This week is a bit of a mixed bag – and perhaps not as long a piece as it could have been, what with all the COVID-19 news.

For those who feel a bit short-changed and want something more to read, I’ve added a few interesting bits to the Military Intelligence page: a paper on COVID in children, a video on COVID and blood clots, another video giving a two minute overview of ICU.

Step down….and step back up

I’ve not been idle. On June 1^st, my hospital will begin stepping down COVID-19 emergency measures. That being the case, I wanted to give a local overview of the pandemic to date, but I’m struggling to find all the patient numbers from the last three months.

There have been so many different communication routes between management and staff (email, Trust intranet pages, Microsoft Teams, Clinibee, many individual Whatsapp groups, etc etc).

Sometimes information is conveyed predictably and regularly via these routes. Sometimes, sporadically. The ping of Whatsapp notifications accompanies all meetings, ward rounds and conversations with patients and relatives. Sometimes information is distributed generally, sometimes it is ‘sensitive’ and limited to key personnel.

Whatever route you choose as a clinician consumer, the hard information that’s directly relevant your own clinical work is now all mixed up with a much larger volume of other stuff.

Stuff like….

(1)Deadlines for everything

(2) Instructions intended for other clinicians

(3) Advice on virtual meeting software

(4) Clinical observations and discussion

(5) Directions to research papers, webinars, news items

(6) Requests for assistance with research/audits

(7) Jokes and memes (plenty – thank goodness)

(8) Recipes

(9) Pointers to psychological support and dermatological services

(10) Questions about PPE, hospital geography, wages, rotas, bicycles, car parking, weather etc etc

(11) News of free food deliveries/offers/discounts (so many the Trust eventually set up an information page)

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Picking through these random announcements, I believe the peak number of mechanically ventilated COVID-positive patients in our Trust must have been around 150. We are now below a third of that – well within our usual critical care capacity. The pop-up ICU on the surgical recovery ward, which once contained 16 ventilated COVID-positive patients, is now empty and ready to take postoperative patients as usual.

This presents its own problems. Among the many issues my anaesthetic colleagues are discussing are:

(1) Which types of non-urgent surgery should be prioritised (e.g. hip replacements vs hernias)

(2) Will COVID-related delays mean that patients coming for surgery are sicker?

(3) Can we establish regular lists with predictable surgeon/anaesthetist partnerships?

(4) How can we help trainee anaesthetists catch up what they have missed?

(5) How can we adhere to principles like ‘All-patients-presumed-COVID-positive’ and ‘Avoidance-of staff-to-patient-COVID-transmission’, and their enormous inherent inefficiencies, now we have a huge backlog of surgical work?

As an anaesthetist working exclusively in the operating theatre before the pandemic, item (5) in the list – theatre productivity – is a subject close to my heart.

The protocols my department introduced to protect operating theatre staff dealing with COVID-presumed patients (ie all patients) have essentially halved the number of patients we can operate on each day. These protocols will be staying in place indefinitely.

This week, then, I’ve been working hard on a proposal for a modified general anaesthetic. Potentially suitable for many types of surgery, this method should not generate the respiratory aerosols in theatre which are thought to have the potential to transmit COVID-19 from patients to staff. If my anaesthetic colleagues choose to adopt it, I hope that theatre turnaround will come back to pre-pandemic levels.

The broad method I’m proposing – ‘ketofol’ – is well-established but very unusual in the UK. Much of the related academic literature comes from lower or middle-income countries, and/or from non-anaesthetists. If you are interested, it’s presented for clinicians on another page in The Plague Pit.

https://plaguepit.com/covid-ga-with-no-agp/

I’m afraid it’s long and technical. I’m working on a short, plain language summary of the rationale and the technique itself. I’ll post this later in the week. I’ll also tell you whether there has been any ‘buy-in’ from my department in the next subscriber update. Here’s hoping.

