New study firmly ties hormone use to breast cancer

By MARILYNN MARCHIONE

SAN ANTONIO (AP) — Taking menopause hormones for five years doubles the risk for breast cancer, according to a new analysis of a big federal study that reveals the most dramatic evidence yet of the dangers of these still-popular pills.
Even women who took estrogen and progestin pills for as little as a couple of years had a greater chance of getting cancer. And when they stopped taking them, their odds quickly improved, returning to a normal risk level roughly two years after quitting.

Collectively, these new findings are likely to end any doubt that the risks outweigh the benefits for most women.
It is clear that breast cancer rates plunged in recent years mainly because millions of women quit hormone therapy and fewer newly menopausal women started on it, said the study's leader, Dr. Rowan Chlebowski of Harbor-UCLA Medical Center in Los Angeles.

"It's an excellent message for women: You can still diminish risk (by quitting), even if you've been on hormones for a long time," said Dr. Claudine Isaacs of Georgetown University's Lombardi Comprehensive Cancer Center. "It's not like smoking where you have to wait 10 or 15 years for the risk to come down."

Study results were given Saturday at the San Antonio Breast Cancer Symposium.
They are from the Women's Health Initiative, which tested estrogen and progestin pills that doctors long believed would prevent heart disease, bone loss and many other problems in women after menopause. The main part of the study was stopped in 2002 when researchers saw surprisingly higher risks of heart problems and breast cancer in hormone users.
Since then, experts have debated whether these risks apply to women who start on hormones when they enter menopause, usually in their 50s, and take them for shorter periods of time. Most of the women in the federal study were in their 60s and well past menopause.

So the advice has been to use hormones only if symptoms like hot flashes are severe, and at the lowest dose and shortest time possible. The new study sharpens that message, Chlebowski said.

"It does change the balance" on whether to start on treatment at all, he said.

Even so, most women will not get breast cancer by taking the pills short-term. The increased cancer risk from a couple of years of hormone use translates to a few extra cases of breast cancer a year for every 1,000 women on hormones. This risk accumulates with each year of use, though.

The Women's Health Initiative study had two parts. In one, 16,608 women closely matched for age, weight and other health factors were randomly assigned to take either Wyeth Pharmaceuticals' Prempro — estrogen and progestin — or dummy pills.
This part was halted when researchers saw a 26 percent higher risk of breast cancer in those on Prempro.

But that was an average over the 5 1/2 years women were on the pills. For the new study, researchers tracked 15,387 of these women through July 2005, and plotted breast cancer cases as they occurred over time.

They saw a clear trend: Risk rose with the start of use, peaked when the study ended and fell as nearly all hormone users stopped taking their pills. At the peak, the breast cancer risk for pill takers was twice that of the others.

Think of it as President Bush's public approval rating, said another study leader, Dr. Peter Ravdin of the University of Texas M.D. Anderson Cancer Center in Houston. "Bush's popularity may be 50 percent on average, but it might have been descending the whole time he was president," Ravdin said.

In the second part of the federal study, researchers observed just 16,121 women who had already been on hormones for an average of seven years and another group of 25,328 women who had never used them. No results on breast cancer risk in these women have been given until now.

Plotting cases over time, researchers saw in retrospect that hormone users had started out with twice the risk of breast cancer as the others, and it fell as use declined. Among those taking hormones at the start of the study, use dropped to 41 percent in 2003, the year after the main results made news.

In the general population, use of hormone products has dropped 70 percent since the study, said another of its leaders, Dr. JoAnn Manson, preventive medicine chief at Harvard's Brigham and Women's Hospital in Boston.
That corresponds with big drops in breast cancer cases, but some scientists have said this could be due to a fall-off in mammograms, which would mean fewer cancers were being detected, not necessarily that fewer were occurring.
The new study puts that theory to rest. Mammography rates were virtually the same among those taking hormones and those not.

