Anaesthesia explained

General anaesthesia

General anaesthesia is a state of controlled unconsciousness during which you feel nothing. You will have no memory of what happens while you are anaesthetised.

A general anaesthetic is required for a very wide range of operations. This includes most major operations on the heart, lungs or in the abdomen, and many operations on the brain or the major arteries.

Anaesthetic drugs are injected into a vein, or anaesthetic gases are given to you to breathe. These drugs stop the brain from responding to sensory messages travelling from nerves in the body.

Anaesthetic unconsciousness is different from a natural sleep. You cannot be woken from an anaesthetic until the drugs are stopped and their effects wear off.

While you are unconscious, the team in theatre look after you with great care. Your anaesthetist stays near to you all the time.

Local anaesthesia

A local anaesthetic numbs a small part of the body where you are having the operation. It is used when nerves can be easily reached by drops, sprays, ointments or injections. You stay conscious, but free from pain. Common examples of surgery using local anaesthetic are having teeth removed and some common operations on the eye.

Regional anaesthesia

This is when a local anaesthetic drug is injected near to the nerves that supply a larger or deeper area of the body. The area of the body affected becomes numb.

Spinal and epidural anaesthesia

Spinals and epidurals are the most common types of regional anaesthetics. These injections can be used for operations on the lower body, such as caesarean section, bladder operations or replacing a hip. You stay conscious, but free from pain.

Other types of regional anaesthesia

Other types of regional anaesthetics involve an injection placed near to a nerve or group of nerves, for example in the arm or leg. This is often called a ‘nerve block’ and can allow you to have the operation without a general anaesthetic.

Nerve blocks are also useful for pain relief after the operation, as the area will stay numb for a number of hours.

For more information, see our leaflet on Nerve blocks for surgery on the shoulder, arm or hand. 

Sedation

Sedation involves using small amounts of anaesthetic drugs to produce a ‘sleep-like’ state. There are different levels of sedation. Commonly, sedation will make you feel drowsy and relaxed about what is happening. You may sleep for a period but the person giving your sedation will speak with you and you may be aware of where you are for some of the procedure.

Some people having a local or regional anaesthetic do not want to be fully awake for surgery. They choose to have sedation as well.

You may remember everything, something or nothing after sedation. However, sedation does not guarantee that you will have no memory of the operation. Only a general anaesthetic can do that.

For more information about sedation, please see our Sedation explained leaflet.

Combinations

Anaesthetic techniques can often be used together. For example, a regional anaesthetic may be given for pain relief after an operation for which you have had a general anaesthetic. The general anaesthetic allows you to remain unconscious and remember nothing.