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The word anaesthesia is derived from a Greek word, meaning absence or loss of sensation. Anaesthesia is one of the most significant developments of modern medicine because it allows once-unbearable medical procedures to be performed while the patient is relaxed and asleep.

Anaesthetists are medical doctors with further training in the specialised field of anaesthesia. They also have expertise in intensive care medicine and pain relief, and are responsible for pain control and anaesthesia for women in labour. However, most of the work of an anaesthetist is in preparing hospital patients for surgery, then caring for them during the operation.

There are 3 principle types of anaesthesia:

  • General anaesthetic - putting people to sleep, and keeping them asleep for surgery or other medical procedures
  • Regional anaesthetic - numbing an area of the body
  • Local anaesthetic - numbing a small part of the body

Often a combination of the above techniques is used to ensure that the minimum doses of drugs are used to ensure successful anaesthesia and a quick recovery.

This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

The word ‘anaesthesia’ comes from the Greek language and means 'loss of sensation'. When you have a general anaesthetic, you’re in a controlled state of sleep (unconsciousness).

General anaesthesia uses a combination of medicines to:

  • make you sleep (be unconscious)
  • give you pain relief through a loss of sensation
  • relax your muscles


If you have a procedure under general anaesthetic, you’ll stay asleep until it’s finished and the anaesthetic wears off; then you’ll wake up. Your anaesthetist will stay with you throughout your procedure. You won’t remember what happened during the procedure.

You’ll meet your anaesthetist to discuss your care. It may differ from what’s described here as it will be adapted to suit you.

Before your procedure

Your surgeon and anaesthetist will visit you in your room before the operation starts. For example, if you smoke, you should consider quitting. This is because it increases your risk of heart and breathing problems during and after your operation, and of getting a wound infection. This means it would take you longer to recover afterwards. If you’re overweight, it’s a good idea to try and lose some weight. Being overweight puts you at greater risk of complications.

They will also ask you about your health and about any previous operations requiring anaesthesia that you have had. It is particularly important that you tell the anaesthetist about any medicines, prescribed or over-the-counter, that you are taking.  Also tell the anaesthetist about any caps, crowns, or dentures you have so that extra care can be taken to protect these when masks and tubes are fitted.


If you feel anxious about your procedure, you may be able to have pre-medication (a ‘pre-med’) half an hour to a couple of hours before. This can:

  • relieve anxiety and help you to relax
  • reduce pain after your procedure
  • reduce the risk of being sick after your procedure


Eating and drinking

You will be given specific advice about this from the hospital. In general, you should not eat for about six hours before surgery so that your stomach is empty. This reduces the chance of complications caused by being sick during the operation. It’s probably best not to drink any alcohol at least 24 hours before having a general anaesthetic. Sipping clear fluids (water and black tea) up to two hours before your operation is usually allowed.

To get ready for surgery, you may be asked to put on a surgical gown and some elastic stockings. These are worn from the knee down and help to maintain the circulation in the veins of your lower legs, so helping to prevent blood clots from forming.

Lastly, many people may be nervous before an operation and you may be offered a pre-medication. This is a drug given as tablets, liquid or by injection. It relieves anxiety and makes you feel relaxed. It can also make you feel quite sedated or even out of it.

Modern anaesthetics are so safe, rapidly acting and effective that most people do not need pre-medication, especially for procedures that do not require an overnight stay. You can discuss this with your anaesthetist.

The operating theatres are usually in a separate area of the hospital - the theatre suite or operating block. You will normally travel from your room to the theatre on a bed or trolley.

At the entrance to this area, you will be handed over to a theatre nurse or theatre technician. At this point in the journey you will be awake.

From the entrance to the theatre suite, you will be taken to the anaesthetic room. This connects with the operating theatre. A technician or a nurse will help the anaesthetist prepare you for the operation.

Your anaesthetist will usually give you the anaesthetic medicines through a fine, plastic tube (called a cannula) into one of your veins. When it’s time for your procedure, you’ll be taken to the anaesthetic room next to the operating theatre. Your anaesthetist will usually put the cannula into a vein on the back of your hand or arm. This may feel sharp, like an injection, but they might use a local anaesthetic to ease this. The cannula means you won’t have to have a separate injection each time your anaesthetist needs to give you medicines or fluids.

Sometimes, your anaesthetist may ask you to breathe in anaesthetic gases and oxygen through a mask as well as or instead of having a cannula.

