# EEG alpha/delta ratio at different propofol-induced sedation levels in children during procedural sedation

## TL;DR

This study examines how the alpha-delta ratio in EEG readings changes with propofol sedation levels in children, finding a non-linear pattern that peaks at a specific sedation depth.

## Contribution

The study is the first to characterize the alpha-delta ratio trajectory across pediatric age groups and hypnotic depths during propofol sedation.

## Key findings

- Relative alpha power increased and delta power decreased with deepening hypnosis until CS=12, then reversed.
- The ADR increased with hypnotic depth, peaked around CS=12, then declined, showing a non-linear trajectory.
- These patterns were consistent across all age groups with no significant age-related differences.

## Abstract

The alpha-delta ratio (ADR) represents the relationship between alpha and delta waves and has emerged as a potential marker of hypnotic depth. However, the trajectory of ADR across pediatric age groups and hypnotic depths during propofol sedation has not been characterized. This study aimed to investigate ADR patterns after midazolam premedication plus propofol sedation across different age groups and hypnotic depths.

This post-hoc analysis from a prospective observational study at a tertiary PICU (October 2020-December 2022) included children aged 6 months to 17.9 years undergoing procedural sedation with propofol. EEGs were recorded using BrainTrend 2.0 monitors with the electrodes placed at Fp1, Fp2, and FpZ positions. Hypnotic depth was assessed using the Comfort Scale (CS) every 5 minutes. The ADR was calculated as relative alpha power divided by relative delta power. Age-stratified analyses were performed (<3, 3-5, 6-11, 12-17 years).

Of 176 patients, 165 had eligible EEG recordings with 1,464 paired CS-EEG observations (8.9±3.5/patient). Median age was 8.8 years (IQR 3.9-14.0). Relative alpha power increased and delta power decreased with deepening hypnosis until CS=12, then reversed at deeper levels. Concordantly, the ADR increased with hypnotic depth, peaking around CS=12, then declined. The total power showed a U-shaped trajectory. These patterns were consistent across all age groups with no relevant age-related differences.

The ADR exhibited a characteristic non-linear trajectory at different depths of pediatric propofol-induced hypnosis, with reversals at very deep hypnosis levels. The curved ADR trajectory suggests that additional clinical assessment and propofol dosing information are essential for accurate interpretation of hypnotic depth.

The online version contains supplementary material available at 10.1186/s12871-026-03667-5.