Blood Transfusion - The downside Blood transfusions may be harmful to recipients due to nitric oxide depletion in stored blood. Two recent studies conducted by Duke University Medical Center reveal that blood cell concentrations of nitric oxide are reduced soon after blood leaves a donor's body. Nitric oxide, a gas, dilates arteries, allowing red blood cells to deliver oxygen to tissues. A lack of oxygen can lead to heart attack, stroke, or death, which are more likely to occur in patients who receive transfused blood. Researchers believe the solution is simple: add nitric oxide back to stored blood. Tests on reintroducing the gas to blood before transfusion have been successful in dogs, a good sign for future trials on humans.