Incidence and Risk Factor for the Development of Hearing Impairment in Infants Treated with Therapeutic Hypothermia for Hypoxic Ischaemic Encephalopathy

Therapeutic hypothermia for moderate to severe hypoxic ischaemic encephalopathy (HIE) has been associated with an increased risk of long-term hearing loss ¹ Our objective was to establish the local incidence of hearing loss in newborns with HIE and to identify risk factors associated with hearing loss.

A retrospective case note review was conducted between June 2012 and March 2016 in a tertiary neonatal intensive care unit in Dublin, Ireland. Eligibility criteria were HIE and enrolment in the National Newborn Hearing Screening Programme (AOAE and AABR).

Information collected included demographic data, labour and delivery details along with detailed neonatal history including resuscitation, ventilation, seizure and medication history. Measures of renal function, gentamycin levels and brain magnetic resonance imaging (MRI) findings were reviewed.

Fishers exact test and both Kruskall Wallis rank and Pearson’s r correlation coefficient were used to analyse continuous and categorical variables respectively.

Fifty-seven newborns received therapeutic hypothermia for HIE. Fifteen infants were excluded from the study (12 died and 3 had incomplete data). Complete data was available for 42 babies, 4 of whom had significant hearing impairment.

The development of hearing loss was associated with the use of nitric oxide (p = 0.046), diuretics (p= 0.002), inotropes (p= 0.032) and abnormal blood glucose levels (p=0.006). Hearing loss was also associated with a low Apgar Score at 1 minute (p= 0.0219), high creatinine on days 1 and 2 of life (p= 0.0172 and 0.0198) and raised liver function tests (AST p= 0.0012, ALT p=0.0037).

Hearing impairment is common in survivors of term HIE treated with hypothermia. Hypoglycaemia should be aggressively treated in this population.

Larger studies are required to fully identify risks associated with hearing impairment in this population.

1. Smit, E. et al. Factors associated with permanent hearing impairment in infants treated with therapeutic hypothermia. J. Pediatr. 163, 995–1000 (2013).