Saturday, June 16, 2012
Transfusions bring experts' blood to boil
CONTRARY TO THEIR BENIGN IMAGE, BLOOD TRANSFUSIONS ARE OVERUSED AND OFTEN HARM PATIENTS, EXPERTS SAY
REFUSE at your own risk: for years that's the message doctors have relayed to Jehovah's Witnesses and others who've declined blood transfusions.
But transfusions are not the wonder procedure of popular, or even medical profession, imagination. Mounting evidence shows they significantly increase the risk of post-operative complications - including infections, kidney failure, lung injury and death.
Yet instead of being saved as a last resort, they are still being performed when other safer options could be used instead.
In fact, more than 25 per cent of blood transfusions currently performed are unnecessary, according to a visiting US expert who spoke at the annual scientific meeting of the Australian and New Zealand College of Anaesthetists (ANZCA) two weeks ago.
Internationally renowned emergency medicine and anaesthiology professor Bruce Spiess told the conference that while blood transfusions have long been "believed to be helpful and a pillar of modern medicine", there was now relatively little evidence to support such claims.
It's a point that has been echoed by several Australian experts, including anaesthesists associate professor Larry McNicol and doctor Peter McCall at Austin Health in Melbourne."Drug options are carefully tested and regulated through prospective, randomised double-blind testing, but blood transfusion stands apart," Spiess says. "It has never been safety or efficacy tested."
"From the point of view of the risk of transmitting infections, blood transfusions are safer than they have ever been," McCall says.
"However, there is an ever-increasing body of research about adverse outcomes in association with them. Still there is a tendency to think that blood transfusions are mystical and lifesaving, and it is better to give them than to withhold them."
The reasons not to make blood transfusion routine are becoming increasingly apparent: a person who has had a blood transfusion after surgery has up to four times the risk of wound infections. People who have blood transfusions during cancer surgery face up to twice the risk of the cancer recurring.
In his conference presentation, Spiess discussed Swedish research on cardiac patients that compared Jehovah's Witnesses who refused blood transfusions to patients with similar disease progression during open-heart surgery. The research found those who refused transfusions had noticeably better survival rates.
There are a few major reasons complications arise following transfusion. For one thing, immune response is impaired as the body responds to the blood as a foreign body, much in the same way it responds to a transplant, experts say. The properties of red blood cells also become altered when blood is stored, reducing their ability to distribute oxygen through the body.
Yet at least 25 per cent of transfusions that are done could be avoided, Spiess says.
A 2005-2006 audit of the use of fresh frozen plasma in hospitals in Tasmania and Victoria found that one-third of the transfusions performed were inappropriate under underguidelines issued by the National Health and Medical Research Council, says associate professor Larry McNicol, who also chairs the Better Safer Transfusion program run by the Victorian Government.
"Essentially these patients really perhaps didn't need it and there might not have been therapeutic benefits," McNicol says.
But there are still circumstances when blood transfusion is necessary, and the patient would probably die if they did not receive one, says University of Sydney professor James Isbister, a consultant on haemotology and blood transfusion who chairs the Red Cross advisory board.
Isbister says blood transfusion can be vital for patients undergoing major surgery after experiencing major trauma or shock when there is major bleeding that is difficult to control quickly. It can also be instrumental in managing hemophilia, where blood does not clot, as well as acute hemorrhages.
"A lot of major surgery would never have developed without the possibility for blood transfusion either - for instance, open heart surgery," Isbister says.
But many of the cases in the Better Safer Transfusion audit involved transfusions that could have been avoided. For example, it was once thought that blood transfusions should be performed any time a patient's hemoglobin level dipped below 10 grams of hemoglobin per decilitre of blood - but now guidelines in varying countries put that between 6 and 8g.
"It used to be that 10g was the acceptable minimum, but now we know that patients are at no detriment by a running a lower count and we can avoid these additional risks," McCall says.
"When the blood count is lower, the heart is able to beat more strongly - so it can actually pump more efficiently to distribute the blood better."
The audit also uncovered a tendency for some doctors to use transfusions as a precaution in patients who were at risk of bleeding, but not yet bleeding - for example, they might have had abnormal test results. In those cases the guidelines recommend doctors wait until bleeding starts.
Other studies have also shown that the likelihood of receiving a transfusion during elective orthopaedic surgery or cardiac surgery can vary enormously between hospitals, despite there being little difference between the patients, Isbister says.
"There's huge variation between hospitals and surgeons depending on where you have your operation - in one hospital you can have an 80 per cent chance of being transfused, and in another hospital 10 per cent chance."
"Most patients undergoing hip and knee surgery should only have a 10 to 20 per cent chance of needing a transfusion - but there's evidence it can be much higher."
There are a number of ways to avoid transfusions, including drugs that minimise blood loss and others that stop clots from being dissolved, as well as anesthetic and surgical techniques to minimise blood loss.
"You don't always have to bring a person's blood pressure up to normal - you can keep it low and that minimises bleeding," he says.
In surgery where there's a risk of major blood loss, doctors frequently use a technique called "red cells salvage", which allows them to reuse the patient's own blood rather than transfusing someone else's. The patient's blood is collected in a machine where it is then washed in a saline solution before being given back to the patient.
But the battle to reduce unnecessary transfusions often begins before surgery.
"One of the ways to minimise transfusions is to prepare patients better before surgery - for example you can give them supplements to get their blood count up before surgery," McCall says.
To that end a 2005 South Australian audit found that 18 per cent of people who had been on waiting lists for elective surgery had anemia, which increases the chances of needing a transfusion. If the anemia had been better managed before surgery some of those patients could have avoided blood transfusions, according to Kathryn Robinson, medical adviser of South Australia's BloodSafe.
But for all the bad news, experts say that change is on the horizon. Various states are developing initiatives to help decrease unnecessary transfusions, and at a conference of federal and state health ministers in March the federal Government said it would fund two initiatives expected to improve the safety of the blood supply and improve outcomes for people who do ultimately need transfusions.
One of those initiatives is the universal testing of platelets, which carry particularly high risks of complications. Unlike other blood products, platelets can't be refrigerated, so they are susceptible to contamination by bacteria. International guidelines recommend all platelets be universally tested for the bacteria, but currently only about 5 per cent of the supply is tested, McNicol says.
At the same meeting the government announced that by 2010 all blood will be processed to remove white blood cells, known as leuko-reduced blood, which has been shown to dramatically reduce complications and is already in widespread use in Canada, New Zealand, Western Europe and elsewhere.
"There are three randomised controlled studies in heart surgery, where patients who were deemed appropriate to be transfused got either leuko-reduced blood or blood with white cells present," Spiess says.
"The death rate in those with leuko-reduced blood was roughly half that in those with blood with white cells," Speiss says. "In the patients that got no blood, there were no deaths at all."