Effect of depth of anesthesia on the phase lag entropy in patients undergoing general anesthesia by propofol

Abstract

The PLEM100 (Inbody Co., Ltd., Seoul, Korea) is a device for measuring phase lag entropy (PLE), a recently developed index for the quantification of consciousness during sedation and general anesthesia. In the present study, we assessed changes in PLE along with the level of consciousness during the induction of general anesthesia using propofol. PLE was compared with the bispectral index (BIS), which is currently the most commonly used index of consciousness. After obtaining Institutional Review Board approval and written informed consent, we enrolled 15 patients (8 men, 7 women; mean age: 37 ± 9 years; mean height: 168 ± 8 cm; mean weight; 68 ± 11 kg) undergoing nasal bone reduction. PLE and BIS sensors were attached simultaneously, and general anesthesia was induced via target-controlled infusion (TCI) of propofol. PLE and BIS scores were recorded when the calculated effect site concentration shown on the TCI pump was equal to the target concentrations of 1.5, 2.0, 2.5, 2.8, 3.0, 3.2, 3.4, and 3.5 μg/mL (and at each 0.1 μg/mL increase, thereafter). Observer's Assessment of Alertness/Sedation (OAA/S) scores were also recorded until unconsciousness was achieved. Throughout the anesthesia period, all pairs of PLE and BIS data were collected using data acquisition software. The partial correlation coefficients between OAA/S scores and PLE, and between OAA/S scores and BIS were 0.778 ( P < .001) and 0.846 ( P < .001), respectively. Throughout the period of anesthesia, PLE and BIS exhibited a significant positive correlation. The partial correlation coefficient prior to the loss of consciousness was 0.838 ( P < .001), and 0.669 ( P < .001) following the loss of consciousness. Intra-class correlation between the 2 indices was 0.889 ( P < .001) and 0.791 ( P < .001) prior and following the loss of consciousness, respectively. PLE exhibited a strong and predictable correlation with both BIS and OAA/S scores. These results suggest that PLE is reliable for assessing the level of consciousness during sedation and general anesthesia.

Phase Lag Entropy as a Surrogate Measurement of Hypnotic Depth during Sevoflurane Anesthesia

“…Each EEG monitors have their own algorithms to calculate the index for the target of general anesthesia [23]. For example, 40-60 of BIS, 25-50 of PSI, and 40-60 of PLE is a range of index for adequate general anesthesia [11,23]. Phase lag entropy also showed high prediction probability in our study.…”

“…Similar neural circuit mechanisms are involved, as evident by the similar EEG dynamics induced by sevoflurane and propofol [4]. Looking for common EEG features, propofol and sevoflurane anesthesia were depicted by alpha (8)(9)(10)(11)(12) and slow (<1 Hz) oscillations [4]. The EEG features of sevoflurane were discriminable from that of propofol because of increased power and coherence in the theta wave (4-7 Hz) [4].…”

“…Phase lag entropy exhibits the depth of anesthesia by computing the various interconnection of phase relationships between two EEG signals [7]. Recently developed phase lag entropy has been closely associated with the level of propofol sedation [8][9][10][11][12]. No study has evaluated the relationship between phase lag entropy and sevoflurane anesthesia to the knowledge of the authors.…”

Comparison of the effect of electromyogram activity during emergence on anesthetic depth monitoring between phase lag entropy and bispectral index: a prospective observational study

“…Therefore, theoretically, the PLE score could be less affected by EEG than the BIS; however, there have been few studies on the relationship between the PLE score and PLE-EMG. Although several studies showed PLE score has correlation with BIS for evaluating consciousness and depth of anesthesia during general anesthesia (11,12,24), the present study is meaningful since it is the first to investigate the PLE-EMG effect on the PLE score.…”

“…A previous study reported no changes in the BIS score even after 10 min of sugammadex reversal (22); however, the EMG activity was a single entity rather than dividing it into low and high groups, which may differ from other studies. The PLE monitor has been recently approved for clinical use, with several studies assessing its usefulness and comparison with the BIS; moreover, it has been shown as useful for LOC evaluation in general anesthesia (11,12,23,24). PLE employs EEG signals with ranges of 0.1-1 and 32-45 Hz while PLE-EMG uses signals >45 Hz.…”