On haemodilution therapy for patients with sudden loss of hearing: clinical and rheological results.

In cases of sudden loss of hearing, it must be assumed that a microcirculatory disturbance is involved, on the basis of a vasospasm of the afferent blood vessels and a "sludging phenomenon" in the region of the distal end-arteries of the cochlea. The microcirculatory disturbance results in an impairment of the O2 concentration in the perilymph, which can bring about disturbances, which are usually of short duration, and reversible changes in metabolism and structure of the hair cells. For this reason the therapeutic objective should be a reduction in the blood viscosity and flow resistance, plus a reduction in surface tension and an influence on the glycogenolytic metabolism of the erythrocytes. The therapeutic concept here is to be sought in a hypervolaemic haemodilution therapy with plasma substitutes. Care should be taken in the selection of the plasma substitute that not only parameters crucial to the macrocirculation are influenced, such as PCV and whole blood viscosity, but also those significant for the microcirculation, such as plasma viscosity and erythrocyte aggregation. A rheologically effective plasma expander would appear to have been found in the 10% hydroxyethyl starch 200/0.5, which together with naftidrofuryl would appear to be a proven agent in the combination therapy for sudden loss of hearing, due to its positive effect on plasma viscosity and erythrocyte aggregation, as shown by the significantly better mean increase in hearing on completion of therapy.