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What happens to your brain when you go under anaesthesia

More than 3.5 million patients are put under the care anaesthetists every year in the UK

Kate Ng
Saturday 07 November 2015 16:13 GMT
Different types of anaesthetic drugs produce different effects in the brain
Different types of anaesthetic drugs produce different effects in the brain (Getty)

Before the invention of anaesthesia, patients could only hope to counter the pain of surgery with more pain (stinging nettles were used to distract a patient) or herbal solutions, including the use of marijuana. To date, more than 3.5 million patients are put under the care of anaesthetists every year in the UK, according to a 2014 survey by The Royal College of Anaesthetists (RCOA). Yet there are still a number of questions surrounding the drug and its effects on a person, particularly to the brain.

Anaesthetists often use a combination of drugs based on a patient’s health profile. Research using functional magnetic resonance imaging (fMRI), researchers have been able to see how different drugs and doses cause different effects in the brain.


What is it?
A general anaesthetic used to induce or maintain unconsciousness in patients undergoing surgery.

How does it affect my brain?
Low doses of sevoflurane are enough to affect memory-related region of the brain, including the primary visual cortex and its association cortex. Researchers found that increased levels of blood flowing in the brain influenced the way brain cells tried to survive as well as perform their usual tasks, which slows everything down.

What are the side effects?
Coughing, dizziness, drowsiness, increase in saliva, nausea, shivering and vomiting.

In short:
The memory loss you experience after surgery under anaesthetic can be attributed to this drug.

Propofol and ketamine

What is it?
Propofol is a widely used hypnotic drug that causes both unconsciousness and amnesia. It is used to help patients relax, as well as for critically ill patients who require a breathing tube connected to a ventilator. Ketamine is often used alongside propofol as a painkiller.

How does it affect my brain?
When a person becomes unconscious, it doesn’t happen straightaway like flicking a light switch off. Rather, researchers found that consciousness fades away. Propofol works by binding to receptors in the brain, starting in the middle and spreading outward to different regions of the brain. Ketamine inhibits a person’s senses, judgement, and coordination for up to 24 hours.

What are the side effects?
Propofol may cause mild itching or a rash, fast or slow heart rate, and slight stinging around the IV needle. Ketamine side effects include a dream-like state of mind, blurred or double vision, mild dizziness, nausea and insomnia.

In short:
Propofol and ketamine both sedate you and provide painkilling benefits.

What happens when a child or an elderly person is exposed to anaesthesia?

Exposing a child to anaesthesia can put them at higher risk or neurodevelopmental problems and changes in brain structure. According to a review published in the journal Pediatrics, children under 4 years old who received general anaesthesia scored “significantly lower in listening comprehension and performance IQ” when tested. Another study from 2012 also found that young children exposed to anaesthetics were twice as likely to develop learning disabilities ebfore the age of 10.

On the other end of the spectrum, researchers have found that older patients who undergo anaesthesia can take up to six months to recover from its effects. 35 per cent of elderly patients were placed at higher risk for dementia, according to their study. Researchers believe anaesthesia causes inflammation to neural tissues, increasing elderly patients’ chances of developing precursors to Alzheimer’s disease.

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