Background:
Mild to moderate hypothermia are the basis of neuroprotective strategies during cardiopulmonary bypass operations. Mild hypothermia has a protective role on the cochlea and could prevent its damage during long lasting operations. However, deep hypothermia may result in cochlear cells injury. This research aims to assess the effect of different hypothermic techniques on cochlear functions in children after open heart surgery.

Material and Methods:
Forty children with various acyanotic heart diseases who underwent open heart surgery were included in this study. They were subdivided into two groups; Group I: twenty patients who were subjected to mild hypothermic technique (33° to 37°C), Group II: twenty patients who were subjected to moderate hypothermic technique (28° to 32°C). Audiological assessment included basic evaluation and otoacoustic emissions testing.

Results:
All patients had normal hearing. Both study groups had Distortion product otoacoustic emissions (DPOAEs) amplitude >3 dB SPL at all frequencies. However, group II showed lower amplitude at all frequencies with statistically significant difference at high frequencies (4.416–8.837 KHz) compared to group I (P<0.01). TEOAEs showed partial pass in three patients of group I (15%) and in 15 patients of group II (75%). Moreover, Group II showed statistical significant reduction in the overall TEOAEs amplitude as well as at high frequencies (2–4 KHz) (P<0.01).

Conclusions:
Patients exposed to moderate hypothermic technique had subtle cochlear dysfunction. Care should be taken for choice of moderate hypothermic technique in open heart surgeries for children at risk for sensorineural hearing loss.