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What is an anaesthetic?

An anaesthetic is a combination of drugs that causes loss of sensation.

  • General anaesthetic – A combination of drugs that produce deep sleep. You will not be aware of what is happening and afterwards you will not remember anything that has happened.
  • Epidural or spinal anaesthetic – Involves injecting local anaesthetics and other painkillers near your spinal cord to give pain relief in certain areas of your body.
  • Local anaesthetic – Temporarily stops nerves working so that you do not feel pain. The anaesthetic can be injected just around the area where the operation is going to take place. It is possible to numb the nerves to your arm or leg (a nerve block).

What are the benefits of an anaesthetic?

  • You may need to have an operation or procedure – So that your surgeon or doctor can perform the operation safely, you need to be in a state where you do not move and your muscles are relaxed. A safe way to achieve this is to give you an anaesthetic.
  • You may be in pain because you have had surgery or have a particular condition – Anaesthetics, usually given by an epidural, can give you pain relief and keep you comfortable.

How is a general anaesthetic given?

Most people are sent to sleep by injecting the anaesthetic through a drip (small tube) in a vein. It takes about 30 seconds to work.

For some people it may be more appropriate to go to sleep by breathing an anaesthetic gas through a face mask. This also takes about 30 seconds to work.

How is an epidural or spinal anaesthetic given?

An epidural works by temporarily numbing your nerves to give pain relief. A fine catheter (tube) is inserted in the epidural space, near your spinal cord.

Figure showing a catheter in the epidural space

Local anaesthetics and other painkillers are injected down the catheter into the epidural space to numb your nerves.

The technique for a spinal is similar but usually involves only one injection into the subarachnoid space (bag of fluid that surrounds your spinal cord).

How is a local anaesthetic given?

The simplest form of local anaesthesia is to inject the anaesthetic just around the area where the operation is going to take place.

For a nerve block, local anaesthetics and other painkillers are injected near the major nerves to the part of your body to be operated on.

What complications can happen?

Some of these can be serious and can even cause death.

General anaesthetic

There are a number of possible minor complications (not disabling or life-threatening) such as feeling sick, sore throat, difficulty passing urine and headache.

The following are the possible serious complications.

  • Loss or change of hearing
  • Eye injury
  • Nerve injury
  • Heart attack
  • Stroke
  • Chest infection and other breathing problems
  • Allergic reaction

Epidural or spinal anaesthetic

  • Failure of the epidural or spinal
  • Low blood pressure
  • Headache
  • Infection around your spine
  • Cardiovascular collapse (where your heart stops)
  • Short-term nerve injury
  • Blood clot around your spine
  • Paralysis or death

Local anaesthetic

  • Not enough pain relief
  • Allergic reaction
  • Bleeding
  • Nerve damage
  • Absorption into your bloodstream

Why choose The London Clinic?

The London Clinic is dedicated to providing the best, personalised healthcare with over 600 world-renowned consultants available to offer informed health advice and treatment.

Spanning Harley Street and Devonshire Place, The London Clinic is situated in the heart of London’s internationally-known medical district. This central location, together with state-of-the art technologies and facilities that are not widely available in other hospitals, makes The London Clinic the hospital of choice for around 120,000 patients every year.

The London Clinic is an HTA licensed and JACIE accredited cancer centre with an ‘Excellent’ MacMillan Quality Environment Mark and with access to a Level 3 intensive care unit.

Offering affordable and competitive self-pay packages and expert support from Clinical Nurse Specialists and our specialised multidisciplinary team, over 98% of our patients said they would recommend The London Clinic to their friends and families.


The London Clinic offers affordable, competitive self-pay packages for certain treatments. Please call +44 (0)20 3219 3315 to speak to our helpful team to find out more and to book an appointment.


There are different forms of anaesthesia that can be used to provide a safe and effective way for you to have an operation or procedure, and to give you pain relief. Most people do not have any problems and are satisfied with their anaesthetic.


The operation and treatment information on this website is published under license by The London Clinic from EIDO Healthcare UK and is protected by copyright laws. Other than for your personal, non-commercial use, you may not copy, print out, download or otherwise reproduce any of the information. The information should not replace advice that your relevant health professional would give you.

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