The effects of fatal hemorrhage on the cochlear vasculature.

The condition of the cochlear vasculature was evaluated in 7 normal guinea pigs subsequent to fatal aortic hemorrhage. The cochleas were prepared for histological analysis using a soft surface preparation technique. The data analysis revealed two statistically significant differences: an increase in the number of aggregations and plasma gaps in the vessel at the vestibular membrane ( VSVM ) and in the vessel of the spiral prominence ( VSSP ). In eight instances, a statistical tendency toward a difference was demonstrated. On the whole, the changes observed were small, scattered and inconsistent and were interpreted as indicative of no local circulatory response to hemorrhage. These findings suggest that the cochlear vasculature is either controlled by a marked autoregulation or that histological evidence of a sympathetically mediated vasoconstriction may be counteracted by an elevated PCO2 level causing vasodilation of the constricted inner ear vessels during a state of O2 deficiency. Further, it is proposed that these same mechanisms may also account for the relatively discrete changes seen in the vasculature following noise exposure.