Bispectral Values Research Articles

Doppler transcraneal, BIS y entropía como medición indirecta del flujo cerebral durante la anestesia inhalatoria en pacientes pediátricos

Transcranial Doppler ultrasound is a noninvasive technique for monitoring the velocity of blood flow in the main intracranial arteries, particularly those in the circle of Willis. Our aim was to assess whether changes in cerebral arterial blood flow in pediatric patients under sevoflurane anesthesia demonstrated by pulsed Doppler ultrasound correlate with changes in the bispectral (BIS) index and electroencephalographic state and response entropy (ES and ER, respectively). Prospective, blinded observational study of 36 pediatric patients (age range, 5 to 11 years; ASA physical status classification, 1-2) under sevoflurane anesthesia for minor surgical procedures. Anesthesia was induced with sevoflurane and maintained with 2.5% sevoflurane in an inspired oxygen fraction of 50% in air. A continuous perfusion of remifentanil was provided for analgesia. In all patients we monitored hemodynamic and respiratory patterns, gases, temperature, and hypnosis (BIS, ES and ER) as well as cerebral blood flow estimated by pulsed Doppler ultrasound in the middle cerebral artery. The resistance index, pulsatility index, mean velocity, and estimated baseline cerebral blood flow were calculated from the Doppler sonogram. Correlations (Pearson's r) were calculated between BIS, ES, ER, the pulsatility index, resistance index, mean flow velocity, estimated cerebral blood flow, fraction of end-tidal carbon dioxide, and temperature. A regression model was constructed. Induction caused a pattern of high velocity (elevated mean velocity and normal or reduced pulsatility index) until the lowest BIS and ES values of 31 and 29, respectively, were reached. During maintenance, the Doppler sonogram pattern was slower (normalization of the pulsatility index, the resistance index, and mean velocity). Changes in flow and absolute entropy and BIS values were statistically correlated (Pearson's r values > or = 0.91); there was 95.6% agreement between Doppler values and BIS and agreement between BIS and ES values of 35 to 45. On awakening, flow velocities approached baseline values when BIS and ES rose to between 90 and 98. The estimated cerebral blood flow underwent fluctuations coinciding with an approximately concomitant increase or decrease in BIS (r > 0.95); the BIS response occurred with a slight delay of no more than a minute. The entropy measurements did not reflect the fluctuations. We show Doppler ultrasound patterns during anesthetic induction with sevoflurane. Systems for monitoring hypnosis could be considered indirect measurements of cerebral blood flow; BIS measurements are more sensitive to change. Transcranial Doppler ultrasound facilitates the observation of changes in blood flow that occur at different levels of hypnosis during anesthesia.

Doppler transcraneal, BIS y entropía como medición indirecta del flujo cerebral durante la anestesia total intravenosa en pacientes pediátricos

Transcranial Doppler ultrasound is a noninvasive technique for monitoring the velocity of blood flow in the main intracranial arteries, particularly those in the circle of Willis. Our aim was to assess whether changes in cerebral arterial blood flow in anesthetized pediatric patients detected by pulsed Doppler ultrasound correlate with changes in the bispectral (BIS) index and electroencephalographic state and response entropy (ES and ER, respectively). Prospective, blinded observational study of 36 pediatric patients (age range, 5 to 11 years) under total intravenous anesthesia for minor surgical procedures. Propofol and fentanyl were used for induction; propofol and remifentanil in continuous perfusion and a single dose of cisatracurium were used for maintenance. In all patients we monitored hemodynamic and respiratory patterns, gases, temperature, and hypnosis (BIS, ES and ER) as well as cerebral blood flow estimated by pulsed Doppler ultrasound in the middle cerebral artery. Raw data were subjected to statistical smoothing. The resistance index, pulsatility index, mean velocity, and estimated baseline cerebral blood flow were calculated from the Doppler sonogram. We then studied the correlations between the Doppler-derived values and BIS, ES, ER, fraction of end-tidal carbon dioxide, and temperature. The variables were entered into logistic regression. The pattern at induction indicated high resistance (low mean velocities and high pulsatility indexes) until the lowest BIS and ES values of 31 and 29, respectively, were reached. During maintenance, the Doppler sonogram pattern was slower (normalization of the pulsatility index, the resistance index, and mean velocity). Changes in flow and absolute entropy and BIS values were statistically correlated (Pearson's r values > or = 0.91); there was 95.6% agreement between Doppler values and BIS and agreement between BIS and ES values of 35-45. On awakening, flow velocities approached baseline values when BIS and ES rose to between 90 and 98. The estimated cerebral blood flow underwent fluctuations coinciding with an approximately concomitant increase or decrease in BIS (r > 0.95); the response of BIS was slightly delayed by no more than a minute but there was no corresponding response of entropy measurements. We report Doppler ultrasound patterns during anesthesia with propofol. Systems for monitoring hypnosis could be considered indirect measurements of cerebral blood flow; BIS measurements are more sensitive to flow change. Transcranial Doppler ultrasound facilitates the observation of changes in blood flow that occur at different levels of hypnosis during anesthesia.