"It is clear that changing mammography patterns cannot explain the dramatic reductions in breast cancer risk," Manson said.
"The data are getting stronger," said Dr. C. Kent Osborne, a breast cancer specialist at Baylor College of Medicine in Houston.
Women who do need the pills should not panic, though the doubling of risk — a 100 percent increase — for long-term users is quite worrisome, cancer specialists say. Although the new study does not calculate risks in terms of actual cases, previous research showed that the average increased risk of 26 percent meant a difference of a few extra cases a year for every 1,000 women on hormone pills, compared with nonusers.

"Hormone therapy remains a good health care choice to relieve moderate to severe menopausal symptoms," says a statement from Wyeth, which made the pills used in the study.

"Most women should be able to discontinue hormones in three to four years," or at least reduce their dose, Manson said.
A future analysis will look at other women in the study who took only estrogen, generally women who have had hysterectomies.

On the Net:
Cancer conference: http://www.sabcs.org
Hormone study: http://www.nhlbi.nih.gov/whi/estro_pro.htm

Stress hits even before pregnancy

Premature birth can cause long-term health problems

Stress in the six months before conception increases the risk of giving birth prematurely, research suggests.
Mothers who experience a death or serious illness in the family before falling pregnant are more likely to have a preterm baby, a study found.

The link was particularly strong in mothers who had experienced "severe life events" in older children, the Human Reproduction journal reported.

Effects of stress hormones in the womb, may explain the findings, experts said.
Records from 1.35m mothers in Denmark were analysed in the study, which comes on the back of earlier research suggesting stress during pregnancy is a risk factor for premature birth.

Serious illness or death in older children in the six months prior to conception, increased the risk of birth before 37 weeks by 23% and the risk of birth before 33 weeks by 59%.

Death or illness in close relatives, such as parents, siblings or a partner in the last six months before becoming pregnant increased the risk of birth before 37 weeks by 16%.

Mothers who had experience stress and were also missing a parent or who did not have a partner were significantly more likely to have a premature birth, the study showed.

Hormones
The researchers suggested several possible explanations for the findings including increased levels of stress hormones or lifestyle changes in response to stress, such as increased consumption of tobacco or alcohol.

Study leader, Professor Philip Baker, from the Maternal and Fetal Health Research Group at the University of Manchester said most research to date had focused on stress during pregnancy.
"Yet these results suggest that the impact could be greater in the period preceding conception.
"Although relatively subtle its still a real effect."
He added they had chosen to look at death and serious illness in close relatives as they were undoubtedly very stressful events for anyone.

"This should help our understanding of the causes of premature birth," he added.
Tommy's, the baby charity, who funded the research said around 50,000 babies are born prematurely each year in the UK, putting them at risk of long-term health problems such as chronic lung disease, learning difficulties and blindness.
Ronald Lamont, consultant obstetrician at North West London Hospitals NHS Trust and spokesman for the Royal College of Obstetricians and Gynaecologists, said the results were a "little surprising".

"It's quite interesting and fits with what we knew about stress during pregnancy.
"The fact that the risk of pre-term birth was increased if pregnant women were missing a parent or partner shows the importance of close support."

Stem cell cure hope for back pain

Millions suffer debilitating back pain

A patient's own stem cells could soon be used to cure chronic back pain, say researchers.
The team from the University of Manchester hope their treatment will be available within three years.

They are perfecting a way to rebuild the soft shock-absorbing discs which separate the vertebrae in the spine.

Damage to these intervertebral discs (IVDs) is a common cause of debilitating low back pain which affects around 12 million in the UK.

BackCare
A treatment which effectively cured the problem could potentially save the UK economy as much as £5 billion a year.

The new therapy, developed by Dr Stephen Richardson, uses mesenchymal stem cells (MSCs) from adult bone marrow to regenerate spinal discs.

MSCs are a class of stem cell which can grow into many different cell types, including bone, cartilage, fat and muscle.

Dr Richardson has succeeded in turning MSCs into the cells which make up the gel-like nucleus pulposus (NP) tissue separating the vertebrae.

He plans to begin pre-clinical trials next year, with full patient trials to follow on.

