Plasmapheresis and plasma exchange are related but not identical. Plasmapheresis is the broader process of separating plasma from blood. Plasma exchange is a specific treatment that uses plasmapheresis to remove a patient’s plasma and replace it with a substitute fluid. In everyday medical conversation, the two terms are often used interchangeably, which is where the confusion comes from.
How the Two Terms Relate
Think of plasmapheresis as the technique and plasma exchange as one application of that technique. Plasmapheresis simply means drawing blood and running it through a machine that separates the liquid plasma from the blood cells. That process has more than one use. Blood banks use plasmapheresis to collect donor plasma from healthy volunteers. Hospitals use the same separation process therapeutically, removing a sick patient’s plasma, swapping in replacement fluid, and returning the blood cells to the patient. That therapeutic version is plasma exchange.
Because plasma exchange is by far the most common reason plasmapheresis is performed in a clinical setting, many doctors, nurses, and even medical resources treat the words as synonyms. If your doctor says you need “plasmapheresis,” they almost certainly mean plasma exchange. But technically, plasmapheresis is the step within the procedure, not the full treatment itself.
How Plasma Gets Separated
Two methods are used to pull plasma away from blood cells, and both are effective. The first is centrifugation, which spins the blood at high speed so that components separate by density: heavier red and white blood cells settle to the outside while lighter plasma collects in the center. The second is membrane filtration, which pushes blood through a filter with pores small enough to hold back cells but large enough to let plasma pass through. Filtration can sometimes be less efficient at clearing very large molecules, so the choice between the two methods depends on what substance the treatment is trying to remove and what equipment is available.
What Happens During a Session
A typical plasma exchange session processes between one and one and a half times your total plasma volume. For a rough estimate, your plasma volume in liters is about 0.04 times your body weight in kilograms, so a 70 kg (154 lb) person has roughly 2.8 liters of plasma. The machine draws blood from one IV line (or one port of a specialized catheter), separates out the plasma, mixes replacement fluid with the remaining blood cells, and returns everything through a second line.
The replacement fluid is usually albumin, a protein solution that carries a low risk of side effects and is widely available. In certain conditions where clotting factors need to be replenished, fresh frozen plasma from donors is used instead. Albumin-based exchanges are generally smoother, but they can lower your platelet count and clotting protein levels over repeated sessions, so your care team monitors for signs of unusual bleeding.
What It Feels Like
Most people tolerate plasma exchange well. The machine uses an anticoagulant called citrate to keep blood from clotting in the tubing, and citrate temporarily lowers calcium levels in your bloodstream. That can cause tingling around the lips, fingertips, or toes, a metallic taste, or mild chills. These symptoms are usually brief and manageable. In clinical studies, ionized calcium drops modestly during a session (from about 1.08 to 1.03 mmol/L) without causing serious problems. Blood pressure can also dip slightly as fluid shifts during the exchange.
When fresh frozen plasma is used as the replacement fluid, mild allergic reactions like hives are possible, though they typically resolve quickly with antihistamines. Serious reactions are uncommon.
Why It’s Done
Plasma exchange is used when harmful substances dissolved in plasma are driving a disease. Autoimmune conditions are the most common reason: your immune system produces antibodies that attack your own tissues, and removing the plasma removes those antibodies. Conditions treated this way include myasthenia gravis, Guillain-Barré syndrome, certain types of kidney inflammation, and a blood-clotting disorder called thrombotic thrombocytopenic purpura, among others. The number of sessions varies by condition, but a course typically involves several exchanges over one to two weeks.
Plasma exchange is not a cure on its own. Because your body continues producing the problematic antibodies, the treatment is usually paired with medications that suppress the immune response or address the underlying disease. The exchange buys time by rapidly lowering the concentration of harmful molecules while longer-acting therapies take effect.