Spectral Edge Frequency Values Research Articles

P 11. Intraoperative EEG parameters associated with the Frailty-Syndrome

Background. Frailty is a multidimensional geriatric syndrome characterized by a decline across multiple physiological systems [1]. It is accompanied by an increased vulnerability to stressors and is associated with adverse postoperative outcomes [2]. Frailty is linked to poor cognitive function and dementia, as well as structural changes of the brain [3,4]. However, it has not been investigated whether frail patients present with alterations in the electroencephalogram (EEG). We compared pre- and intraoperative EEG parameters in frail and non-frail patients. Methods. Patients aged ≥65 years undergoing elective surgery were included in this prospective observational study (NCT02265263; EA2/092/14). Frailty was assessed one day before surgery using a modified version of the Fried frailty phenotype comprising five criteria: slowness, weakness, exhaustion, weight loss and a level of low activity. Continuous frontal EEGs were recorded and analysed during 2 min periods before induction of anesthesia (preoperative) and during a stable intraoperative period (intraoperative). Only patients who received propofol for induction and volatile anesthetics for maintenance of anesthesia were included in the analyses. We compared the power spectrum within different frequency bands (δ: 1.5-4Hz, θ: 4-8Hz, α: 8-12Hz; β: 12-30Hz), as well as the spectral edge frequency (SEF) of frail and non-frail patients. Results. Of the 112 patients included in this study 14 (12,5%) were frail. No significant difference in power or SEF was found during the preoperative EEG measurements between the two groups. In the intraoperative EEG, frail patients presented with significantly lower a-power compared to non-frail patients (a-power: non-frail −3.67 [−7.77; −1.08] dB vs frail −8.71 [-13.75; −7.11] dB, p = 0.006). Moreover, intraoperative SEF values were significantly lower in frail patients (SEF: frail 10.71 [7.96; 11.34] Hz vs non-frail 13.70 [11.36; 15.62] Hz, p=0,001). In a multiple linear regression model adjusting for age, sex, ASA score, GDS Score, dose of anesthetics and cognitive abilities, frailty remained significantly associated with lower SEF values ( p = 0,011). Conclusion. Preoperative frailty was associated with lower intraoperative a-power, as well as lower SEF values. This should be taken into consideration when interpreting intraoperative EEGs of elderly patients.

