We analysed the association of independent variables with non-verbal cognition at 6 years in children with complete data (3441 from a cohort of 9901), of whom 415 were anaesthetised before the age of 5 years. Using multivariable regression, cognition was reduced by a mean (95% CI) score for children: anaesthetised before the age of 5 years, 2.1 (0.7-3.5), p = 0.004; born prematurely, 9.8 (4.1-15.4), p = 0.001; whose mothers smoked while pregnant, 2.3 (0.8-3.8), p = 0.004; whose mothers had lower IQ scores, 0.3 (0.2-0.3) for each unit reduction in maternal IQ, p < 0.0001. The association of child IQ with exposure to anaesthetic drugs was sensitive to missing data.

Summary Electroencephalographic density spectral array monitoring has been developed to facilitate the interpretation of unprocessed electroencephalogram signals. The primary aim of this prospective observational study, performed in a tertiary children's hospital, was to identify the clinical applicability and validity of density spectral array monitoring in infants and children during sevoflurane anaesthesia. We included 104 children, aged < 6 years, undergoing elective surgery during sevoflurane anaesthesia. We investigated the correlation between non‐steady state end‐tidal sevoflurane and the expression of the four electroencephalogram frequency bands β, α, θ and δ, representing density spectral array. Patients were divided into three age groups (< 6 months, 6–12 months, > 12 months). There was a significant correlation between end‐tidal sevoflurane and density spectral array in the age groups 6–12 months (p < 0.05) and 1–6 years (p < 0.0001). In infants < 6 months of age, the relative percentages of density spectral array did not correlate with end‐tidal sevoflurane. The main finding was that different end‐tidal concentrations of sevoflurane produce age‐dependent changes in the density spectral array power spectrum. In infants younger than 6 months‐old, α and β coherence are absent, whereas θ and δ oscillations have already emerged. In cases where anaesthesia was too deep, this presented as burst suppression on the electroencephalogram, θ disappeared, leaving the electroencephalographic activity in the δ range. Future research should address this issue, aiming to clarify whether the emergence of θ oscillations in infants helps to prevent sevoflurane overdosing.

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The relationship between anesthesia and the electrical activity of the brain has been described as early as in the 1940's. 1 Development in this field has been extended to the investigation of the relationship between the brain activity and depth of anesthesia. 2 Research of the brain activity as a surrogate to monitor the depth of hypnosis during anesthesia has mostly focused on the spontaneous electroencephalogram (EEG). However, the spontaneous EEG does not mature before adult age, which could influence its reliability in children. 3 Although Mid-Latency auditory evoked potentials (MLAEP) are electrical brain activity, they are fundamentally different from the spontaneous EEG. These potentials are electric responses of the brain to an auditive stimulus.They occur at about 8-50 ms after the stimulus, which is after the auditory brainstem response (0-8 ms) and before the late cortical response (>50 ms). Needless to say, an impaired auditory pathway and/or inadequate delivery of the acoustic stimulus (poor fit of the earbuds in children) will make the recording of a MLAEP unreliable or even impossible.A typical MLAEP waveform consists of 3 troughs (labelled with N for negative polarity) and 2 peaks (labelled with P for positive polarity) of a few microvolts (Figure 1). To put in perspective, the EEG is about ten times stronger and the ECG is about 100 times stronger. The weak signal of the MLAEP makes it susceptible to noise and diminishes its signal quality. The peaks and troughs are commonly labeled as N 0 , P 0 , Na, Pa and Nb and occur, in the awake adult, at about 9 ms, 12 ms, 16 ms, 25 ms and 36 ms, respectively, after the application of an auditive stimulus. 4 The MLAEP is believed to be generated from the medial geniculate body and primary auditory cortex. 5 In anesthetized adult patients, the peaks and troughs decrease in amplitude and the interval when they occur, which are called latencies, increases. [5][6][7][8][9] Myelination of the brain in de developing child strongly influences evoked potentials, this makes it difficult to elicit these in infants having an age of less than 1 year and very difficult in infants less than 6 months of age.MLAEP mature after the first decade of life, around 10-12 years. [10][11][12][13] Mid-Latency auditory evoked potentials could be a parameter to measure the depth of hypnosis in anesthetized children. This narrative review summarizes the current literature concerning the use of MLAEP and its implications in anesthetized children. | ME THODSThis study adheres to the Preferred Reporting Items for Systematic Reviews and MetaAnalysis (PRISMA) guidelines, since it was initiated