Packed red blood cells are a blood product created by concentrating red blood cells from donated whole blood after the plasma has been removed. This product is used in transfusions to increase the oxygen-carrying capacity of a patient’s blood.
Composition and Preparation of Packed Red Blood Cells
Packed red blood cells (PRBCs) originate from whole blood collected from a donor. The blood is drawn into a sterile bag containing an anticoagulant, which prevents clotting and allows for the separation of its components.
The whole blood undergoes centrifugation, a process that spins it at high velocity to separate it into layers based on density. The heavier red blood cells settle at the bottom, the lighter plasma rises to the top, and a thin “buffy coat” containing white blood cells and platelets forms in the middle.
To create PRBCs, most of the plasma and the buffy coat are removed. This results in a concentrated product of red blood cells with a hematocrit, or cell volume, of approximately 60-70%. The removal of most white blood cells, a process called leukoreduction, is a standard practice that reduces the risk of transfusion reactions. The final unit contains about 150 to 250 milliliters of concentrated red cells.
A special preservative solution is added to provide nutrients and stabilize the cell membranes during storage. These additives allow PRBCs to be refrigerated at 2-6°C for up to 42 days, ensuring a stable supply for patients.
Medical Indications for Transfusion
The primary purpose of a PRBC transfusion is to increase the blood’s oxygen-carrying capacity when a patient’s red blood cell count is too low. The decision to transfuse is based on the patient’s symptoms and specific laboratory measurements.
One of the most common reasons for a transfusion is symptomatic anemia. This condition can result from chronic diseases like kidney failure, where red blood cell production is impaired, or from disorders where red blood cells are destroyed prematurely. Patients with severe anemia often experience fatigue, shortness of breath, and a rapid heart rate.
Acute blood loss is another major indication for a PRBC transfusion. Patients who experience significant bleeding from trauma or major surgery require rapid replacement of lost red blood cells to maintain organ function and prevent complications from severe hemorrhage.
Patients undergoing cancer treatments like chemotherapy may also require PRBC transfusions. Chemotherapy can suppress bone marrow function, leading to a decrease in red blood cell production and causing anemia. Transfusions help patients better tolerate their cancer therapy, with the decision often guided by hemoglobin levels falling to a specific threshold (e.g., 70-80 g/L).
The Transfusion Administration Process
Administering packed red blood cells begins with safety checks. Two healthcare professionals verify the patient’s identity and confirm the PRBC unit’s blood type is compatible with the patient’s. This involves checking the patient’s wristband, the blood bag label, and associated paperwork to prevent a harmful transfusion reaction.
Once safety protocols are confirmed, a healthcare professional establishes an intravenous (IV) line. The bag of PRBCs is connected to the IV tubing, and the transfusion is started slowly for the first 15 minutes to monitor for any immediate adverse reactions.
The patient’s vital signs, including temperature, blood pressure, heart rate, and respiratory rate, are closely monitored throughout the process. Checks are performed before the transfusion, after the first 15 minutes, and periodically until completion to quickly identify any potential complications.
A single unit of PRBCs is infused over two to four hours, with the rate adjusted based on the patient’s clinical condition. After the unit is administered, the IV line is flushed with a saline solution to ensure the patient receives all the contents from the tubing before the IV is removed.
Physiological Response and Post-Transfusion Monitoring
After a transfusion, the new red blood cells immediately begin circulating and transporting oxygen. They integrate with the patient’s existing blood, increasing the overall concentration of hemoglobin available to deliver oxygen to tissues throughout the body.
Many patients experience a noticeable improvement in symptoms like fatigue, dizziness, and shortness of breath within 24 to 48 hours. This relief is a direct result of the increased oxygen supply to the body’s organs and muscles and is a primary indicator of a successful transfusion.
To objectively measure the transfusion’s effectiveness, healthcare providers order a follow-up complete blood count (CBC) to check hemoglobin and hematocrit levels. A single unit of PRBCs is expected to increase an adult’s hemoglobin by approximately 1 g/dL and their hematocrit by about 3%, providing quantitative evidence of success.