Protective effect of dexmedetomidine on noise-induced hearing loss.

OBJECTIVES/HYPOTHESIS Noise generated by instruments, such as mastoid or craniotomy drills, may cause hearing damage by reducing the cochlear blood flow (CoBF). This study investigated whether dexmedetomidine can lessen noise-induced hearing loss (NIHL) in a guinea pig model. STUDY DESIGN Animal study using noise stimulation and measurement of hearing and CoBF in guinea pigs. METHODS Guinea pigs (n = 8 animals/group) were treated by saline vehicle (control group), dexmedetomidine (1, 3, and 10 μg/kg dex groups), saline and noise (noise group), or 3 μg/kg dexmedetomidine and noise (dex+noise group). For noise exposure, octave band noise at 124 dB sound pressure level was administered to animals for 2 hours. Blood pressure (BP) and CoBF were monitored continuously. Auditory function was measured by the auditory brain-stem response (ABR) before and 1 hour, 3 hours, 8 hours, and 10 days after noise exposure. Plasma norepinephrine (NE) was measured at baseline and 30, 60, 90, and 120 minutes after noise exposure by high-performance liquid chromatography (HPLC). RESULTS Noise exposure caused temporary and permanent hearing damage. Dexmedetomidine concentrations of 1 μg/kg and 3 μg/kg dose dependently improved CoBF. Administration of 10 μg/kg dexmedetomidine drastically reduced BP and CoBF. Pretreatment with 3 μg/kg dexmedetomidine alleviated the noise-induced reduction in CoBF and improved hearing function by decreasing the permanent and temporary threshold shifts. CONCLUSION Dexmedetomidine displayed protective effects against NIHL in this animal model, suppressing activation of the sympathetic nervous system and improving CoBF. These findings could have clinical relevance and deserve further investigation.