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Death or brain damage from anaesthesia

The risk of dying in the operating theatre under anaesthetic is extremely small. For a healthy person having planned surgery, around 1 person may die for every 100,000 general anaesthetics given.

Brain damage as a result of having an anaesthetic is so rare that the risk has not been put into numbers.

When faced with the prospect of having an anaesthetic, it is perfectly normal to have fears or worries.

The most important thing to point out, however, is that the chance of dying or developing brain damage whilst having an anaesthetic is incredibly small.

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What is 'risk'?

When looking at risk it is important to remember that everything we do in life contains an element of risk. Some things that we do will be more risky than others.

Using sport as an example, we're all aware that the risk of getting hurt whilst playing rugby is far greater than the risk of getting hurt whilst playing snooker. Whilst there are other considerations in decisions around which sport to play, we make judgments based upon risk as part of our daily lives.

Also the level of risk for the same activity can be different in different circumstances. Take, for example, drinking a cup of tea. There is a risk that the tea will be too hot and you might scald your mouth. Before you drink the tea, you instinctively do things to reduce this risk - for example, leaving it to cool down. When you do drink your tea, even though you have left it for a while, there remains a small risk that it will still be too hot. Consider now if a young child were to drink a cup of tea. They may not be as aware of the risk of scalding and therefore they may not leave the tea to cool down. Their risk of drinking hot tea and scalding their mouth would be much higher than with an adult.

Your anaesthetist will weigh up your risks and discuss these with you.

What is the risk of dying from a general anaesthetic?

The risk of dying in the operating theatre under anaesthetic is extremely small. For a healthy person having planned surgery, around 1 person may die for every 100,000 general anaesthetics given. To put that into perspective, Wembley stadium is the largest in the UK, holding 90,000 people. If we gave all the people in Wembley stadium a general anaesthetic, 1 person may die. However, these statistics don't reveal the true picture - although not always the case, it is highly likely that the one person who might die has a very complex medical history or is undergoing very difficult surgery.

Most deaths that occur around the time of surgery are NOT caused by the anaesthetic itself


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What else may increase the risk of dying?

There are a few reasons why an individual may have an increased risk of dying. Your anaesthetist and surgeon will be able to give you information about your individual risk. You can use this time to ask any question you might have about the operation, risks and care after the operation.

Let's look at the reasons one at a time.

Long-term medical conditions

Medical problems such as diabetes, heart disease, lung problems or kidney problems can make giving an anaesthetic more challenging, and slightly increase risk. Such conditions become more common as we age. It can be more difficult for an older person to recover from an operation than it is for a younger person.

If the person is very unwell before the operation

Even in someone who is normally well, a severe illness or surgical problem (such as bleeding or a severe infection) may make the stress and trauma of the operation too much for the body to cope with, reducing the patient's chances of recovering from the operation. In this situation, it is most likely the person will die in the immediate postoperative period in the Intensive Care Unit (ICU) or on the ward. It is most unusual for a patient to die in the operating theatre.

When a patient who is very sick needs an operation, a lot of experienced doctors (surgeons, anaesthetists and intensive care doctors) will get together and discuss the patient. They will consider the risks of having the operation versus the risks of not having the operation, or of having a smaller operation first until the patient is more stable. Sometimes, in discussion with the patient and relatives, it will be decided that the operation poses such a risk of dying or causing significant injury that it is not in the patient's best interests to go ahead with the operation.

If the surgery is on delicate structures, such as the heart, lungs, brain, major blood vessels or bowel

Every surgery has some level of risk attached to it. Sometimes the operation is extremely complicated and delicate. Certain types of surgery carry a greater risk of dying. If the patient is having major surgery it is likely that they will go to the ICU or High Dependency Unit (HDU) after the operation. The surgeon will discuss the risks of a particular operation with the patient prior to surgery.

If the surgery is being done as an emergency

This is very similar to the other situations discussed. Surgery that needs to be done as an emergency has a greater risk of complications than surgery that is planned in advance. The patient is likely to be unwell, and the surgery more complicated.

How might anaesthetics be fatal?

As we have already said, an anaesthetic itself is very rarely the cause of death. However, when this does happen it's usually because of one of the following reasons:

  • An allergic reaction to the medications that are given during an anaesthetic.

  • Difficulties putting in the breathing tube.

  • Reduced blood supply to major organs.

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How can a general anaesthetic sometimes lead to harm or death?

A general anaesthetic itself is very rarely the cause of death. The reasons why a person might experience harm or may die because of a general anaesthetic include:

An allergic reaction to the medications that are given during an anaesthetic

The risk of having a life-threatening allergic reaction is very low (less than 1 in 10,000) and most of those will recover completely. Your anaesthetist will be highly skilled in dealing with such situations. When the anaesthetist comes to see you before your operation it is important that you tell them about any allergies that you have, or if anyone in your family has had a problem with an anaesthetic in the past.

