Sickle cell anaemia: haemorheological aspects

The maintenance of erythrocyte shape and membrane integrity is bound to the modification of deformability and/or permeability. Usually, this features are not investigated with normal laboratory tests. The membrane stiffness, the cell geometry, and the viscoelasticity components are influencing factors on survival and functionality of the erythrocytes. Only few studies have analyzed the viscoelastic characteristics of red blood cells, even less are the studies on patients affected by sickle cell disease (SCD), a pathology characterized by acute and chronic impairment of cell flexibility due to the formation of intracellular sickle haemoglobin (Hb S) polymers. A critical point of SCD is represented by the rheologic alterations of sickle cells determined by the transition from sol to gel of haemoglobin producing a dramatic change in cell viscosity and viscoelastic properties. We have investigated the behaviour of the blood in SCD, from an original rheological point of view, by evaluating the viscoelastic properties of sickle cells in oscillating harmonic sinusoidal mode. A comparison between patients with different severity of the disease, with transfusion dependence (TD) or without transfusion dependence (NTD), has been carried out. This study has confirmed the rheologic impairment of SC blood. The TD patients showed a minor heterogeneneity of rheologic behaviour in comparison with NTD patients, because of the normalizing effect of transfusion. The analysis of viscoelastic properties might be an additional useful tool for monitoring transfusional and pharmacological treatments.