The haemoglobin polymer forms a firm gel that damages the cellular membrane. The damaged membrane causes movement of potassium and water out of the cell thus leading to dehydration and more polymer formation. This damage also causes the negatively charged phosphatidylserine to move to the membrane surface and the red cell becomes deformed in shape, more rigid and more adherent to the vascular endothelium. The result of these are easy fragmentation of the membrane and extra vascular haemolysis, complement mediated lysis of the cell and intravascular haemolysis, shortened red cell survival to 4 to 25 days, trapping of rigid irreversible sickle cells in the post capillary venules which is promoted by leukocytosis, platelet activation and inflammatory cytokines.