When someone donates blood, about a pint of blood is usually drawn into a plastic bag. The bag contains a solution that keeps the blood from clotting and helps preserve the red cells . Each bag, with its attached tubing and the needle that goes into the donor's arm, comes as a sterile unit in a sealed pouch and is used only once.
The blood is stored in a refrigerator under carefully controlled conditions until it's used. If it isn't used within five or six weeks, the blood has to be discarded because changes in the red blood cells during storage make it less effective and possibly dangerous, although in special circumstances, red blood cells can be frozen and stored for years. What part of this stored blood is transfused depends on your condition and your needs.
Whole Blood This is used only when a patient is hemorrhaging large amounts of blood in a short time. Almost always, the blood bank separates each unit of blood into red cells, platelets and plasma.
Red Cells Because of your cancer or your treatment, you may become anemic to the point where breathing becomes difficult, your heart pounds or you become very weak. If that happens, red blood cells will be transfused. If your marrow is not doing its job, it may be necessary to transfuse red blood cells every three to four weeks. Red blood cells will also be transfused when there is a lot of bleeding, as there may be during surgery.
