Age-related changes in EEG power spectra in infants during sevoflurane wash-out

Few electroencephalography (EEG) data are available in anaesthetized infants. This study aimed to identify EEG characteristics that might warn of awakening (AW) from sevoflurane anaesthesia in infants. Twenty intubated infants [aged 39–77 weeks post-menstrual age (PMA)] were studied after surgery during sevoflurane wash-out. EEG was recorded at the end of surgery and throughout emergence. Changes in EEG time and frequency domains were described. At the end of surgery, mean end-tidal sevoflurane concentration was 2.3% (range 1.5–3.5) before wash-out and reduced to 0.3% (0.1–0.6) when AW began. On AW, movement artifacts made signals difficult to interpret. Before awakening, most power was within frequencies ≤4 Hz, but trends over time were variable. Summated power in frequencies between 20 and 70 Hz was almost always 52 weeks PMA had obvious summated power in the frequency range 5–20 Hz (P5–20 Hz) (mean 308, median 320, range 110–542 µV2), which decreased before awakening began [mean decrease 252 µV2 (95% CI 153–351)], whereas younger infants had low P5–20 Hz throughout. P5–20 Hz during anaesthesia increased with age; power in this frequency band of ∼100 µV2 separated infants younger and older than 52 weeks PMA. During sevoflurane wash-out, decreasing P5–20 Hz might warn of impending AW in infants >3 months old, but not in younger infants.