Objectives: To evaluate the effect of extra-corporeal (cardiopulmonary) bypass on hearing during coronary artery bypass grafting.
Design: Prospective (single-blinded) controlled study.
Setting: District General Hospital.
Participants: Fifty-two patients undergoing coronary artery bypass grafting completed this study. Comparison was made between 14 control patients undergoing off-pump coronary artery bypass grafting and 38 study patients undergoing on-pump coronary artery bypass grafting. The age range of patients was 48–81 years, with 50% between 64 and 66 years.
Main outcome measures: Pure tone audiograms were performed in all patients before and after coronary artery bypass grafting. Data were analysed for any significant difference between pre- and post-operative pure tone audiograms.
Results: Mann–Whitney U-test demonstrated no difference between the area generated between mean pre- and post-operative audiograms (P = 0.754). No significant difference between off versus on pump was demonstrated for average differences at 250–500 Hz, 4 kHz, 4–8 kHz and 8 kHz. Wilcoxon matched-pairs signed-rank test demonstrated no difference between right and left ears for each individual frequency. Spearman's test to analyse the effect on vessel number or minutes on bypass pump revealed no significant difference at 4–8 kHz (P = 0.550 for number of vessels and P = 0.276 for minutes on pump.)
Conclusion: In this study, it was not possible to demonstrate any statistically significant deleterious effect of extra-corporeal (cardiopulmonary) bypass on hearing during coronary artery bypass grafting.