Effects of cardiopulmonary bypass surgery on auditory function: a preliminary study

Area of Science:

• Otolaryngology
• Cardiology
• Audiology

Background:

• Cardiac surgery with cardiopulmonary bypass (CPB) is associated with hearing loss.
• Preoperative hearing assessments are not standard, potentially leading to unnoticed hearing deficits.
• The inner ear's high metabolic rate and lack of collateral circulation make it vulnerable during CPB.

Purpose of the Study:

• To investigate the incidence and characteristics of hearing loss following CPB surgery.
• To assess changes in auditory function using comprehensive audiological tests.
• To explore the potential mechanisms behind CPB-induced hearing impairment.

Main Methods:

• Thirty patients (50-70 years) with myocardial infarction undergoing CPB surgery were included.
• Detailed audiological assessments included pure-tone audiometry (extended high frequencies), speech audiometry, and otoacoustic emissions (OAE).
• Testing was performed preoperatively and two weeks postoperatively.

Main Results:

• Significant differences (P < 0.0001) were observed in pure-tone audiometry at 10, 12, and 16 KHz between pre- and postoperative measurements.
• Otoacoustic emissions testing revealed a significant difference (P < 0.05) in signal-to-noise ratio (SNR) post-surgery.
• These findings indicate a measurable decline in hearing function after CPB procedures.

Conclusions:

• Cardiopulmonary bypass surgery can lead to significant high-frequency hearing loss.
• Hypothesized mechanism involves blood redistribution away from the inner ear during CPB.
• Damage to inner ear microcirculation may reduce cochlear potentials, resulting in hearing loss.