Shifts in auditory brainstem response latencies following plasma-level-controlled aminoglycoside therapy

Auditory Brainstem Response in Preterm Infants in the Neonatal Intensive Care Unit

OBJECTIVE

To analyze auditory brainstem response (ABR) findings of preterm and term infants in the neonatal intensive care unit (NICU) with perinatal problems.

STUDY DESIGN

Case series with chart review.

SETTING

Secondary care hospital.

METHODS

Analysis consisted of a consecutive series of 101 infants (69 preterm and 32 term) admitted in the NICU of Hospital Fernando Fonseca between 2016 and 2018 with perinatal problems who underwent an ABR evaluation.

RESULTS

The major perinatal problems identified were hyperbilirubinemia, intravenous gentamicin >5 days, mechanical ventilation >5 days, congenital cytomegalovirus infection, meningitis, and periventricular hemorrhage. Gentamicin use significantly increased the absolute latency of wave I in preterm infants (95% CI, 0.01-0.37; P = .037). Mechanical ventilation significantly decreased the latency of wave V and intervals I-V and III-V in preterm infants (95% CI, -0.35 to -0.22; P = .026; 95% CI, -0.33 to -0.00; P = .001; 95% CI, -0.46 to 0.12; P = .049). Congenital cytomegalovirus significantly decreased interval III-V in preterm infants (95% CI, -0.36 to -0.01; P = .042).Multivariate analysis revealed that gentamicin use, lower gestational age, and lower birth weight predicted an increased ABR threshold in preterm infants (95% CI, 1.64-15.31; P = .016; 95% CI -1.72 to -0.09; P = .030; 95% CI, -14.55 to -0.63; P = .033). ABR measurements in term infants were not significantly altered, with the exception of an increased latency of wave III with a lower gestational age (95% CI, -0.49 to -0.01; P = .038).

CONCLUSIONS

These findings suggest that perinatal problems in the NICU significantly impair the ABR threshold and the auditory pathway maturational process in preterm but not term infants.

Acupuncture does not influence brainstem auditory evoked potentials: a volunteer crossover study

BACKGROUND

Although acupuncture is effective for treating several conditions, its site specificity is questionable.

OBJECTIVE

To investigate whether acupuncture influences the brainstem auditory evoked potentials (BAEP).

METHODS

10 healthy volunteers were enrolled according to inclusion criteria. One of four acupuncture points-TE3, GB43 (both auditory system-specific, according to traditional Chinese medicine) and non-specific acupuncture points HT7 and ST44-was needled during each session. Each volunteer received four sessions of acupuncture, with a 1-week interval between the sessions.

RESULTS

Peak latencies and amplitudes of the BAEP were registered before and during each session of acupuncture. Pain intensity and the incidence of paraesthesia (Qi sensation) during acupuncture were also registered. The peak latencies and amplitudes of the BAEP registered during acupuncture had not changed from the baseline levels. Needling of acupoint HT7 was most painful and induced the maximal incidence of Qi sensation.

CONCLUSIONS

Findings suggest that monitoring the BAEP is not a suitable technique for studying the immediate effects of acupuncture.

Auditory and electroencephalographic effects of midazolam and alpha-hydroxy-midazolam in healthy subjects

AIMS

Whereas cortical EEG effects of benzodiazepines are well characterized, information about benzodiazepine effects in other areas of the central nervous system is sparse. This study investigated the action of midazolam and its active metabolite alpha-hydroxy-midazolam on different parts of the auditory pathway in six healthy volunteers in a randomized, double-blind, three-way cross-over study.

METHODS

Acoustically evoked short (SLP) and middle (MLP) latency potentials, transitory evoked otoacoustic emissions (TEOAE), and EEG power spectra were analysed after short i. v. injections of placebo, or 0.15 mg kg-1 midazolam, or alpha-hydroxy-midazolam, respectively.

RESULTS

All subjects fell asleep during the 4 min infusion of active drug. SLP showed a significant transient increase of Jewett wave V 10 min after injection for midazolam and alpha-hydroxy-midazolam while the latency of wave I was unchanged. Both benzodiazepines induced a marked and long-lasting MLP amplitude decrease for 240 min with slow recovery over the following 360 min. No changes of TEOAE were observed. In agreement with earlier reports, increases in EEG beta activity and decreases in alpha activity were observed after administration of either drug.

CONCLUSIONS

Systemically administered benzodiazepines modulate the auditory pathway above the level of the cochlea. While SLP changes were closely associated with sedation and high plasma benzodiazepine concentrations, MLP effects persisted for hours after sedation even at low benzodiazepine plasma levels. Evoked potentials may therefore be more sensitive than EEG as a tool to monitor benzodiazepine effects.