The Change of Hearing Threshold and Perilymphatic Lactate Concentration in Guinea Pigs with Induced Hypoxia

Ahn, Joong Ho; Kang, Hun Hee; Chung, Jong Woo

Abstract

BACKGROUND AND OBJECTIVES: Authors aimed to observe the change of hearing threshold and the concentration of perilymphatic lactate in guinea pigs with hypoxia. MATERIALS AND METHOD: Healthy guinea pigs were anesthetized with xylazine and ketamine and perfomed thracheotomy with ventilatory care. After shaving around vertex and mastoid area, the minimum ABR threshold was checked until the wave I was normally traced. Hypoxic condition was induced by the increase of N2 and the decreased O2 saturation was confirmed via monitor, and then the ABR threshold was rechecked. Then, the mastoid cavity was opened and round window was identified under microscopic view. Labyrinthine perilymphatic fluid was collected from a round window by Hamilton's syringe and the lactate level was calculated. Three guinea pigs were used as controls and the perilymphatic fluids were collected.
RESULTS
In the guinea pig with normal Preyer's reflex, the initial hearing threshold was 29.5+/-3.6 dB SPL (mean+/-SD) and the average ABR threshold of guinea pig with hypoxic state was 71.0+/-11.4 dB SPL. The average perilymphatic lactate level was 5.339+/-0.07 mg/dL in the guinea pig of normal hearing and 60.024+/-1.66 mg/dL in the guinea pig of hypoxic state.
CONCLUSION
Authors observed that hearing threshold was decreased and perilympahatic lactate level was elevated via induced hypoxia. Through these findings, authors can draw the conclusion that lactate may be one of the possible factors explaning the mechanism of the change in the hearing threshold by tissue ischemia.