Hemoconcentration as a possible pathogenic factor of sudden hearing loss

Abstract

Hemodilution is considered to be a useful therapy for sudden hearing loss by improving cochlear blood flow (COBF) as a result of decreasing viscosity of the whole blood. The purpose of this investigation was to evaluate whether hemoconcentration actually leads to a diminished COBF and impaired function of the cochlea to thus play a role in the pathogenesis of sudden hearing loss. Ten New Zealand White rabbits were anesthetized and ventilated. Cochlear function was evaluated by measuring distortion products of otoacoustic emissions (DPOAEs) at the beginning of each experiment and after 120 min. In the interim, each test animal’s hematocrit was raised by an infusion of packed red cells. Control animals were not infused, so hematocrits were left unchanged. Reproducibility of DPOAE measurements were found to be dependent upon the stimulus level. Correlation coefficients were 0.83 for 65 dB SPL and 0.78 for 45 dB SPL. Although no changes in the absolute level of DPOAEs were observed after raising the hematocrit, correlation coefficients were diminshed to 0.68 at 65 dB SPL and 0.58 at 45 dB SPL. Hemoconcentration caused no apparent changes in the cochlear function in our animals. Although these findings may reflect species differences, hemoconcentration might still be a factor causing sudden hearing loss in older, atherosclerotic patients.