A team of scientists from the Alabama University has discovered that blood stored for longer durations may be less safe for patients suffering from severe blood loss and shock.

In the cases of severely injured patients with excessive bleeding, the need of the hour would be a blood transfusion. But if older stored blood were to be used, it could lead to life-threatening symptoms such as pneumonia, dysfunction in blood flow, and an increased inflammation in organs. The research team found a link between older stored blood transfusion and subsequent bacterial pneumonia.

Stored blood transfusion releases the inflammation mediator HMGB1, which is a part of the body's immune response.

Heme is a part of hemoglobin pigment, which gives red blood cells their red color. Heme could be safe in red blood cells but when heme is freed from a globin component, it becomes toxic and leads to tissue injury.

When the blood is stored for a long duration, the red blood cells release free heme during transfusion. Free heme releases the inflammation mediator HMGB1, a part of the body's immune response, induces inflammation and causing sepsis in major organs of the body. This condition may even lead to sudden death.

Rakesh Patel from the University of Alabama at Birmingham in the US said, "An adverse role for heme suggests that finding ways to limit heme exposure or prevent heme toxicity may improve the safety of stored red blood cell transfusions."