Each year, up to five million Americans receive a lifesaving blood transfusion. Blood, when collected from a donor, is screened for viruses and bacteria, and if it tests positive, will not be given to someone in need of blood. However, adverse reactions to other people’s blood does sometimes occur.
When blood is donated, it has been out of a body for some time. It is preserved at an optimal temperature, but its contents are somewhat different from what they were in the body. During storage, the blood loses an important gas, nitrous oxide. Nitrous oxide in the blood helps the vessels to dilate and allow blood to flow into them. Similarly, the gas can help hemoglobin molecules in red blood cells hang onto oxygen molecules in order to ensure that oxygen makes it to its intended destinations. Without the gas, vessels may not dilate enough and the blood becomes unable to deliver oxygen to the body.
The full article is located at Medical Daily