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Bispectral index monitoring is useless during cardiac arrest patients’ resuscitation

Aim It has been suggested that out-of-hospital bispectral (BIS) index monitoring during advanced cardiac life support (ACLS) might provide an indication of cerebral resuscitation. The aims of our study were to establish whether BIS values during ACLS might predict return to spontaneous circulation, and whether BIS values on hospital admission might predict survival. Materials and methods This was a prospective observational study in 92 patients with cardiac arrest who received basic life support from a fire-fighter squad and ACLS on arrival of an emergency medical team on the scene. BIS values, electromyographic activity, and signal quality index were recorded throughout resuscitation and out-of-hospital management. Results Seven patients had recovered spontaneous cardiac activity by the time the medical team arrived on scene. Of the 92 patients, 62 patients died on scene and 30 patients returned to spontaneous cardiac activity and were admitted to hospital. The correlation between BIS values and end-tidal CO 2 during the first minutes of ACLS was poor ( r 2 = 0.02, P = 0.19). Of the 30 admitted patients, 27 died. Three were discharged with no disabilities. There was no significant difference in BIS values on admission between the group of patients who died and the group who survived ( P = 0.78). Conclusions Although BIS monitoring during resuscitation was not difficult, it did not predict return to spontaneous cardiac activity, nor survival after admission to intensive care. Its use to monitor cerebral function during ACLS is therefore pointless.

The Comparability of Bispectral Index and State Entropy Index During Maintenance of Sufentanil-Sevoflurane-Nitrous Oxide Anesthesia

Manufacturers recommend maintaining Bispectral (BIS) or Spectral Entropy (State Entropy, SE) indexes between 40 and 60 during the maintenance of anesthesia. We compared these indexes during this period. Data were obtained from 58 patients receiving sufentanil-sevoflurane-nitrous oxide anesthesia. The anesthesiologist was blinded to BIS and SE. Artifact-free concurrent BIS and SE values (7792 pairs), automatically recorded at 1-min intervals, were compared using Bland-Altman analysis, Kappa coefficient for agreement and crude proportion of agreement. The occurrence of errors of judgment (Type 1 defined as one parameter <40 and the other >60, or Type 2 defined as BIS and SE values on different sides of a threshold [40 or 60]) was also counted. Bias was -2 with limits of agreement of -18 and 9. Kappa BIS/SE obtained from all patients was 0.537 +/- 0.147; crude agreement >0.80 was observed in 45% of patients. Type 1 number of errors of judgment corresponded to two instances. Median and interquartile values of Type 2 number of errors of judgment were 4.5 [3.0-6.0] when considering a difference between BIS and SE more than 5. Although limits of agreement between BIS and SE were large, Kappa value moderate, and crude agreement <0.80 in more than half of the patients, making completely contradictory decisions (e.g., deepening the anesthetic based on one parameter and lightening it based upon the other) would have been exceptional. More common would have been a risk of error between no change versus increasing or decreasing anesthetic depth.

Electroencephalographic Responses to Laserneedle and Punctual Stimulation Quantified by Bispectral (BIS) Monitoring: A Pilot Study to Evaluate Methods and Instrumentation

Laserneedle is a new optical stimulation method. Electrical punctual stimulation (P-Stim) also represents a new stimulation method in body and auricular acupuncture. Whereas laserneedle stimulation has been extensively investigated within scientific literature, only few studies exist in referenced journals regarding P-Stim. Fifteen healthy volunteers (mean age ± SD: 29.1 ± 2.8 years; range: 24 33 years) were examined in a randomized cross-over study using two different acupuncture schemes, including a placebo stimulation. The EEG-bispectral index (BIS), heart rate (HR) and non-invasive measurement of mean arterial pressure (MAP) were evaluated before, during and after stimulation of sedating acupoints and conditions of placebo. During optical (I) and electrical (II) activation significant (p < 0.05; ANOVA, Tukey test) stimulation induced reductions in BIS-values occurred, however, the combination of both methods (III) and placebo stimulation (IV) resulted in insignificant changes of BIS values. HR and MAP did not show any significant changes during all stimulation procedures (I IV). Laserneedleas well as punctual stimulation of sedating acupoints led to significant changes in bioelectric brain activity. However, the response patterns were different and the combination of both methods did not intensify the effects quantified by BIS values. These neuro-modulating effects require further investigation in a larger population sample.