English

Introduction Fifty-two American Society of Anesthesiologists II-III patients undergoing elective coronary artery bypass surgery were included in the study. Materials and methods We examined haemodynamic and cerebral responses to induction and intubation in cardiac surgery using different doses of an opioid. Before induction, T1 values of systolic arterial pressure, mean arterial pressure, diastolic arterial pressure, heart rate, saturation, bispectral index, latencies of auditory evoked potential waves (V. wave, Na wave, Pa wave and Nb wave) and spectral edge frequency values were measured. The patients were divided into four groups, each comprising 13 individuals. During induction, the patients were administered opioids as follows: Group 1: propofol 2.5 mg/kg + rocuronium 0.7 mg/kg Group 2: propofol 2.5 mg/kg + rocuronium 0.7 mg/kg + fentanyl 3 mcg/kg Group 3: propofol 2.5 mg/kg + rocuronium 0.7 mg/kg + fentanyl 6 mcg/kg Group 4: propofol 2.5 mg/kg + rocuronium 0.7 mg/kg + fentanyl 9 mcg/kg Above-mentioned parameters were repeated in the first minute of induction (T2). Intubation was performed in the third minute of induction, then the measurements were repeated (T3). Results Demographics were similar among all four groups. According to the systolic arterial pressure, mean arterial pressure, diastolic arterial pressure and heart rate values, a significant increase was found in group 1 compared to group 4 at T3. There was also a significant difference between group 1 and group 3 in mean arterial pressure and heart rate measures. No significant difference was found between the groups in terms of bispectral index. There was also no significant difference between the groups in terms of spectral edge frequency1-2. Auditory evoked potential wave latencies (V. wave, Na wave, Pa wave, Nb wave) were found to be different between the time intervals. Wave latencies were increased at T2 compared to T1 and decreased at T3 compared to T2 in all the groups. The statistically significant difference was found between fentanyl 0 group and fentanyl 9 mcg/kg group in terms of Nb wave latency values. Conclusion Auditory evoked potential is found to be more reliable than bispectral index and electroencephalogram with regards to the responses to induction and intubation using fentanyl. We also observed that Nb wave latency response is the most significant latency of auditory evoked potential waves. Introduction Recently, various techniques and tools have been introduced in order to be aware of the adverse haemodynamic effects that may arise due to insufficient or overdose of anaesthetic agents and also to avoid economic losses1. Electroencephalogram (EEG), bispectral index (BIS) analysis and auditory evoked potentials (AEPs) are the monitorisation methods developed to determine the intraoperative anaesthetic depth. In this study, haemodynamic and cerebral effects during induction and intubation were evaluated using BIS, AEP and EEG in patients who are undergoing coronary artery bypass surgery. Materials and methods This work conforms to the values laid down in the Declaration of Helsinki (1964). The protocol of this study has been approved by the relevant ethical committee related to our institution in which it was performed. All subjects gave full informed consent to participate in this study. After local ethic committee approval, 52 patients aged > 18 years, American Society of Anesthesiologists (ASA) II-III, undergoing elective coronary artery bypass surgery were included in the study. Exclusion criteria were as follows: ejection fraction (EF) 2 mg/dL, aspartate aminotransferase > 40 U/L, alanine aminotransferase > 40 U/L, hematocrit < 30%), opioid and propofol * Corresponding author Email: drozkanonal@selcuk.edu.tr 1 TurkiyeYuksekIhtisas Education and Research Hospital, Anesthesia Clinic, Ankara, Turkey 2 Medical Faculty, Anesthesia and Reanimation Department, Selcuk University, Konya, Turkey

The Study of Muscle Fatigue and Risks of Musculoskeletal System Disorders from Text Inputting on a Smartphone

Objective: This study aims to analyze and evaluate fatigue in upper trapezius muscles of adults when inputting text on a smart phone, thereby examining the risk of cumulative trauma disorders in the musculoskeletal system of the upper extremity. Method: Forty-five healthy adults were divided equally into three groups: a smartphone group, a notebook group, and a desktop group. A surface electromyogram was placed on the upper trapezius muscle of each participant, after which they inputted text for ten minutes within an ergonomic setting; their side posture was recorded on video and analyzed. Results: The spectral edge frequency values for the smartphone group, as recorded from the upper right trapezius muscles on the surface electromyogram, showed a significant decrease(p<.05). Regarding the RULA, all three groups had results indicating

On-Pump Beating Heart Versus Hypothermic Arrested Heart Valve Replacement Surgery

Comparison of neurological parameters in patients undergoing prosthetic heart valve replacement with two operating techniques-either cardioplegic arrest of the heart under hypothermic cardiopulmonary bypass (CPB) or the heart beating on normothermic bypass, with or without cross-clamping the aorta, without cardioplegic arrest. methods: Fifty valvular surgery patients were randomly assigned into three groups. Sixteen patients underwent beating heart valve replacement with normothermic bypass without cross-clamping the aorta, 17 patients underwent the same procedure with cross-clamping the aorta and retrograde coronary sinus perfusion, and the remaining 17 patients had conventional surgery with hypothermic bypass and cardioplegic arrest. Two-channel electroencephalography (EEG) was recorded to assess changes in cerebral cortical synaptic activity and 95% spectral edge frequency values were recorded continuously. Bispectral monitoring was used to measure the depth of anesthesia. Blood flow rates in middle cerebral artery (MCA) were measured by transcranial Doppler (TCD). Reduction in spectral edge frequency (>50%) or bispectral index (BIS) (<20) or transcranial Doppler flow velocity (>50%) was detected in four patients in Group 1, five patients in Group 2, and three patients in Group 3. BIS or EEG values never reached zero, which indicates isoelectric silence during surgery. Gross neurological examinations were normal in all patients postoperatively. There is no difference regarding neurological monitoring results between on-pump beating heart and hypothermic arrested heart valve replacement surgery. Also no significant difference was encountered among the groups regarding the clinical outcomes.

