A commonly used anaesthetic could cause
changes in the brain linked to Alzheimer's, a US study
suggests.
The anaesthetic isoflurane is linked
to cell death.
The researchers said the Journal of Neuroscience
findings from cell tests suggested caution was needed
regarding the anaesthetic's use for the elderly.
Alzheimer's experts said work was needed
to check if similar effects occurred in patients, and
anaesthetists urged caution over the study.
Alzheimer's disease is a progressive,
degenerative and irreversible brain disorder.
It is characterised by the formation
of plaques made of amyloid beta protein, which kills brain
cells.
More than 41,000 people in the UK are
currently affected by the condition.
Cell activity
Some studies have suggested that general
anaesthesia might increase the risk of developing Alzheimer's
disease.
It also is known that a small number
of surgical patients experience a form of dementia after
their operation.
But there has been no evidence of a direct
link between anaesthesia and the risk of dementia.
The team from the Massachusetts General
Hospital carried out tests on brain cells.
They found isoflurane boosts the activity
of an enzyme called capase, which plays a major part in
causing cells to die - a process called apoptosis - and
in the development of amyloid protein.
Dr Zhongcong Xie, of the Massachusetts
General Institute for Neurodegenerative Disease who led
the research, said: "Our studies have shown that isoflurane
may induce a vicious cycle of apoptosis, amyloid-beta
generation, and further rounds of apoptosis.
"If future studies support these findings,
they suggest that caution be used in choosing this anaesthetic
for elderly patients, who already are at increased risk
for Alzheimer's and for postoperative cognitive dysfunction."
The team plan to carry out further research
to assess if the same effects would be seen in patients.
Dr Susanne Sorensen, head of research
at the UK's Alzheimer's Society, said: "Around 10% of
people who are given anaesthetic for major surgery experience
'post-operative cognitive decline.'
"This involves lasting problems with
their memory and attention, but it is not yet clear whether
this decline may increase a person's risk of Alzheimer's
disease."
She said the study had raised interesting
questions, and added: "It is crucial that more work is
now done to establish whether this same reaction can occur
in the human brain. "
Dr Keith Myerson, a spokesman for the
Royal College of Anaesthetists: "We take this report very
seriously, but we would advise caution in extrapolating
these findings to humans."
He added: "We know it's important to
maintain blood flow to the brain when dealing with elderly
patients and monitor blood pressure carefully.
"It's also important that the level of
carbon dioxide in the blood is not allowed to drop too
low."
