Thousands of heart surgery patients may be at risk from transfusions of blood that has been stored for two weeks or more.

A study of more than 9,000 patients in the US has shown that those given blood more than 14 days old are 65 per cent more likely to die before discharge, and 50 per cent more likely to die within a year.

Recipients of older blood are also at much higher risk of blood poisoning and multi-organ failure, according to the survey at the Cleveland Clinic in Ohio.

Blood is usually more than ten days old before it even reaches British hospitals, so patients here are at least as likely as those in America to receive blood that is more than two weeks old. As there are at least 30,000 cardiac operations a year in Britain, half involving blood transfusions, many patients could be at risk.

Professor Peter Weissberg, the medical director of the British Heart Foundation, said that the safety of blood transfusions given to heart surgery patients should urgently be reviewed.

“This research suggests that the longer transfused blood has been stored, the greater the risk of complications following cardiac surgery. Further research is urgently needed to clarify the indications for transfusion and the effects of blood storage on outcome,” he said.

He said that research carried out for his foundation in Bristol last year indicated that many transfusions given to heart patients did more harm than good. “Together, these studies suggest that only those whose lives are at serious risk without a transfusion should receive blood,” he said.

The Cleveland Clinic researchers, writing in The New England Journal of Medicine, say that changes are needed urgently to prevent unnecessary deaths among this large but vulnerable group of patients. According to Colleen Koch, the lead researcher, the results suggest “that blood should be classified as outdated earlier than current recommendations”.

On the basis of earlier laboratory studies, Dr Koch speculates that by the age of two weeks the structure of stored red blood cells has begun to break down. This, she says, may increase the risk that they will block blood vessels and reduce their capacity to carry oxygen.

Her team studied the records of patients who had major heart surgery at the hospital between June 1998 and January 2006. A total of 2,872 patients received blood that had been stored for 14 days or less, and 3,130 patients received blood that was more than 14 days old. The mean storage age was 11 days for the newer blood and 20 days for the older blood.

The number dying in hospital was significantly higher among those who were given older blood: 2.8 per cent compared with 1.7 per cent, while death rates a year on, at 11 per cent, were nearly half as high again as those who were given newer blood (7.4 per cent). There was no significant difference in the amount of blood received by the patients in the two groups.

Gavin Murphy, a senior lecturer in cardiac surgery at the University of Bristol who led last year’s British Heart Foundation study, said that the routine use of transfusions for heart surgery patients put them in danger and was a huge drain on resources.

Giving transfusions and treating transfusion-related illnesses increased the overall cost of staying in hospital by more than 40 per cent.

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