during dozens of procedures in four NHS operating theatres in Bristol over a three-week period.

Patients were admitted to theatre for urgent orthopaedic and brain surgery.

None of the patients were known to have Covid-19 infection.

The study was led by Dr Jules Brown, of North Bristol NHS Trust, and Professor Jonathan Reid of Bristol University's Aerosol Research Centre.

They were surprised to discover that tube insertion generated approximately one thousandth of the aerosols released by a single cough, while tube extraction produced less than a quarter.

They also "detected no increases in aerosolised particles during face-mask ventilation, airway suction or repeated attempts at intubation".

The findings, published in the journal Anaesthesia, "should trigger a re-evaluation" of guidelines which have "reduced operating theatre turnover, decreased hospital productivity and increased waiting times for elective and cancer surgery", write the authors.

They add: "De-escalation of these high-level protective measures would have a substantial impact on our ability to deliver healthcare to patients within the NHS and internationally.

“If we can agree these procedures do not generate aerosols we can reduce the PPE we wear and we can eliminate the major delays that currently exist between one patient leaving the operating room and starting the next case.”

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Professor Michael Griffin OBE, President of the Royal College of Surgeons of Edinburgh, said: "This is certainly a positive move forward and the findings of this research could help speed up waiting times for patients, however, it will still take a long time to fully recover from the large backlog of elective surgery which has built up over the course of the pandemic.

"It will be very welcome news if this contributes to reducing waiting times for elective surgery at a time when many hospitals are operating at a vastly reduced capacity."

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Dr Brown and colleagues describe the existing evidence base for the restrictions as "weak" and largely derived from retrospective studies from the SARS epidemic - a deadlier strain of coronavirus which killed 774 people in South-East Asia between 2002 and 2003.

These studies found an association between acquiring SARS and being in the room during intubation "but without any measure of aerosol generation", say the researchers.

They add that since the SARS patients were unwell with a respiratory infection they "may have been coughing during the intubation sequence", or that virus particles could have been spread by touching contaminated surfaces rather than from aerosol transmission.

They stress that they "made no measurements from subjects known to have Covid-19" but, on the basis of their results, tube insertion during anaesthesia "should not be considered a high-risk procedure".