Plain talking

Talking of plain language, I just wanted to say thank you to all the website’s student contributors so far – Alfred Beadman, Angel Chen and Adrian Tsui. There are more student authors and articles in the pipeline – and that’s just as well.

One of the purposes of The Plague Pit is to provide an early opportunity for young science writers. Writing about science for the public can be a rewarding  career in its own right, as the growing number of MA degrees in Science Communication shows. A good science writer can earn a living working in media, journalism, museums and advertising – also in pharmaceutical and other companies, grant-giving and research bodies, and in the communications departments of academic institutions.

That’s even before we consider the increasing importance of good writing and public engagement skills in traditional scientific careers. I can speak for medicine but I’m almost certain the same is true for other areas of scientific life.

Doctors are now closely involved in writing about diseases and treatments for their patients, for publication in hospital information leaflets or on websites. There’s an example in the next section of this article.

Leaving aside routine clinical work, all research grant applications now require a ‘plain language’ summary. Increasingly, funders considering large projects also want to know what the grant applicant is going to do about consulting public stakeholders on research design. And after that, how they plan to engage the public during the course of the research and when the results come out.

Alright, then! Seeing as you asked……

I suppose I’d better return to the clinical world. Last time, my colleague was about to perform an tracheal emergency intubation in Casualty on a hypoxic COVID-19 patient, in order to start mechanical ventilation.

Tracheal intubation under these circumstances is a bit different from the pre-pandemic, routine technique anaesthetists used to intubate non-urgent surgical patients in theatres. First, it’s more difficult. Full PPE restricts vision, movement and communication. The risk of contamination means there are a few other subtle but important technical modifications.

In Casualty intubations, whether COVID-19 or not, the space and equipment may be less familiar to the anaesthetist than theatres. The patients are also unprepared – specifically, they often have a full stomach.

Patients coming for routine surgery are asked to refrain from food for six hours before their operation so that the stomach has a chance to empty. Patients requiring immediate intubation in Casualty for their car crash/sporting injury/COVID induced respiratory failure can’t plan ahead in the same way.

A full stomach means they are at risk of regurgitating their acidic gastric contents during the process – and then inhaling them. Not helpful, especially for COVID lungs .There are ways round this problem (another time, perhaps…) but it’s an important one.

Unlike their everyday surgical counterparts, patients requiring intubation in Casualty, COVID-19 or otherwise, also tend to be very unwell. The margin for anaesthetist difficulty or error is much smaller.

As I wrote last week, COVID-19 patients often start off hypoxic and are using oxygen fast. With a few exceptions (see below), patients don’t breathe during intubation. That is, ‘apnoeic’. So if the intubation proves tricky and takes longer than usual, there is a risk that the COVID-19 patient may become even more hypoxic.

A digression on tricky intubations

For most tracheal intubations, emergency or otherwise, anaesthetists will use drugs beforehand to induce anaesthesia, rendering the patient unconscious, apnoeic and paralysed. Then they usually put a laryngoscope into the patient’s mouth to help them see where the tube should go. Here’s a picture of one – in a meme from early on in the pandemic.

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The bit on the left has a light on the end and goes into the mouth, over the tongue and down the throat a short way. The anaesthetist slides the endotracheal tube over the laryngoscope, through the vocal cords and down into the trachea

This technique is fine for most intubations – but not all. I worked in a Hong Kong hospital a few years ago where they did lots of maxillofacial surgery. Sometime the patients had conditions which meant their mouths didn’t open very much. This problem often persists under general anaesthesia. No mouth opening means no laryngoscopy – and that’s very inconvenient for an anaesthetist. Sometimes worse than inconvenient. Here’s why.

If I induce anaesthesia in patients and find I am unable to get a laryngoscope and tube in, that’s not necessarily the end of the world. Most of the time I can apply a tight facemask to the unconscious patient. I can attach this to a bag like the one below, itself connected to an oxygen supply, and squeeze oxygen into the lungs (‘manual ventilation’) while I prepare the next move. The facemask goes where the red safety cap is.

