Plasmapheresis Indications

Therapeutic plasma exchange (TPE), also called plasmapheresis, removes the patient’s plasma while returning the cellular blood components with replacement fluid. The discarded plasma may contain an autoantibody, immune complex, paraprotein, or protein-bound toxin that is driving organ injury. TPE therefore removes a circulating mediator; it does not stop that mediator from being produced. The treatment is rational only when the target is sufficiently large, mostly intravascular, and cleared slowly by the body. A substance that is predominantly stored in tissue, rapidly regenerated, or too small to be meaningfully removed will not respond reliably to exchange alone. This is why TPE can rapidly improve paraprotein-related hyperviscosity but cannot treat the malignant clone producing the paraprotein. A typical procedure exchanges 1.0–1.5 estimated plasma volumes. That removes approximately 65–80% of an intravascular substance. Exchanging substantially more than 1.5 plasma volumes in one session produces diminishing returns because the remaining substance is progressively diluted rather than efficiently removed. Estimated plasma volume incorporates height, weight, sex, and haematocrit. The indication determines the replacement fluid and the other treatment that must accompany TPE. Albumin replaces volume...