Once your anaesthetist gives you the anaesthetic medicines, you’ll fall asleep and won’t wake up until after your procedure. When you’ve fallen asleep, your anaesthetist might put a tube in your mouth to help you breathe during your procedure. You’ll be given more anaesthetic medicines during your procedure to make sure you stay asleep.

Your anaesthetist may also give you:

  • oxygen (via a tube in your mouth)
  • strong painkillers to prevent pain during and after your procedure
  • medicines to relax your muscles, so that your surgeon can operate more easily
  • antibiotics to prevent infection
  • anti-sickness medicines to prevent you from feeling sick after the procedure
  • medicines to control your blood pressure
  • intravenous fluids (a drip) to keep you hydrated


You’ll be connected to machines the whole time that you’re under anaesthesia. These monitor the activity of your heart and other systems in your body. Your anaesthetist will be with you throughout the operation and will watch the monitors and make any necessary adjustments, although some equipment does this automatically. At the end of your operation, they’ll turn off the anaesthetic medicines and you’ll begin to wake up.

When the operation is finished, you will be moved to the recovery room where a nurse provides one-to-one care. This is where you will wake up from the anaesthetic. The care includes constant monitoring of your heart rate, breathing, blood pressure and other vital body functions. Its routine to be given oxygen through a face mask.

Its normal to feel sleepy or disorientated in the first 15 minutes or so after you first come round. You may also have a sore throat caused by the tube that was placed there to keep your airway open. You may feel sick, although preventive medicines are now given routinely for many procedures. You should not experience serious pain.

Returning to your room

Once you have recovered from the anaesthetic, and the anaesthetist is happy with your progress, the connections to the monitoring equipment will be taken off. You will then be able to return to your room on the trolley or bed.

When you no longer need intravenous medicines or fluids, the cannula or drip will be removed.

After complex operations you may need further close monitoring. This takes place in a high dependency ward where one nurse looks after no more than two patients at a time. Attachment to the monitoring machines and connection to a drip will be continued.

Pain relief

This is also known as analgesia. Depending on the type of operation you have had, you may need pain relief medication which will be tailored to the expected amount of pain you may experience. This is often simple painkillers such as paracetamol, but for more severe pain, there are other drugs available.

Controlling pain after an operation is very important as pain can interfere with your recovery.

Patient-controlled analgesia (PCA)

PCA is used for some but not all procedures. It consists of a pump connected to a vein in your hand or arm that allows you to regulate how much medication you receive. Patients who are in control in this way tend to use a smaller amount of pain relief medicine than if its administered in set doses at regular intervals.

You will be shown how to use the pump, which is usually operated by a simple button. Its designed so that you cannot take a harmful amount of the painkiller.

Going home

If your operation has been planned as a day case, you will need to rest on your bed for a couple of hours or so before going home.

Modern anaesthetics are quickly flushed out of your system. However, you should follow the advice of the nurses about how much activity you should do and this will depend on the type of operation you have had.

Get someone to drive you home and avoid operating machinery or making important decisions in the 24 hours after your operation.

Once you get home, you can ring the hospital for information or advice at any time.

Anaesthesia has made surgery much safer. The routine use of high technology, such as equipment that constantly measures the amount of oxygen in the blood, has made it safer still.

However, there are still some risks. These can be divided into the risk of side-effects and the risk of complications.


These are unwanted but mostly temporary effects of successful treatment. They include:

  • feeling sick and vomiting – although steps are usually taken to prevent this
  • a headache
  • feeling dizzy
  • shivering
  • a sore throat
  • feeling tired and confused
  • feeling itchy
  • blurred vision
  • backache
  • bruising where the cannula was put in

 These side-effects usually only last for a few hours, but occasionally they can last for several days. If they don’t get better, contact your hospital.



Serious complications, and death, as a result of anaesthesia do occur, but they are very rare. Older people in good health are not necessarily at higher risk than younger people. Complications of general anaesthesia can include the following:

  • A serious allergic reaction, which is called anaphylaxis. It may be triggered by the anaesthetic but it’s very rare. One or two people in every 20,000 who have an anaesthetic are estimated to get anaphylaxis. Your anaesthetist will be on hand to treat you immediately if you do develop the condition.
  • Awareness. Very rarely, people feel they are partly or completely awake and aware of what's happening while under general anaesthesia. See FAQ: Will I be aware? for more information.
  • Damage to your teeth, lips or tongue – this isn’t usually serious but it can happen if your anaesthetist puts a tube into your mouth. You might just have some minor bruising or cuts in your lips, but you could have some damage to your teeth. This happens to about one in 4,500 people who have a general anaesthetic.
  • Dying during general anaesthesia. This risk is very small and it can be difficult to tell whether it’s because of the anaesthetic or another risk of your procedure. It’s not possible to be definite but it’s thought that less than one in 100,000 people die as a result of having a general anaesthetic.
  • If you have a pre-existing health condition, it may get worse as a result of having an operation under general anaesthesia.