Power spectral analysis of two-channel EEG in hypoxic–ischaemic encephalopathy

Aims Power spectral analysis combined with a two-channel EEG system may be useful in management of newborn term infants at risk of hypoxic–ischaemic encephalopathy (HIE). This pilot study aimed to determine differences in the EEG power spectrum between normal term infants, infants who were at risk of but had not developed HIE, and infants who had developed HIE. Design Observational. Methods EEG recordings from normal term newborn infants and term infants at risk of HIE were analyzed using fast Fourier transforms. EEG total power (TP), TP variance, TP coefficient of variation (TP CV) and spectral edge frequency (SEF) were compared between three groups: control infants ( n = 15); at-risk infants who had not developed clinically diagnosed HIE ( n = 4); and at-risk infants who had developed HIE ( n = 7). Results Total power was similar in all groups. Variation of TP (variance and CV) was higher ( p < 0.05) in control infants than in infants at risk of HIE, regardless of whether they had developed HIE. SEF values were similar across all three groups. Conclusion Reduced variation of EEG power is a feature of infants at risk of HIE.

Specific Problems in Interpretation of Absolute Values of Spectral Edge Frequency (SEF) in comparison to Bispectral Index (BIS) for Assessing Depth of Anesthesia

The spectral edge frequency (SEF) is a milestone in the computer-assisted EEG analysis for assessing the depth of anesthesia. The SEF as well as the bispectral index (BIS) are numerical descriptors of the EEG. For both, SEF and BIS, limits have been reported within which recall and hemodynamic or motor responses to surgical stimuli are unlikely. We studied the SEF at four different states of anesthesia based on individual observations. Further, we compared the SEF and BIS values in relation to the proposed limits at different endtidal concentrations of sevoflurane (1.2 and 2.4 Vol%et) and desflurane (3.0 and 6.0 Vol%et). The SEF and BIS values were assessed according to the proposed limits for SEF (13.65 and 12 Hz) and BIS (60). We found a high interindividual variability and low intrapersonal stability of the SEF values in the awake state. These findings impair the discrimination of awake and sleep state. The mean SEF was outside the target range at both endtidal concentrations of sevoflurane and desflurane. In contrast, mean BIS values at all measuring phases during anesthesia met the goal of < 60. The increased concentrations of anesthetics are not reflected adequately in the phases of excitation and burst suppression activity. Summarizing, a suitable, statistically calculated approximate target limit of SEF as a tool to guide the depth of anesthesia does not seem to be available at the present time.

Effects of acupressure, manual acupuncture and Laserneedle® acupuncture on EEG bispectral index and spectral edge frequency in healthy volunteers

Background and objective: The main purpose of this study was to investigate the effects of sensory (acupressure and acupuncture) and optical stimulation (Laserneedle® acupuncture) on electroencephalographic bispectral index, spectral edge frequency and a verbal sedation score. Methods: Twenty-five healthy volunteers (mean age ± SD: 25.5 ± 4.0 yr) were investigated during the awake state. The acupuncture point Yintang and a placebo control point were stimulated. The study was performed as a randomized, controlled and partly blinded cross-over trial. Results: Bispectral index and spectral edge frequency values both decreased significantly (P < 0.001) during acupressure on Yintang to values of 62.9 (minimum 35) ± 13.9 bispectral index and to 13.3 (minimum 2.9) ± 8.1 Hz (spectral edge frequency right) and 13.8 (minimum 2.7) ± 7.3 Hz (spectral edge frequency left), respectively. Bispectral index was also significantly (P < 0.05) affected by Laserneedle® acupuncture and acupressure on the control point but the changes were not clinically relevant, 95.4 ± 4 and 94.2 ± 4.8, respectively. All interventions significantly (Yintang: P < 0.001; control point: P < 0.012) reduced verbal sedation score. Conclusions: The study highlights the electroencephalographic similarities of acupressure induced sedation and general anaesthesia as assessed by bispectral index and spectral edge frequency.

