Effect of anesthesia on susceptibility to acoustic trauma.

In an effort to ascertain whether differences in susceptibility to noise depend on general condition, awake and anesthetized guinea pigs were given a 4 kHz pure tone overstimulation under identical conditions. Cochlear hair cells were histologically examined four weeks after the noise exposure. The damage was localized in the upper part of the first turn and the lower part of the second turn. One fourth as much damage occurred in the anesthetized group. The distribution of damage in the four rows of sensory cells was different in the two experimental groups. In both groups of animals the damage was localized mainly to the outer hair cells, the first row sustaining the major damage.