Plasma exchange

Plasma exchange is performed by accessing a patient's venous circulation, typically via a central venous catheter or peripheral veins, and passing blood through a cell separator that uses centrifugation or membrane filtration to separate plasma from blood cells. The removed plasma is discarded, and a replacement fluid—usually 5% albumin or fresh frozen plasma—is infused to maintain oncotic pressure and clotting factors. The goal is to remove large-molecular-weight substances such as autoantibodies, immune complexes, cryoglobulins, and toxins that contribute to disease pathology. The procedure is usually performed in a series of sessions, with each session exchanging 1–1.5 times the patient's estimated plasma volume. The effectiveness depends on the half-life of the pathogenic substance and the rate of its re-synthesis.

Plasma exchange is a first-line or adjunctive therapy for several conditions. In neurology, it is used for Guillain-Barré syndrome, myasthenia gravis, and chronic inflammatory demyelinating polyneuropathy, where it removes pathogenic antibodies. In hematology, it is used for thrombotic thrombocytopenic purpura (TTP), where it removes ultra-large von Willebrand factor multimers and replenishes ADAMTS13 protease. It is also used in renal disorders such as anti-glomerular basement membrane disease and ANCA-associated vasculitis, and in transplant medicine for antibody-mediated rejection. The American Society for Apheresis (ASFA) publishes evidence-based guidelines categorizing indications by strength of evidence, with TTP and Guillain-Barré syndrome among the strongest (Category I) indications.

Plasma exchange is generally safe but carries risks related to vascular access, citrate anticoagulation, and replacement fluids. Common adverse effects include hypotension, allergic reactions to fresh frozen plasma, and citrate-induced hypocalcemia, which can cause perioral paresthesia or muscle cramps. Serious complications include catheter-related infections, thrombosis, and bleeding due to depletion of clotting factors, especially when albumin is used as replacement. The procedure also removes beneficial plasma components, such as immunoglobulins and complement, increasing infection risk. Mortality directly attributable to plasma exchange is low, estimated at less than 0.05% per procedure. Careful patient selection and monitoring are essential to minimize complications.

Beyond its common uses, plasma exchange has niche applications in conditions such as hyperviscosity syndrome due to Waldenström macroglobulinemia, severe hypertriglyceridemia-induced pancreatitis, and poisoning with protein-bound toxins like paraquat. It has also been explored in sepsis, though evidence remains inconclusive. Historically, plasma exchange was used in the 1960s for conditions like rheumatoid arthritis, but its use declined with the advent of biologic therapies. A notable edge case is its use in pregnancy, where it can be used for conditions like TTP or myasthenia gravis, but requires careful management of fluid balance. Additionally, plasma exchange is sometimes used in ABO-incompatible kidney transplantation to reduce antibody titers. The procedure's effectiveness in removing drugs is limited to those with high protein binding and low volume of distribution.

Apheresis

A procedure in which blood is withdrawn, a component is separated and removed, and the remainder is returned to the donor or patient.

ADAMTS13

A protease that cleaves von Willebrand factor; its deficiency leads to thrombotic thrombocytopenic purpura.

Fresh frozen plasma

Plasma that is frozen within hours of collection and contains clotting factors; used as a replacement fluid in plasma exchange.

Citrate

An anticoagulant used in apheresis that binds calcium, potentially causing hypocalcemia.