Sickle cell anaemia – Rheology of the steady state and vaso-occlusive crisis

Abstract

Copley (1) reminds us that the science of haemorheology includes study of the vessel wall as well as the components of the blood. This concept is particularly relevant to rheological studies in patients with sickle cell anaemia who exhibit a complex prothrombotic abnormality affecting vasomotor tone and vascular endothelium as well as the plasma and red cells. Such rheological complexity is further compounded by acute-phase changes secondary to cytokine release from ischaemic tissue. Serial longitudinal study of homozygous patients in the asymptomatic steady state has now suggested a fluctuating balance between accumulation and removal of poorly deformable and dense sickle cells which is associated with sub-clinical episodes of tissue ischaemia. In the prodromal phase of the painful sickle-cell crisis, there is also an accumulation of rheologically compromised dense cells which may be of aetiological significance in relation to the vaso-occlusion that results in established crisis.