The researchers found that the red blood cells' capacity to deliver oxygen begins to deteriorate after 21 days and said that blood that is transfused after three weeks lose the capacity to squeeze through the body's smallest capillaries to deliver oxygen to tissue.
The researchers acknowledged that their suggestion could increase the strain on the blood banks that already struggle to provide the required amount of blood but said that the banks should consider whether storing the blood up to six weeks is of any use. The study has been published in the journal Anesthesia & Analgesia
However the findings have been questioned by some of the experts, including Sheila MacLennan, who is a consultant haematologist at NHS Blood and Transplant. "There is no definitive evidence at present that transfusing 'older' blood is significantly worse for patients. This is why studies like this are being done. Until we have clearer and more robust evidence of the relative safety of 'older' versus 'younger' blood and the patient outcomes, we should not risk running short of blood for patients who desperately need transfusions to survive", she said.