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 ANY 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 problems
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 as well as antibiotics such as metronidazole. 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.
In practice most patients can leave hospital without any restrictions due to their anaesthetic. However, many patients need narcotics or other pain killers, they may not have eaten properly and they may have physical restrictions so we advise everyone not to work that day. There are also legal restrictions on driving – please look at my blog on this. None of this reflects harm to the brain
You may read otherwise on the web, because 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. Even in these groups we believe 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 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.
This all assumes a straight forward uneventful procedure. We know that the use of a heart lung machine where the heart I stopped for open heart surgery can affect the brain, possibly due to small amounts of air or clotting in the blood. Long term ventilation on ITU, and even critical illness also results in behavioural changes in a significant minority of patients. And finally long term illness such as cancer patients undergoing chemotherapy can result in psychological changes. but none of this is related to a general anaesthetic so I will leave them for another blog!
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