Over the past decade a number of studies have found that, far from saving lives, blood transfusions can actually harm many patients. The problem is not the much-publicised risk of blood-borne infectious agents, such as HIV, but the blood itself. Study after study has shown that transfusions, particularly those containing red blood cells, are linked to higher death rates in patients who have had a heart attack, undergone heart surgery, or who are in critical care. The exact nature of the link is uncertain, but it seems likely that chemical changes in ageing blood, their impact on the immune system, and the blood's ability to deliver oxygen are key. In fact, most experts now agree that the risk posed by the transfused blood itself is far greater than that of a blood-borne infection. "Probably 40 to 60 per cent of blood transfusions are not good for the patients," says Bruce Spiess, a cardiac anaesthesiologist at Virginia Commonwealth University in Richmond, US. Such claims have led this week to the US National Institutes of Health issuing a call for proposals to study the problem. Also this week, the Joint Commission in Chicago, which accredits US hospitals, is holding the first of several meetings to look for ways to reduce the risks. It is expected to at least conclude that hospitals should be more selective in the use of transfusions. Blood transfusion became a mainstay of medicine during the two world wars, where it was used as a last resort to save soldiers who had suffered massive blood loss. But now, far from being restricted to catastrophic bleeding, transfusions are routinely used as an optional treatment, most commonly for patients in intensive care or undergoing major surgery. In these situations, mostly small volumes of red cells are transfused, usually after they have been stored at 4 °C for anything up to 42 days. The rationale behind such blood transfusions seems incontrovertible. Red cells deliver vital oxygen to tissues, and seriously ill patients who are also anaemic fare less well, so a transfusion should help. Those assumptions went untested for the better part of a century. Things started to change in 1999 with a randomised controlled trial on 838 critical care patients in Canada that used haemoglobin levels to determine when a blood transfusion was given. Normal levels of haemoglobin, the oxygen-carrying protein in red cells, range from 120 to 170 grams per litre. A normal haematocrit - the proportion of red cells in the blood - ranges from 36 to 50 per cent. Doctors decide whether to give a transfusion based on a number of factors, including haemoglobin levels and haematocrit, and the patient's overall robustness. Many guidelines exist, and practice varies from one hospital or doctor to another, but it is common for patients to receive transfusions when their haemoglobin dips to between 70 and 100 g/l or their haematocrit to 21 to 30 per cent. But the Canadian study found significantly fewer patients died in hospital, 22 versus 28 per cent, if they received transfusions only when their haemoglobin fell below 70 g/l rather than when it fell below 100 g/l. ...continue reading here