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General anaesthetic

5-minute read

Key facts

  • A general anaesthetic makes you unconscious during surgery, so you won’t be aware, move or feel pain.
  • Medicines are given through a drip in your vein and through a breathing mask.
  • Tell your anaesthetist about your health, allergies, medicines and any past problems with anaesthetics.
  • You will need to fast before a general anaesthetic.
  • You might feel tired, nauseous or cold or have a sore throat for a short time after the anaesthetic.

What is a general anaesthetic?

A general anaesthetic uses medicines to make you unconscious so you will not feel pain, move or be aware during surgery.

Why might I need a general anaesthetic?

General anaesthetics are used for major and some minor operations. Some operations can only be done under general anaesthetic.

Alternatives to a general anaesthetic are:

  • local anaesthetic, which numbs a small part of your body
  • regional anaesthetic, which numbs a whole area of your body
  • sedation, which makes you sleepy

The best anaesthetic for you depends on the procedure, your health and your and your doctors’ preferences. You can discuss this with your doctor or anaesthetist before surgery.

Sometimes children have a general anaesthetic to help them keep still for a procedure, such as an MRI.

How do I prepare for a general anaesthetic?

Meeting your anaesthetist

You will usually meet with your anaesthetist before the surgery. This might be in the few days before your surgery, especially if you are having major surgery or have any health concerns. Usually, it will be in the hours before surgery.

Your anaesthetist will ask you about your health and if you or your family have had any problems with anaesthetics in the past. They may also ask about the medicines you take, whether you have allergies and whether or not you smoke. You should provide any medical information you may have from a previous anaesthetist.

They might examine your mouth, teeth and veins and may listen to your heart and lungs.

Your anaesthetist will explain the type of anaesthetic you will have and what could possibly go wrong. They may ask you to sign a consent form. The form says you agree to the anaesthetic and understand why you are having it and the risks involved.

Your anaesthetist may arrange tests to prepare you for surgery.

You should discuss any questions or concerns with your anaesthetist.

Before surgery

You will need to fast before you have a general anaesthetic. This is so you do not vomit up food in your stomach and inhale it into your lungs (known as aspiration). This can cause serious complications. Your anaesthetist will tell you when you need to start fasting.

They may advise you:

  • what medicines you should not take before and on the day of surgery
  • not to drink alcohol from the day before surgery
  • to quit smoking before surgery
  • not to use drugs for at least a week before surgery

How will I get my general anaesthetic?

In most cases, you will receive the general anaesthetic as an injection into a vein on the back of your hand, through a thin plastic tube called a cannula. Sometimes, you will inhale (breathe in) an anaesthetic gas through a mask.

During surgery, your anaesthetist will monitor your level of consciousness, breathing, oxygen level, heart rate and blood pressure. They will usually put a breathing tube into your mouth and give you oxygen.

They will continue giving you anaesthetic medicines through your vein or through a mask to keep you unconscious. Your anaesthetist can adjust the amount of anaesthetic you receive based on what your need at the time.


What happens once I wake up from my anaesthetic?

When you wake from the general anaesthetic, you might feel sleepy, nauseous or cold. You will probably be in the recovery room when you wake up. A nurse will monitor you. You may need medicines to reduce nausea or pain.

If you are staying in hospital, you will be transferred to a ward once you are fully awake.

You can go home after day surgery when you are:

  • fully conscious, alert and mobile
  • able to manage any side effects
  • drinking fluids
  • able to urinate (wee)

You can’t drive home after a general anaesthetic. You should arrange for someone to pick you up or help you get home. It’s best to be with someone for the next 24 hours so they can check on you.

What are the risks and side effects of a general anaesthetic?

Common side effects include:

Older people may have confusion and memory loss.

Other possible risks include:

In rare cases, patients may lose their sight, have a stroke or brain damage, or die.

Some people are frightened that they might be aware during the operation or feel pain. This is rare. Your anaesthetist will monitor you throughout the operation to make sure this is very unlikely to happen.

If you are worried about risks and side effects, talk to your anaesthetist before surgery.

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Last reviewed: July 2022


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