 1. Will I be aware of what’s happening?


It's possible, although very rare, that you might become aware of things during your procedure if you don’t receive enough of the anaesthetic medicines. You could partly or fully wake up and this is called 'accidental awareness under general anaesthesia'.


Most studies suggest that one or two people in every 1,000 who have a general anaesthetic develop awareness when having a general anaesthetic. Most people don't have any pain, but may see, hear and even feel the tube in their throat. Some people who have memories of the recovery room confuse these with the operating theatre but this isn’t awareness. 

Doctors don’t yet know the exact reasons why some people develop awareness under general anaesthesia. But they think it’s more likely to happen if you're having an operation where a lower level of anaesthetic is used. Such operations include:

  • open heart surgery
  • surgery after a major accident
  • a caesarean
  • surgery on your chest 


Your risk can also increase if you’re very ill or if you’re taking some types of medicines. Ask your anaesthetist for more information on which ones. They’ll do everything possible to keep you asleep. They’ll monitor your condition throughout the procedure and control the anaesthetic medicine going into your body to make sure you get the right amount.

If you do remember anything from your procedure, tell your anaesthetist as soon as possible.

2. What’s the risk of memory loss or confusion?


Memory loss and confusion after general anaesthesia are more common in older people but it can happen to you at any age. Most people make a full recovery within a few days. 


After having a general anaesthetic, you may feel confused or have trouble with your memory for a while afterwards. You might not be able to remember things, such as your name or why you're in hospital. Or you may behave differently from usual – you might be aggressive, anxious or withdrawn, for example.

You’re more likely to become confused after a general anaesthetic if you: 

  • have had another operation recently
  • had a poor memory or dementia before your general anaesthetic
  • have difficulty walking
  • drink a lot of alcohol

 Other things that can cause confusion after a general anaesthetic, and which can be treated easily, include: 


  • a chest, wound or urine infection – you may be given antibiotics for this
  • poor pain control – your pain relief can be increased
  • not getting enough to eat and/or drink – you’ll be given more
  • difficulty going to the toilet – you can take medicines for constipation


The staff treating and caring for you will be used to dealing with confusion and most people make a full recovery within a few days. But sometimes it can take weeks or even months.

3. What’s post-operative cognitive dysfunction?


Some people notice that they’re confused some time after their operation rather than immediately. This is called post-operative cognitive dysfunction (POCD). 


Memory loss and confusion after general anaesthesia are common and most people get better within a few days. But some people notice this happens later and that their memory, concentration and/or attention are no longer as they were before having the general anaesthetic.

This is called POCD and it’s estimated to affect about one in 10 patients in the first three months after their operation. After a year, only one in 100 patients still have it. You might not notice anything at first and only realise when you start getting back to normal again. It may only be your close friends or family who notice you're having difficulties. 

POCD tends to get better as your body heals after your operation but it can take months or years. Some people never fully get back to normal.

Doctors don’t yet know the exact reasons why some people get POCD. But it seems to be more likely after open heart surgery and after longer operations. Ask your anaesthetist for more information.

This information was published by Bupa Group's Health Content Team and has been reviewed by appropriate medical or clinical professionals. To the best of their knowledge the information is current and based on reputable sources of medical evidence, however Bupa (Asia) Limited makes no representation or warranty as to the completeness or accuracy of the Content.

The information on this page, and any information on third party websites referred to on this page, is provided as a guide only.  It should not be relied upon as a substitute for professional medical advice, nor is it intended to be used for medical diagnosis or treatment. Bupa (Asia) Limited is not liable for any loss or damage you suffer arising out of the use of, or reliance on, the information.

Third party websites are not owned or controlled by Bupa and any individual may be able to access and post messages on them. Bupa is not responsible for the content or availability of these third party websites.

Further Information

The Association of Anaesthetists

American Society of Anesthesiologists

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