Chapter 94: Therapeutic Hemapheresis

Therapeutic apheresis is the application of blood cell separation techniques to treat certain clinical conditions.

A continuous-flow blood separator is usually used.

Table 94–1 contains the principal applications of the technique.

Hemapheresis is usually used in hematologic therapy for acute problems.

Adverse effects infrequent and mild: hypotension, urticaria, hypocalcemia.

Cytapheresis refers to removal or exchange of a blood cell element, e.g., leukapheresis, plateletpheresis, erythrocytapheresis.

Plasmapheresis refers to removal or exchange of plasma.

Thrombocythemia or extreme thrombocytosis can usually be managed pharmacologically.

Plateletpheresis is useful for those who need rapid, temporary reduction of the platelet count in emergent conditions (e.g., ongoing thrombosis) or for patients who cannot tolerate drug therapy (e.g., early pregnancy).

If plateletpheresis is required in patients with thrombocythemia requiring urgent platelet reduction, pharmacologic therapy should be administered simultaneously for long-term control.

Reduction in the platelet count of about 50 percent may be achieved with each procedure, but the platelet count returns to pretreatment value in a few days.

Leukostasis may be ameliorated by leukapheresis with rapid cytoreduction in patients with acute myelogenous leukemia whose leukocyte count is greater than 50 to 100 × 10⁹/L; patients with acute lymphocytic leukemia whose leukocyte count is greater than 75 to 100 × 10⁹/L; or patients with chronic myelogenous leukemia (CML) whose leukocyte count is greater than 300 × 10⁹/L, or who have > 50 × 10⁹/L blasts.

Unfortunately, there are no clearly established thresholds, so that patients with any blast count who have signs of leukostasis should undergo leukapheresis.

Therapeutic leukapheresis prior to chemotherapy reduces tumor burden and may minimize metabolic abnormalities due to tumor lysis.

Therapeutic leukapheresis can lower the white cell counts, reduce organomegaly, and reduce tumor burden in chronic lymphocytic leukemia, but cytotoxic therapy is required for disease control.

Therapeutic leukapheresis may be used in lieu of chemotherapy to treat CML, e.g., in pregnancy, to allow for delay in starting chemotherapy until after the first trimester or longer.

In acute or chronic leukemia, a single therapeutic leukapheresis will reduce the leukocyte count by 25 to 50 percent.

The rate of mobilization of cells and the rate of cell proliferation dictate the frequency of therapeutic leukapheresis required to achieve goal.

Photopheresis, extracorporeal photochemotherapy, can improve erythroderma in cutaneous T-cell lymphoma (Sézary syndrome). Leukocytes removed by cytapheresis are treated with 8-methoxypsoralen and ultraviolet light and returned to patient.

Leukapheresis can be used to harvest lymphocytes, dendritic cells, or allogeneic or autologous blood stem cells for immunotherapy or stem cell transplantation.

Red cell exchange carries the same potential hazards as blood transfusion.

Indications for red cell exchange in sickle cell disease include priapism, unremitting painful crises, acute chest syndrome, stroke, and prior to radiographic studies requiring hyperosmolar contrast medium. Its use during pregnancy, for chronic painful crises, and prior to surgery is controversial.

Acute neurologic symptoms have occurred in sickle cell anemia patients undergoing red cell exchange for priapism.

Red cell exchange has been used to decrease parasite load in severe falciparum malaria and extreme polycythemia.

Plasma exchange is used in disorders in which there is a known or presumed abnormal plasma constituent to remove pathologic material in the plasma (e.g., thrombotic thrombocytopenic purpura or hyperviscosity syndrome in Waldenstrom macroglobulinemia).

An exchange of 1 plasma volume reduces the abnormal plasma constituent by approximately 65 percent and an exchange of 2 plasma volumes reduces the abnormal plasma constituent by approximately 88 percent.

Alterations in plasma components after plasma exchange include reduced levels of coagulation factors after large volume exchange and replacement with albumin and crystalloid, but bleeding is rare. Factor levels are restored over next 72 hours; serum immunoglobulin levels are decreased after repeated 1-volume plasma exchanges and replacement with albumin. It takes several weeks for levels to return to normal.

Mortality associated with the procedure of plasma exchange is less than 3 in 10,000 procedures with today's technology.

Table 94–2 lists disorders for which plasma exchange may be useful, and include thrombotic thrombocytopenic purpura, renal failure associated with multiple myeloma, hyperviscosity syndrome due to paraproteins (esp. macroglobulinemia, cold agglutinin disease with severe hemolysis not responding to other measures, cryoglobulinemia with vasculitis, glomerulonephritis, severe Raynaud syndrome, removal of coagulation factor inhibitors, recipients of ABO-incompatible marrow transplants prior to transplantation, posttransfusion purpura).

See Table 94–3 for other antibody-mediated disease indications.