Blood transfusion in sickle cell disease

Sickle cell disease is characterised by two basically independent but closely interrelated pathophysiological processes, haemolysis and vaso-occlusion. Polymerisation of deoxygenated sickle haemoglobin molecules leads to cell deformity and secondary membrane change. Such cells have a high internal viscosity and relatively inelastic membranes rendering them less likely to negotiate the small vessels in capillary beds. These processes bring about either destruction of the red cell itself or impairment of flow in a capillary bed with avascular necrosis of the tissue supplied.