The Investigation of Behavior Change in EEG Signals During Induction of Anesthesia

Anesthesiology aims to make anesthesia safer and increase the precision of prognoses. Correct assessment of the anesthesia depth is crucial to its safety. At present, intraoperative electroencephalogram (EEG) monitoring is the primary mode of anesthesia depth monitoring and judgment. However, most clinical anesthesiologists rely on commercial anesthesia depth monitors to judge anesthesia depth, such as bispectral index (BIS) and patient state index (PSI). This may lack an understanding of associated changes in brain wave quantization. Therefore, this study conducts quantitative analyses of EEG signals during anesthesia induction. EEG signals are processed within specific time windows and extracted brainpower density spectrum arrays with different frequency bands, brain electrical signal spectra, source frequencies and other key indicators. Analysis and comparison of these indicators clarifies patterns of variation in EEG signals during early anesthesia induction. The spectral edge frequencies (SEFs) of EEG signals within different time windows can be modeled accurately, from which the specific time points of EEG signal changes are derived. Furthermore, the relationship between patient age and the effect of anesthetic drugs is preliminarily investigated by analyzing the SEF variations of different age groups. This study quantifies changes in the EEG signals of patients at the initial stage of anesthesia induction and drug-related effects are observed, which opens a way for further exploration of EEG changes in patients under general anesthesia.

Ketamine-xylazine anesthesia depth affects auditory neuronal responses in the lateral superior olive complex of the gerbil

Studies of in vivo neuronal responses to auditory inputs in the superior olive complex (SOC) are usually done under anesthesia. However, little attention has been paid to the effect of anesthesia itself on response properties. Here, we assessed the effect of anesthesia depth under ketamine-xylazine anesthetics on auditory evoked response properties of lateral SOC neurons. Anesthesia depth was tracked by monitoring EEG spectral peak frequencies. An increase in anesthesia depth led to a decrease in spontaneous discharge activities and an elevated response threshold. The temporal responses to suprathreshold tones were also affected, with adapted responses reduced but peak responses unaffected. Deepening the anesthesia depth also increased first spike latency. However, spike jitter was not affected. Auditory brainstem responses to clicks confirmed that ketamine-xylazine anesthesia depth affects auditory neuronal activities and the effect on spike rate and spike timing persists through the auditory pathway. We concluded from those observations that ketamine-xylazine affects lateral SOC response properties depending on the anesthesia depth.

Evaluation of the anesthesia depth in experimental animals by parameters of cerebral blood flow and structures of the blood serum solid phase (experimental study)

