结果：120名患者可用于数据分析。所有患者均插管顺利，在原始脑电图采集记录的十分钟内患者血流动力学均保持稳定。1-6组平均BIS值分别为52.2 ± 12.7, 55.0 ± 8.0, 44.5 ± 7.3, 43.8 ± 7.3, 44.2 ± 6.2 and 49.1 ± 6.2(P<0.01)，有明显统计学差异。Bonferroni校正后显示，BIS数值在组3、组4、组5与组1之间存在显著统计学差异（P＜0.05），组3、组4、组5与组2之间也存在显著统计学差异（P＜0.05）。六组均可见θ波，均无α和β波。六组脑电波频率分别为6.0 (5.5-6.0), 6.0 (5.5-6.0), 6.0 (5.5-6.0), 6.0 (6.0-7.0), 6.3 (6.0-7.0) 和6.0 (5.1-6.0)（P＜0.01）.Dunn的多重比较检验仅显示第4组与第6组（P = 0.0279）和第5组与第6组（P = 0.0202）之间的统计学显着性。采用正演方法的多元线性回归分析显示，只有BIS值与脑电波频率有统计学相关性（R2 = 0.063，标准化系数= 0.25，P <0.01）。
Comparing raw EEG waves among different age patients under general anesthesia with 1.0 MAC sevoflurane
BACKGROUND: Analyzing the raw electroencephalography (EEG) waves during anesthesia is still challenging and has not been widely demonstrated. Anesthetic agents are known to act directly on central nervous system; hence, causing alterations of consciousness. These alterations are major clinical endpoints of general anesthesia and can be analyzed and monitored throughout recordings of surface brain electrical activity, called electroencephalography (EEG). Raw EEG is a powerful tool that refers to the recording of the brain's spontaneous electrical activity along the scalp and it can be used to measure voltage fluctuations which result from ionic current flowing within neurons found in the brain. Under general anesthesia, these fluctuations vary spontaneously depending on the concentration and the type of anesthetic used. Different depth of anesthesia generate altering EEG waveforms and the deeper the level of hypnosis, the more suppressed the EEG waves are. Thus, it has become increasingly important to manipulate the hypnotic level accordingly to prevent brain damage. In modern practice, the assessment of the depth of anesthesia is fundamental to the anesthesiologist. Depth of anesthesia and electrical brain activity can be monitored using EEG indices such as theBispectral index monitoring system and M-entropy. These monitors have processed algorithms and software to assess these raw EEG waves in real time and give a standard numeric value. A BIS value of 40-60 indicates sufficient depth of anesthesia without any awareness. However, these EEG monitors is not reliable in young children and infants as the depth of anesthesia does not correlate with the numerical value generated by the monitors’ algorithms. Recent studies have demonstrated that the BIS monitor is not appropriate in assessing the depth of anesthesia in children. The EEG algorithm has been generated for adults and when extrapolated to children, it provides misleading information about the actual level of anesthesia. The raw EEG, in turn is presented with reliable information but many anesthesiologists do not know how to observe and interpret these waves. The raw electroencephalography monitoring and its analysis can indicate hypnotic and analgesic levels during general anesthesia. However, these are based on the underlying changes in the features of the raw EEG signal as the frequencies vary with the level of anesthesia. It has been known that different anesthetic agents such as intravenous or volatile agents have altered raw EEG waveforms. Using raw EEG data, we present a detailed analysis and assessment of the waveforms present under general anesthesia in the hope of shedding some lights on the raw EEG waves and the EEG indices. This study was conducted before any surgical stimulus in different age patients undergoing minor electrivesurgery under general anesthesia with sevoflurane concentration of 1.0 MAC.
OBJECTIVE: The aim of this study was to observe which raw EEG wave frequencies (alpha, theta, gamma and delta) are manifested under inhaled sevoflurane anesthesia of 1.0 MAC and how their frequencies differ in different age groups.
METHODS: A sample of 135 healthy patients were randomly selected and included in this study. After obtaining ethical approval and written informed consent, 135 patients (ASA I and II), aged 0-80 years of either gender undergoing minor elective surgery were enrolled. The selected patients were divided into 6 groups according to their age, 1 month -1 year old (infant period, group 1), 1-3 years old (toddler period, group 2), 3-6 years old (preschool age period, group 3), 6-18 years old (school age period, group 4), 18-65 years old (adults, group 5) and 65-80 years old (the elderly, group 6). The surgeries lasted less than two hours each and were performed under general anesthesia using sevoflurane as the sole hypnotic agent followed by sufentanil or fentanyl and muscle relaxant to facilitate intubation.Data collections started after induction and tracheal intubation. Data related to non-invasive blood pressure, heart rate, respiration rate, oxygen saturation, end tidal sevoflurane, EEG and bispectral index (BIS) values were recorded and analyzed for the 10 min of maintenance anesthesia with sevoflurane. The raw EEG wave was recorded by means of a Universal Serial Bus (USB) which was later on analyzed and processed offline. The different EEG wave frequencies (alpha, delta, theta and gamma) for all age patients under inhaled sevoflurane anesthesia of 1.0 MAC were analyzed and compared.
RESULTS: A total of 120 patients were included in the data analysis. All procedures of tracheal intubations were performed successfully, and hemodynamics was kept constant throughout the 10 minutes of raw EEG analysis. The average BIS value among group 1 to group 6 was 52.2 ± 12.7, 55.0 ± 8.0, 44.5 ± 7.3, 43.8 ± 7.3, 44.2 ± 6.2 and 49.1 ± 6.2 respectively (P<0.01).BIS values were statistically significant among the 6 groups, P<0.01. Bonferroni correction showed statistical significance in the BIS values only between groups 3, 4, 5 vs. group 1(P<0.05) and groups 3, 4, 5 vs. group 2 (P<0.05).Theta power was observed in all the 6 groups and there was no α and β waves present. The median EEG frequency among group 1 to group 6 was 6.0 (5.5-6.0), 6.0 (5.5-6.0), 6.0 (5.5-6.0), 6.0 (6.0-7.0), 6.3 (6.0-7.0) and 6.0 (5.1-6.0) respectively (P<0.01). Dunn’s multiple comparisons test showed statistical significance only between group 4 vs. group 6 (P=0.0279) and group 5 vs. group 6 (P=0.0202).Multiple linear regression with forward methods showed that only BIS value was statistically correlated to EEG wave frequency (R2=0.063, Standardized Coefficients=0.25, P<0.01).
CONCLUSION: Raw EEG provides real time information about the actual depth of anesthesia when standard monitors provide misleading values. Observing the raw EEG waveforms provides accurate reliable data which can be used to assess the depth of anesthesia in different age and can reduce brain injury during general anesthesia.
KEYWORDS: EEG waves, Minimum alveolar concentration, sevoflurane, age, monitoring, anesthetics inhalation, BIS.
Clinical trial registration.ClinicalTrials.gov: identifier: NCT03559504.
English Abstract 2
Materials and methods 9
Statistical analysis 11
Analysis and Discussion 13
Literature review 18