Effects of cardiopulmonary bypass surgery on hearing


© Massimo G./Fotolia

Researchers at the Postgraduate Institute of Medical Education and Research, in Chandigarh, India, have studied the effects of cardiac surgery with extracorporeal circulation on hearing function, and have confirmed earlier reports of complications affecting hearing, thought to have an incidence of 1/1,000 cases.

The team, which included specialists from the Speech and Hearing Unit, and the Departments of Otolaryngology and Cardiothoracic and Vascular Surgery, evaluated 30 male and female subjects aged between 50 and 70 years with myocardial infarction, who were to undergo cardiopulmonary bypass surgery (CPB). Preoperative audiological testing is not common, with the corresponding risk that possible hearing loss may go undetected. In this study, it was therefore decided to first assess hearing function preoperatively via pure tone audiometry, speech audiometry and otoacoustic emissions (OAE) testing, and then to reassess two weeks after CPB.

Highly significant differences were found between pre- and postoperative mean values at 10, 12, and 16 KHz in both ears on pure tone audiometry (p < 0.0001), and on OAE for signal-to-noise ratio (p < 0.05). The researchers postulate that when cardiopulmonary bypass temporarily takes over the function of the heart and lungs during surgery, blood is easily redistributed to other organs but is deviated from the inner ear possibly leading to a lack of oxygen for ciliated cells and to local damage.

The study also mentions that comorbidities such as hypertension and diabetes mellitus may contribute to auditory dysfunction. The team plans to conduct a larger-scale study with one-year follow-up in the near future.

Source: Munjal SK, et al. Effects of Cardiopulmonary Bypass Surgery on Auditory Function: A Preliminary Study. ISRN Otolaryngology 2013 Aug 29;2013:453920.