[When transfusion and hemapheresis are medicine].

Blood transfusion frequently consists in bringing blood components in patients presenting with global deficiency of cells or of certain factors allowing, i.e. hemostasis or oxygenation; transfusion is thus performed on a short period, or on a period that corresponds to the recovery of the bone marrow (that is deficient either quantitatively or qualitatively). In some other circumstances, patients must receive transfusions as the one treatment of their pathology; this can be for life, when the deficiency has a genetic origin, or episodically in the case of autoimmune disorders. Once hemotherapy is initiated, one must appreciate the balance between the benefits and the risks or overload, and adjust with subtractions and exchanges (of blood components). This paper presents examples of two cases: hemotherapy in sickle cell patients, and patients undergoing plasma exchange programs.