Benefits and risks of anaesthesia


The risk to you as an individual will depend on:

  • whether you have any other illness
  • personal factors, such as whether you smoke or are overweight
  • surgery which is complicated, long or done in an emergency.

Everyone varies in the risks they are willing to take. Anaesthetists and patients may also hold different views about the importance of risk.


To understand a risk, you must know:  

  • how likely it is to happen
  • how serious it could be
  • how it can be treated.

The more complicated the anaesthesia and surgery are, the more chance there is of complications and side effects. It is the responsibility of the anaesthetist to advise you on what anaesthetic techniques will give you greatest benefit and reduce as far as possible these risks.

Side effects and complications of anaesthesia

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. Unpleasant side effects do not usually last long. Some are best left to wear off and others can be treated.  Examples would be a sore throat or sickness after a general anaesthetic.

Complications are unexpected and unwanted events due to a treatment. Examples would be an unexpected allergy to a drug or damage to your teeth caused by difficulty in placing a breathing tube.

Index of side effects and complications


People vary in how they interpret words and numbers. This scale is provided to help.

Very Common              1 in 10

Common                     1 in 100

Uncommon                  1 in 1000

Rare                          1 in 10,000

Very Rare                   1 in 100,000


Using this index


There is also a key to show which side effect or complication is relevant to which type of anaesthetic.

RA = This may occur with a regional anaesthetic.

GA = This may occur with a general anaesthetic.

If you see the symbol ** next to the item, this means you can find detailed information about this risk on our website.

Very common and common side effects and complications
Feeling sick and vomiting after surgery** GA RA 
Sore throat**GA  
Dizziness and feeling faintGA   RA
Shivering**GA   RA
HeadacheGA   RA
Itching GA   RA
Aches, pains and backacheGA   RA
PainGA   RA
Bruising and sorenessGA   RA
Confusion or memory loss** GA  

Uncommon side effects and complications
Chest infection**  GA  
Bladder problems  GA   RA
Muscle pains   GA  
Breathing difficulties  GA   RA
Damage to teeth, lips or tongue**GA  
An existing medical condition getting worseGA   RA
Awareness** GA  
Rare or very rare complications
Damage to the eyes** GA  
Serious allergy to drugs** GA   RA
Nerve damage** GA   RA
Death or Brain Damage**  GA   RA
Equipment failure** GA   RA


Page last updated: 09/06/2016
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South Infirmary

Victoria University Hospital

A teaching hospital

of University College Cork