The influence of acute venous congestion on the guinea pig cochlea.

The effects of sudden occlusion of the vein of the cochlear aqueduct (VCAQ) on the cochlear blood flow, endocochlear potential (EP), endolymphatic and perilymphatic fluid pressures (PE and PP) were studied in the guinea pig. Cochlear blood flow showed a sudden decrease, and EP began to drop within 90 s, ranging from 50 to 70 mV in 5 of 11 animals studied, recovering to normal levels when the animals were placed on a continuous inhalation of carbogen. The PE and PP increased simultaneously (max. PE = 3.4 +/- 1.4 mm Hg; max. PP = 2.5 +/- 1.0 mm Hg) and returned to their initial values after 5 min. The EP was sustained within the normal range, even when there was an apparent decrease in cochlear blood flow (61.4 +/- 8.4%). We believe that variations in EP following VCAQ occlusion were due to anatomical differences in collateral venous communications among the animals studied. Carbogen inhalation produced uniform recovery patterns, indicating that individual collateral vessel responses were eliminated.