Will I Wake Up During My Operation?

This is a major concern for many patients who have an impending date for surgery. It seems to be a primal fear, lying there, unable to speak, unable to move, in pain. But is it going to happen? A golden rule in medicine is that nothing ever ‘never’ happens, but it’s very unlikely. ‘Awareness’ is reported in 1 in 19000 anaesthetics. But the idea of it is terrifying, isn’t it?

There was even a film!

It’s made the news because of the NAP 5 audit. This is a ginormous study involving every public hospital in the UK, looking for incidences of AAGA – accidental awareness during general anaesthesia, undertaken by the Royal College of Anaesthetists (RCoA) with the Association of Anaesthetists of Great Britain and Ireland (AAGBI). It’s commendable that the speciality would examine itself in this open and honest way.

Awareness. It’s a broad term. It could be someone who remembered their breathing tube coming out at the end of an operation, it could be someone who remembered something happening whilst they were sedated (and not supposed to be completely unconscious). It could be someone who was not adequately sedated when being moved from the operating theatre to the intensive care. In the study, awareness was most likely to occur when just going to sleep (induction) or when being woken up at the end of the operation (emergence) rather than in the middle of operations.

To get your head round the results, it might help to know a bit about anaesthesia itself. Skip this bit if you’ve ever given one.

Anaesthesia is an oft-misunderstood medical speciality. I think we should remember the incredible contribution that advances in anaesthesia have made to the world. Surgery that was once either completely intolerable or technically impossible is now performed safely and regularly. However, when I started my training (I only did 18 months before changing specialty) I was asked if I was still a doctor!

It has been compared to being an airline pilot, where all the action’s in taking off and landing and you can just kick back for the middle bit. Like being a pilot, you need to be trained for the worst-case scenarios. Unlike it, emergencies arise frequently. During the operation, it might look like the anaesthetist is not doing much, but they are monitoring, adjusting gas flows, giving antibiotics, analgesia and planning the next phase of the procedure. They have to constantly modify their techniques depending on how the operation is going or the patient is doing. But what is ‘an anaesthetic’?

Anaesthesia can be local – you cut yourself and need stitches and the A&E doctor injects some local anaesthetic (LA) to numb the immediate area. Many minor operations in operating theatres happen under LA alone, without an anaesthetist present.

A surgeon or anaesthetist may administer regional anaesthesia by targeting one or a group of nerves to numb a larger area, for example in foot surgery. This can occur alone, or in combination with a general anaesthetic.

A neuraxial block may be used – an injection into the space around the spinal cord will numb everything from the waist down and is handy for knee surgery etc. An epidural works in a similar way. These are often used in combination with sedation, where consciousness is reduced with medication, but the patient is not fully anaesthetised.

A general anaesthetic (GA) is where a patient is given medications to render them unconscious. This usually starts in the anaesthetic room and involves several stages:

1)            Induction – Drugs are given, usually straight into a vein, to temporarily render them unconscious. Once this happens, the patient can no longer protect their airway and a device is inserted to keep it open and allow the delivery of oxygen and anaesthetic gases later. If a breathing tube is to be inserted, then the patient must be paralysed, to relax all the muscles in the mouth and throat and allow the tube to pass.

2)            Maintenance – The patient is transferred to the operating theatre and is kept asleep. This is usually with anaesthetic gases but can be with a continuous infusion of medicine into the vein. The patient may breathe for themselves, depending on the operation. For certain operations, such as abdominal procedures, continuous muscle relaxation is needed so the patient remains paralysed and the breathing is done by a ventilator.

3)            Emergence – Once the operation is finished, the anaesthetic gases are turned off and the patient starts to wake. If they have been paralysed, then a reversal agent is given first so their muscles can work again and they can breathe. Any artificial airway is removed and the patient can be taken for further monitoring in the recovery room.

There are many more ways to give an anaesthetic than to skin a cat, I would imagine. You have to consider the patient and the procedure. In some ways it’s a very scientific speciality, built as it is on the three P’s of physics, pharmacology and physiology but in others it’s an art. You can learn what the right anaesthetic is for a particular operation and the dose of a drug that the average patient of a particular size, sex, age and fitness will need, but it must be individualised and you must respond to all the information that is available. You might be watching the patient and two screens with many variables displayed whilst getting information from the surgeon and the rest of the team and administering five or even ten different drugs and vapours. Anaesthetists are very well trained but you can see how there are opportunities for error.

Why not just give more?

Fair question. Unfortunately, all the sleepy drugs have side effects. Probably most importantly effects on blood pressure. Also, the more you get, the worse you feel afterwards.

So what did the audit find? The headline figure is that AAGA is reported once for every 19000 anaesthetics. This means that you are more likely to be killed in a traffic accident in any single year than experience awareness during a single anaesthetic.

However, the chances very much depend on the type and technique used. When neuromuscular blockade is used (paralysis) then the incidence rises to 1:8000.

Why and when does awareness happen? Well, there are several reasons...

During the induction phase, the anaesthetist needs to secure the airway. This can be straightforward or take a little longer. The longer it takes, the more chance the patient has of becoming aware of what’s going on. They then need to be moved to the operating theatre and are not connected to the anaesthetic machine at this time.

During maintenance, there are a variety of ways that the anaesthetist determines whether enough anaesthetic is being delivered. Sometimes EEG brain monitoring is used. The anaesthetic machine may give a display of how much anaesthetic gas is being breathed out by the patient (a good approximation of how much is in the brain). Small rises in pulse rate might indicate that the patient is not ‘deep’ enough. Another is that a patient may cough on the airway device or move on the table. This is not to say that they are conscious, just that some primitive reflexes are being stimulated and the patient needs more anaesthetic. Neuromuscular blocking drugs prevent this movement and so take this valuable warning sign away.

As the patient wakes during the emergence phase after the op, if the neuromuscular blocking drug is not adequately reversed, it can be that the anaesthetic wares off before the paralysis. This could lead to awareness without being able to move. For emergency procedures, the patient must be more awake before the breathing tube is removed, to ensure that their airway is protected if they were to vomit. There is a chance that they could remember the tube coming out.

Particular operations are higher risk for AAGA as well – heart surgery and C-sections as different drug combinations are needed in these patients. Pregnancy poses many particular challenges to anaesthetists, due to altered body shape and physiology and the need to care for two patients.

The study makes particular mention of reducing drug errors and how institutions can change lists and practices to reduce avoidable errors.

I think the main thing to pick out is that awareness is rare but not absent. When it occurs it can cause significant psychological harm. Awareness includes many experiences that are not 'waking up in the middle of the operation'. But the report is positive in that in identifies many ways in that the risks can be reduced. So things will get better.

So will you wake up during your operation? It’s extremely unlikely and will become even less so.