Transfusion support for haemoglobinopathies.

The indications and management of blood transfusion in the haemoglobinopathies have been reviewed. The sickle cell diseases that require transfusion support are sickle cell anaemia, sickle haemoglobin-C and -D diseases and sickle beta-thalassaemia. Homozygous beta-thalassaemia (Cooley's anaemia) is the major problem among the thalassaemias. The pathophysiology of the sickle cell disorders is largely based on the secondary effects of increased blood viscosity, whereas in the thalassaemias the defect is ineffective haematopoiesis. In the former the major problems occur as manifestations of vaso-occlusive crises with disseminated bone and abdominal pain, priapism, stroke and leg ulcers. Bone infarction and aseptic necrosis occur but the widespread bone changes, underdevelopment and haemochromatosis that complicate the thalassaemia are not prominent. Transfusion therapy in the sickle cell diseases is mainly episodic and is guided by the frequency of crises and the severity of vaso-occlusive complications. Partial exchange transfusion and the maintenance of haemoglobin A concentrations at 40 to 50 per cent is frequently indicated. In the thalassaemias, maintenance of haemoglobin levels is essential for normal growth and development. The problem of haemochromatosis is very serious. With hypertransfusion regimens the haemoglobin and haemotocrit are maintained above 12-13 g/dl and 35 per cent. The resulting benefit appears to be reduced blood volume, less iron turnover, and less intestinal iron absorption. The splenomegaly in these disorders is frequently associated with hypersplenism requiring well-timed splenectomy. Chronic and intensive chelation is necessary to prevent the ravages of iron overload. The availability of automated equipment for in vivo and ex vivo blood cell separation has brought new possibilities for improving the management of these haemoglobinopathies. It is feasible, but not as yet practical, to offer transfusions of neocytes (red cells with a mean age of 30 days) which have a 50 per cent longer survival than routine red cell preparations (mean age of 60 days). Neocytes can be prepared ex vivo from fresh routine blood donations using blood cell separator devices. The result is reduced transfusion requirements. A more recent suggestion for using the new technology is to remove the patient's oldest and most abnormal corpuscles on the basis of buoyant density and replacing them with neocytes . Thus the short-lived abnormal red cells would be removed before they could unload their iron. With automation it is possible to perform these procedures on an outpatient basis.