I am often asked by patients if an anaesthetic, or repeated anaesthetics, cause long-term harm. The
simple answer is no. The risk of an anaesthetic is very low and if you have no other medical problems
the risk of a catastrophic complication is 1 in 83,000 – about the same risk as being knocked down by
a car walking round the streets of London for two years.

Repeated anaesthetics do not increase risk. Until 20 years ago we used a drug called halothane
where repeated exposure could damage the liver. Halothane is no longer used and in general an
anaesthetic can be repeated without increased risk. Indeed, in my paediatric practice I regularly
anaesthetise children for radiotherapy every day five days a week for many weeks without any

Most anaesthetic drugs are either broken down or eliminated from the body in a matter of hours
and sometimes even minutes. Any trace levels that remain have no effect on the body and although
a small number of patients complain of feeling unwell for days after an operation this is not due to
the anaesthetic but due to the response of the body to the surgery – the so called stress response –
or due to other drugs such as painkillers. The only common exception to this is nausea which can
persist in a small number of patients and for which there is a separate blog on my site
However in 1955 West reported damage to brain cells in rats after anaesthesia. For the past 60+
years anaesthetists have investigated and argued about the relevance of this to humans and modern
anaesthetic practice and even today massive debates occur at international meetings. It is very
difficult to measure the effect of an anaesthetic on the brain because any change is very subtle.
Humans only have general anaesthetics because they are ill and therefore it is difficult to compare
them with controls who are not ill. Even today there is a real possibility that no anaesthetic produces
any long-term brain damage
Nevertheless the inconclusive evidence has resulted in the National Institute of Health in the United
States suggesting general anaesthesia should be restricted in some patients such as young children.
So what might be the risks?

The suggestion is that any damage to brain cells caused by anaesthetic agents are limited to children
under perhaps four years of age and people over 60. Anaesthetics of up to an hour and possibly two
hours are ‘safe’. A single anaesthetic is probably safe as well.
In practice very few young children have multiple lengthy anaesthetics unless they are suffering from
cancer where the benefit of surgery far outweighs any risk. We tend to remove fewer tonsils and put
in fewer grommets but this is because we realise that many operations have been unnecessary in
the past not because of the risk of brain damage

The older patient appears to be less at risk than children and again lengthy operations and repeated
anaesthetics are normally restricted to people with significant illnesses were surgery is unavoidable.
Certain drugs and particularly benzodiazepines such as valium and temazepam appear to be the
number one culprits and personally I avoid sleeping tablets in my patients around the time of
operations and I do not use these drugs for sedation any more. Certain anaesthetic agents appear to
provide protection to the brain and these can be selected. Excessive or ‘deep’ general anaesthesia is
also implicated as a cause of cerebral brain cell death or apoptosis and for this reason I routinely
monitor the EEG or brainwaves of all patients where it is possible. By doing so I can not only analyse

the 'age' of the brain and identify people who might be more at risk but also ensure that the amount
of drugs given is restricted so that patients are never over anaesthetised.
So in summary this is a fascinating area of investigation but there is no hard evidence that an
anaesthetic can cause long-term damage. We do not anaesthetise children particularly under the
age of four unless it is necessary. In older adult patients we should avoid certain drugs and excessive
amounts of anaesthetic drugs as well as monitor the EEG, but I believe that if we do so there is little
cause for concern