Changes of bispectral index during recovery from general anesthesia with 2% propofol and remifentanil in children

The bispectral (BIS) index is a pharmacodynamic measure of the effect of anesthesia on the central nervous system. The aim of this study was to investigate the relationship between BIS index and predicted plasma concentration of propofol delivered by target controlled infusion (TCI) during emergence in children. With approval of IRB, 30 patients (2-7 years) were included in this study. Anesthesia was with TCI propofol 3-5 microg.ml(-1) and remifentanil 7.5 ng.ml(-1) to maintain BIS 40-60 and the propofol concentration was fixed at 3 microg.ml(-1) Remifentanil infusion was stopped 10 min before the end of surgery. BIS values were recorded after reducing propofol in decrement of 0.2 microg.ml(-1). BIS values were checked when spontaneous respiration occurred and children were able to obey a command (eye opening or hand grasping). Spearman's correlation analysis showed negative correlation between BIS and propofol plasma concentration (r = -0.559, P < 0.001). When respiration returned, mean BIS was 77.2 +/- 5.3 and propofol plasma concentration 1.6 +/- 0.3 microg.ml(-1) and when a verbal command was obeyed, BIS was 82.4 +/- 5.6 and propofol plasma concentration 1.5 +/- 0.3 microg.ml(-1). In preschool children, BIS moderately correlated with the predicted plasma concentration of propofol.

Efficacy of Bispectral Monitoring as an Adjunct to Nurse-Administered Propofol Sedation for Colonoscopy: A Randomized Controlled Trial

Bispectral (BIS) monitoring provides an objective, non-invasive measure of the level of consciousness in sedated patients. BIS has been shown to lag behind the level of sedation during induction and emergence of sedation with propofol. In this study, we sought to determine whether BIS is a useful adjunctive maneuver to registered nurse-administered propofol sedation (NAPS) as measured by reductions in recovery time and doses of propofol administered. A randomized controlled trial of 102 outpatients presenting for colonoscopy was performed. BIS values were recorded continuously in all subjects. Patients were randomized to receive NAPS with BIS visible to nurse and endoscopist versus BIS invisible to nurse and endoscopist. In phase 1 (47 patients), the nurse and endoscopist team were instructed to consider BIS (when visible) as only adjunctive information with regard to titrating sedation. In phase 2 (55 patients), the nurse endoscopist team was instructed to use BIS as the primary endpoint for titration of sedation, and to target BIS to greater than 60 (60-70 is deep sedation). In phase 1, the mean (SD) BIS value from scope-in (SI) to scope-out (SO) for BIS was 59.3 (9.9) and was not different from controls at 59.9 (10.1; p= 0.82). The mean (SD) propofol dose (mg/min) was 15.8 (5.6) and 17.2 (6.2) for BIS and controls, respectively (p= 0.45). The mean (SD) recovery time with BIS visible in phase 1 was 20.6 min (5.5) versus 19.2 min (4.5) in controls (p= 0.34). In phase 2, the mean (SD) BIS from SI to SO in those randomized to have BIS visible was 64.1 (5.4) versus 63.1 (8.5) in controls (p= 0.58). The mean (SD) dose of propofol (mg/min) was 16.1 (11.2) and 16.4 (12.3) for BIS and control groups, respectively (p= 0.92). The mean (SD) recovery time in phase 2 with BIS visible was 18.7 (3.5) versus 20.1 (5.6) in controls (p= 0.27). BIS did not lead to reductions in mean propofol dose or recovery time when used as an adjunct to NAPS for colonoscopy, or when used as the primary target for sedation. No clinically important role for BIS monitoring as an adjunct to NAPS has yet been established.

Conscious sedation of children with propofol is anything but conscious.

