Monitoring Equipment and Computers
Background and Goal of Study: The Auditory evoked potential index (AEPex) has been promoted as AEP-based anaesthesia depth monitor. The EEG changes with brain maturation, but there are limited published data describing the characteristics of midlatency auditory evoked potentials (MLAEP's) in children, and some data suggest that MLAEP's are less reliable in young children. The aim of this study was to compare the performance of the AEPex as a measure of anaesthetic effect in different age groups.
Materials and Methods: With approval of the local ethic committee 35 children (age range 2–17 years, mean 11,2 ± 4,7 years) were included in a prospective observational study. Neurological disease or hearing deficits was an exclusion criterion. Anaesthesia was maintained using propofol and remifentanil. The remifentanil infusion rate was kept constant with 0.2 mcg/kg/min., whereas propofol was adjusted according to clinical needs by an anaesthetist blinded to AEP monitoring. The AEPex was recorded at the awake (unpremedicated) state, intraoperative state (defined as measure-points during skin incision, 1, 5, 10 and 15 min. after incision, respectively) and at emergence (during and 1 min. after extubation). For analysis children were divided into three age groups: gr. 1: 2-<10 yr. (n = 12), gr. 2: 10-<14 yr. (n = 12), gr. 3: 14-<18 yr. (n = 11). A Mann-Whitney-U-test was used for inter-group comparison; significant for p=<0.05 (*) or 0.01 (**).
Results and Discussion: The AEPex decreased significantly as age increased in children (Figure 1). The AEPex values at awake and intraoperative state were significantly higher in the 2-<10 yr. age group compared to the 14-<18 yr. age group (awake p=0.05; for all measure-points at intraoperative state p=<0.04). The interquartile range tended to be larger in younger children. During emergence differences between the groups were not significant. Recommended depth of anaesthesia values (by the manufacturer: 30–45) were only reached in the 10-<14 and 14-<18 yr. age group.
Conclusion(s): This preliminary study suggests that age has a significant impact on the AEPex in the awake and intraoperative state in children. Age-related processing algorithms of the MLAEP should be implemented.