Important information about your Anaesthetic


Many people will be anxious or concerned before coming to hospital for an operation. This webpage explains the process of having an anaesthetic and tries to answer common questions along the way.

This page is about your anaesthetic only. It does not contain specific information on what you should do to prepare for coming to hospital, your surgery or what will happen when you go home. There are other leaflets available covering these topics: please ask if you would like to see them, or click on the link below.

Giving your consent

In order for you to be able to consent for anaesthesia it is essential that you read all of this information.

If you wish to have more information, please request our second leaflet More about your anaesthetic.

Who needs an anaesthetic?

If you are having an operation you will need some form of anaesthetic. Some patients will be unconscious (general anaesthetic), while others stay awake for surgery but are kept pain-free with a special injection (local anaesthetic). If the plan is that you remain awake during surgery you may be given drugs to ensure you are comfortable and drowsy (sedation).

What will happen to me?

What happens to you individually will depend on exactly what operation you are having. This web site does not replace individual discussions with your anaesthetist prior to surgery but provides general information.

To make it easier for you we have split the information in this web site into:

Before the operation

Who will give the anaesthetic?

Your anaesthetic care is provided by a Consultant anaesthetist. All anaesthetists are qualified doctors. Consultant anaesthetists will have undertaken a long period of training and examinations after medical school in a process identical to other hospital doctors and surgeons.

Meeting the anaesthetist

Your Consultant anaesthetist will visit you before your surgery. The Consultant anaesthetist will ask you questions and explain what happens to you during your time in theatre. The Consultant anaesthetist may also examine you. This is the best opportunity for you to ask any questions you may have. Please make sure you raise any concerns you have about anaesthesia at this time. It may be useful to make a list of questions beforehand.

Not eating before your operation

You will not be allowed to eat or drink for several hours before your operation. This is purely for safety reasons. It is important that your stomach is empty before you are anaesthetised. As a general rule you should not eat food or sweets for six hours before anaesthesia. Clear fluids (hot drinks without milk, fruit squash, water but not milk or fruit juice) may be drunk until three hours before anaesthesia. Chewing gum and eating sweets are not allowed. Please follow instructions you are given prior to admission.

Normal medicines before your operation

You should take all your normal medications unless requested not to.

The drugs you may be asked to stop before your surgery include anticoagulants (blood thinners) and medicines for diabetes. If you are taking these drugs you should be given specific instructions by the pre-admissions team.


Please let the Consultant anaesthetist know about any dental problems (i.e. loose teeth and the presence of caps, crowns or dentures – even if in good condition) when you meet. While every effort is made to protect all teeth there is an increased risk of damage to damaged teeth, caps and crowns, especially at the front of the mouth. The overall risk of damage is very small indeed. If you have false teeth you will usually be asked to remove them before your anaesthetic. This is for reasons of safety. This can be done in the operating theatre if you wish. Your dentures will be returned to you as soon as you wake up after your operation.


You may be given drugs before surgery (a ‘pre-med’). This most frequently includes a pain-killer, or a drug to reduce sickness. Sometimes it also includes a drug to reduce anxiety. If you would like something to relax you before your operation please discuss it with your anaesthetist at your preoperative visit.

Leaving the ward

When ready you will walk to theatre or be taken on a trolley. You will be asked to confirm who you are and what operation you are having. These careful checks ensure the right person arrives for the right operation.

In theatre

Arriving in the anaesthetic room

In the anaesthetic room you will be asked some questions again, to make sure the right person has arrived and that everyone understands precisely what surgery is planned. Although repetitive, this ‘check-list’ system is carried out to protect you, as it improves safety. We use the World Health Organization approved safety checklist for this purpose.

Getting ready for your anaesthetic

The Consultant anaesthetist will insert a small tube into a vein, usually in your hand. You may find this uncomfortable for a few seconds. All the anaesthetic drugs go through this tube without the need for more needles. You may feel light-headed, dizzy or sleepy as you are taken into theatre.

Having a general anaesthetic: ‘going to sleep’

Once you are on the operating table and safe the anaesthetic will start. You will be asked to breathe some oxygen from a facemask, which you may hold. The Consultant anaesthetist’s assistant will put monitors (to measure oxygen levels, heart rate and blood pressure) on you. You may feel light-headed. You may have an odd taste in your mouth. Your hand or arm may feel cold, or occasionally sore. These feelings will last only a few seconds as the anaesthetic starts to work. Once anaesthetised, you will not be aware of anything until after your operation has finished, when you will be woken up.

