Old blood increases the risk of infection

The risk of blood poisoning or pneumonia apparently doubles once the 29 day mark is reached, researchers from Cooper Hospital, New Jersey have found. Researchers called for increased care over the way that blood is stored.

In the US blood can only be stored for 42 days. Britain only stores blood for 35 days, which is similar in South Africa. After two weeks in storage, red blood cells start to undergo changes which lead to the release of chemicals called "cytokines".
These are known to hinder immune function, and in high levels could possibly make patients more susceptible to infection. Researchers looked at the rate of hospital infections in 422 patients against the age of the blood transfusion they received. They found that the average age of the blood was 26 days, and 70 percent of patients had received blood older than 21 days.

In total, 57 patients developed an infection - and these patients had received older blood than the others - on average it had been stored for three and a half days longer.Patients who had received blood older than 28 days were twice as likely to develop an infection, and the more units of blood given, the higher was the chance of infection.