[Determination of hearing thresholds in children using auditory brainstem responses : Influence of sedation and anaesthesia on quality and measurement time].

backgroundA fundamental prerequisite for successful application of auditory brainstem responses (ABR) in paedaudiological diagnostics is to ensure a high quality of the measurement. This is commonly quantified by means of the residual noise. Key factors are the averaging number and the magnitude of spontaneous electroencephalogram (EEG). This is the first study to quantify the influence of different forms of sedation (anaesthesia, sedation with chloral hydrate or melatonin, natural sleep) on the individual EEG magnitude in children. MATERIALS AND

methodsABR measurements of 80 children aged between 1 month and 6 years were analysed retrospectively. Individual mean EEG amplitude was calculated from the averaging number and the residual noise. The results were analysed statistically with the type of sedation as a factor. From the mean EEG amplitudes, a theoretical recording time for a residual noise level of 35 nV was estimated.

resultsThe spontaneous EEG activity is, on average, 2.5-times larger in awake children than in naturally sleeping children and more than 4‑times larger than in sedated children. Although the EEG amplitude in intubation anaesthesia was smaller than with the other three types of sedation, this difference was not significant. The theoretical measurement time for 35 nV of residual noise was 10-times larger in awake than in sedated children.

conclusionThe large difference in spontaneous EEG activity between awake and sedated children indicates that sedation should be used for estimation of hearing thresholds on the basis of ABR. Only in rare cases is a reliable estimate of hearing thresholds likely to be obtained from ABR in awake children. Since different types of sedation do not influence the measurement time significantly, selection can be made solely on the basis of age and medical indication.