What exactly is a general anaesthetic?

A general anaesthetic is the use of a combination of drugs to make you temporarily unconscious. You will be given several drugs to make you unconscious (send you to sleep) followed by other drugs to keep you unconscious and safe.

What do they do after I’m anaesthetised?

Your anaesthetist stays with you throughout your operation and keeps you safe. The Consultant anaesthetist carefully fine tunes the anaesthetic in response to the surgery and your responses to it. The Consultant anaesthetist controls your breathing and cardiovascular system and gives pain killers, other drugs and fluids as necessary. The details vary widely according to the type of operation. The Consultant anaesthetist takes overall care of your wellbeing and safety while the Consultant surgeon concentrates on the surgery. At the end of surgery the Consultant anaesthetist ensures you wake up safely and that your recovery is safe and comfortable.

Local anaesthetic techniques

Some operations may take place using a local anaesthetic rather than a general anaesthetic. Local anaesthetic methods include spinal and epidural blocks, which involve an injection into the back. For shoulder and arm operations the anaesthetic will often include a nerve block combined with general anaesthesia or sedation. More information on these techniques is available separately.


The Consultant anaesthetist may use sedation during your operation; generally combined with a local anaesthetic technique. During sedation you are not unconscious but are given drugs that make sensations less clear and more comfortable. Perhaps the best description is of ‘dozing’. You may fall into a natural sleep during sedation. Some patients have some recall of events while sedated but many do not. Your Consultant anaesthetist will adjust the sedation to your needs.

Immediately after your operation

When you wake up, once your condition is stable, you will be transferred to a different room, called the recovery room or post-anaesthesia care unit. However you may not remember waking up until you reach the recovery room, or even the ward. You will be looked after by a specialised nurse. This nurse will ensure you are safe. If you have any pain or feel sick this will be treated. You will also routinely be given oxygen through a face-mask.

Drugs used ‘off licence’ during anaesthesia

See appendix 1.

After the operation

Will I be visited by the Consultant anaesthetist?

Usually the answer is yes. However some patients (having ‘day surgery’ procedures) are able to leave the hospital even before the operating list has finished. In this case the Consultant anaesthetist will still be busy in the operating theatre. You may wait if you have specific questions you wish to ask.

Pain relief

All operations may cause pain. Pain-killers will effectively control this and you should usually have little more than mild pain. If you do have pain after your operation, ask for treatment as soon as you can.

Nausea and vomiting

Some people feel sick after operations, because of the operation, the anaesthetic, pain killers or other factors such as antibiotics. Some people are particularly sensitive. If you do feel sick after your operation, ask for treatment as soon as you can.

Is anaesthesia safe? What complications can occur?

Yes anaesthetics are very safe. However no medical intervention is without risk and in this respect anaesthesia is no different from other medical specialties. However, in anaesthesia, perhaps more than in any other field of medicine, training and practice is centred on patient safety. The risk of serious complications from an anaesthetic for a healthy patient is very small indeed. Anaesthesia is, for instance, considerably safer than surgery! For patients who are less healthy, surgery and anaesthesia may be associated with greater risks.

When we describe risk in this document we use the following terms.

General anaesthesia

Common minor complications that may occur after an anaesthetic include:

  • Sore or dry throat that usually settles within 24 hours.
  • Nausea that may be due to surgery or anaesthesia.
  • You may have a small bruise at the site of a cannula (drip).
  • You may feel light-headed or tired for some time after surgery and anaesthesia.

Other complications are uncommon (occurring less than 1 in 100 cases).

Serious complications are possible, but unusual, and once again are more common for patients who are ill before surgery. Anaesthetists are trained to treat complications if they occur.

  • Allergy to anaesthetic drugs is very uncommon and anaesthetists are trained to treat allergic reactions.
  • Feeling the operation (an ineffective anaesthetic, also known as ‘awareness’) is uncommon. Reports of awareness vary between 1 in 600 and 1 in 20,000. The most recent and largest ever study reported that 1 in 20,000 patients reported awareness after general anaesthesia. If this were to happen in most circumstances you would not feel any pain. During the anaesthetic drugs may be used that stop your muscles moving so you would feel unable to move. This would be temporary and would stop at the end of the operation. It is important you let your Consultant anaesthetist know if you think this has happened.
  • Severe heart or lung disease that exists before surgery may be made worse both by surgery and anaesthesia and in elderly patients such conditions may be revealed by the stress of surgery and anaesthesia.

