The word anaesthesia means ‘loss of sensation’. It can involve a simple local anaesthetic injection which numbs a small part of the body, such as a finger or around a tooth. It can also involve using powerful drugs which cause unconsciousness.

These drugs also affect the function of the heart, the lungs and the circulation. As a result, general anaesthesia is only given under the close supervision of an anaesthetist, who is trained to consider the best way to give you an effective anaesthetic but also to keep you safe and well.

The drugs used in anaesthesia work by blocking the signals that pass along your nerves to your brain. When the drugs wear off, you start to feel normal sensation again.

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

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

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

Other 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’. This 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.

Sedation involves using small amounts of anaesthetic drugs to produce a ‘sleep-like’ state. It makes you physically and mentally relaxed, but not unconscious.

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

If you have sedation, you may remember little or nothing about the operation or procedure. However, sedation does not guarantee that you will have no memory of the operation. Only a general anaesthetic can do that.

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 essential for a very wide range of operations. This includes all major operations on the heart or lungs or in the abdomen, and most operations on the brain or the major arteries. It is also normally needed for laparoscopic (keyhole) operations on the abdomen.

Anaesthetic drugs are injected into a vein, or anaesthetic gases are given for the patient 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.

Anaesthetic techniques are often combined. For example, a regional anaesthetic may be given for pain relief afterwards, and a general anaesthetic makes sure you remember nothing.

assessing whether you are fit enough to have the anaesthetic for your operation;talking to you about which type of anaesthetic might be best and getting your permission (consent) for it;giving the anaesthetic and organising pain control afterwards; and looking after you immediately after the operation in the recovery room or in an intensive care unit.

Anaesthetists are doctors who have had specialist training in anaesthesia.