Bispectral index values and spectral edge frequency at different stages of physiologic sleep.

Bispectral index (BIS) and spectral edge frequency (SEF) are used as measures of depth of anesthesia and sedation. We tested whether these signals could predict physiologic sleep stages, by taking processed electroencephalogram measurements and recording full polysomnography through a night's sleep in 10 subjects being investigated for mild sleep apnea/hypopnea syndrome. Computerized polysomnograph signals were analyzed manually according to standard criteria, classifying each 30-s epoch as a specific sleep stage. The BIS and SEF values were taken at the end of each period of sleep when the same stage had lasted for at least 2 min. Before sleep, median values for BIS were 97 +/- 12.1 and for SEF 23 +/- 4.2 Hz. After sleep initiation, the median BIS values for arousal, light, slow wave, and rapid eye movement sleep were 67 +/- 20.2, 50 +/- 16.5, 42 +/- 11.2, and 48 +/- 7.1, respectively, and the median SEF values were 20 +/- 4.7, 15 +/- 3.6, 10 +/- 2.6, and 19 +/- 4.1 Hz, respectively. Although both BIS and SEF decreased with increasing sleep depth, the distribution of values at each sleep depth was considerable, with overlap between each sleep stage. Neither BIS nor SEF reliably indicated conventionally determined sleep stages. In addition, the response of the BIS was slow and patients could arouse with low BIS values, which then took some time to increase. Although computer processing of the electroencephalogram can provide an adequate index of depth of anesthesia, the same processing cannot reliably convey depth of natural sleep. At each sleep stage, the output signal has a wide range of possible values.

The effects of nitrous oxide and ketamine on the bispectral index and 95% spectral edge frequency during propofol–fentanyl anaesthesia

In this study, we have sought to establish whether N2O and ketamine alter the bispectral index during propofol-fentanyl anaesthesia. Fourteen surgical patients were randomly assigned to one of two groups: the N2O group (n = 7) and the ketamine group (n = 7). In both groups, anaesthesia was induced with propofol 1.5-2 mg kg-1 and fentanyl 2 micrograms kg-1 and maintained with propofol 5-7 mg kg-1 hr-1 to target the bispectral index between 40 and 50. After the bispectral index value had stabilized the propofol infusion rate was fixed. In the N2O group, the following concentrations of N2O were subsequently inhaled at 20-min intervals; 20, 40, 60 and 70%, and then N2O was terminated. In the ketamine group, ketamine (0.4 mg kg-1 + 1.0 mg kg-1h-1) was given. The bispectral index and 95% spectral edge frequency were recorded 20 min after each change in concentration of N2O or ketamine infusion. The bispectral index and 95% spectral edge frequency did not change significantly in the N2O group, but increased significantly from 44.1 +/- 0.7 and 16.0 +/- 0.5 to 58.6 +/- 1.4 and 19.5 +/- 0.3 (P < 0.01), respectively, in the ketamine group. Additional N2O or ketamine did not decrease the bispectral index and 95% spectral edge frequency values. The depth of sedation should be assessed carefully using a bispectral index monitor when these anaesthetic agents are used together.

Movement response to skin incision: analgesia vs. bispectral index and 95% spectral edge frequency

