Anaesthetics Overview

This page will provide you with information about anaesthetics. For further details, you should speak to your GP or other relevant health professional.

Anaesthetic— a description

An anaesthetic is a drug mixture that when administered, causes sensation loss. They are grouped into the following:

  • General anaesthetic:- induces a deep sleep. The patient is not aware of what happens at the time, and they will not remember the operation when then wake up.
  • Local anaesthetic:- a temporary measure to alleviate pain by stopping nerve function. The anaesthetic is injected around the area where you will have the operation. Another option is a nerve block, which numbs the nerves to the patient’s arm or leg.
  • Spinal or epidural anaesthetic:- injection of local anaesthetics and painkillers near the spinal cord, resulting in pain relief in certain areas of the patient’s body.

Your surgeon or anaesthetist will talk through the various options with you and recommend the best type, but it you will make the final decision about which anaesthesia you wish to receive. This document will provide details outlining the benefits and risks in order to help you in your decision, and let you make an informed choice. If you have questions that this document does not answer, it is recommended that you ask your surgeon, anaesthetist, or healthcare team.

The benefits of anaesthetics

— If you suffer from a specific condition or are in pain, anaesthetics can provide pain relief. In this case, they will usually administered by an epidural.

— In an operation or procedure, you will be required to be in a state where your muscles are relaxed and you are not moving. An anaesthetic is given to ensure this is achieved, so the surgeon or doctor can perform the procedure safely.


Local anaesthetic can either be given by the surgeon or anaesthetist.

General, epidural or spinal anaesthetics are given by an anaesthetist (a doctor trained in anaesthesia). They will often be assisted by a healthcare practitioner (who will also have had the relevant training).

General anaesthetic

These are usually injected through a drip (small tube) into a vein. Within about 30 seconds, most people are asleep. Although the injection may ache slightly at the time, the uncomfortable feeling will often be gone by the time you wake up.

It is also an option to administer anaesthetic as a gas. This will be through a face mask, and should also take effect in about 30 seconds.

During your operation, more of the same anaesthetic is administered either by the drip or by anaesthetic gases in order to keep you asleep. Sometimes the anaesthetist may also administer further medication to limit any sickness or pain afterwards.

When the operation is over, the anaesthetic wears off, which enables you to wake up.

Local anaesthetic

It is possible to give different combinations of anaesthesia, so the operation can proceed with the smallest amount of discomfort to you. An example of this is a local anaesthetic being given to a patient before a general anaesthetic.

The simplest way to give a local anaesthesia is to inject it around the area which is going to have the procedure. It may burn or sting initially, but the area should go numb after a couple of seconds.

When it comes to nerve blocking, a combination of local anaesthetics and painkillers will be injected to the part of your body on which you be operated, near to the major nerves of this area.

Epidural or spinal anaesthetic

1. Epidural

This will temporarily numb the nerves to give you pain relief. A fine tube called a catheter is inserted near into the epidural space near the spinal cord. Most of your nerves pass through this space. (see figure 1).

Figure 1

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  1.  Inserting a needle into the back
  2. A test is carried out to check the position is correct, once the catheter has reached the epidural space.
  3. A catheter is put into the epidural space. The needle is taken away.

Once the catheter is in place, a mixture of painkillers and local anaesthetics are injected into the epidural space, and your nerves should be numbed.

2. Spinal

This technique is similar, but with a spinal anaesthesia you will only receive one injection. This is inserted into the bag of fluid surrounding the spinal cord.

Safety of anaesthetics

For most patients all types of anaesthesia are safe. If you require a general anaesthetic, it may be necessary to undergo a couple of tests before the operation, to see how safe this will be. These tests will allow the healthcare team to choose what other options are available and if they need to carry anything out differently.

Death following an operation is nearly always because an individual’s body cannot cope with the surgery itself. This risk increases if you have ill health and require emergency surgery.

The anaesthetist may also recommend that you see your GP, to discuss improving your medical condition beforehand. These include angina, asthma, anaemia or high blood pressure.

A succesfull procedure

  • Lifestyle alterations

If you smoke, you reduce the risk of developing complications, as well as improving your long-term health by stopping smoking at least several weeks beforehand.

Exercising regularly also helps prepare you for the procedure, as well as aiding recovery.