To determine the depth of sedation required for bone marrow aspiration and intrathecal injection of chemotherapeutic agents in children using a bispectral (BIS) index monitor and clinical assessment by an independent observer. Sixteen children who were undergoing 19 intrathecal chemotherapy and bone marrow aspirations were enrolled in the study. Their ages ranged from 23 months to 190 months with a mean of 79 months. The BIS index was recorded every 5 minutes by an independent observer. The patients received only intravenous propofol for sedation. There were no complications during the procedures. The mean BIS score was 62.8+/- 9.6. The mean low BIS score was 29.7 +/- 13.7, indicating a level of deep sedation and/or general anesthesia was necessary to induce the desired stated of consciousness that would permit the practitioner to perform the procedure. The average dose of propofol was 166 +/- 47 microg/kg/min. Mean Aldrete score for level of consciousness was 0.9 +/- 0.4, indicating a depressed level of consciousness. The mean activity level was 1.0+/- 0.4, indicating impaired movement. Children who undergo conscious sedation with propofol for intrathecal chemotherapy and bone marrow aspiration demonstrate BIS values and clinical assessments consistent with deep sedation. Because of an increased risk of adverse events when children undergo deep sedation, appropriate parental informed consent, age-appropriate resuscitative equipment, and skilled anesthesia personnel should be present for rescue in the event of cardiovascular and respiratory complications from deep sedation.

Does bispectral analysis of the electroencephalogram add anything but complexity?

Analysis of the bispectrum of EEG waveforms is a component of the proprietary BIS index-a commonly used commercial monitor of depth of anaesthesia. Does the use of the bispectrum give more information about depth of anaesthesia than the power spectrum? We collected and analysed EEG waveforms during induction of general anaesthesia in 39 patients, comparing the changes in bispectral parameter (SynchFastSlow), with an analogous power spectrum-based parameter (PowerFastSlow). Both compare the logarithmic ratio of high frequency components (40-47 Hz) with the total (1-47 Hz). Because the changes in bispectrum are affected by signal amplitude, we also calculated a third parameter (SFSbicoh) from the bicoherence, which is an amplitude-independent statistic. The SynchFastSlow and PowerFastSlow were correlated (r=0.84) and neither was superior in predicting the awake or anaesthetized state (area under receiver operating characteristic curves = 0.85 vs 0.93). There was no change in the SFSbicoh over the induction period, and it did not correlate with SynchFastSlow (r=0.07). We could not show that bispectral analysis gave more information than power spectral-based analysis. Most of the changes in the bispectral values result from decreases in the relative high frequency content of the EEG caused by anaesthesia.

The use of bispectral analysis in patients undergoing intravenous sedation for third molar extractions

Purpose:The bispectral (BIS) index has been used to interpret electroencephalogram (EEG) recordings to predict the level of sedation and loss of consciousness in patients undergoing general anesthesia. It was the purpose of this project to assess the usefulness of BIS technology in determining the level of sedation in patients undergoing third molar extraction under conscious sedation. Patients and Methods: Twenty-five subjects undergoing third molar extraction in an outpatient setting were analyzed. The EEG activity was recorded continually during surgery using a microcomputer (Aspect-1050 Monitor; Aspect Co, Natick, MA) with real-time bispectral data obtained by EEG skin electrodes through a frontotemporal montage. The Observer's Assessment of Alertness and Sedation (OAA/S) scale was used to subjectively assess the level of sedation observed by the anesthetist before initiating the sedation procedure and then at 5-minute intervals until the end of the procedure. The BIS level was simultaneously recorded. The initial sedation was accomplished using a standard dose of midazolam (0.05 mg/kg) and fentanyl (1. 5 μg/kg) followed by a 10- to 30-mg bolus of propofol until a level of sedation at which the patient's eyes were closed and he or she was responsive only to vigorous stimulation or repeated loud calling of their name (OAA/S level of 1 to 2). Local anesthesia was then administered. Additional doses of sedative medication (midazolam or propofol) were given during the procedure to maintain the desired level of sedation (an OAA/S level of 2 to 3). The time and dose of the drug given were recorded. The level of sedation based on a single anesthetist's interpretation (OAA/S) and the BIS readings were then compared. Results:A strong positive relationship between the BIS index and OAA/S readings was found ( P < .0001). Pairwise comparisons of mean BIS index and its corresponding OAA/S level were significantly different from each other ( P < .003) except for OAA/S levels 2 and 3 ( P = .367). Conclusion:BIS technology offers an objective, ordinal means of assessing the depth of sedation. There was a strong relationship between the objective BIS values and subjective assessment (OAA/S scale) of the depth of anesthesia. This can be invaluable in providing an objective assessment of sedation in oral and maxillofacial surgery where it may be difficult to determine the level of sedation clinically.

