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Blood has been called the river of life because it carries oxygen and nutrients throughout your body. Blood is essential to life, a precious gift that you can share as a volunteer donor. Blood donations are typically seperated into three components, which are used for transfusion to patients in need. These include:
- red blood cells
- plasma
- platelets
Since patients seldom require all of the components of whole blood, it makes sense to transfuse only that portion of blood needed by the patient for a specific condition or disease, saving the remaining components of the blood for other patients in need. This treatment, referred to as "blood component therapy," allows several patients to benefit from one unit of donated whole blood. Improvements in cell preservative solutions over the last 15 years have increased the shelf life of red blood cells to 42 days.
Whole Blood
Whole blood is living tissue circulating through the heart, arteries, veins and capillaries, carrying nourishment, electrolytes, hormones, vitamins, antibodies and oxygen to the body's tissues. Whole blood contains red blood cells, white blood cells and platelets, suspended in a watery fluid called plasma.
If blood is treated to prevent clotting and permitted to stand in a container, the red blood cells, weighing the most, will settle to the bottom; the plasma will stay on top; and the white blood cells and platelets will remain suspended between the plasma and the red blood cells. A centrifuge may be used to hasten this separation process. The platelet-rich plasma is then removed and placed into a sterile bag, and it can be used to prepare platelet concentrates and cryoprecipitated antihemophilic factor (AHF).
To make platelets, the platelet-rich plasma is centrifuged, causing the platelets to settle at the bottom of the bag. Plasma and platelets are then separated and made available for transfusion. The plasma may also be pooled with plasma from other donors and further processed, or fractionated, to provide purified plasma proteins such as albumin, immunoglobulin and clotting factors.
Red Blood Cells
Red blood cells (RBCs) are perhaps the most recognizable component of whole blood. RBCs contain hemoglobin, a complex iron-containing protein that carries oxygen throughout the body and gives blood its red color.
The percentage of blood volume composed of red blood cells is called the "hematocrit." The average hematocrit in an adult male is 47 percent. There are about one billion red blood cells in two to three drops of blood, and for every 600 red blood cells, there are about 40 platelets and one white cell.
Manufactured in the bone marrow, RBCs are continuously produced and broken down. They live for about 120 days in the circulatory system and are eventually removed by the spleen. Red blood cells are prepared from whole blood by removing the plasma, or the liquid portion of the blood, and can raise the patient's hematocrit and hemoglobin levels while minimizing an increase in blood volume.
Patients who benefit most from transfusions of red blood cells include those with chronic anemia resulting from kidney failure, malignancies or gastrointestinal bleeding and those with acute blood loss resulting from trauma. Since red blood cells have reduced amounts of plasma, they are well-suited for treating patients with congestive heart failure or those who are elderly or debilitated.
Prestorage Leukocyte-Reduced Red Blood Cells
This form of RBCs requires special preparation by removing leukocytes (white blood cells) by filtration within 48 hours of donation. This is done because leukocytes remain in a unit of red blood cells during the storage process. These leukocytes, or the chemicals they produce, cytokines, cause blood recipients to develop reactions, such as fever and chills when receiving blood transfusions.
Plasma
Plasma is the liquid portion of the blood--a protein-salt solution in which red and white blood cells and platelets are suspended. Plasma, which is 90 percent water, constitutes 55 percent of blood volume.
Plasma contains albumin (the chief protein constituent,) fibrinogen (responsible, in part, for the clotting of blood) and globulins (including antibodies.) Plasma serves a variety of functions, from maintaining a satisfactory blood pressure and volume, to supplying critical proteins for blood clotting and immunity. It also serves as the medium of exchange for vital minerals such as sodium and potassium, helping maintain a proper balance in the body, which is critical to cell function.
Plasma is obtained by separating the liquid portion of blood from the cells. Fresh frozen plasma (FFP) is frozen shortly after donation to preserve clotting factors, stored up to one year and thawed just before use. It is transfused for bleeding disorders which have no factor-specific concentrate treatment.
Cryoprecipitated Antihemophilic Factor
Cryoprecipitate is the portion of plasma rich in clotting factors, including Factor VIII and fibrinogen. "Cryo" is removed from plasma by freezing and then slowly thawing the plasma. It is used to prevent or control bleeding in those with hemophilia and von Willebrand syndromes, the most common inherited major coagulation abnormalities. Another use is to mix it with thrombin. Called fibrosealant, it is applied at a wound site to prevent bleeding.
Plasma Derivatives
Plasma derivatives are concentrates of specific plasma proteins prepared from pools (many units) of plasma. Plasma derivatives are obtained through a process, known as fractionation, developed during World War II, and are heat-treated and/or solvent detergent-treated to kill certain viruses, like those that cause AIDS and hepatitis B and C. Plasma derivatives include:
- Factor VIII Concentrate
- Factor IX Concentrate
- Anti-Inhibitor Coagulation Complex (AICC)
- Albumin
- Immune Globulins, including Rh Immune Globulin
- Anti-Thrombin III Concentrate
- Alpha 1-Proteinase Inhibitor Concentrate
Platelets
Platelets (or thrombocytes) are small blood components that help the clotting process by sticking to the lining of blood vessels. Platelets are made in the bone marrow and survive in the circulatory system for about nine days before being removed from the body by the spleen. Platelets help prevent massive blood loss and blood vessel leakage resulting from trauma.
Platelets are prepared by using a centrifuge to separate the platelet-rich plasma from the donated unit of whole blood. The platelet-rich plasma is then centrifuged again to concentrate the platelets further. Platelets may also be obtained from a donor by a process known as apheresis, or plateletpheresis. In this process, blood is drawn from the donor into an apheresis instrument, which, using centrifugation, separates the blood into its components, retains the platelets, and returns the remainder of the blood to the donor. The resulting component contains about six times as many platelets as a unit of platelets obtained from whole blood.
Platelets are used to treat a condition called thrombocytopenia, in which there is a shortage of platelets, and platelet function abnormalities. Platelets are stored at room temperature and must be transfused within five days.
White Blood Cells
White blood cells are responsible for protecting the body from invasion by foreign substances such as bacteria and viruses. The majority of white blood cells are produced in the bone marrow, where they outnumber red blood cells by 2 to 1. However, in the blood stream, there are about 600 red blood cells for every white blood cell. There are several types of white blood cells. Granulocytes and macrophages protect against infection by surrounding and destroying invading bacteria, and lymphocytes aid in the immune defense. Granulocytes are prepared by apheresis or by centrifugation of whole blood. They are transfused within 24 hours after collection and are used for infections that are unresponsive to antibiotic therapy.
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