Maintaining a healthy weight prevents you from developing complications that would have a greater risk of occurring if you are overweight.

  • Stay warm

It is vital that you keep warm in the time around the operation. Be aware that the hospital might be colder than at home, so take warm clothes with you, for example a dressing gown. It is also important that you tell the healthcare team if you are feeling cold. If your body temperature gets too low you could increase your risk of developing complications, including surgical site infections or heart problems. The anaesthetist will be ensuring your body temperature is stable during the procedure.

Potential complications

The healthcare team will take every precaution to make sure that the anaesthetic is safe, but complications can occur. Be aware that your surgeon or anaesthetist will be able tell you if your particular case is at a higher or lower risk of complication.

  1. General anaesthetic

Minor complications (not disabling or life-threatening)

  • Headache
  • Sore throat
  • Sickness

Serious complications

  • Eye injury— Risk of short-term blurred vision: 1 in 20

— Risk of serious damage requiring further treatment: 1 in 1,000

— Risk of sight loss: 1 in 125,000

  • Change or loss of hearing — 1 in 10,000. This usually improves over time.
  • Minor breathing problems— 1 in 20.
  • Chest infection— less common than breathing problems. Higher risk if you are a smoker, have lung or chest disease, or are having a chest or abdominal operation.
  • Nerve injury — 1 in 1,000. Usual area of damage is the ulnar nerve running behind the elbow. This damage is usually mild and improves, but damage may be permanent.
  • Allergic reaction— this would be to the medication used in the anaesthetic. Your anaesthetist will be skilled in detecting and treating these reactions, but a reaction could be life-threatening (1 in 10,000).
  • Stroke— loss of brain function caused by the blood supply to the brain being interrupted. Unusual in a fit individual. More common in those with diabetes, high blood pressure, heart disease, or with a history of strokes, but still unusual.
  • Heart Attack — Unusual in a fit individual. More common in those with diabetes, heart disease, or high blood pressure, but still unusual.

Please refer to the information document entitled “A01 General Anaesthetic”, for further details on the complications associated with general anaesthetics.

Local Anaesthetic

  • Allergic reaction to local anaesthetic. Unusual.
  • Not enough pain relief. You should tell your doctor or surgeon know if you are in pain.
  • Bleeding. This is where the the needle catches a blood vessel.
  • Nerve damage— 1 in 5,000.
  • Absorption into the blood stream. This can be serious if the heart and brain are affected for a short time. The anaesthetic dose is always limited, and the surgeon will take great care to ensure it isn’t injected into the blood stream. Absorption into your blood stream is rare.

Please refer to the information document entitled “A03 Local Anaesthetic” for further details on the complications associated with general anaesthetics.

Epidural or Spinal anaesthetic complications

Overall risk of permanent, significant harm, either from an epidural or spinal anaesthetic, is 1 in 12,550 to 1 in 24,000.

Main complications

  • Epidural or spinal failure.
  • Headache— 1 in 100. Caused by the puncture of the fluid bag around the spinal cord.
  • Low blood pressure.
  • Short-term nerve injury— 1 in 50,000 (epidural) or 1 in 2,000 (spinal). Should fully recover.
  • Infection around the spine— 1 in 50,000. In the form of an abscess or meningitis and causing permanent damage.
  • Blood clot around the spine — 1 in 20,000 (epidural)
  • Cardiovascular collapse— 1 in 100,000.
  • Paralysis or death— (1 in 26,300— 1 in 63,000)

Please refer to the information document entitled “A02 Epidural Anaesthetic” and “ A05 Spinal Aesthetic”, for further details on the complications associated with epidural and spinal anaesthetics.

If there is anything you are unsure about, discuss these possible complications with the surgeon or anaesthetist.


Anaesthesia in its different forms can be used to provide a safe and effective way for you to undergo a operation, as well as giving you the necessary pain relief. An awareness of them will also help you to detect and treat any potential problems at an early stage. Complications can occur, although usually people do not have any issues and are satisfied with the anaesthetic. In order to make an informed decision about an anaesthetic, it is important that you are aware of these complications.

Please use this information leaflet should you need to talk to a healthcare professional.

References:  EIDO Healthcare Limited – The operation and treatment information on this page is produced using information from EIDO Healthcare Ltd and is licensed by Aspen Healthcare. The information should not replace advice that your relevant health professional would give you.