• Hye Won Shin, Kim Hyun Jung HJ Department of Anesthesiology and Pain Medicine, Ewha University Magok Hospital, College of Medicine, Ewha University, Seoul, Republic of Korea., Yoo Kyung Jang, Hae Sun You, Hyub Huh, Yoon Ji Choi, Seung Uk Choi, and Ji Su Hong.
• Department of Anesthesiology and Pain Medicine, Korea University Anam Hospital, College of Medicine, Korea University, Goryodae-ro 73, Seongbuk-gu, 02841, Seoul, Republic of Korea. drhwshin@naver.com.
• BMC Anesthesiol. 2020 Feb 26; 20 (1): 49.

BackgroundPhase lag entropy (PLE) is a novel anesthetic depth indicator that uses four-channel electroencephalography (EEG) to measure the temporal pattern diversity in the phase relationship of frequency signals in the brain. The purpose of the study was to evaluate the anesthetic depth monitoring using PLE and to evaluate the correlation between PLE and bispectral index (BIS) values during propofol anesthesia.MethodsIn thirty-five adult patients undergoing elective surgery, anesthesia was induced with propofol using target-controlled infusion (the Schneider model). We recorded the PLE value, raw EEG, BIS value, and hemodynamic data when the target effect-site concentration (Ce) of propofol reached 2, 3, 4, 5, and 6 μg/ml before intubation and 6, 5, 4, 3, 2 μg/ml after intubation and injection of muscle relaxant. We analyzed whether PLE and raw EEG data from the PLE monitor reflected the anesthetic depth as the Ce of propofol changed, and whether PLE values were comparable to BIS values.ResultsPLE values were inversely correlated to changes in propofol Ce (propofol Ce from 0 to 6.0 μg/ml, r2 = - 0.83; propofol Ce from 6.0 to 2.0 μg/ml, r2 = - 0.46). In the spectral analysis of EEG acquired from the PLE monitor, the persistence spectrogram revealed a wide distribution of power at loss of consciousness (LOC) and recovery of consciousness (ROC), with a narrow distribution during unconsciousness. The power spectrogram showed the typical pattern seen in propofol anesthesia with slow alpha frequency band oscillation. The PLE value demonstrated a strong correlation with the BIS value during the change in propofol Ce from 0 to 6.0 μg/ml (r2 = 0.84). PLE and BIS values were similar at LOC (62.3 vs. 61.8) (P > 0.05), but PLE values were smaller than BIS values at ROC (64.4 vs 75.7) (P < 0.05).ConclusionsThe PLE value is a useful anesthetic depth indicator, similar to the BIS value, during propofol anesthesia. Spectral analysis of EEG acquired from the PLE monitor demonstrated the typical patterns seen in propofol anesthesia.Trial RegistrationThis clinical trial was retrospectively registered at ClinicalTrials.gov at October 2017 (NCT03299621).

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