Актуальность. Важным патогенетическим звеном развития осложнений при введении наркоза является нарушение дыхания в виде апноэ, которое может переходить в агонию. Вместе с тем, не существует работ по регистрации мозгового кровотока в период агонии. Несмотря на многочисленные результаты исследований на животных, демонстрирующих, что общая анестезия приводит к нейродегенерации и когнитивным нарушениям, на сегодняшний день чёткого консенсуса о влиянии анестетиков на человека всё ещё не достигнуто. Цель исследования: выявить маркёры стадий наркоза у экспериментальных животных по структурам твёрдой фазы сыворотки крови (СК) и показателям мозгового кровотока (МК). Материалы и методы. Исследования проведены на половозрелых беспородных крысах-самцах. Животные наркотизировались хлоралгидратом: контрольные группы получали дозу 400 мг/кг, в/б, а опытные - 500-600 мг/кг, в/б. В разные фазы действия наркоза регистрировали системное артериальное давление (АД), МК, частоту дыхания и частоту сердечных сокращений. МК регистрировали прибором ЛАКК-02 (ЛАЗМА). АД измеряли монитором MEC8 Mindray. Структуры твёрдой фазы СК животных исследовали методом краевой дегидратации на тест-картах диагностического набора «Литос-система». Микроскопию структур СК проводили в поляризованном свете при увеличении × 200 и × 400 (микроскоп DM2500 фирмы «Leica»). Результаты. В контрольных группах показатели МК, частоты дыхательных движений и частоты сердечных сокращений достоверно не различались. В опытных группах через один час после дачи повышенной дозы наркоза наблюдали снижение частоты сердечных сокращений, частоты дыхания и показателей АД (р < 0,05). Сразу после начала апноэ МК начинал быстро снижаться вслед за падением АД. Амплитуда сердечного ритма в спектре колебаний МК повышалась в три раза по сравнению с контролем. От начала апноэ время снижения МК до нуля составляло от 60 до 240 с. До введения наркотического средства структуры СК были представлены в виде сферолитов и веерных образований, которые характерны для физиологического состояния организма. В стадии апноэ сферолиты и веерные структуры СК были испещрены множеством мелких изотропных включений, а также имели единичные мелкие и обширные изотропные разломы. В агональной стадии большинство структурных образований СК было представлено фрагментами сферолитов с многочисленными полосками и ветвистыми образованиями с высокой анизотропией, множественными разломами с изъеденными границами. Заключение. Динамика морфофункциональных показателей экспериментальных животных в результате воздействия наркотизирующих средств определяется перестройкой, возникающей в структуре белковых молекул, строение которых визуализируется при переводе СК в твёрдую фазу. Особенности патологических структур твёрдой фазы СК указывают на глубину наркотизации организма. Эти изменения согласуются с динамикой показателей сердечно-сосудистой и дыхательной систем экспериментальных животных после наркотизации. Результаты указывают на возможность применения анализа структур твёрдой фазы СК при ретроспективной оценке динамики МК, глубины наркотизации и побочных эффектов, вызываемых различными наркотизирующими средствами у пациентов с последующим использованием этих данных для выбора вида и оптимальной дозы наркотизирующего вещества при предстоящих хирургических вмешательствах. Background. An important pathogenetic step in the development of anesthesia complications is a breathing disorder in the form of apnea, which may transform into agony. However, there are no reports of cerebral blood flow (CBF) during the period of agony. Despite numerous animal studies showing that general anesthesia leads to neurodegeneration and cognitive impairment, there is still no clear consensus on effects of anesthetics in humans. Aim of the study. To identify markers of anesthesia stages in experimental animals by structures of blood serum (BS) solid phase and by indexes of CBF. Materials and methods. The study was carried out on sexually mature outbred male rats. The animals were anesthetized with chloral hydrate: control groups received a chloral hydrate dose of 400 mg/kg, i.p., and experimental groups received 500-600 mg/kg, i.p. Blood pressure (BP), CBF, respiratory rate and heart rate were recorded during different phases of anesthesia. CBF was recorded with a LAKK-02 device (LAZMA); BP was measured with a MEC8 Mindray monitor. BS solid phase structures were studied using the method of marginal dehydration on test cards of the “Litos-system” diagnostic kit. BS structures were examined under a microscope in polarized light at a magnification of ×200 and ×400 (DM2500 microscope, Leica). Results. In the control groups, indexes of CBF, respiratory rate, and heart rate did not significantly differ. In the experimental groups, one hour following administration of the increased anesthetic dose, the heart rate, respiratory rate, and BP were decreased (p < 0.05). Immediately after the onset of apnea, the drop in blood pressure was followed by a rapid decline in CBF. The heart rate amplitude in the spectrum of CBF oscillations was increased three times compared to the control. The time from the apnea onset to zero CBF ranged from 60 to 240 s. Before the drug administration, the BS structures represented spherulites and fan-shaped formations characteristic of the physiological state of the body. During the apnea stage, BS spherulites and fan-shaped structures were dotted with many small isotropic inclusions, and also had single small and extensive isotropic faults. During the agonal stage, most of the BS structural formations represented fragments of spherulites with numerous stripes and branched formations with high anisotropy and multiple faults with corroded boundaries. Conclusion. The changes in morpho-functional indexes under the action of anesthetics are determined by structural rearrangement of protein molecules as visualized during the BS transformation into the solid phase. The features of BS solid phase pathological structures indicate the anesthesia depth. These changes are consistent with changes in cardiovascular and respiratory parameters in anesthetized animals. The results indicate a possibility of using the analysis of the BS solid phase structures for a retrospective assessment of changes in CBF, the depth of anesthesia, and side effects caused by various anesthetics in patients. Subsequently, these data may be used for selecting the anesthetic type and its optimum dose for upcoming surgical interventions.