Dr Richardson said: "Once we have extracted the bone marrow from the patient and have purified the MSCs, they will be grown in culture and our patented method of differentiation will be applied.

"They will then be embedded within a gel which can be implanted back into the patient."

No rejection

Since the stem cells are taken from the patient's own body, there is no chance of them being rejected by the immune system.

The gel is based on a natural collagen similar to one already used for the treatment of cartilage defects.

It is implanted using an arthroscope, a thin tube device slipped through a small incision in the back.

Dr Richardson said there was no reason why a patient should not return home on the same day as the procedure, or the day after.

He said: "Once implanted, the differentiated MSCs would produce a new NP tissue with the same properties as the original and would both treat the underlying cause of the disease and remove the painful symptoms."

Currently, low back pain is treated with a combination of painkillers, physiotherapy or surgery.

In severe cases tissue is removed to relieve the pain, or vertebrae fused together.

However, success is limited, and these techniques do not solve the root cause of the problem.

Dries Hettinga, research and information manager at the charity BackCare, said: "This is a really exciting area of research and although it is still early days, the initial results look very promising."

Surgery beneficial in heartburn

By Emma Wilkinson
BBC News health reporter

Proton pump inhibitors are the standard treatment for reflux
People with persistent heartburn should be considered for early surgery to prevent a lifetime of popping pills, NHS research suggests.

A year after keyhole surgery, only 14% of patients were still taking medication, compared with 90% of those treated with drugs alone.

The £1m trial of 800 patients suggests surgery should be done more routinely in patients with chronic acid reflux.
Experts said there was a view among GPs that surgery was "too extreme".
Researchers at the University of Aberdeen co-ordinated the trial of laparoscopic fundoplication at 21 hospitals around the UK.

For some people, it is a serious problem which could potentially mean a lifetime of tablet taking
Professor Roger Jones, King's College London

The results so far suggest the procedure, although expensive at £2000 per patient, is cost-effective because reflux sufferers no longer have to take medication and their quality of life improves.

But they are following the patients for five years to check the benefits are long-term.

The operation involves wrapping a piece of the stomach around the oesophagus to create a new valve to prevent acid backing up from the stomach.

It used to be done by opening up the chest cavity, but with the advent of keyhole surgery is now a lot safer.
Common problem

Reflux is a very common condition with 20% of the population experiencing it at some point in their lives.
Those at the more severe end of the spectrum end up taking tablets for the rest of their lives - potentially for 20 to 30 years in younger patients - and few currently receive surgery.

Study leader, Professor Adrian Grant, said: "It looks pretty promising.
"I think these results will mean that surgeons will be suggesting the operation in those patients who are not quite so bad."
He added: "Like all surgery, fundoplication has some risks, but the more troublesome the symptoms, the greater the potential benefit from the operation."

Professor Roger Jones, head of general practice at King's College London and chair of the Primary Care Gastroenterology Society said surgery was often regarded as "too extreme" for something which is not a serious problem.

"But for some people, it is a serious problem which could potentially mean a lifetime of tablet taking."

Diabetes aspirin use questioned

Aspirin makes it harder for blood clots to form
Aspirin should not routinely be used to prevent heart attacks in people with diabetes, Scottish research suggests.

The British Medical Journal reported that in 1,300 adults with no symptoms of heart disease the drug, which can cause stomach bleeds, had no benefit.

The findings contradict many guidelines which advocate people with diabetes use aspirin to counter the underlying high risk of heart attack and stroke.

But there are key high-risk groups who still need the drug, experts said.
Patients with concerns are advised to consult their GP before changing medication.
In people who have already had a heart attack or stroke, or have been diagnosed with coronary artery disease, aspirin has been shown to reduce the risk of future "events" by around 25%.

However, in recent years doctors have begun to focus on people who have not yet developed so-called cardiovascular disease, but are at high-risk of having it in the future - such as people with diabetes.
There are around two million people over 40 with diabetes in the UK.
Around 80% of people with diabetes die of cardiovascular disease including strokes and heart attacks.
A daily dose of aspirin is recommended by several UK guidelines as a "preventive" treatment in these groups.

