Whole blood refers to unprocessed blood circulating within the body. It encompasses all its constituents. This fluid is collected directly from a donor, typically combined with an anticoagulant solution to prevent clotting.
What Whole Blood Contains
Whole blood is a complex fluid with several key components. Approximately 55% of whole blood is plasma, a yellowish liquid that is over 90% water. Plasma acts as a transport medium, carrying blood cells, proteins, hormones, nutrients, and waste products throughout the body. It also helps regulate body temperature and maintain fluid balance.
Red blood cells, also known as erythrocytes, make up about 45% of the blood’s volume and give blood its characteristic red color. These cells contain hemoglobin, a protein that binds to oxygen in the lungs and delivers it to tissues throughout the body. They also transport carbon dioxide, a waste product, back to the lungs for exhalation. Red blood cells have a lifespan of approximately 120 days before being replaced by the body.
White blood cells, or leukocytes, are a smaller percentage of whole blood but are fundamental to the body’s immune system. These cells identify and neutralize foreign invaders such as bacteria, viruses, and fungi. There are several types of white blood cells, each specializing in different aspects of immune defense. Platelets, also called thrombocytes, are small cell fragments that play a role in blood clotting. They aggregate at injury sites to form a plug, helping to stop bleeding and initiate the repair process.
The Role of Whole Blood in Medicine
Whole blood is used in specific medical situations, particularly when a patient experiences significant blood loss. Transfusions of whole blood are often administered in cases of severe trauma or during major surgical procedures where rapid volume replacement and restoration of oxygen-carrying capacity are necessary. This approach delivers all blood components simultaneously, addressing multiple needs from a single source.
The use of whole blood has a history in military settings and is increasingly being re-evaluated for civilian trauma care. It can provide a balanced resuscitation, supplying red blood cells for oxygen transport, plasma for volume expansion and clotting factors, and platelets for hemostasis. Studies suggest that early administration of whole blood in massive hemorrhage can improve patient outcomes and simplify resuscitation efforts.
Whole Blood and Its Separated Components
Whole blood is often separated into individual components for medical use. This separation allows for targeted therapies, meaning patients receive only the specific blood component they require for their condition. For example, a patient with anemia might receive only red blood cells, while someone with a clotting disorder might receive plasma or platelets. This method maximizes the utility of each donation, as one unit of whole blood can benefit multiple patients.
The separation process typically involves centrifugation, which spins the blood at high speeds to separate components based on density. This yields red blood cells, plasma, and a layer containing white blood cells and platelets. Each component has different storage requirements and shelf lives, which is another reason for separation. For instance, red blood cells can be refrigerated for several weeks, while platelets have a much shorter shelf life and require specific storage conditions.
Apheresis is a specialized donation process that directly collects specific blood components from a donor while returning the remaining blood back to them. This technique can be used to collect a larger quantity of a particular component, such as platelets or red blood cells, from a single donor. Apheresis allows for more efficient collection, providing a higher concentration of the needed component for patients with specific medical needs.