The role of continuous-flow blood fraction separators in clinical practice

Continuous-flow blood fraction separators facilitate the efficient exchange of large volumes of plasma or red cells and therefore have clinical application in the rapid correction of abnormalities located predominantly in either of these compartments. Plasmapheresis has been successfully used in managing 2 patients with previously refractory myasthenia gravis, in reducing the antibody titre in a rhesus-sensitized woman, and in diminishing anti-A titre in a patient requiring bone marrow transplantation from an ABO-incompatible but HLA- and MLC-identical sibling. Continuous-flow red cell exchange effectively reduced the haemoglobin S concentration in an individual with sickle cell disease prior to general anaesthesia and abdominal surgery. Complications were not encountered although the procedures were carried out repetitively over prolonged periods of time. All 5 patients tolerated their exchanges without discomfort. As with any new and expensive technique, caution should attend the introduction of continuous-flow plasma or red cell exchange into clinical medicine. Careful evaluation of the safety and the benefits is needed to establish perspective and to distinguish between established and developmental indications.