Having a General Anaesthetic

This information sheet is for people having a general anaesthetic. This information can be used in conjunction with further information about the operation which you are about to undergo.

What is a general anaesthetic?

A general anaesthetic (or GA) is the way in which an anaesthetist puts patients to sleep for an operation. It usually involves either breathing in some gas which contains a mixture of oxygen and an anaesthetic agent, and/or an injection of medicine into a vein. The anaesthetic will mean that you will not remember or feel anything during the operation.

Preparing for the anaesthetic and operation

You will already have had a discussion with your surgeon about having the operation, and you may have attended a preadmission clinic appointment either by telephone or in person at which your other medical conditions and general overall fitness will have been assessed.

It is advisable to stop smoking for at least 4 weeks prior to the operation as this will significantly reduce your risk of getting a chest or wound infection after the surgery.

Please see separate information sheet ‘Preparing for your operation’ for further information.

On the day of the operation

Have a bath or shower at home on the day of the operation, taking care to remove any jewellery and make-up particularly if within the area to be operated on. For sensitive items of jewellery such as a wedding ring which you may not want to remove, these can be covered with sticky tape. Also remove any hearing aids, glasses and contact lenses just prior to going to the theatre.


Make sure you follow the fasting instructions given to you at the preadmission appointment, as having an empty stomach reduces the chance of feeling sick or of vomiting whilst unconscious. Typically this involves not eating or drinking milk within 6 hours of a GA, although small quantities of clear fluids can usually be consumed up until 2-4 hours before the operation. Please consult your anaesthetist for further advice in case of doubt.

Preparation for the anaesthetic

The anaesthetist will visit you prior to the operation and will answer any questions that you may have. Both your surgeon and anaesthetist know that most people are more anxious about the anaesthetic than about the operation itself, and this is entirely understandable. Pre-medication drugs which can relieve anxiety may be offered to you. In certain circumstances you may be asked to wear compression leg stockings to reduce the chance of developing a DVT (deep vein thrombosis) although this is not always required.

In the anaesthetic room

You will be moved from your room on the ward to the anaesthetic room, which connects to the theatre. An assistant will help the anaesthetist prepare you for the anaesthetic. This will involve attaching you to some monitoring equipment, and also putting a small plastic cannula or tube into one of the veins either on the back of your hand or inner aspect of the elbow. Through this you may be given a drip to keep you well hydrated. You will also be asked to breathe in some oxygen.

The exact anaesthetic given will vary from person to person. For most operations this will involve breathing in a mixture of oxygen and anaesthetic gases, as well as receiving a drug injected through the cannula. You will fall asleep within seconds and won’t wake up again until after the operation is finished. The anaesthetic is then maintained for the duration of the operation, either by inhaling gases or with a continuous infusion of drugs through the cannula. The gases will be given to you through a flexible plastic tube put into your windpipe, which is inserted after you have fallen asleep so you will not be aware of it.

An important part of the anaesthetist’s job is to ensure that you have adequate pain relief during and after the operation. This may be injected through the cannula, given via the gases mixture or given as a suppository through the back passage. A drug may also be given to relax your muscles to allow the surgeon to operate more easily.

During the operation you will remain connected to machines that monitor your heart rate, blood pressure, breathing pattern and oxygen levels in the blood. Your anaesthetist will keep a close check on all of these parameters throughout the operation and will fine tune the medications (s)he gives you accordingly to ensure as smooth an anaesthetic as possible.

Waking up from the anaesthetic

At the end of the operation, the anaesthetic gases are stopped and you will begin to wake up. If a muscle relaxant has been used you will be given another drug to counteract its effects. You will then be moved into the recovery area where a nurse will provide one-to-one care and will monitor your vital signs closely, including pulse rate, blood pressure, oxygen level in your body and breathing pattern. You will also be given oxygen to breathe in via a face mask. You may experience a sore throat resulting from the tube used to help you breathe during the operation, and may feel a little sick although medicines are available to reduce this.

It is quite normal that you will feel sleepy and possibly disorientated for 15-30 minutes after you are awake. This time period is extremely variable and can last longer in some individuals. This will gradually pass and once you are moved back to your room on the ward you should start to feel more awake and aware of your surroundings.

A nurse will continue to monitor your progress closely, and after a short period of time you will be allowed something to drink and eat, the timing of which may in part depend on the type of operation you have had. You may also become aware of some discomfort at the site of the operation as the effects of the anaesthetic gradually wear off. Do not hesitate to ask the nurse for pain relief at any point.

Pain relief

There is a wide range of drugs available to ensure that any pain you experience is minimised. The key thing to remember is that pain relief is always more effective when given before the pain reaches its peak, so do not be afraid to ask your nurse for help at the earliest sign of discomfort. Sometimes local anaesthetics or sedation is used during the operation, the effects of which persist into the postoperative period, although you will certainly need some painkillers once the local anaesthetic numbness wears off.

Patient controlled analgesia (PCA) is used after some procedures, which consists of a pump attached to the drug which allows you to control how much pain control medication you need (within reason!).

Going home

If the operation has been planned as a day case, your surgeon and ward nurse will decide when they are happy for you to be discharged home. By this stage you will have had something to eat and drink, been to the toilet, and mobilised out of bed. Even though you may feel quite alert at this stage, it is important that you do not drink alcohol, sign legal documents or operate heavy machinery for a period of 48 hours following the surgery. This is because, even though most modern anaesthetics filter out of your system relatively quickly, they can temporarily affect your co-ordination and reasoning skills. You will also need to make arrangements for someone to collect you from the hospital, and there will need to be someone else at home with you at least for the first night in case there are any problems and also to offer you help when required. Also you may need to make alternative childcare arrangements.

You may have been given some medication on discharge from the hospital which you should continue to take as prescribed. This will probably include painkillers, and it is important to take these as directed by your surgeon as the effects of the anaesthetic will wear off quite rapidly and discomfort may occur.

Risks of a general anaesthetic

The vast majority of operations performed under a general anaesthetic pass without any problems, although on rare occasions complications can occur. Thankfully the majority of these are relatively minor and easily corrected.

Common minor side effects include a sore throat, feeling sick, headaches, disorientation and partial loss of memory for events at or just after recovery from the anaesthetic. It is possible to develop a chest infection after the procedure although this is very unlikely in fit, healthy individuals and is more likely to occur in people with pre-existing lung problems or if the operation takes place shortly after having a cold or ‘flu.

More serious complications such as heart problems, deep vein thrombosis (DVT) or stroke are extremely rare, and usually only occur in higher risk patients. Smoking is a significant risk factor for developing complications following anaesthetic, in particular breathing difficulties and can also reduce the quality of wound healing. There are therefore several good reasons for stopping smoking for at least 4 weeks before the operation to maximise the chance of a good result and minimise complications.

It is thought that serious complications leading to death occur in one in every 250,000 anaesthetics given. This is an average figure and for the majority of individuals the risk is considerably lower. Ask your anaesthetist to explain how these risks apply to your particular circumstances.