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Sometimes, though, general anaesthesia and muscle relaxation cause the tissues around the airway itself to collapse and obstruct. When that happens, manual ventilation may be ineffective. So it’s not possible (1) to insert a laryngoscope and tracheal tube or (2) to get oxygen into the patient’s lungs with the facemask.

This situation is called “Can’t Intubate, Can’t Ventilate” – (CICV). It’s immediately life-threatening. Even healthy patients can only survive a few minutes without oxygen.

The video below features Martin Bromiley – an airline pilot and a bit of a hero to many anaesthetists. He was kind enough to speak at a workshop I ran a few years ago on medical error. His wife died in 2005, during a routine anaesthetic, when a CICV situation arose and was not managed correctly with an emergency tracheostomy.

https://www.youtube.com/watch?v=JzlvgtPIof4

Instead of suing everyone, Martin decided to bring the lessons from his professional life to ours. He established the Clinical Human Factors Group in 2007 to promote research and discussion between patients and doctors on medical error and its prevention. He was later awarded an OBE.

In Elaine Bromiley’s case, the fact that she had a ‘difficult airway’ was not apparent pre-operatively. With my Hong Kong patients, it generally was – so I could make a plan in advance, to avoid CICV.

Like my hospital in Hong Kong, The Queen Victoria Hospital (QVH) in East Grinstead specializes in maxillofacial surgery. [There’s a really fascinating wartime history behind that – one for another time, perhaps]. QVH come across many preoperative patients who are predicted to have a high risk of CICV.

They made a video for them, to explain how anaesthetists avoid the problem.

https://www.youtube.com/watch?v=XnvK-Gx0qUw

IN the video, the tube is introduced through the nose (‘awake nasal fibreoptic intubation’ – ANFI). Nevertheless, the view of the larynx is like the one I get, when I put a laryngoscope in the mouth of an unconscious patient in theatres.

Unfortunately, ANFI is of limited use in COVID-19 patients. That’s because it’s a technique that does not always go quite as smoothly as it does in the QVH video. Especially if the anaesthetist is a bit out of practice. These days, when I am obliged to choose ANFI ( for non-infective) patients, there’s generally a bit of coughing, spluttering and aerosol dissemination….

COVID-19 intubation and an experiment for you

The last thing I wanted to mention – before the drugs go into our COVID-19 patient and the tube goes down the trachea – is lung volumes. These are absolutely central to respiratory physiology. The details are here (https://en.wikipedia.org/wiki/Lung_volumes).

Of all the lung volumes, the really important one is the functional respiratory capacity (FRC). This is the volume left in the lung at the end of a normal expiration. It’s usually filled with air.

If you give patients 100% oxygen to breathe for long enough before their intubation – typically 5 minutes – nearly all that air is replaced by oxygen. Anaesthetists call this ‘pre-oxygenation’. We are very careful to do it properly in COVID-19 patients before we induce anaesthesia to intubate them for mechanical ventilation. That way, if we find the intubation is difficult, it gives us more time before the (apnoeic) patient becomes dangerously hypoxic

Here’s the life-saving maths. We’ll use a male patient as an example as they make up 75% of COVID-19 patients on ICU:

Average male FRC is 2.4l. Oxygen content in air is 21%. If you fill the FRC with 100% oxygen instead of air, it contains 2400ml vs 504ml. The rate at which a healthy, resting, adult male patient uses up oxygen is about 250ml/min. So an air filled FRC will ‘last’ the patient about two minutes – an oxygen-filled one about ten minutes. A physiologist might quibble with the precise numbers, but the general principle is sound.

Now set the QVH video at the start. It has been edited to 3:45 minutes, but I’ll give them the broad benefit of the doubt. Let’s say a tricky intubation takes four minutes.

Take a deep breath to ensure your FRC is full. That’s full of air with 21% oxygen – not with 100% oxygen, as it would be after pre-oxygenation.

Hold it.

Now press play.

How did you get on?

The Good Soldier