EEG profiles during general anesthesia in children: A comparative study between sevoflurane and propofol

Abstract

Background

In this prospective randomized study we describe the electroencephalographic profiles in children anesthetized with sevoflurane or propofol: Bispectral Index (BIS)‐Concentration relationship and raw electroencephalogram were analyzed.

Methods

Seventy‐three subjects (11 years, range 5‐18) were included and randomly assigned to two groups according to the anesthetic agent. Anesthesia was performed by Target Controlled Infusion of propofol (group P) or by sevoflurane inhalation (group S). Steady state periods were performed at a fixed randomized concentration between 2, 3, 4, 5 and 6 μg.ml⁻¹ of propofol in group P and between 1, 2, 3, 4, 5% of sevoflurane in group S. Remifentanil was continuously administered throughout the study. Clinical data, BIS and raw EEG were continuously recorded. Relationship between BIS and anesthetic concentrations was studied using non‐linear regression. For all steady state periods, EEG traces were reviewed to assess the presence of epileptoid signs, and spectral analysis of raw EEG was performed.

Results

Under propofol, BIS decreased monotonically and EEG slowed down as concentrations increased from 2 to 6 μg.ml⁻¹. Under sevoflurane, BIS decreased from 0 to 4% and paradoxically rose from 4 to 5% of expired concentration: this increase in BIS was associated with the occurrence of fast oscillations and epileptoid signs on the EEG trace. Propofol was associated with more delta waves and burst suppression periods compared to sevoflurane.

Conclusion

Under deep anesthesia, the Bispectral Index and electroencephalographic profiles differ between propofol and sevoflurane. For high concentrations of sevoflurane, an elevated BIS value may be interpreted as a sign of epileptoid patterns or EEG fast oscillations rather than an insufficient depth of hypnosis.

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