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    Therapeutic Plasmapheresis Calculator

    Estimates amount of a substance (e.g. antibody) remaining in the intravascular space after a given number of plasma volume exchanges.
    When to Use
    Why Use

    Patients who require therapeutic plasma exchange typically have a pathologic substance in circulation (e.g. an autoantibody) requiring removal. The amount of this substance remaining varies with the number of plasma volumes exchanged, with a plateau typically reached over time as the efficiencies of the procedure are reduced as higher amounts of replacement fluids are removed than the substance initially targeted.

    • This is a theoretical calculation applicable primarily to plasma exchange procedures; removal efficiencies will vary somewhat in practice based on what is being removed and its total body distribution.
    • The equation assumes a strictly intravascular substance; this is not necessarily true in routine clinical practice and the less intravascular a substance, the poorer the efficiency of removal.
    • Can be useful to determine the number of plasma volumes to be exchanged to achieve a reduction in a targeted substance, particularly at the onset of a therapeutic plasma exchange procedure.
    • Provides a sense of the futility of doing many plasma exchanges, as it shows the degree of diminishing returns once a plateau for efficient removal is reached.


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    Next Steps


    Discuss with apheresis nursing and technical staff the number of plasma volumes to be exchanged.


    Residual relative concentration, % = 100 * e-x

    Where x = plasma volume, mL x number of plasma volumes to be exchanged / total blood volume, mL

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