Plasma donation, known as plasmapheresis, is a procedure where whole blood is drawn from a donor, the plasma component is separated, and the remaining red blood cells and other cellular components are returned to the donor. Plasma is used to create life-saving therapies for individuals with various medical conditions, including immune deficiencies, bleeding disorders, and severe burns. To prevent blood clotting within the collection system, an anticoagulant is introduced during the donation, allowing for successful collection and processing.
Citrate: The Anticoagulant for Plasma Donation
Sodium citrate is the primary anticoagulant used in plasma donations. Its preference stems from its favorable safety profile, effectiveness, and the reversible nature of its effects once it enters the donor’s bloodstream.
Citrate is the sodium salt of citric acid, a natural organic acid found in citrus fruits. Its chemical properties make it suitable for preventing blood clotting without causing lasting systemic issues for the donor.
How Citrate Prevents Blood Clotting
Citrate acts as an anticoagulant by binding with calcium ions in the blood, a process known as chelation. Calcium ions are fundamental to the blood clotting cascade, which leads to blood clot formation. Without sufficient free calcium, these clotting factors cannot be activated.
By sequestering these calcium ions, citrate effectively halts the coagulation process in the collected blood as it circulates through the apheresis machine. This allows for the efficient separation of plasma from other blood components. The ratio of citrate to blood flow is carefully controlled by the apheresis machine to ensure effective anticoagulation without excessive systemic impact on the donor.
Managing Citrate’s Effects on Donors
A small amount of citrate inevitably enters the donor’s bloodstream when the red blood cells and other components are returned. This can temporarily lower the level of ionized calcium in the donor’s body, leading to what is known as a citrate reaction. Most people experience no side effects from this temporary drop in calcium.
Common, mild side effects include tingling sensations, particularly around the lips, fingers, and toes. Donors might also experience chills, shivering, lightheadedness, or muscle twitching. These symptoms occur because calcium plays a role in nerve and muscle function.
Plasma donation staff are trained to monitor donors for these signs and symptoms. If a donor experiences a citrate reaction, staff can slow the donation rate to reduce the citrate infusion, allowing the body more time to metabolize it. For more pronounced symptoms, calcium supplements may be provided to quickly restore calcium levels and alleviate discomfort. The body rapidly metabolizes citrate, primarily in the liver, and restores calcium levels, typically within 30 to 60 minutes after the donation is complete.