Whole blood in transfusion medicine refers to the product collected directly from a donor that has not been separated into its individual components. It is the original, unprocessed state of blood, typically collected as a unit of about 450 to 500 milliliters into a special bag containing an anticoagulant and preservative solution. Although it is the starting material for nearly all transfused blood products, whole blood itself is not the most common form of transfusion used in hospitals today.
Understanding the Components of Whole Blood
Whole blood is a complex biological fluid composed of four primary elements, each contributing to its function within the body. Approximately 55% of the total volume is plasma, a straw-colored liquid that is mostly water but contains proteins, hormones, nutrients, and stable clotting factors. Plasma serves as the liquid matrix, allowing the other components to circulate through the body’s vascular system.
The remaining 45% of the volume consists of cellular elements, primarily red blood cells (RBCs), which give blood its deep red color. These cells contain hemoglobin, a protein that binds oxygen in the lungs and delivers it to tissues throughout the body. White blood cells function as the body’s immune system cells. Platelets, which are cell fragments, initiate clotting and are responsible for the initial plug that stops bleeding, working alongside the clotting factors found in the plasma.
Whole Blood Versus Separated Blood Products
While whole blood is the standard product collected from donors, it is rarely transfused in its original form for routine patient care. The majority of donated whole blood units undergo a process called fractionation or component separation. This process involves placing the unit of blood into a specialized centrifuge, where centrifugal force separates the components based on their different densities.
Separation allows a single unit of donated blood to be used to help multiple patients, with each receiving only the specific component they need. The most common resulting products include Packed Red Blood Cells (PRBCs) for patients with anemia, and Fresh Frozen Plasma (FFP) to replace clotting factors for patients with bleeding disorders. Separating the components also allows for optimized storage conditions and shelf life. For instance, PRBCs can be refrigerated for up to 42 days, while plasma is frozen for long-term storage.
When Whole Blood is Used in Patient Care
Despite the widespread use of component therapy, whole blood is still the preferred product in a few specific, time-sensitive medical scenarios. Its primary application is in cases of massive hemorrhage, such as severe trauma or major surgical blood loss, where a patient is losing large volumes of blood rapidly. In these situations, the patient is losing red cells, plasma, and platelets all at once, and whole blood provides an immediate, balanced replacement for everything that has been lost.
The ability of whole blood to simultaneously deliver oxygen-carrying capacity, volume expansion from the plasma, and coagulation factors is highly beneficial in trauma resuscitation. This simplifies the transfusion process, which is especially important in high-stress, austere environments like military combat zones or pre-hospital settings. The use of whole blood in civilian trauma centers is currently experiencing a resurgence, as studies confirm its benefit in rapidly stabilizing patients who are bleeding profusely.