Plasma is the pale yellow, liquid component of blood, composed primarily of water, proteins, antibodies, and clotting factors. It transports red cells, white cells, and platelets throughout the body. The donation process, called plasmapheresis, involves drawing whole blood, separating the plasma in a specialized machine, and returning the remaining blood components to the donor. The sensations felt during plasmapheresis are unique and vary, though the experience is generally mild.
The Initial Sensation of Venipuncture
The first sensation is venipuncture, the insertion of a needle into a vein, usually in the arm. This is often described as a brief, sharp pinch or sting, similar to a standard blood draw. The feeling is momentary, lasting only until the phlebotomist correctly places the needle.
Once the needle is seated, the sharp sensation is replaced by a dull pressure at the insertion site. As whole blood flows into the apheresis machine, some donors report a slight, localized pressure or a gentle pulling sensation. The specialized needle used for plasmapheresis is slightly larger than those used for basic blood tests, but the discomfort generally fades quickly.
Sensations During the Apheresis Cycle
The sensory experience unfolds during the apheresis cycle, where the machine draws and returns blood components. During the draw phase, when whole blood is collected, the arm sensation remains a mild, steady pressure, sometimes accompanied by the rhythmic sound or low vibration of the machine. Plasma separation occurs within the machine using centrifugation to isolate it from the red blood cells.
The most distinct sensation occurs during the return phase, when the machine sends the red blood cells, mixed with saline and anticoagulant, back into the vein. Because this mixture is not body temperature, it causes a sudden, localized feeling of coolness entering the arm. This sensation can spread up the arm and is a common experience. The pressure in the vein also alternates rhythmically between the draw and return cycles, corresponding to the machine’s operation.
Systemic Physical Reactions
Donors may experience systemic effects, primarily due to the anticoagulant, typically citrate. Citrate is added to the drawn blood to prevent clotting in the machine. A small amount of this citrate returns to the donor’s bloodstream, where it temporarily binds with calcium ions.
This temporary reduction in circulating ionized calcium can cause hypocalcemia, which manifests as distinctive systemic feelings. The most common sensation is paresthesia, a tingling or buzzing often felt around the lips, nose, tongue, or extremities. Some individuals may also notice a transient metallic or sour taste. Less frequently, a donor may feel mild lightheadedness or nausea due to this chemical shift or a slight drop in blood pressure. These symptoms are generally mild and resolve quickly, but they should be reported to staff immediately.
Immediate Aftermath and Recovery
Once the donation is complete and the needle is removed, firm, localized pressure must be applied to the puncture site to stop residual bleeding. This pressure, held for several minutes, may cause a subsequent mild throbbing or ache at the venipuncture location. After the site is bandaged, it is normal to feel a dull soreness or tenderness in the area for a few hours.
Following the procedure, donors often report mild fatigue or weakness related to the temporary loss of fluid volume. This fatigue is usually mild and can be minimized by following post-donation care instructions, such as resting and increasing fluid intake. Over the next 24 hours, some donors may notice slight bruising or a small hematoma forming at the puncture site as the body heals.