Preparing yourself for anaesthetic

  • It is difficult to separate the risks of anaesthesia from the risks of the operation and your general health. The risks to you as an individual depend on whether you have any other illnesses and personal factors, such as whether you smoke or are overweight.
  • If you smoke, giving up for several weeks before the operation reduces the risk of breathing problems and improves healing of the tissues. If you cannot stop, cutting down will help.
  • If you are very overweight, reducing your weight will reduce many of the risks of having an operation and anaesthetic.

What will happen before my surgery?

You will meet your anaesthetist before your operation. They will ask you questions about your health, previous anaesthetics and usual medicines and will need to check your answers to other questions. They may need to examine your chest with a stethoscope and examine your neck and mouth. Please ask questions and tell them of any worries you may have.

You will receive clear instructions when to stop eating and drinking before your operation. It is very important to follow these or your operation may be delayed or cancelled.

It is important you continue to take all your usual medications, including inhalers, unless otherwise advised.

Types of anaesthesia


Your surgery will usually be performed under a spinal anaesthetic. This is an injection of local anaesthetic into the back which causes numbness below the waist for several hours. During the operation, some patients may wish to be awake and listen to music, or watch a film. Others may wish to be more asleep either with light sedation or a general anaesthetic.

Spinal anaesthesia allows excellent pain relief in the immediate postoperative period. There is some evidence that it may improve or enhance the speed of your post-operative recovery. There is good evidence that it reduces the likelihood of post-operative confusion and delirium, particularly in older patients. There is strong evidence that it reduces the likelihood of post-operative nausea and vomiting.

As with all types of anaesthetic, spinal anaesthesia carries risk. Generally they are considered safe, as or safer than general anaesthetics. Many people often worry about back pain. There is no association between spinal anaesthesia and the development of back pain. Common side effects are related to the actions of the local anaesthetic on nerves and include low blood pressure, shivering and itching. These tend to resolve quickly after the spinal wears off (within a few hours).

Uncommonly (less than 1 in 200) some patients may get a headache afterwards. This will often be self-limiting, but may require further intervention. Nerve damage resulting in prolonged weakness or numbness is very rare (less than 1 in 10,000). Paralysis is extremely rare (less than one in a million). Your anaesthetist can discuss these risks with you if you are concerned.

General anaesthesia

Nowadays general anaesthesia (GA) on its own is uncommon for hip or knee replacement surgery, as it does not provide any pain relief.

It is usually used in combination with a spinal anaesthetic or a nerve block. A GA consists of a combination of drugs, which are given to make you completely unconscious. During a general anaesthetic you do not feel anything and will not be aware of what is going on around you. When the operation is finished the anaesthetic is stopped and you regain consciousness.

Modern general anaesthesia is very safe. However, common side effects include a sore throat, feeling sick or vomiting, shivering or a headache.

Less common complications include chest infection, an existing medical problem getting worse, muscle pains, damage to the teeth, lips or eyes, and excessive drowsiness or slow breathing.

Serious complications related to general anaesthesia are rare but include: life threatening allergy to drugs, failure to maintain a clear airway and serious cardiac or respiratory complications, such as heart attack and stroke. Awareness or becoming conscious during your operation is also rare for this type of surgery. Nerve Block (Regional Anaesthesia) some patients may not be suitable for spinal anaesthesia for a variety of reasons. In this situation you may be offered a GA in combination with a nerve block. A nerve block is an injection of local anaesthetic near to the nerves that go to your leg. Most of the upper part of the leg will be numb and pain free usually for about 12 to 24 hours afterwards. You may not be able to move your leg properly during this time. The injection may be given before the general anaesthetic or when you are asleep. Due to the impact that this has on you mobilising on the day of and day after surgery, nerve blocks are being used less frequently