Monitoring of anesthetic depth and EEG band power using phase lag entropy during propofol anesthesia.

BACKGROUND: Phase 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. METHODS: In 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. RESULTS: PLE 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). CONCLUSIONS: The 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 REGISTRATION: This clinical trial was retrospectively registered at ClinicalTrials.gov at October 2017 (NCT03299621).

Postoperative respiratory difficulty due to asymptomatic anterior cervical osteophyte after brain tumor surgery: a case report.

Anterior cervical osteophytes are commonly found in elderly patients, but rarely produce symptoms. When symptoms occur, they can range from mild symptoms of dysphagia, dysphonia, and foreign body sensation to severe symptoms of airway obstruction due to compression of the pharynx or larynx. We report the case of a 59-year-old man who underwent brain tumor surgery, and developed post-operative respiratory difficulty due to progressive pharyngo-laryngeal edema, requiring urgent endotracheal intubation, secondary to the presence of a previously asymptomatic anterior cervical osteophyte. It is paramount to recognize that asymptomatic anterior cervical osteophytes are a potential cause of life-threatening post-operative respiratory complications that can rapidly progress to life-threatening airway obstruction after surgeries in the prone position, especially in elderly patients.