- Canadian study found a general anaesthetic can cause long-term memory loss because drugs trigger a persistent reaction in the brain
- Third of patients who undergo anaesthesia experience some cognitive impairment including confusion and poor brain function following an op
- Post-operative cognitive dysfunction is short-lived for most but sufferers have a higher risk of developing dementia
Jenny Hope, Daily Mail Medical Correspondent
12:24 EST, 4 November 2014
14:08 EST, 4 November 2014
Having a general anaesthetic before an operation can cause long-term memory loss because the drugs used may trigger a persistent reaction in the brain.
A new Canadian study suggests memory cells which should be blocked as a temporary measure to facilitate surgery may never recover.
Until now, scientists have not understood why about a third of patients who undergo anaesthesia and surgery experience some kind of cognitive impairment – including confusion and poor brain functioning – during the days following the operation.
Having a general anaesthetic before an operation can cause long-term memory loss because the drugs used may trigger a persistent reaction in the brain, claim researchers (File picture)
Post-operative cognitive dysfunction (POCD) after a general anaesthetic is a short-lived phenomenon for most, although recent research suggests some POCD sufferers have a higher risk of developing dementia.
However, one-tenth of patients still suffer cognitive impairments three months later and many relatives complain their loved ones were ‘never quite the same’ after a major operation.
Previous experimental studies suggest some anaesthetic drugs can promote inflammation of brain tissue in a way that is characteristic of dementia.
Another theory is that insufficient oxygen to the brain may have an effect in vulnerable patients.
But the latest study suggests another mechanism involving memory-loss receptors in the brain, which are activated by anaesthetic drugs to ensure patients don’t remember traumatic events during surgery.
Professor Beverley Orser and her team at the University of Toronto’s Faculty of Medicine found the activity of memory loss receptors remains high long after the drugs have been eliminated from the patient’s body.
Animal studies showed this chain reaction has long-term effects on the performance of memory-related tasks.
Professor Orser, an anaesthesiologist at Sunnybrook Health Sciences Centre, said: ‘Patients – and even many doctors – think anaesthetics don’t have long-term consequences.
A third of patients who undergo anaesthesia experience some cognitive impairment – including confusion and poor brain function – following an operation
‘Our research shows that our fundamental assumption about how these drugs work is wrong.’
In the study led by researcher Agnes Zurek the team gave healthy male mice a low dose of anaesthetic for just 20 minutes.
The results showed receptor activity remained at higher levels a week later, even when memory performance had been restored in the animals.
The findings suggest a ‘previously unrecognised long-term effect’ on the memory loss receptors.
There appear to be compensatory changes in the brain that can circumvent the problem, according to a report published in the Journal of Clinical Investigation.
The team is now looking at drugs that can stop the continuing impact on the receptors and restore memory loss. While they are still in the early stages of research, some of the drugs show very promising results in animal studies, it is claimed.
However, Professor Orser said the results suggest a patient’s learning and memory can be severely impaired during a time when they are receiving critical information about their care.
Post-operative cognitive dysfunction (POCD) after a general anaesthetic is a short-lived phenomenon for most, although recent research suggests some POCD sufferers have a higher risk of developing dementia. (Pictured, brain scans of an Alzheimer’s patient)
‘There’s a lot going on after surgery, which can alter our ability to think clearly. Loss of sleep, new environments and medications can all impact a patient’s mental function. Anaesthetics likely compound these issues,’ said Professor Orser.
She recommends doctors and family members carefully monitor patients after surgery for any signs of memory loss.
She said: ‘Patients should write everything down or have a second pair of ears with them after surgery.
‘For high-risk groups, physicians need to inform patients about these possible side effects and help manage the impact on recovery and overall health.’
The likelihood of a patient experiencing cognitive impairment depends on their age, health, type of surgery and the anaesthetic, with chances increasing for more intricate procedures.
The incidence is highest in the elderly or those undergoing major surgery such as cardiopulmonary bypass.
Prof Orser warned: ‘Anaesthetics don’t put you to sleep – they induce a pharmacological coma. We shouldn’t take these drugs lightly.’