Protective effect of propofol on noise-induced hearing loss

Purpose: Iatrogenic noise produced by mastoid or craniotomy drills may cause hearing damage, which is induced by the generation of reactive oxygen species (ROS) and the reduction of cochlear blood flow (CoBF). This study investigated whether propofol could reduce noise-induced hearing loss (NIHL) in a guinea pig model. Methods: Sixty-four male pigmented guinea pigs were randomly and equally divided into 4 groups: control, noise, propofol and propofol + noise. Propofol was infused intravenously for 20 min prior to noise exposure with a loading dose of 5 mg·kg−1 for 5 min and a maintenance infusion of 20 mg·kg−1·h−1 for 135 min. For noise exposure, an octave band noise at a 124 dB sound pressure level (SPL) was administered to animals for 2 h. The mean arterial pressure (MAP) and CoBF were monitored continuously. Auditory function was measured by the level of distortion product otoacoustic emission (DPOAE) before and at 1 h, 72 h and 240 h after noise exposure. Cochlear levels of 8-iso-Prostaglandin F2alpha (8-iso-PGF2α) were measured immediately after the termination of noise exposure. Cochlear silver nitrate staining and outer hair cell (OHC) counting were performed after the final functional test. Results: Noise exposure caused decreases in the CoBF and DPOAE amplitudes, over-generation of 8-iso-PGF2α and the loss of OHCs. Pre-treatment with propofol significantly increased the CoBF and DPOAE amplitudes, decreased 8-iso-PGF2α and the loss of OHCs. Conclusions: Propofol exerted protective effects against NIHL in this animal model by suppressing a lipid peroxidation reaction and improving CoBF.