title: Painful sickle cell crises precipitated by stopping prophylactic exchange transfusions.
abstract: A patient with homozygous sickle cell disease showed a reduced incidence of painful crises as a result of regular exchange transfusion, but on three occasions when transfusion treatment was interrupted, a painful crisis occurred. Onset of painful crisis was associated with raised packed cell volume (PCV) or percentage of haemoglobin S (HbS%), or both. Measurement of whole blood viscosity using in vitro mixtures of blood group compatible normal (AA) and sickle (SS) cells showed that above an HbS of 25% any increase in PCV caused a disproportionate increase in whole blood viscosity. These clinical observations and laboratory data suggest that when regular exchange transfusions are terminated both HbS% and PCV should be carefully monitored. Prophylactic venesection should be considered for patients who maintain their PCV after transfusion as HbS% rises.
mesh_terms: D000328:Adult; D000755:Anemia, Sickle Cell / Q000097:blood / Q000209:etiology* / Q000517:prevention & control; D001809:Blood Viscosity; D005078:Exchange Transfusion, Whole Blood; D006400:Hematocrit; D006451:Hemoglobin, Sickle / Q000032:analysis; D006801:Humans; D008297:Male
chemical_list: D006451:Hemoglobin, Sickle