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Patient Information

General Anaesthetic and Sedation

A general anaesthetic gives a state of controlled unconsciousness during which you feel nothing. You will receive:

  • Anaesthetic drugs (an injection into the cannula placed in your vein or a gas to breathe)
  • Strong pain relief drugs (morphine or something similar)
  • Oxygen to breathe
  • Sometimes, a drug to relax your muscles

The anaesthetic drugs will be carried to your brain by the blood. They stop the brain recognising messages coming from the nerves in the body. Anaesthetic unsconsciousess is different from unconsciousness due to disease or injury and it is different from sleep. You will need a breathing tube in your throat whilst you are anaesthetised to make sure that oxygen and anaesthetic gases can move easily into your lungs. If you have been given drugs that relax your muscles, we will support your breathing with a breathing machine (ventilator). At the end of your surgery the anaesthetic drugs wear off, you will breathe for yourself and your consciousness starts to return. A general anaesthetic alone does not provide pain relief after the operation. You will need strong pain-relieving medicines, which can make some people feel drowsy and nauseous. Alternatively, you may wish to consider a regional anaesthetic in combination with a general anaesthetic such as spinal, epidural anaesthesia or a nerve block.


Sedation is different from a general anaesthetic. It is achieved by injecting anaesthetic drugs at very low doses through a drip, cannula in your vein. It makes you relaxed, sleepy and forgetful during the operation, but you are not unconscious. It is often used in combination with regional anaesthesia such as a spinal block, epidural or a nerve block. Sedation can either be light or deep, depending on your preferences. Light sedation means you are relaxed but awake. Deep sedation means you are more likely to be asleep and less likely to recall what happened during the operation. Whether you are suitable for sedation, or a general anaesthetic will depend on the type of operation you are having.

Anaesthetic risks

Anaesthetic risks are thought of in terms of side effects and complications. Side effects are secondary effects of drugs or treatment. They can often be anticipated but are sometimes unavoidable. Almost all treatments (including drugs) have side  effects of some kind. Often side effects can just be left to wear off, such as a sore throat or itching, others can be treated, for example nausea and vomiting. Complications are unexpected and unwanted events due to a treatment. Examples would be an unexpected allergy to a drug or damage to your teeth that is caused by difficulty in placing a breathing tube. Modern equipment, techniques, training and drugs have made anaesthesia a safe procedure. The risk of serious complications is very low.  It cannot be removed completely but our anaesthetic team takes all precautions to reduce any risks mentioned in this leaflet. More information is available on

The following scale is to help you understand how likely it is that a side effect or complication might occur:
Very common - 1 in 10 - someone in a family
Common - 1 in 100 - someone in a street
Uncommon - 1 in 1,000 - someone in a village
Rare - 1 in 10,000 - someone in a small town
Very rare - 1 in 1,000,000 - someone in a large town

The type of possible side effects and complications of sedation and general anaesthesia are comparable. However, they are less common during sedation because your heart, circulation, brain and breathing are less affected, as you require fewer drugs.

Common and very common side effects or complications

  • Sickness – treated with anti-sickness drugs
  • Sore throat or damage to lips or tongue – treated with pain relief drugs
  • Drowsiness, headache, shivering, blurred vision – may be treated with fluids or drugs
  • Difficult breathing at first – this usually improves rapidly
  • Confusion and memory loss are common in older people, but are usually temporary
  • Pain around injections sites, general aches and pains
  • You may have difficulty passing water. Sometimes you will require a catheter (a soft plastic tube in your bladder) for a short period of time to drain the urine.

Uncommon side effects or complications

  • Heart attack or stroke
  • Damage to teeth
  • Chest infection
  • Awareness (becoming conscious during a general anaesthetic)
  • Rare or very rare side effects or complications
  • Serious allergic reactions to drugs
  • Damage to nerves as a result of pressure depending on the position
  • Damage to eyes as a result of pressure depending on the position
  • Vomit getting into your lungs
  • Death

Further information

Patient information | The Royal College of Anaesthetists (

More information

Contact POAC on 0121 685 4035 weekdays from 8:30am - 4pm

The Royal Orthopaedic Hospital | T: 0121 685 4000 |