Spectral edge frequency during general anaesthesia: A narrative literature review

Abstract

Previous studies have attempted to determine the depth of anaesthesia with different anaesthetic agents using electroencephalogram (EEG) measurements with variable success. Measuring depth of anaesthesia is confounded by the complexity of the EEG and the fact that different agents create different pattens. A narrative review was undertaken to examine the available research evidence on the effect and reliability of spectral edge frequency (SEF) for assessing the depth of anaesthesia in adult patients under general anaesthesia. A systematic search of the PubMed®, Scopus®, CINAHL and Cochrane databases identified six randomized controlled trials and five observational studies. The findings of these studies suggest that SEF varies according to the anaesthetic drugs used. Remifentanil and age are two factors that can affect SEF, while other opioids and benzodiazepine (administered separately) seem to have no effect. No patients experienced intraoperative awareness. However, this does not indicate that SEF can provide full protection against it and the number of articles in which intraoperative awareness was studied was too small to afford any certainty. None of the studies demonstrated a reliable SEF interval associated with adequate general anaesthesia. SEF must be adapted to the anaesthetic drug used, the patient’s age and state while under general anaesthesia.

Effect of Repeated Exposure to Sevoflurane on Electroencephalographic Alpha Oscillation in Pediatric Patients Undergoing Radiation Therapy: A Prospective Observational Study

“…Although we found no broad changes in the EEG spectral power in our cohort, 8 of the 18 patients (44.4%) showed a significant reduction in the alpha power across sessions, a finding that was corroborated by the mixed-effect model in which a random effect for the subject was included. This change was accompanied by a reduction in the SEF95 to lower frequencies, indicating that, overall, there was a shift in the EEG signal to lower frequencies 26 . However, this result should be interpreted with caution.…”

“…This change was accompanied by a reduction in the SEF95 to lower frequencies, indicating that, overall, there was a shift in the EEG signal to lower frequencies. 26 However, this result should be interpreted with caution. No previous publication has reported a reduction in alpha power in infants, and only a single case of an adult patient exhibiting a reduction in frontal alpha power over 3 surgeries and across the course of 7 months has been published.…”

A Pilot Investigation Evaluating Relative Changes in Fronto-Occipital Alpha and Beta Spectral Power as Measurement of Anesthesia Hypnotic Depth

“…Practically, an SEF-95 of 10 to 12 Hz likely represents adequate anesthesia, indicating alpha oscillation presumably underscored by prominent delta and slow waves. 13 In contrast, a low SEF-95 between 2 and 6 Hz likely represents a delta-dominated EEG as during hypothermy and cardiopulmonary bypass. 14 During preanesthesia, we often observed a wide range of FO-RPAB values in the recording.…”

Comparison of relevance in patient status index (PSI) and spectral edge frequency (SEF) with end-expiratory sevoflurane concentration (ETSEV) during general anesthesia surgery

“…Compared to the original EEG, SEF simpli es the form of power variation of various waves in the range of 0-30 Hz. The smaller the value of SEF suggests that 95% of the total EEG power is concentrated in the low-frequency region and the depth of anesthesia deepens, and vice versa [15,16] . It has been shown that SEF is not in uenced by age and brain development, can more accurately and visually re ect EEG changes, correlates with the blood concentration of various anesthetic drugs, and can better re ect the intraoperative role of anesthetic drugs in maintaining the depth of anesthesia [17,18] .…”