Encapsulation of human hemoglobin in liposome vesicles represents a useful method to attenuate the vasoactivity observed with conjugated or polymerized hemoglobin solutions currently under experimental and clinical investigation. Another advantage of hemoglobin vesicles is that oxygen affinity of the solution can be adapted by modifying the amount of coencapsulated pyridoxal 5′-phosphate, an allosteric effector.

In May and September 2003, The American Journal of Physiology – Heart and Circulatory Physiology published two experimental studies aimed at documenting the potential therapeutic efficacy of this new oxygen carrier in hypoxic conditions obtained by ischemia (vascular obstruction).

In the first study, Erni et al. demonstrated that oxygenation in acutely ischemic, collateralized flap tissue can be improved by normovolemic hemodilution with hemoglobin vesicles solutions. This effect was achieved by an increase in microcirculatory blood flow which in turn was dependent on the oncotic and viscosity properties of the suspended medium.

In the present study, the same group was able to show that the oxygenation in the ischemic flap tissue could be improved by increasing the degree of hemodilution with hemoglobin vesicles solutions and by increasing their oxygen affinity.

These very preliminary results emphasize the potential therapeutic effect of specific hemoglobin vesicle formulations to improve tissue oxygenation in hypoxic conditions related to ischemia.

– Philippe Van der Linden