The association between hearing loss and coronary artery bypass grafting

Abstract

Hearing loss has been reported to occur in coronary artery bypass grafting surgery with the use of the cardiopulmonary bypass machine. There is seldom any pre-operative hearing testing before such surgery, and hence, any post-operative hearing loss may go unnoticed. The aim of the study was to investigate whether in the local population undergoing coronary artery bypass grafting in Malta hearing loss is a complication of such surgery. 40 participants having a mean age of 63 years, and were scheduled to undergo coronary artery bypass grafting were recruited using the consecutive sampling technique. Their pre-operative hearing capacity was evaluated using pure-tone audiometry, non-word speech in quiet and in noise speech audiometry, and the self assessment of communication and significant other assessment of communication questionnaires. These tests were then repeated in the immediate post-operative period (approximately 5 days), and five weeks post surgery. With pure-tone audiometry the difference between pre- and post-surgery mean scores for both ears for the 2000 Hz, 4000 Hz, and 8000Hz showed highly significant differences (p = <0.05). The non-word testing similarly portrayed a significant reduction in whole word scoring between pre-operative and post-operative values (p = <0.05). The questionnaires did not portray a worsening in the subjective hearing perception between the pre-operative and the immediate post-operative session, but instead showed a difference (worse hearing capacity perception) between the immediate post-operative session and the five week post-operative session. The study also suggested that mechanical ventilation and the presence of hypertension and diabetes mellitus may contribute to the hearing loss. It is hypothesised that CPB and mechanical ventilation produce noxious effects which target the micro-circulation and the inner hair cells which can produce this hearing loss. Finally it is recommended that pre-operative and post-operative hearing testing is routinely introduced for patients undergoing coronary artery bypass grafting, so that any hearing loss is treated without adverse effects.