Presented at the Neonatal Society 2013 Spring Meeting (programme).
Smit E1,2, Liu X1, Jary S1,2, Sabir H1, Gill H1, Thoresen M1,2,3
1 School of Clinical Sciences, University of Bristol, Bristol, United Kingdom
2 University Hospitals Bristol, St Michael’s Hospital, Neonatal Unit, Bristol, United Kingdom
3 Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
Background: Infants with perinatal asphyxial encephalopathy (PAE) are at risk of developing hearing loss. The large RCTs of hypothermia versus normothermia for PAE found 4-8% severe hearing loss in cooled infants (1). Therapeutic hypothermia (TH) has been standard practice in our NICU since 2007; furthermore many infants were enrolled in the ongoing cooling trials. Gentamicin in combination with penicillin is a common first-line drug combination in cooled infants. Gentamicin has been described as potentially oto and nephrotoxic. The objective of this study was to define the incidence of hearing loss, document plasma gentamicin concentrations and identify factors associated with permanent hearing loss in infants undergoing TH for moderate to severe PAE.
Methods: With ethical permission, data (demographic and clinical variables, gentamicin dose and trough level, creatinine values) were collected prospectively in our tertiary neonatal unit, which is the regional cooling centre. Cooled infants >36 wks gestation with moderate to severe PAE were included if a full data set was available. We administer gentamicin as a single dose of 4 mg/kg/d and routinely check a trough level prior to administration of the 3rd dose. All infants underwent a newborn hearing screen prior to discharge from hospital and were at least 1-year old on follow-up, when full hearing investigation and diagnosis had taken place. Stepwise logistic regression was used to identify factors associated with hearing loss.
Results: A total of 108 infants were included. Nine infants died and amongst the survivors 10.1% developed a permanent hearing impairment. Thirty-seven percent of infants in our cohort had a trough gentamicin level above the recommended cut-off of 2mg/L. Stepwise logistic regression showed that high trough gentamicin levels, poor cord pH and hypoglycaemia following birth were all significantly associated with hearing loss.
Conclusion: High trough serum gentamicin levels, poor cord pH and hypoglycaemia were associated with permanent hearing impairment in infants undergoing TH for PAE.
Corresponding author: marianne.thoresen@bristol.ac.uk
References
1. Edwards AD, et al., Neurological outcomes at 18 months of age after moderate hypothermia for perinatal hypoxic ischaemic encephalopathy: synthesis and meta-analysis of trial data. BMJ, 2010;340:c363