No benefit
But in the latest study in adults over 40 years with type 1 or type 2 diabetes and no symptoms of cardiovascular disease, there was no difference over seven years in heart attacks or strokes between those given aspirin and those given a dummy pill.

ASPIRIN USE
It can reduce the risk of people who have had strokes or heart attacks being ill again
But this study shows no benefit for people with diabetes who have no signs of heart disease
There is a known risk that taking the drug can cause stomach bleeds
People should talk to their GP before they stop taking the drug

Study leader Professor Jill Belch, from the University of Dundee, said aspirin was one of the most common causes of hospital admission for gastrointestinal bleeding.
"We have got a bit ahead of ourselves with aspirin.
"We need to think again about using it for primary prevention."
However she stressed the drug was beneficial in people who had already had a heart attack or stroke.

Professor Peter Sever, an expert in clinical pharmacology and therapeutics at Imperial College London, said the study was "extremely important".
"It confirms many concerns we have that aspirin is very widely used in the general population without an evidence base to support its overall benefits.
"Thousands of people buy aspirin over the counter - I'm forever saying to patients you shouldn't be taking this.
"I have had a couple of patients admitted to hospital with major gastrointestinal bleeding when there was no evidence it was doing any good."

The number of people diagnosed with diabetes and as having a high risk of cardiovascular disease is set to increase, with government plans in England to introduce a national screening programme for the over-40s next year.
Professor Steve Field, chair of the Royal College of GPs, said it would be worth revisiting the guidelines.
"But patients shouldn't panic or stop taking aspirin," he said.

Judy O'Sullivan, cardiac nurse at the British Heart Foundation, said: "This study adds weight to the evidence that aspirin should not be prescribed to prevent disease of the heart and circulation to people with diabetes, and other high risk groups, who do not already have symptoms of the disease."

Fatty acids clue to Alzheimer's

Scientists want to know more about the brain changes that lead to Alzheimer's

Controlling the level of a fatty acid in the brain could help treat Alzheimer's disease, an American study has suggested.
Tests on mice showed that reducing excess levels of the acid lessened animals' memory problems and behavioural changes.
Writing in Nature Neuroscience, the team said fatty acid levels could be controlled through diet or drugs.
A UK Alzheimer's expert called the work "robust and exciting".

There are currently 700,000 people living with dementia in the UK, but that number is forecast to double within a generation.

Over-stimulation
Scientists from Gladstone Institute of Neurological Disease and the University of California looked at fatty acids in the brains of normal mice and compared them with those in mice genetically engineered to have an Alzheimer's-like condition.
They identified raised levels of a fatty acid called arachidonic acid in the brains of the Alzheimer's mice.

This is cause for cautious optimism, as fatty acid levels can be controlled to some extent by diet and drugs
Rebecca Wood, Alzheimer's Research Trust

Its release is controlled by the PLA2 enzyme.
The scientists again used genetic engineering to lower PLA2 levels in the animals, and found that even a partial reduction halted memory deterioration and other impairments.

Dr Rene Sanchez-Mejia, who worked on the study, said: "The most striking change we discovered in the Alzheimer's mice was an increase in arachidonic acid and related metabolites [products] in the hippocampus, a memory centre that is affected early and severely by Alzheimer's disease."

He suggested too much arachidonic acid might over-stimulate brain cells, and that lowering levels allowed them to function normally.

Dr Lennart Mucke, who led the research, added: "In general, fatty acid levels can be regulated by diet or drugs.
"Our results have important therapeutic implications because they suggest that inhibition of PLA2 activity might help prevent neurological impairments in Alzheimer's disease.

"But a lot more work needs to be done before this novel therapeutic strategy can be tested on humans."
'Cautious optimism'

Rebecca Wood, chief executive of the UK's Alzheimer's Research Trust, said: "This research on mice suggests a connection between fatty acids and the abnormal brain activity that exists in Alzheimer's disease.
"This is cause for cautious optimism, as fatty acid levels can be controlled to some extent by diet and drugs.
"However, it is not yet clear if these findings are applicable to humans, and a lot more research is needed before any human trials can be conducted."