THE BISPECTRAL INDEX AS A PREDICTOR OF OUTCOME AFTER HEAD INJURY

S56 The bispectral (BIS) index, a parameter derived from the electroencephalogram, has been recently reported as a quantifiable measure of the depth of sedation and the degree of awareness during and after general anesthesia [1,2]. The purposes of this study were (1), to compare BIS to Glasgow Coma Scale score (GCS) in prediction of outcome after head injury, and (2), to study the relation between BIS and GCS during follow up of these patients. METHODS: After institutional approval, we studied 25 patients ages 18-75 (av. 36) y. Head injury was severe (initial GCS <or=to 8 in 18 patients, and moderate (initial GCS 9-12) in 7 patients. Daily assessment included GCS and BIS evaluation during the first week postinjury. Cerebral perfusion pressure (CPP) was continuously monitored (CPP = mean blood pressure-intracranial pressure). Glasgow outcome scale (GOS) was used to assess outcome at discharge. GOS scores were compared to average BIS [obtained from area under the curve for BIS x time/total time] for 7 days postinjury, and av. GCS for 7 days postinjury. Daily BIS values were also compared to simultaneously recorded GCS & CPP values. Data were analyzed by Spearman rank correlation analysis; GOS was ranked as 1 to 5 for good recovery (GR), moderate disability (MD), severe disability (SD), persistent vegetative state (PVS), and death, respectively. RESULTS: There were strong correlations between GOS and both av. BIS and av. GCS for the first week postinjury (Figure 1 and Figure 2). An av. BIS >or=to 60 was associated with good outcome, whereas, an av. BIS <or=to 40 was associated with poor outcome. Also, BIS correlated with simultaneous GCS evaluation but not with simultaneous CPP values (Table 1).Figure 1Figure 2Table 1CONCLUSION: Our data suggest that both av. BIS and av. GCS over the first week postinjury appear to be good predictors of outcome after head trauma. However, BIS does not replace CPP for monitoring patients with brain injury.

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.

FFT-based bispectrum computation on polar rasters

The objective is to introduce fast-Fourier-transform based algorithms for the computation of the bispectrum of deterministic real signals on polar rasters, in the triangular region that corresponds to angle 0 degrees < theta <45 degrees . This region is enough for a completed description of the bispectrum. These algorithms compute the bispectral values by employing the time-domain signal directly. Three different algorithms are described and compared: the direct approach, the zero-padding approach, and the super-FET approach. A generalization of these three algorithms for efficient computation of the trispectrum is also given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Syndrome of intermittent insufficiency of the basilar arterial system.

<h3>Background and Objectives</h3> The impact of anesthesia techniques in patients experiencing hip fracture is controversial. This study compares the effects on blood pressure of 3 anesthesia techniques that are considered safe for the elderly. <h3>Methods</h3> Forty-five patients older than 75 years, with American Society of Anesthesiologists physical status III or IV, with cardiac comorbidities, and undergoing surgery for hip fracture, were randomized to receive continuous spinal anesthesia (CSA), propofol target-controlled infusion (TCI), or sevoflurane (SEVO). In CSA patients, a T10 metameric level target was achieved by titration of 2.5 mg of bupivacaine boluses. In patients on TCI and SEVO, a bispectral value target of around 50 guided the concentration of propofol or sevoflurane. Analgesia in the TCI and SEVO groups was provided with remifentanil. Hypotension was defined as a 30% decrease in mean arterial pressure and was treated with an intravenous bolus of ephedrine. <h3>Results</h3> The number of hypotension episodes was lower in the CSA group: 0 (range, 0–6) versus 11.5 (range, 1–25) in the TCI group and 10 (range, 1–23) in the SEVO group (<i>P</i> &lt; 0.001). Both TCI and SEVO patients needed more ephedrine compared with CSA patients (30.5 [15.5], 26 [23], and 1.5 [2.5] mg, respectively, <i>P</i> &lt; 0.001). The maximal decrease in mean arterial pressure was lower in the CSA group (26% [17%]) compared with that in the TCI group (47% [8%]) and the SEVO group (46% [12%]; <i>P</i> &lt; 0.001). <h3>Conclusions</h3> In elderly patients, spinal anesthesia using titrated doses of bupivacaine provided better blood pressure stability than propofol or sevoflurane anesthesia.