Any complications that may concern you are best discussed with your Consultant anaesthetist before surgery.

‘Local’ and ‘regional’ anaesthesia

Local anaesthetic techniques are very safe and complications are uncommon. The area numbed or anaesthetised by the nerve block will feel weak and you may not be able to move it for many hours.

  • The commonest problem with nerve blocks is that occasionally they do not work fully. This occurs in about one in 100 spinal anaesthetics, 1 in 20 epidural anaesthetics, and 1 in 10 arm or leg blocks. It is important you tell the anaesthetist if you think a local anaesthetic block is not working. If this happens the Consultant anaesthetist will ensure you are comfortable by other means.
  • Bruising after local anaesthetic blocks is usually minor.
  • Headaches affect up to 1 in 100 younger patients after spinal and epidural anaesthetics and these can be severe. In middle aged and older patients this is much less common.
  • Temporary areas of numbness or mild weakness after a nerve block occur in about 1 in 50-100 cases (depending on the area blocked).
  • Permanent problems occur rarely. Permanent major problems (such as permanent areas of weakness, numbness, pain or paralysis) occur about.
    • 1 in 50,000 times after a spinal anaesthetic
    • 1 in 6,000-12,000 times after an epidural anaesthetic
    • <1 in 5,000 after an arm or leg block

In less healthy patients the benefits of local anaesthetic techniques are likely increased, but the risk of complications is also increased.

If you would like to discuss any of these risks further please ask your Consultant anaesthetist.

Going home and getting back to normal

You will be allowed to leave hospital when you are safe and well. As anaesthetic drugs disappear rapidly from your body, these are likely to have little effect on your recovery. However you are advised to take things easy for the first 24 hours after an anaesthetic.

  • You must be accompanied by a responsible adult during this time.
  • You must not return to work, operate machinery or drink alcohol, for 24 hours after an anaesthetic.
  • You must not make important decisions or sign legal documents during this period.
  • You must not drive for a minimum of 36 hours after an anaesthetic. Your insurance will not be valid if you do: as insurers vary in their rules if you need to drive please check with your own insurer.
  • If you are taking opioid painkillers (e.g. codeine, dihydrocodeine, tramadol, morphine or oxycodone) or any other drugs that might make you sleepy you should not drive.

You will normally be given some pain killers to take home with you, and you will receive instructions on how to take them. If you normally take pain killers at home please inform your anaesthetist, so that they may advise you on when to re-start these.

It may take you considerably longer to recover from surgery than anaesthesia. Your recovery will be helped by getting the right balance between rest and activity. Taking painkillers you have been prescribed will assist you to do this.

Dr Tim Cook,
Consultant Anaesthetist
The Bath Anaesthetic Group LLP
November 2015

More information

You may obtain more general information from your GP before you arrive in hospital, or from the nurse looking after you on the ward. If you have access to the internet the following websites may be helpful:

Children’s anaesthesia:

Appendix 1.

Drugs used ‘off licence’ during anaesthesia

When a drug manufacturer wishes to market (advertise) a drug it must specify the circumstances or ‘indications’ the drug is to be used for.

After due process the company then receives ‘market authorisation’ (previously known as a licence) to advertise the drug for this use. While the drug may only be advertised for uses that have ‘market authorisation’ the drug may also be useful for other conditions.

Doctors are not restricted to using drugs only for those indications that companies advertise them for. As an example most drugs cannot be advertised for use in children, but that does not prevent doctors being able to use them in children where necessary. When doctors use a drug outside of its ‘market authorisation’ this is referred to as ‘off label’ or ‘off licence’ use. Where possible it is good practice to inform patients of use of drugs in such a manner. During an anaesthetic your anaesthetist may use several drugs ‘off licence’.

The most common circumstances are when your anaesthetist uses a drug to stabilise your blood pressure, or to improve pain relief either after a general anaesthetic or as part of a regional anaesthetic (spinal or epidural). During hip and knee replacement operations your anaesthetist may also use a drug ‘off licence’ to reduce bleeding and lower the likelihood of you needing a blood transfusion or becoming anaemic. These drugs will only be chosen for these uses when they are considered by your anaesthetist to be appropriate; balancing the drug’s effectiveness and safety with those of alternative drugs, if there are any.

This section is included to inform you of the possibility of use of drugs in this manner. If you would like to discuss this further please ask your anaesthetist. A full article on the topic is available at ( p17-18) : newsletter Feb 2010.

For patient information in other languages, please follow this link.