Anaesthesia means "loss of sensation". Medicines that cause anaesthesia are called anaesthetics.

Anaesthetics are used during tests and surgical operations to numb sensation in certain areas of the body or induce sleep.

This prevents pain and discomfort, and enables a wide range of medical procedures to be carried out.

Local anaesthetics and general anaesthetics are 2 commonly used types of anaesthetics:

Types of anaesthesia

As well as local and general anaesthetic, there are a number of other types of anaesthesia.

Unlike general anaesthetic, these do not make you unconscious – they just stop you feeling pain in a particular area of your body.

The different types of anaesthetic are:

Different types of anaesthesia can be used in combination. For example, a regional anaesthetic can be used with a general anaesthetic to relieve pain after an operation.

A sedative is also sometimes used with a regional anaesthetic to help you feel relaxed and calm, as well as pain-free, during an operation.

How anaesthetics are given

An anaesthetic can be given in a number of ways:


Anaesthetists are doctors who have received specialist training in anaesthesia. They'll give you your anaesthetic and be responsible for your safety and wellbeing during your procedure.

Before the procedure, your anaesthetist will discuss a number of things with you, including:

They'll plan your anaesthetic and pain control with you, taking into account any preferences you have for a particular type of anaesthetic. You should ask your anaesthetist to clarify anything you're unsure about.

If you have a general anaesthetic, your anaesthetist will carefully monitor you throughout your operation and make sure you wake up comfortably afterwards. They may also help with any pain relief you might need after the procedure.

Side effects

Anaesthetics consist of a number of medicines that can cause side effects in some people. Your anaesthetist will tell you about any side effects you may experience after having a specific type of anaesthetic and measures that will be taken to reduce these.

Some common side effects that can occur after a general anaesthetic or some regional anaesthetics include:

The side effects of anaesthetic usually do not last very long and, if necessary, some of them can be treated.

Tell the healthcare professionals treating you if you experience any of the above side effects, or if you're in pain after your procedure.

Risks and complications

In recent years, having anaesthesia has become very safe. Advances in equipment, medicine and training mean serious problems are rare.

However, as with any type of surgery or medical procedure, there's a potential risk of complications.

The benefits and risks of surgery and anaesthesia will be carefully weighed up and explained to you before you have any operation.

The complications of anaesthesia listed below are very rare.

Permanent nerve damage

This can cause numbness or paralysis (inability to move a part of the body), although this may be a result of the surgery itself.

If the damage is slight, you may get better in a few days to a few weeks. Permanent damage to the peripheral nerves, which run between the spinal cord and the rest of the body, occurs in around 1 in 1,000 people having a general anaesthetic.

An allergic reaction to an anaesthetic medicine

Although an allergic reaction (anaphylaxis) can be severe, appropriate treatment is on hand to enable the best chance of dealing with this immediately and effectively.

It's not clear exactly how often anaesthetics cause anaphylaxis, but the best estimate is that a life-threatening allergic reaction occurs in 1 in 10,000 anaesthetics. More than 95 per cent of these will survive and generally recover well.


If you're a healthy patient having non-emergency surgery, death is very rare at around 1 in 100,000 people having general anaesthetic. However, this may increase depending on certain factors.

Factors affecting risk of complications

Your risk of developing complications will depend on a number of factors, including:

Before your procedure, your anaesthetist will explain if there are any particular risks of developing possible complications.

In most cases, the benefits outweigh the risks. Any concerns you have should be discussed with your anaesthetist before surgery.

More information

You can find out more about specific types of anaesthesia:

Also see the Royal College of Anaesthetists' patient information.

Page last reviewed: 23 September 2021
Next review due: 23 September 2024