Studying the benefits of blood transfusions after heart surgery

11 March 2015        

Surgeons operating

People who have had heart surgery do not benefit if doctors wait until they are substantially anaemic before giving a blood transfusion, according to the results of a major new clinical trial involving two BHF Professors.

Heart surgery can lead to significant levels of blood loss causing severe anaemia and a transfusion is the preferred treatment. Doctors detect this anaemia by measuring the haemoglobin levels - when they get low, a blood transfusion is given. But there has been limited evidence as to the benefits of giving a transfusion before haemoglobin levels get so low.

There has been some evidence that giving a transfusion before a heart surgery patient's levels get low could be harmful and increase risk of complications such as infections, heart attacks and strokes therefore it was vital to investigate this treatment further.

What was studied?

The trial, led by researchers at the University of Bristol, is the largest of its kind and involved comparing two groups of 1,000 patients - one which had transfusions when haemoglobin levels were low and the other had transfusions when they were at a higher level. The researchers then followed up with the patients to see whether they suffered any complications in the first three months after the operation.

Blood drip

They found that slightly more patients had serious complications in the group which had transfusions when substantially anaemic (35 per cent) compared with the group where transfusions were given when patients were only moderately anaemic (33 per cent).  And more patients died in the delayed transfusion group (4.2 per cent) than the group that got a transfusion at higher haemoglobin levels (2.6 per cent).

Unnecessary blood transfusions may also increase healthcare costs because of their direct cost and due to complications associated with them. But this study found that healthcare costs were similar for both groups so there is no economic benefit for only giving transfusions once anaemia becomes more serious.

A new theory for transfusions

Based on these findings, the researchers propose a new theory that it would be better to have a more liberal threshold for when blood transfusions are given after heart surgery.

BHF Professor of Cardiac Surgery Gavin Murphy, formerly of Bristol’s School of Clinical Sciences and now at the University of Leicester, who led the trial, said:

“Existing national and international transfusion guidelines recommend that blood transfusions only be given to patients who develop very low haemoglobin concentrations. We have shown that this strategy may increase the number of deaths in cardiac surgery.

Patients can be reassured

Our Medical Director, Professor Peter Weissberg, said:

“Donated blood is a precious commodity and needs to be used safely and effectively. While emergency blood transfusions are life saving in patients who are bleeding heavily, it is unclear whether ‘topping up’ blood levels in patients with reduced blood counts after major surgery is beneficial. Indeed, some previous studies have suggested it may be harmful.

“This research did not show that topping up patients with modestly low blood counts was harmful. The results showed that it may actually reduce deaths in the weeks following surgery, although more research is needed to determine if this was a direct consequence of their transfusion or something else. Patients undergoing heart surgery in the UK can be reassured that they have a very good outcome regardless of the transfusion policy of their surgical unit.”

The research also involved BHF Professor of Cardiac Surgery Gianni Angelini and was published in the New England Journal of Medicine.

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