Painful crisis and dense echinocytes: effects of hydration and vasodilators

We have conducted a series of studies using discontinuous arabinogalactan density gradient ultracentrifugation of erythrocytes from the peripheral blood of: patients with sickle cell anemia (SCA), in and out of pain crisis; hydrated SCA, hemoglobin SC, and normal individuals all of whom were pain-free; and patients with SCA given short courses of oral vasodilator compounds. Our results indicate that in pain crisis patients develop an echinocytic change that is most prominent in the denser layers (specific gravity greater than 1.128 g/ml) of the discontinuous gradient and effects both irreversibly sickled cells (ISC) and non-ISC. This echinocytic change, we have previously shown, correlates with a decrease in erythrocyte reduced glutathione, a major intraerythrocyte anti-oxidant compound. We could find no consistent change in the percentage of dense cells in pain crisis versus out of crisis. However, out of crisis, hydration led to a marked increase in the percentage of dense erythrocytes in sickle cell anemia and in a HbSC patient, compared to the same individual out of crisis and on ad lib fluids. There was no consistent change in echinocytic forms. Because hydration may be expected to have produced an increase in intravascular volume and vasodilation, we determined whether short courses of three different vasodilators would increase the dense fraction in patients with SCA who were pain-free. There was no change in percentage of dense erythrocytes or in the percentage of echinocytes. We concluded that painful crisis occurs in association with an echinocytic change that may be induced by oxidant injury and that in the pain-free state, hydration, but not short courses of vasodilator drugs, increased the percentage of dense erythrocytes but not the degree of echinocytosis they displayed. The differential effect of hydration, with respect to painful crisis, may indicate that these dense cells are bound to vascular endothelium or trapped in blood vessels at the time of crisis but mobilized by hydration in the out-of-crisis state.