Difficulties putting in the breathing tube

After the anaesthetic medications have been given and the patient is asleep, a breathing tube is put in to allow a ventilator to breathe for the patient whilst they are asleep. Very occasionally the anaesthetist might have difficulty putting in the breathing tube. There are several things about the patient or the type of surgery that the patient is having that will alert the anaesthetist to potential problems. If, in your case, the anaesthetist feels that inserting the breathing tube may be difficult, they will discuss this with you at your pre-op assessment.

Reduced blood supply to major organs

Most anaesthetic medications cause the blood pressure to fall a little. Your anaesthetist will be skilled at managing this and have medication on hand to correct it. Particularly in people with 'furred' or 'hardened' arteries (atherosclerosis), organs including the kidneys and the brain can become damaged from a lack of blood supply in this situation.

What about brain damage?

It is normal to feel drowsy, be slightly confused or have a headache after having a general anaesthetic. Sometimes these feelings can carry on for a few days or weeks after the operation but this does not mean that your brain has been damaged.

Brain damage as a result of having an anaesthetic is so rare that the risk has not been put into numbers.

The risk of developing brain damage as a result of an anaesthetic is extremely small.

Brain damage is caused by the death or damage of brain cells. This can occur as a result of a wide range of causes, including major head injury or severe infections like meningitis. However, in the context of an anaesthetic, it usually occurs because the brain cells are deprived of oxygen in some way.

Symptoms of moderate or severe brain damage
These include:

  • Fitting (convulsions).

  • Abnormal dilation of the eyes.

  • Inability to awake from sleep.

  • Weakness in extremities.

  • Loss of coordination.

  • Confusion.

  • Aggressive, abnormal behaviour.

  • Slurred speech.

  • Coma.

There are two main reasons why a patient may develop brain damage during an anaesthetic.

1. Having a stroke during the anaesthetic

Commonly during a stroke, a blood clot blocks the blood supply to part of the brain. If the blood supply has been stopped, no oxygen will be able to reach that part and if the blood supply is not restored quickly, the cells in that area will die or be damaged.

The risk of having a stroke during surgery is higher:

  1. In older people.

  2. In people with 'furred' or 'hardened' arteries (atherosclerosis).

  3. In anyone who's had a stroke before.

  4. In people having surgery on the head, neck or heart.

It is usually the combined effects of the surgery and the anaesthetic that cause the stroke. A stroke can happen up to 10 days after surgery.

2. Not enough oxygen getting to the brain

Very, very rarely, brain damage can be caused by not getting enough oxygen to the brain. This might be caused by problems putting in the breathing tube. The breathing tube allows oxygen to be delivered to the lungs, and therefore the brain, during an anaesthetic.

What do anaesthetists do to prevent complications?

All anaesthetists have had extensive training and are expert in giving an anaesthetic and looking after you during the operation. Your anaesthetist will either be a doctor who's specialised in anaesthesia, or another type of health professional supervised by a senior anaesthetic doctor. Your anaesthetist will see you before your operation and ask about:

  • Your general health.

  • Any medicines that you take.

  • Any allergies you may have.

  • Other things about yourself.

They will explain about the operation you are due to have. They will use all the information you have discussed to give you the type of anaesthetic that is best and safest for you.

During the operation your anaesthetist and their assistant will be with you the whole time. From the time of the initial anaesthetic and throughout the operation they will use a number of monitors. These give the anaesthetist information about your heart, your breathing and the anaesthetic being given. Your anaesthetist will use the information given by these monitors, along with their clinical expertise, to keep you safe.

What can you do to reduce the risk of death or brain damage?

If the surgery is done as an emergency then the simple answer is that there is little you can do.

If, however, your surgery is planned for some time in the future then there are several things that you can do to minimise your personal level of risk:

  • Stop smoking. If you smoke, even stopping smoking for a few days before surgery will help. There are several sources of help and information to help you. Your GP or local pharmacy will be able to support you.

  • Lose weight if you are overweight. Set yourself an achievable goal and make a start. The changes in your diet need to be sustainable and NOT a short-term fix.

  • Eat well to improve your nutrition before surgery. Vegetables and fruit with a small amount of protein (for example, nuts or meat) are a good start for most people.

  • Take regular exercise to improve your heart and lungs. It is recommended that you do one hundred and fifty minutes of moderate-intensity (enough to have you out of breath) exercise a week - that's just 2½ hours a week.

  • If you have any long term medical problems, such as diabetes, breathing problems or high blood pressure, make sure they are well controlled before your operation. You might need to go to see your GP to make sure that you are as well as you possibly can be before your operation.

Further reading and references

  • Dr S White; Risks associated with your anaesthetic - Section 15: Death or brain damage; Royal College of Anaesthetists, 2017
  • Mashour GA, Woodrum DT, Avidan MS; Neurological complications of surgery and anaesthesia. Br J Anaesth. 2015 Feb;114(2):194-203. doi: 10.1093/bja/aeu296. Epub 2014 Sep 8.

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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