Lipid Emulsion And Isoflurane: The Quality Assessment of Anesthesia Parameters In Pigeons

An objective was to evaluate the efficacy of intravenous (IV) emulsified isoflurane formulation for maintenance of general anesthesia and to compare with IV lipid emulsion infusion with inhalation isoflurane in pigeons. The animals was total of 21 healthy, mature pigeons (Columba livia domestica), weighing 318 ± 13 g. Pigeons were anesthetized by emulsified isoflurane (treatment IΙΙ), inhalation isoflurane with IV lipid emulsion (treatment ΙΙ ), and inhalation isoflurane (treatment Ι) alone. Over 50 minutes, wing tone, toe pinch (pedal), and feather pluck reflex were tested every 10 minutes. Data was recorded at 10, 20 and 30 minutes for temperature (T), peripheral hemoglobin oxygen saturation (SpO2) heart rate (HR), and respiratory rate (fR). A scoring system was used to assess parameters related to anesthesia duration and depth. There were no significant differences in hemodynamic variables between the treatment Ι and treatments ΙΙ and IΙΙ, in treatments associated with fat emulsion have shown faster induction, longer anesthesia, more immobilization, and longer recovery time. Furthermore, in anesthesia depth percentages evaluation it was observed that emulsified isoflurane entered the anesthesia deep stage earlier and was removed immediately after discontinuation of administration.Administration of 8% v/v emulsified isoflurane IV was effective in anesthesia rapid induction, stability in depth of anesthesia, rapid withdrawal from anesthesia depth by discontinuation of the infusion, delayed recovery, cardiorespiratory and (T) stability.

Poincaré Plot Area of Gamma-Band EEG as a Measure of Emergence From Inhalational General Anesthesia

The Poincaré plot obtained from electroencephalography (EEG) has been used to evaluate the depth of anesthesia. A standalone EEG Analyzer application was developed; raw EEG signals obtained from a bispectral index (BIS) monitor were analyzed using an on-line monitoring system. Correlations between Poincaré plot parameters and other measurements associated with anesthesia depth were evaluated during emergence from inhalational general anesthesia. Of the participants, 20 were adults anesthetized with sevoflurane (adult_SEV), 20 were adults anesthetized with desflurane (adult_DES), and 20 were pediatric patients anesthetized with sevoflurane (ped_SEV). EEG signals were preprocessed through six bandpass digital filters (f0: 0.5–47 Hz, f1: 0.5–8 Hz, f2: 8–13 Hz, f3: 13–20 Hz, f4: 20–30 Hz, and f5: 30–47 Hz). The Poincaré plot-area ratio (PPAR = PPA_fx/PPA_f0, fx = f1∼f5) was analyzed at five frequency ranges. Regardless of the inhalational anesthetic used, there were strong linear correlations between the logarithm of PPAR at f5 and BIS (R2 = 0.67, 0.79, and 0.71, in the adult_SEV, adult_DES, and ped_SEV groups, respectively). As an additional observation, a part of EMG activity at the gamma range of 30–47 Hz probably influenced the calculations of BIS and PPAR_f5 with a non-negligible level. The logarithm of PPAR in the gamma band was most sensitive to state changes during the emergence process and could provide a new non-proprietary parameter that correlates with changes in BIS during measurement of anesthesia depth.