Miguel Lozano, MD, PhD from the Dept. of Hemotherapy and Hemostasis, Hospital Clínic. University of Barcelona in Barcelona, Spain (attribution used with permission) wishes to address a terminological question about plasmapheresis vs plasma exchange by referring the e-Network Forum to a letter that he and a colleague published in Lancet [THE LANCET • Vol 361 • May 17, 2003 - page 1750] which reads as follows (see below). He would appreciate any feedback:

"Sir—We draw your attention to the worrying fact that the term plasma apheresis (or plasmapheresis) is increasingly used in the published work as a synonym for, or instead of, the term plasma exchange.¹

The term apheresis derives from the Greek word aphairesis, meaning taking out or removal. Thus, the word plasmapheresis refers to the act of removing plasma from an individual; so long as the individual can tolerate the volume of plasma removed (generally up to an acute plasma volume reduction of about 600 mL), no replacement fluid needs to be used.

When plasma removal is indicated for therapeutic reasons, however, the efficacy of the procedure can only be attained by the extraction of huge volumes of plasma (at least one plasma volume—ie, about 3000 mL in an adult weighing 70 kg), which necessitates replacement of the removed plasma with a liquid solution. The replacement solution in the case of thrombotic microangiopathies is fresh frozen plasma, inactivated or not, or cryoprecipitate-poor plasma. The procedure is complex because of the volume of blood processed, and the need to control volume balance, and to prevent and treat adverse effects, such as citrate toxicity, allergic reactions, neurovegetative reactions, electrolyte disturbances, vascular access complications, and transfusion-related acute lung injury.² As such, replacement acquires such importance that plasma removal is overshadowed. Moreover, in the case of thrombotic thrombocytopenic purpura, the therapeutic effect is actually attained through the infusion of plasma with a normal content of ADAMTS 13, the von Willebrand factor-cleaving metalloprotease defective in this condition; the parallel removal of plasma simply allows infusion of greater amounts of the defective metalloprotease that would otherwise be impossible.²

To define this process as plasmapheresis is, therefore, inaccurate, despite the addition of the adjective therapeutic, which only creates ambiguity. The term plasma exchange would be much more suitable, since it describes exactly what is done: removal and, at the same time, infusion—ie, exchange of plasma for a replacement solution.^3,4 We feel, as do others,⁵ that the term plasmapheresis should be reserved to describe situations in which only plasma removal is undertaken—ie, plasma donation, usually in a shorter time (about 45 mins) and using bloodcell separators that, in general, are much simpler than those used in plasma exchange."

*Miguel Lozano, Roberto Mazzara Department of Haemotherapy and Haemostasis, Biomedical Diagnostic Center, Agustí Pi i Sunyer Biomedical Research Institute (IDIBAPS), Hospital Clínic, University of Barcelona, Villarroel 170, 08036 Barcelona, Spain (e-mail: mlozano@clinic.ub.es)

1. Goodnough LT, Shander A, Brecher ME. Transfusion medicine: looking to the future. Lancet 2003; 361: 161–69.

2. Moake JL. Mechanisms of disease: thrombotic microangiopathies. N Engl J Med 2002; 347: 589–600.

3. McMinn JR, Thomas IA, Terrell DR, Duvall D, Vesely SR, George JN. Complications of plasma exchange in thrombotic thrombocytopenic purpura, hemolytic uremic syndrome: a study of 78 additional patients. Transfusion 2003; 43: 415–16.

4. Clark WF, Rock GA, Buskard N, et al. Therapeutic plasma exchange: an update from the Canadian Apheresis Group. Ann Intern Med 1999; 131: 453–62.

5. Bier-Ulrich A, Haubelt H, Anders C, et al. The impact of intensive serial plasmapheresis and iron supplementation on iron metabolism and hemoglobin concentration in menstruating women: a prospective randomized placebo-controlled double- blind study. Transfusion 2003; 43: 405–10.

The following comments have been received.

ADDENDA Feb. 20, 2007

1. According to Dr. Kendall Crookston of the University of New Mexico Department of Pathology (attribution used with permission), while the point made in the above posting by Dr. Lozano is well taken, in American English the term "plasma exchange" might suggest the use of plasma as the replacement fluid to some listeners. Since most procedures are done without using plasma as a replacement fluid, and since we don't want students or patients to think we are using plasma when we are not, this term may sometimes be avoided. In addition, there are many other apheresis procedures besides plasma exchange that involve treating the plasma without exchanging it. The following is from page #1 of "Therapeutic Apheresis: A Physician's Handbook" 1st Edition, AABB and ASFA, 2005: "The term *apheresis* is derived from a Greek word meaning *to take away.* The practical definition of therapeutic apheresis is a procedure in which blood is removed from a patient and a portion is removed or otherwise manipulated, with the remainder being returned to the patient. Therapeutic apheresis procedures can be classified as either cell depletions or blood component exchanges. Examples of cell depletion include leukopheresis and plateletpheresis. Blood component exchange includes red cell exchange and plasma exchange."

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