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Therapeutic Plasmapheresis Calculator
Fractional removal of a plasma-bound substance by a plasma-exchange session.
Therapeutic Plasmapheresis Calculator
Body weight
Hematocrit
%
Plasma volume exchanged
L
Complete the fields above to see the result.
When to use
- Prescribing exchange volume for therapeutic plasma exchange and predicting removal of a plasma-bound toxin, antibody, or paraprotein.
- Explaining diminishing returns of exchanging more than about 1-1.5 plasma volumes in a single session.
Formula
Plasma volume (L) = 0.065 x body weight (kg) x (1 - hematocrit). Fraction of substance remaining = e^(-volume exchanged / plasma volume), modeling a single, continuously mixed compartment with no rebound or interspace equilibration during the procedure.
Pearls and pitfalls
- Assumes instantaneous, complete mixing (single-compartment kinetics); it does not model re-equilibration of extravascular substance into plasma between or after exchanges.
- Each exchange of one plasma volume removes about 60-65% of the target substance; a second immediately following exchange removes a similar fraction of what remains, not of the original amount.