Professor Clive Ballard, director of Research at the Alzheimer's Society, said the work was "robust and exciting".
He added: "This is a novel and potentially exciting area of research, but it is still at a very early stage.
"Much more research is needed to see if fatty acids could lead to a treatment for those living with the devastating effects of Alzheimer's disease."

Antibiotic 'cerebral palsy link'

By Michelle Roberts Health reporter, BBC News

Antibiotics appeared to treble the risk of cerebral palsy
A study has linked a small number of cases of cerebral palsy to antibiotics given to women in premature labour.
The UK study found 35 cases of cerebral palsy in 769 children of women without early broken waters given antibiotics.
This compared with 12 cases among 735 children of women not given the drugs. Advice is being sent to the study's 4,148 mothers and a helpline set up.

Medical experts stressed pregnant women should not feel concerned about taking antibiotics to treat infections.

The Oracle study was the largest trial in the world into premature labour and was set up to investigate whether giving antibiotics - which might tackle an underlying symptomless infection - to women with signs of premature labour would improve outcomes for babies.

One in eight babies in the UK is born prematurely and prematurity is the leading cause of disability and of infant death in the first month after birth.

Premature labour
In 2001, ORACLE found the antibiotic erythromycin had immediate benefits for women in premature labour (before 37 weeks gestation) whose waters had broken. It delayed onset of labour and reduced the risk of infections and breathing problems in babies.

Erythromycin and the other antibiotic studied - co-amoxiclav - showed no benefit or harm for the women whose waters were still intact, however, and doctors were advised not to routinely prescribe them in such circumstances.
To study the longer-term outcomes, the Medical Research Council-funded scientists followed up the children seven years later.

Unexpectedly, both antibiotics appeared to increase the risk of functional impairment - such as difficulty walking or problems with day to day problem solving - and treble the chance of cerebral palsy in the children of the women whose waters had not broken.

Of the 769 children born to mothers without early broken waters and given both antibiotics, 35 had cerebral palsy, compared with 12 out of 735 whose mothers did not receive antibiotics in the same circumstances.
The reasons behind this link are unclear, particularly as there was no increased risk of cerebral palsy in women whose waters had broken.

Hostile environment
The researchers believe cerebral palsy is unlikely to be a direct effect of the antibiotic but rather due to factors involved in prolonging a pregnancy that might otherwise have delivered early.
Researcher Professor Peter Brocklehurst of Oxford University said: "We have a suspicion that infection is implicated in premature labour.

"Antibiotics may merely suppress levels of infection to stop preterm labour, but the baby remains in a hostile environment."
Infections during pregnancy or infancy are known to cause cerebral palsy.

In a letter to doctors and midwives advising them about the findings, Chief Medical Officer Sir Liam Donaldson says: "Pregnant women should not feel concerned about taking antibiotics to treat infections.

"It is important to note that these women had no evidence of infection and would not routinely be given antibiotics."
Where there is obvious infection, antibiotics can be life-saving for both mother and baby, the CMO says.

The Royal College of Obstetricians and Gynaecologists said: "These findings do not mean that antibiotics are unsafe for use in pregnancy. Pregnant women showing signs of infection should be treated promptly with antibiotics."
Cerebral palsy can cause physical impairments and mobility problems.

It results from the failure of a part of the brain to develop before birth or in early childhood or brain damage and affects one in 400 births.

Arthritis knee op 'does not work'

The surgery is not recommended in the UK
An operation offered to ease the symptoms of osteoarthritis makes no difference, say Canadian doctors.
Patients given knee arthroscopy showed no improvement beyond that provided by physiotherapy and painkillers.
Arthritis experts in the UK said some surgeons were still carrying out the operation, against national guidance.
They said New England Journal of Medicine study showed doctors still relying on the technique to treat osteoarthritis were misguided.

