Effect of gentamicin and levels of ambient sound on hearing screening outcomes in the neonatal intensive care unit: A pilot study

Abstract

Objective Hearing loss rates in infants admitted to neonatal intensive care units (NICU) run at 2–15%, compared to 0.3% in full-term births. The etiology of this difference remains poorly understood. We examined whether the level of ambient sound and/or cumulative gentamicin (an aminoglycoside) exposure affect NICU hearing screening results, as either exposure can cause acquired, permanent hearing loss. We hypothesized that higher levels of ambient sound in the NICU, and/or gentamicin dosing, increase the risk of referral on the distortion product otoacoustic emission (DPOAE) assessments and/or automated auditory brainstem response (AABR) screens. Methods This was a prospective pilot outcomes study of 82 infants (<37 weeks gestational age) admitted to the NICU at Oregon Health & Science University. An ER-200D sound pressure level dosimeter was used to collect daily sound exposure in the NICU for each neonate. Gentamicin dosing was also calculated for each infant, including the total daily dose based on body mass (mg/kg/day), as well as the total number of treatment days. DPOAE and AABR assessments were conducted prior to discharge to evaluate hearing status. Exclusion criteria included congenital infections associated with hearing loss, and congenital craniofacial or otologic abnormalities. Results The mean level of ambient sound was 62.9 dBA (range 51.8–70.6 dBA), greatly exceeding American Academy of Pediatrics (AAP) recommendation of <45.0 dBA. More than 80% of subjects received gentamicin treatment. The referral rate for (i) AABRs, (frequency range: ~1000–4000 Hz), was 5%; (ii) DPOAEs with a broad F2 frequency range (2063–10031 Hz) was 39%; (iii) DPOAEs with a low-frequency F2 range (<4172 Hz) was 29%, and (iv) DPOAEs with a high-frequency F2 range (>4172 Hz) was 44%. DPOAE referrals were significantly greater for infants receiving >2 days of gentamicin dosing compared to fewer doses (p= 0.004). The effect of sound exposure and gentamicin treatment on hearing could not be determined due to the low number of NICU infants without gentamicin exposure (for control comparisons). Conclusion All infants were exposed to higher levels of ambient sound that substantially exceed AAP guidelines. More referrals were generated by DPOAE assessments than with AABR screens, with significantly more DPOAE referrals with a high-frequency F2 range, consistent with sound- and/or gentamicin-induced cochlear dysfunction. Adding higher frequency DPOAE assessments to existing NICU hearing screening protocols could better identify at-risk infants to be referred for diagnostic evaluation.

Monitoring neonates for ototoxicity

“…This may increase the risk for poor neurodevelopmental outcome for these highly vulnerable infants because intervention before six months of age are thought to be associated with improved language and communication skills by age two to five years (Yoshinaga-Itano, Sedey et al, 1998; Sininger et al, 1999; Thompson et al, 2001). Another specific issue for screening neonates in the NICU is the comparatively higher levels of ambient sound levels that will increase the noise floor during DPOAE or aABR screening (Garinis et al, 2017). This could result in inconclusive screens or false referrals requiring re-screening or diagnostic referrals that consume limited resources and unduly stress the parents.…”

Assessment of Neonatal Intensive Care Unit Sound Exposure Using a Smartphone Application

“…Preterm infants are at increased risk of hearing impairment due to multiple factors such as intrauterine infection, perinatal hypoxia, aminoglycoside exposure, hyperbilirubinemia, apneic spells, and hypothermia. [1][2][3][4] Intermittent and chronic noise exposures in the neonatal intensive care unit (NICU) are potentially significant modifiable environmental factors that contribute to the increased risk of hearing impairment in preterm infants. 5 In 1997, the American Academy of Pediatrics (AAP) recommended that sound exposure in the NICU should not exceed a level greater than 45 dB.…”

Aminoglycoside-Induced Cochleotoxicity: A Review

“…Identifying the physiologic or genetic mechanisms behind these variations could establish who is at elevated risk of acquired hearing loss. These studies are clinically relevant as aminoglycosides are systemically administered in NICU, where sustained levels of higher ambient sound levels (Williams et al, 2007 ; Garinis et al, 2017b ) could increase the risk of aminoglycoside-induced cochleotoxicity.…”

“…In the NICU, aminoglycosides, especially gentamicin, are often obligatory treatments to treat life-threatening sepsis (Cross et al, 2015 ). NICU environments have loud ambient sound levels (Williams et al, 2007 ; Garinis et al, 2017b ), and a significantly increased incidence of hearing loss in NICU graduates (Yoon et al, 2003 ) that may be due to the synergistic effect of ambient sound levels increasing cochlear uptake of aminoglycosides (Li et al, 2015 ). Thus, efforts to reduce ambient sound levels in the NICU will be welcomed.…”