BIS and Entropy in the elderly

Meta-analysis of the effect of entropy-assisted general anesthesia on the quality of postoperative recovery

BACKGROUND

To evaluate the effect of the quality of postoperative anesthetic resuscitation in patients with entropy index monitoring assisted general anesthesia versus standard clinical practice.

METHODS

The randomized controlled trials on the application of entropy index monitoring in general anesthesia were searched in PubMed, Web of Science, Embase, The Cochrane Library, CNKI, Wanfang, VIP, and other databases by computer. The data were collected from inception to January 2022. Two researchers independently screened the retrieved literature according to the inclusion and exclusion criteria and used Cochrane's risk-of-bias assessment criteria to evaluate the quality of the literature. The evaluation indicators included respiratory recovery time, extubation time, consciousness recovery time, emergence agitation, postoperative nausea and vomiting (PONV), and intraoperative awareness. The RevMan 5.4.1 software was used for the meta-analysis of the data.

RESULTS

A total of 860 patients from 10 eligible randomized controlled trials were included in this study. The results showed that compared with the control group, the respiratory recovery time (MD = -3.37, 95% CI: -5.09 to -1.85, P < .0001), extubation time (MD = -4.57, 95% CI: -6.08 to -3.95, P < .00001), and consciousness recovery time (MD = -4.95, 95% CI: -7.21 to -2.70, P < .00001) in the entropy index group were significantly shortened. The incidence of emergence agitation in the entropy index group (RR = 0.23, 95% CI: 0.11-0.47, P < .0001) decreased significantly. The incidence of PONV (RR = 0.46, 95% CI: 0.27-0.79, P = .004) was significantly reduced. However, the incidence of intraoperative awareness (RR = 0.33, 95% CI: 0.04-3.16, P = .34) wasn't significantly different.

CONCLUSION

The application of the entropy index can improve the recovery quality of patients under general anesthesia, not only shortening the postoperative recovery time but also reducing the occurrence of agitation and PONV. It does not affect the incidence of intraoperative awareness.

PRISMA: accuracy of response entropy and bispectral index to predict the transition of consciousness during sevoflurane anesthesia: A systematic review and meta-analysis

Background:

Bispectral index (BIS) and response entropy (RE) are used to monitor the depth of anesthesia.

Objectives:

To collect published data and compare the accuracy of BIS and RE in detecting the transition of consciousness during sevoflurane anesthesia.

Data sources:

Studies indexed in the PubMed, Embase, or Cochrane databases.

Study eligibility criteria:

Participants:

Patients who need to use BIS and RE to monitor sevoflurane anesthesia depth simultaneously.

Interventions:

A random-effects model was fitted using RevMan 5.3. Subgroup analyses were performed on patient age. The Cochrane I 2 methodology was used to determine the heterogeneity of the statistical results, while GRADE Pro served to assess the quality of evidence.

Results:

Overall, 195 articles were identified, of which 7 were finally included. The meta-analysis results showed that BIS is more accurate than RE in predicting loss of consciousness (LOC) during sevoflurane anesthesia (MD, .06; 95% confidence interval [CI], .02–.09; P  = .009; I 2  = 92%). In contrast, there was no significant difference between BIS and RE for recovery of consciousness (ROC; MD, .01; 95% CI, .00–.02; P  = .79; I 2  = 83%). Subgroup analyses revealed no significant differences in LOC (MD, .02; 95% CI, .01–.05; P  = .13; I 2  = 60%) and ROC (MD, −.01; 95% CI, −.06–.04; P  = .58; I 2  = 95%) in children. However, the results in adults demonstrated that BIS is more accurate than RE in predicting LOC (MD, −.07; 95% CI, .05–.10; P  = .002; I 2  = 76%).

Limitations:

First, this meta-analysis was affected by a large study heterogeneity. Second, this analysis only included publications in English, therefore, some studies may have been omitted.

Conclusion:

BIS is more accurate than RE in predicting LOC during sevoflurane anesthesia in adults. However, no significant differences were identified in children.