Thousands of people in the UK suffer from osteoarthritis in the knee, which can be painful and limit movement.
The operation involves inserting instruments through small incisions to try to flush out loose fragments of cartilage, and to smooth the surfaces of the joints, in the hope that this will relieve symptoms.
A group of 178 men and women, with an average age of 60, were enrolled in the trial at the University of Western Ontario.
All of them were given physiotherapy and painkilling drugs such as ibuprofen, but half of the volunteers were also given the "lavage and debridement" procedure.

When their symptoms were compared at various points afterwards, the group who had the operation were faring no better than those who had not received it.

Guidelines breached
Dr Brian Feagan, one of the researchers, said: "This is definitive evidence that arthroscopic surgery provides no additional therapeutic value when added to physical therapy and medication for patients with moderate osteoarthritis of the knee."
This type of surgery is still recommended for some other knee conditions, including more severe osteoarthritis where the knee is "locked" in position, but is not recommended for moderate osteoarthritis by the National Institute for Health and Clinical Excellence, which formulates UK guidelines.

A spokesman for the Arthritis Research Campaign said there was no longer any excuse for performing it in patients with less severe arthritis.

"Arthroscopic lavage and debridement is still commonly performed in the US but more rarely in the UK over the past ten years, and is no longer accepted as an effective treatment for osteoarthritis of the knee in this country.
"Surgeons still performing this operation need to ask themselves why they are doing it."

Lead, mercury and arsenic were found in the traditionally Indian herbal mixtures at levels that would surpass California safety guidelines, says a researcher who is calling for FDA curbs.
By Alan Zarembo, Los Angeles Times Staff Writer
August 27, 2008
Ayurvedic medicines -- herbal mixtures dating back thousands of years in India and increasingly popular in the West -- are frequently contaminated with lead, mercury or arsenic, according to a study published today.

A fifth of the nearly 200 concoctions tested contained levels of the toxic metals that, if taken at the maximum recommended doses, would surpass California's safety guidelines.

Dr. Robert Saper, a Boston University professor of family medicine who led the study, said the findings should spur the Food and Drug Administration to start clamping down on the largely unregulated world of pills, herbs and powders classified as dietary supplements.

"It shouldn't be me trying to figure this out," Saper said.

Ayurveda is a traditional Indian practice that takes a holistic approach to wellness, employing herbal medicine, meditation and exercise to promote good health. It exists alongside modern medicine in India, with its own network of clinics, hospitals and colleges serving hundreds of millions of patients.

It has spread to the U.S. and Europe with the migration of South Asians around the world and been popularized by figures such as bestselling author Deepak Chopra.

There are about two dozen ayurvedic training programs in the United States. A 2002 survey estimated that 750,000 U.S. residents have used the herbal preparations, sold under both traditional Indian names and more marketable labels such as GlucoRite and Ezi Slim.

Saper got interested in the supplements in 2003 after a man of Indian origin showed up at a Boston-area emergency room with seizures. The culprit turned out to be lead in the man's ayurvedic medicines. In an initial study published in 2004, Saper bought 70 ayurvedic herbal products imported from India and found that toxic metals were common components.

It was an unsettling finding, because most of the preparations are intended to be taken as part of a daily regimen to improve health.

"Many, many studies are showing that even small levels of lead in the blood can increase the risk of high blood pressure, kidney dysfunction and decreased IQ," Saper said.

Ayurvedic practitioners lashed out at the research as alarmist, saying that it only showed there were problems with mixtures from India, not with U.S.-made products.

They pointed out that in India, many of these metals are purposely blended with herbs as part of the medicinal recipe. Those metallic mixtures are rarely used in the United States, they said.

In the new study, published in the Journal of the American Medical Assn., Saper and his team analyzed 193 products purchased from 25 websites for Indian and U.S. manufacturers. The vast majority supposedly contained only herbs and no metals.

About 80% of the samples showed no detectable metal content.

But among the remaining samples, the toxic metals showed up at similar rates in both U.S. and Indian-made products.

