The Effect of Electromyogram (EMG) Activity on Anesthetic Depth Monitoring

Overview

Currently, a lot of equipments based on Bispectral index (BIS) is used clinically in order to measure the depth of anesthesia. Although BIS is used for the measurement of the presence of consciousness or degree of sedation during general anesthesia, it could be influenced by factors that affect or interfere with the activity of EEG because it is a numerical value which is measured by analyzing EEG. The BIS electrode for EEG analysis should be attached to the patient's forehead and the EEG signal is 0.5 - 30 Hz, the EMG signal is 30 - 300 Hz, and the BIS analyzes the 0 - 47 Hz signal. Therefore, 30 -47 Hz EMG signal may influence the BIS value and the BIS value may differ from the actual. In patients with complete muscle relaxation, the change in BIS varies in proportion to the concentration of anesthetic, but in a state with less muscle relaxation or arousal period of anesthesia when recovery of muscle relaxation occurs, BIS value may not accurately reflects the change in the depth of anesthesia. Although there is a study on the influence of the degree of muscle relaxation on BIS value, there is no study on whether phase lag entropy (PLE) measuring anesthesia depth based on different mechanism from BIS is affected by status of muscle relaxation. After measuring BIS and PLE at the same time, I will compare both of them and investigate the reliability of the measurement of the depth of anesthesia of PLE and how electromyogram activity affects PLE.

Intravenous administration of 2% propofol and remifentanil would be done for total intravenous anesthesia. After intravenous injection of rocuronium 0.6 mg/ kg for muscle relaxation, endotracheal intubation would be performed. Then, anesthesiologist attaches the sensors of BIS and PLEM 100 on the forehead of the patient, and adheres the neuromuscular monitoring device on the medial side of the wrist and the ipsilateral thumb to continuously monitor the state of consciousness and muscle relaxation before, during and after surgery. Before the end of surgery, the degree of neuromuscular relaxation should be within deep block (TOF count \<2) and the concentration of 2% propofol should be adjusted for maintaining BIS between 50 and 60. Reversal of muscle relaxant could be performed by intravenous injection of sugammadex 4 mg/ kg in the case of deep neuromuscular relaxation, and 2 mg / kg in the case of shallow muscle relaxation degree under neuromuscular monitoring. After then, monitor and record the values of BIS, phase lag entropy monitor (PLEM) 100, and neuromuscular monitoring in 1 minute increments for 5 minutes.