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Background and Objectives:It is wel known that hearing loss can occur by the decreased cochlear blood flow. Because lactate is known to accumulate when there is ischemia in the tissue, we designed this study to analyze the effect of lactate (ABR). Materials and Method:We used 22 guinea pigs (GPs) with normal Preyers reflex, and used 6 GPs (12 ears) to investigate the efect of lactate concentration on the change of hearing threshold and used 6 GPs (12 ears) to investigate the efect of osmolarity on the change of hearing threshold. We determined the concentration of lactate to exclude the effect of osmolarity on the change of hearing threshold. Ten GPs were divided into a control group (n=5, 10 ears) and a study group (n=5, 10 ears). The mas-toid cavity was opened to expose the round, and then HBSS buffer (300 mOsm) was applied on the round window. Hearing threshold was measured by ABR after application of 10mM lactate and buffer solution as control. Results:In the control group, the initial hearing threshold was 29.5 dB± 3.6 dB (mean± SD) and changed to 33.5 dB± 4.7 dB when buffer was ap-plied to the round window. It changed to 33.0 dB± 4.2 dB 1 hour after applying the buffer, and 37.5 dB± 3.5 dB 4 hour later. ± 5.8 dB. The thresholds right after the buffer was applied to the round window, one hour and four hour later were 32.5 dB± 4.8 dB, 48.0 dB± 4.2 dB, and 54.5 dB± 5.9 dB, respectively. There were significant statistical differences betwen the two groups with regard to the threshold after 1 hour and 4 hours (p<0.05). Conclusion:We could observe the elevation of hearing threshold after applying lactate on the round window of guinea pigs. Through these findings, we can draw the conclusion that lactate may be one of the factors raising the hearing threshold by tissue ischemia. (Korean J Otolaryngol 2002;45:7-12)


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