About anaesthetics

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

Anaesthetics are used during tests and surgical operations.

How anaesthetics work

Nerve signals usually keep you awake and aware. Anaesthetics work by stopping nerve signals from reaching your brain.

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

After the anaesthetic has worn off, the nerve signals will be able to reach your brain. This will cause consciousness and feeling to return.

Types of anaesthesia

There are 2 commonly used types of anaesthetic:

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

Unlike general anaesthetic, these don't make you unconscious. Instead, they stop you feeling pain in a particular area of your body. These include:

  • regional anaesthetic - gives extensive numbness or pain relief to a specific area
  • epidural anaesthesia - usually used to numb the lower half of the body, for example during labour or childbirth
  • spinal anaesthetic - gives total numbness to the lower parts of the body for about 3 hours
  • sedation - makes you feel sleepy and relaxed, both mentally and physically

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

A sedative is sometimes used with a regional anaesthetic to help you feel relaxed, calm and pain-free.

How anaesthetics are given

An anaesthetic can be given in a number of ways, including as:

  • an ointment
  • a spray
  • drops
  • an injection into a vein
  • a gas you breathe in


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

Before the procedure, your anaesthetist will discuss some things with you, including:

  • the types of anaesthetic appropriate for the procedure you're having
  • any risks or side effects associated with different types of anaesthetic

Anaesthetists will plan your anaesthetic and pain control with you. If you have any preferences for a particular type of anaesthetic, they'll consider this.

You should ask your anaesthetist to clarify anything you're unsure about.

If you have a general anaesthetic, the anaesthetist will supervise the procedure. They'll also make sure that you're comfortable afterwards.

Side effects of anaesthetics

Anaesthetics consist of many medications that can cause side effects in some people. Your anaesthetist will tell you about any side effects you may experience. They'll also explain what measures will be taken to reduce these side effects.

Some common side effects of anaesthetics include:

  • feeling sick
  • vomiting
  • dizziness
  • feeling faint
  • feeling cold or shivering
  • headache
  • itchiness
  • bruising
  • soreness
  • difficulty passing urine
  • aches and pains

The side effects of anaesthetic don't usually last very long and, if necessary, some of them can be treated.

Tell the healthcare professionals treating you if you experience any side effects. You should also tell them if you're in pain after your procedure.

Risks and complications

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

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

The benefits and risks of surgery and anaesthesia will be carefully weighed up. Your clinician will then explain them to you before you have any operation.

Very rare possible complications of anaesthetics include:

  • permanent nerve damage – this can cause numbness or paralysis (inability to move a part of the body)
  • an allergic reaction to an anaesthetic medication (anaphylaxis)

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

  • your medical history – whether you have any other serious medical conditions or illnesses
  • personal factors – for example, whether you smoke or are overweight
  • the type of procedure – whether it's a planned or an emergency procedure, or whether it's a major or minor procedure
  • the type of anaesthetic

Before your procedure, your anaesthetist will explain if there are any particular risks.

In most cases, the benefits outweigh the risks. You should discuss any concerns you have with your anaesthetist before surgery.

Last updated:
04 November 2022