Blood is a living tissue that carries needed oxygen and nutrients to the cells in the body and helps transport cellular waste products. The components that make up blood help fight infections, heal wounds, and perform many other vital functions. Currently, donors are the only source of blood for patients who need it.
Whole blood is composed of 4 primary components: red blood cells (RBCs), white blood cells (WBCs), platelets, and plasma.
Red blood cells
Most people associate blood with RBCs. And perhaps rightly so—they are the component in greatest demand for transfusions. RBCs contain hemoglobin, which enables cells to deliver oxygen throughout the body and gives blood its red color. Because of the high demand for RBCs, critical shortages are common.
White blood cells
WBCs play an important role in the human immune system. They protect the body against bacteria, viruses, and other pathogens that cause illness.
Platelets
Platelets are small, disk-shaped blood components. They are critically important to the blood clotting process. Platelets stick together, or coagulate, along the lining of blood vessels. Without them, we would not survive the common, everyday blood vessel leakage that can occur in any of us.
Plasma
Plasma is the liquid portion of blood. (It’s 90% water!) It contains RBCs, WBCs, and platelets. Not only does plasma help maintain satisfactory blood pressure and body fluid volume, it also provides proteins that fight infections and diseases, and promotes proper clotting.
When a person loses a significant amount of blood, or when the blood’s functioning has been impaired, he or she may receive blood through a blood transfusion.
In the United States, nearly all blood that is transfused comes from volunteer donors.
Volunteer blood donors typically give a whole blood donation or apheresis donation. In a whole blood donation, a pint of blood is collected and then divided into its therapeutic components for transfusion. With an apheresis donation, a donor gives a specific therapeutic component(s)—platelets, plasma, or RBCs.
Health care professionals usually transfuse only the specific component(s) needed to treat a certain condition or disease, a process called blood component therapy:
Platelets are used in chemotherapy, cardio-thoracic surgery, general surgery, or trauma treatments. Platelet transfusions also help patients who have a shortage of platelets or whose platelets are not functioning normally. Approximately 1.7 million units of platelets are transfused annually to patients.
Plasma and the proteins it contains are used in liver transplants and for treating burn victims and people with certain bleeding disorders. Approximately 4 million units of plasma are transfused annually to patients.
Red blood cells are used to offset blood loss during surgery or following a severe accident or trauma. They also help treat patients with chronic anemia. As the blood component in greatest demand, with approximately 14 million units transfused annually, RBCs are widely used for people undergoing chemotherapy, open heart surgery, organ transplants, and many other common medical procedures.