Monitoring of Anesthetic Depth and EEG Band Power Using PLE (Phase Lag Entropy) During Propofol Anesthesia

Anesthetic Depth Using PLE (Phase Lag Entropy)

The evaluation of the anesthetic depth monitoring using PLE (Phase Lag Entropy) during propofol anesthesia

The devices using EEG are commonly used for measuring the depth of consciousness during anesthesia. However, the existing devices are largely dependent on the biphasic analysis of 1-channel EEG signals, and thus do not provide proper information for anesthetic depth.

Recent study reported that the complexity or diversity of communication between the brain regions is related to the level of consciousness. In particular, during anesthesia, the phase synchronization (phase shift) between EEG signals at the front of the brain increases, indicating a reduction in communication diversity and a close relationship with loss of consciousness. Therefore, to predict the depth of sleep, a technique for precisely quantifying the complexity of inter-domain communication in the frontal brain is needed. Recently, PLEM™ (Inbody co., ltd, Republic of Korea), developed using the phase lag entropy (PLE), is a 4-channel EEG monitoring device that measures the entropy of the phase difference pattern between two channels of prefrontal and frontal brain. In addition, PLEM™ is able to observe changes in band power of EEG (Gamma, Beta, Alpha, Theta, and Delta waves). As the depth of anesthesia increases, the amplitude and frequency of EEG decreases. Generally, Beta waves (13-30 Hz) are seen in awake conscious patients and Alpha waves (8-12 Hz) are seen in patients resting with eyes closed. And Theta waves (4-7 Hz) and Delta waves (0-3 Hz) can be present in a patient who is sleeping or anesthetized.

The purpose of this study was to evaluate the efficacy for anesthetic depth monitoring of PLEM™ monitor during propofol anesthesia. The primary outcome of this study was to investigate the changes of PLE value and band power of EEG (Gamma, Beta, Alpha, Theta, Delta waves) on the PLEM™ monitor while varying the depth of anesthesia using propofol target controlled infusion (TCI) during anesthetic induction. The secondary outcomes of this study were to investigate whether the muscle relaxant affects the PLE value, and to compare the PLE values with BIS (bispectral index) (Aspect medical system, USA) that was the most widely used to measure the depth of anesthesia.

Inclusion Criteria:

• The patients undergoing elective general anesthesia with American Society fo Anesthesiologist (ASA) physical status I or II (20-60 years)

Exclusion Criteria:

• Patients with difficulty airway
• Patients with cardiovascular disease
• Patients with cerebrovascular disease
• Patients with respiratory disease