Effect of isoflurane anesthesia on noise-induced hearing loss in guinea pigs

Abstract

Objective To evaluate the effect of isoflurane anesthesia on noise-induced hearing loss in guinea pigs.Methods Forty-eight healthy adult male guinea pigs,aged 3 months,weighing 400-500 g,were randomly divided into 4 groups (n =12 each) using a random number table:control group (C group),isoflurane group (I group),noise-induced hearing loss group (N group),and isoflurane + noise-induced hearing loss group (I + N group).Isoflurane was inhaled for 140 min at a concentration of 1％ in I and I + N groups.N and I + N groups were exposed to the noise of 4 kHz center frequency and 118-122 dB sound pressure level for 120 min starting from 20 min after administration.Mean arterial pressure (MAP) was recorded at 10,40,70,100 and 120 min of exposure to noise and cochlear blood flow (CoBF) was recorded before administration and at 10,40,70,100 and 120 min of exposure to noise.Auditory brainstem response (ABR) threshold was recorded before administration and at 1 h,72 h,and 10 days after the end of exposure to noise.Arterial blood samples were obtained and the plasma noradrenaline (NE) concentration was detected by HPLC before exposure to noise and immediately after the end of exposure to noise.Results Compared with group C,MAP and the change rate of CoBF were significantly decreased,and the plasma NE concentration was increased immediately after the end of exposure to noise in I group,and MAP was increased,the change rate of CoBF was decreased,and the plasma NE concentration immediately after the end of exposure,and ABR threshold after the end of exposure were increased in N and I + N groups.Compared with N group,MAP was significantly decreased,the change rate of CoBF was increased,the plasma NE concentration immediately after the end of exposure,and ABR threshold at 1 and 72 h after the end of exposure were increased,and no significant was found in ABR threshold at 10 days after the end of exposure in I + N group.Conclusion Isoflurane anesthesia exerts temporary but not permanent protective effects against noise-induced hearing loss in guinea pigs and partial inhibition of activation of sympathetic nerve and increased CoBF may be involved in the mechanism. Key words: Isoflurane; Anesthesia,inhalation; Hearing loss, noise-induced