Impact of propofol on mid-latency auditory-evoked potentials in children.

BACKGROUND: Propofol is increasingly used in paediatric anaesthesia, but can be challenging to titrate accurately in this group. Mid-latency auditory-evoked potentials (MLAEPs) can be used to help titrate propofol. However, the effects of propofol on MLAEP in children are unclear. Therefore, we investigated the relationship between propofol and MLAEP in children undergoing anaesthesia. METHODS: Fourteen healthy children aged 4-16 yr received anaesthesia for elective surgery. Before surgery, propofol was administered in three concentrations (3, 6, 9 µg ml(-1)) through a target-controlled infusion pump using Kataria and colleagues' model. MLAEPs were recorded 5 min after having reached each target propofol concentration at each respective concentration. Additionally, venous propofol blood concentrations were assayed at each measuring time point. RESULTS: Propofol increased all four MLAEP peak latencies (peaks Na, Pa, Nb, P1) in a dose-dependent manner. In addition, the differences in amplitudes were significantly smaller with increasing propofol target concentrations. The measured propofol plasma concentrations correlated positively with the latencies of the peaks Na, Pa, and Nb. CONCLUSIONS: Propofol affects MLAEP latencies and amplitudes in children in a dose-dependent manner. MLAEP measurement might therefore be a useful tool for monitoring depth of propofol anaesthesia in children.

Effects of increasing sevoflurane MAC levels on mid-latency auditory evoked potentials in infants, schoolchildren, and the elderly.

BACKGROUND: Detection of mid-latency auditory evoked potentials (MLAEPs) is a technology to monitor central nervous structures. As seen in adults and children, general anaesthesia influences the MLAEP latencies. MLAEP detection seems to be a promising tool to assess different levels of anaesthesia depth in adults and children. METHODS: MLAEPs were recorded in 10 infants (2 months-3 yr), 12 schoolchildren (6-14 yr), and 10 elderly (75-89 yr) under general anaesthesia with increasing concentrations of sevoflurane at steady state. In addition, MLAEPs were detected before and after the application of sufentanil. RESULTS: At all different ages, MLAEP latencies increased significantly with higher volume percentages of sevoflurane. These results were also detectable when MAC values of sevoflurane were compared with MLAEP peaks. An age-dependent effect could be displayed as elderly people need lower absolute sevoflurane concentrations to achieve the same MLAEP peak increase. Overall, the application of sufentanil under steady-state sevoflurane application at 1 MAC did not importantly affect the MLAEP latencies. CONCLUSIONS: MLAEP latencies increase at the influence of sevoflurane in a dose-dependent manner and in relation to age. These results imply that MLAEP detection is a reasonable tool for monitoring hypnotic effects at all ages. Further studies are required to standardize MLAEP alterations related to effects of medication used for general anaesthesia at all different ages.