Of the U.S. products, 21% contained lead, 3% contained mercury and 3% had arsenic. Among the Indian-made medicines, 17% had lead, 7% had mercury and none contained arsenic.

The researchers and other experts surmised that the contamination had less to do with the manufacturing process than with the soils in which the herbs were grown.

"The raw material is all coming from India," said Kush Khanna, who runs Bazaar of India in Berkeley, a manufacturer of ayurvedic medicines started by his father in 1971.

Heavy metals showed up in 17 of the products the researchers ordered from his company.

Khanna said two labs in India routinely tested the 80 or so ingredients he imported.

The problem is that there are no unified standards for what is considered safe.

Lead levels allowed by the World Health Organization are 500 times the California limits.

"Based on WHO standards, our products are perfect," Khanna said. "They have not exceeded any limits."

The researchers found only two products that exceeded the WHO standards for lead content. Both mixtures were from India and purposely prepared with metals as ingredients.

In California, the Safe Drinking Water and Toxic Enforcement Act of 1986 requires that products containing certain levels of toxic metals carry warning labels. But the act has no power to ban products, and companies with fewer than 10 employees, such as Khanna's, are exempt from the labeling requirements.

The FDA does not specify any limits for metal content in dietary supplements, leaving it to the manufacturers to ensure that their products are safe.

Jennifer Rioux, a medical anthropologist who runs the Integral Ayurveda clinic in Chapel Hill, N.C., said the research underscored the need for consumers to consult with ayurvedic experts instead of buying and taking products on their own.

She noted that the study showed many medicines to be perfectly safe, but she worried that its conclusions would tar her profession.

"All people need is one study to provoke fear about an entire system of medicine," she said.

Anaesthetics 'could worsen pain'

Some anaesthetics are irritant chemicals
Some general anaesthetics could actually worsen the pain following surgery, say scientists.

So-called "noxious" anaesthesia drugs - used commonly worldwide - stimulate nerves to cause irritation long after the operation is over. The US research, published in Proceedings of the National Academy of Sciences journal, could prompt the choice of different drugs. A UK expert said solving post-surgical pain was a priority for anaesthetists.

Anaesthetists have known for some time that certain drugs, such as the gas isoflurane, while very effective at rendering and keeping patients unconscious, are actually irritant chemicals. Some already use a painkilling drug to lessen this effect before delivering the anaesthetic itself. The latest finding, by research staff at Georgetown University Medical Center however, suggests that effects of the irritant is not just short-lived, but lingers on long after both the painkiller and the anaesthetic have worn off.

The drugs act on the same receptors on nerve cells which are activated by contact with other irritants, such as garlic, mustard or chilli.

Mice bred without these receptors were unaffected by the "noxious" anaesthetic gases.
If strongly activated, these can lead not just to an immediate sensation of pain, but also a longer oversensitisation of pain pathways in the nervous system.

In patients, this might mean that the pain they feel after an operation is significantly increased.

Switching drugs
Dr Gerard Ahern, who led the study, said: "It was not really recognised that use of these drugs results in the release of lots of chemicals that recruit immune cells to the nerves, which causes more pain of inflammation.
"The choice of anaesthetic appears to be an important determinant of post-operative pain."

He said that while this effect could be reduced by using other types of anaesthetic, these might not perform as well in other ways.

Professor Ian Power, from the University of Edinburgh, said that post-operative pain remained a serious problem, despite advances in anaesthesia over the decades.
"We are very aware that acute post-operative pain can persist and become chronic and long-lasting, and we have been looking for reasons for that - perhaps this research may provide those.
"If this research were to be validated and proved correct, it would be fairly easy for anaesthetists to move from one type to another."

Professor Richard Langford, a consultant in anaesthesia and pain management at Bart's and The London NHS Trust, said that while the findings were interesting, there was no guarantee a similar effect would be detected in humans undergoing surgery.
"There are a myriad of different factors that combine to produce the experience of pain, including the degree and size of the surgery, and the mood or level of anxiety in the patient."