The metallic taste, medically termed dysgeusia, is a common sensation experienced by many people during plasma donation (plasmapheresis). This distinct, sometimes sour, flavor is a temporary side effect directly linked to the mechanics of the donation procedure itself. Understanding the physiological reason behind this taste can help donors feel more prepared and comfortable. This sensation is a benign sign of the body’s reaction to a necessary substance introduced into the bloodstream during the separation process.
The Role of Citrate in Plasma Donation
The core reason for the metallic taste lies with an anticoagulant called citrate, which is added to the blood as it is drawn into the apheresis machine. Citrate is necessary to prevent the blood from clotting while it is outside the body and being processed. Whole blood is continuously drawn and mixed with the citrate solution before entering the machine that separates the plasma from other components.
The separated components, minus the plasma, are then returned to the donor’s bloodstream along with some of the citrate solution. The concentration of citrate in the machine’s extracorporeal circuit is maintained to ensure effective anticoagulation. This return of citrate is what triggers the subtle, systemic reaction that causes the taste sensation.
Citrate works by acting as a chelating agent, meaning it binds to specific minerals in the blood. Its target is ionized calcium, which is required for blood to clot. By temporarily lowering the level of available ionized calcium, citrate effectively halts the coagulation cascade within the apheresis circuit.
How Citrate Affects Taste Receptors
The temporary drop in ionized calcium levels within the donor’s body is the direct cause of the metallic taste and other mild sensations. Calcium ions play a broad role in the human body, including the transmission of nerve signals throughout the nervous system. This systemic effect extends to the sensory nerves associated with taste perception.
When the chelated calcium and citrate complex enters the donor’s circulation, the slight and momentary reduction in free calcium alters the signaling pathways of the nerves. This disruption is perceived as a metallic or unusual flavor, which is a mild form of a citrate reaction. The metallic taste is a referred sensation, much like the tingling that some donors feel in their lips or fingers.
The body quickly metabolizes the citrate, primarily in the liver, which allows the ionized calcium levels to return to normal. The taste is self-limiting and usually disappears soon after the donation process concludes. For many donors, this change in taste is the only noticeable sign that their calcium levels have been transiently affected by the anticoagulant.
Practical Steps for Managing the Metallic Taste
Donors can take proactive steps to minimize the likelihood of experiencing the metallic taste or to manage it if it occurs. Proper hydration before the donation is highly recommended, as being well-hydrated helps the body process the citrate more efficiently. Eating a balanced meal that contains calcium before the appointment can also help maintain steady electrolyte levels.
If the metallic taste begins during the procedure, immediately informing the staff is the most important step. A technician can often adjust the speed of the blood return, slowing the rate at which the citrate is infused back into the donor. This allows the body more time to break down the compound and can often resolve the taste sensation quickly.
It is important to distinguish the mild metallic taste from signs of a more pronounced citrate reaction. If the taste is accompanied by tingling or numbness in the lips, fingers, or toes, muscle twitching, or lightheadedness, it is essential to alert staff without delay. These symptoms indicate a need for immediate attention, which may include administering an oral calcium supplement to quickly restore the body’s calcium balance.