Imagine monitoring the depth of a swimming pool, but the way you measure it varies depending on the age of the swimmer. Just like age affects how we experience things differently, such as time or technology, it also plays a role in the response to anesthesia. In a recent study, researchers examined how age influences electroencephalogram (EEG) measures of anesthesia hypnosis. They recorded EEG data from patients spanning a wide range of ages and analyzed four different measures: Bispectral Index (BIS), Alpha Power, Lempel-Ziv complexity (LZc), and permutation entropy (PE). The results revealed that BIS, Alpha Power, and LZc were influenced by age, while PE remained consistent across different age groups. These findings suggest that when designing and interpreting EEG monitors for anesthesia, it’s essential to consider the age-related biases in certain measures. In other words, just as each swimmer requires an accurate measurement regardless of their age, healthcare providers need reliable measures of hypnotic depth in patients of all ages to ensure safe and effective anesthesia administration. To dive deeper into this fascinating research, check out the full article!

BackgroundImproving anesthesia administration for elderly population is of particular importance because they undergo considerably more surgical procedures and are at the most risk of suffering from anesthesia-related complications. Intraoperative brain monitors electroencephalogram (EEG) have proved useful in the general population, however, in elderly subjects this is contentious. Probably because these monitors do not account for the natural differences in EEG signals between young and older patients. In this study we attempted to systematically characterize the age-dependence of different EEG measures of anesthesia hypnosis.MethodsWe recorded EEG from 30 patients with a wide age range (19–99 years old) and analyzed four different proposed indexes of depth of hypnosis before, during and after loss of behavioral response due to slow propofol infusion during anesthetic induction. We analyzed Bispectral Index (BIS), Alpha Power and two entropy-related EEG measures, Lempel-Ziv complexity (LZc), and permutation entropy (PE) using mixed-effect analysis of variances (ANOVAs). We evaluated their possible age biases and their trajectories during propofol induction.ResultsAll measures were dependent on anesthesia stages. BIS, LZc, and PE presented lower values at increasing anesthetic dosage. Inversely, Alpha Power increased with increasing propofol at low doses, however this relation was reversed at greater effect-site propofol concentrations. Significant group differences between elderly patients (>65 years) and young patients were observed for BIS, Alpha Power, and LZc, but not for PE.ConclusionBIS, Alpha Power, and LZc show important age-related biases during slow propofol induction. These should be considered when interpreting and designing EEG monitors for clinical settings. Interestingly, PE did not present significant age differences, which makes it a promising candidate as an age-independent measure of hypnotic depth to be used in future monitor development.

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