We studied the movement response to skin incision in 68 adult (males/females) ASA I-II patients receiving propofol ± fentanyl intravenous anaesthesia using the bispectral index and 95% spectral edge frequency monitoring with an A-1050 EEG monitor. Following Ethics Committee approval, patients were randomly assigned to one of the following four treatments: Group P (n=17): propofol infusion, 1 mg kg−1 min−1 intravenous for 2 min, followed by propofol infusion, 200 μg kg−1 min−1, until skin incision; Group PF1 (n=17): fentanyl bolus, 1 μg kg−1 intravenous + propofol infusion as in Group P; Group PF2 (n=17): fentanyl bolus, 2 μg kg−1 intravenous + propofol infusion as in Group P; and Group PF3 (n=17): fentanyl bolus, 3 μg kg−1 intravenous + propofol infusion as in Group P. The bispectral index and 95% spectral edge frequency were monitored continuously and recorded prior to induction of anaesthesia (base-line) and at skin incision. Twelve, 10, 4 and 4 patients responded to skin incision in Groups P, PF1, PF2 and PF3, respectively (P and PF1 vs. PF2 or PF3; P=0.0001, and 0.006). The bispectral index and 95% spectral edge frequency were significantly lower at skin incision compared with the base-line values in all the four treatment groups. However, only bispectral index values were significantly lower in the nonmovement as compared with the movement (M) category (32.6 ± 8.9 vs. 37.4 ± 10.3; P=0.04). Though deeper levels of hypnosis to lower bispectral index and 95% spectral edge frequency values may be effective in preventing the movement response to skin incision, provision of adequate analgesia rather than lower bispectral index and 95% spectral edge frequency (clinical maintenance) values may be more reliable for preventing the response to skin incision as bispectral index and 95% spectral edge frequency measure the hypnotic component of the anaesthetic effect. Lower bispectral index values may be more discriminatory as compared with 95% spectral edge frequency values for preventing the movement response to skin-incision.

Electroencephalographic bispectral index correlates with intraoperative recall and depth of propofol-induced sedation.

The bispectral (BIS) index and 95% spectral edge frequency (SEF) of the electroencephalograph (EEG) have been used to study the anesthetic and sedative effects of intravenously (i.v.) administered drugs. This prospective study was designed to evaluate the effectiveness of the BIS index and 95% SEF for assessing the level of propofol-induced sedation and amnesia during regional anesthesia. Ten consenting adult patients undergoing surgery with regional anesthesia were administered propofol in increments of 10-20 mg i.v., every 5-10 min until they became unresponsive to tactile stimulation (i.e., mild prodding or shaking). The BIS index and 95% SEF were continuously recorded from a bifrontal montage (Fp1-Cz and Fp2-Cz) using the Aspect B500 monitor. The depth of sedation was assessed clinically at 5- to 10-min intervals using the observer's assessment of alertness/sedation (OAA/S) scale, with 1 = no response to tactile stimulation to 5 = wide awake. Each patient was shown a picture of an animal (cat) prior to administration of an initial dose of propofol, 40 mg i.v.. Subsequently, patients were administered intermittent bolus doses of propofol, 10-20 mg i.v., and shown different pictures upon achieving OAA/S scores of 4, 3, and 2 during the onset of and recovery from propofol-induced sedation. Picture recall was tested upon arrival of the patient in the postanesthesia care unit (PACU). Of the two EEG variables studied, the BIS index exhibited a better correlation with the OAA/S scores during both the onset (Spearman's rho = 0.744) and recovery (Spearman's rho = 0.705) phases of propofol-induced sedation. With the increasing depth of sedation, there was a progressive decrease in the BIS index (OAA/S score of 5, BIS = 94.5 +/- 2.9; 4, 93.3 +/- 3.3; 3, 89 +/- 6.1; 2, 80.1 +/- 8.7; 1, 75.6 +/- 7.5; mean +/- SD). Conversely, there was a progressive increase in the BIS value during recovery from propofol sedation (OAA/S score of 1, BIS = 75.6 +/- 7.5; 2, 82.4 +/- 10.5; 3, 84.9 +/- 5.9; 4, 93.8 +/- 0.8). Although the changes in the 95% SEF values were less consistent during the onset phase, this EEG variable increased from 16.4 +/- 5.0 to 19.3 +/- 5.6 as the OAA/S score increased from 1 to 4 during the recovery phase. Patient recall of the intraoperative pictures decreased with increasing depth of sedation and decreasing BIS values (OAA/S:% BIS:% recall = 5:94.5 +/- 2.9:100%; 4:93.4 +/- 3:63%; 3:87.3 +/- 6.1:40%; 2:80.8 +/- 8.3:0%; 1:75.6 +/- 7.5:0%). The BIS index appears to be a useful variable for assessing the depth of propofol-induced sedation. Increasing depth of sedation was associated with a significant decrease in intraoperative picture recall.