Registration number (PROSPERO):

CRD42020163119

The influence of moderate or deep neuromuscular block status on anesthetic depth monitoring system during total intravenous anesthesia using propofol and remifentanil: A randomized trial

The neuromuscular block state may affect the electroencephalogram-derived index representing the anesthetic depth. We applied an Anesthetic Depth Monitoring for Sedation (ADMS) to patients undergoing laparoscopic cholecystectomy under total intravenous anesthesia, and evaluated the requirement of propofol according to the different neuromuscular block state. Adult patients scheduled to undergo laparoscopic cholecystectomy were enrolled and randomly assigned to either the moderate (MB) or deep neuromuscular block (DB) group. The UniCon sensor of ADMS was applied to monitor anesthetic depth and the unicon value was maintained between 40 and 50 during the operation. According to the group assignment, intraoperative rocuronium was administered to maintain proper neuromuscular block state, moderate or deep block state. The unicon value, electromyography (EMG) index, and total dose of propofol and rocuronium were analyzed. At similar anesthetic depth, less propofol was used in the DB group compared to the MB group (6.19 ± 1.36 in the MB mg/kg/h group vs 4.93 ± 3.02 mg/kg/h in the DM group, p = 0.042). As expected, more rocuronium were used in the DB group than in the MB group (0.8 ± 0.2 mg/kg in the MB group vs 1.2 ± 0.2 mg/kg in the DB group, p = 0.023) and the EMG indices were lower in the DB group than in the MB group, at several time points as follows: at starting operation (p < 0.001); at 15 (p = 0.019), 45 (p = 0.011), and 60 min (p < 0.001) after the initiation of the operation; at the end of operation (p = 0.003); and at 5 min after the administration of sugammadex (p < 0.001). At similar anesthetic depth, patients under the deep neuromuscular block state required less propofol with lower intraoperative EMG indices compared to those under the moderate neuromuscular block state during general anesthesia.

Changes in the Bispectral Index in Response to Loss of Consciousness and No Somatic Movement to Nociceptive Stimuli in Elderly Patients

Background:

Bispectral index (BIS) is considered very useful to guide anesthesia care in elderly patients, but its use is controversial for the evaluation of the adequacy of analgesia. This study compared the BIS changes in response to loss of consciousness (LOC) and loss of somatic response (LOS) to nociceptive stimuli between elderly and young patients receiving intravenous target-controlled infusion (TCI) of propofol and remifentanil.

Methods:

This study was performed on 52 elderly patients (aged 65–78 years) and 52 young patients (aged 25–58 years), American Society of Anesthesiologists physical status I or II. Anesthesia was induced with propofol administered by TCI. A standardized noxious electrical stimulus (transcutaneous electrical nerve stimulation, [TENS]) was applied (50 Hz, 80 mA, 0.25 ms pulses for 4 s) to the ulnar nerve at increasing remifentanil predicted effective-site concentration (Ce) until patients lost somatic response to TENS. Changes in awake, prestimulus, poststimulus BIS, heart rate, mean arterial pressure, pulse oxygen saturation, predicted plasma concentration, Ce of propofol, and remifentanil at both LOC and LOS clinical points were investigated.

Results:

BIS_LOC in elderly group was higher than that in young patient group (65.4 ± 9.7 vs. 57.6 ± 12.3) (t = 21.58, P < 0.0001) after TCI propofol, and the propofol Ce at LOC was 1.6 ± 0.3 μg/ml in elderly patients, which was significantly lower than that in young patients (2.3 ± 0.5 μg/ml) (t = 7.474, P < 0.0001). As nociceptive stimulation induced BIS to increase, the mean of BIS maximum values after TENS was significantly higher than that before TENS in both age groups (t = 8.902 and t = 8.019, P < 0.0001). With increasing Ce of remifentanil until patients lost somatic response to TENS, BIS_LOS was the same as the BIS_LOC in elderly patients (65.6 ± 10.7 vs. 65.4 ± 9.7), and there were no marked differences between elderly and young patient groups in BIS_awake, BIS_LOS, and Ce of remifentanil required for LOS.

Conclusion:

In elderly patients, BIS can be used as an indicator for hypnotic-analgesic balance and be helpful to guide the optimal administration of propofol and remifentanil individually.

Trial Registration:

CTRI Reg. No: ChiCTR-OOC-14005629; http://www.chictr.org.cn/showproj.aspx?proj=9875.

Comparison of C₅₀ for Propofol-remifentanil Target-controlled Infusion and Bispectral Index at Loss of Consciousness and Response to Painful Stimulus in Elderly and Young Patients

BACKGROUND

In this prospective randomized study, we compared the predicted blood and effect-site C 50 for propofol and remifentanil target-controlled infusion (TCI) and the bispectral index (BIS) values at loss of consciousness (LOC) and response to a standard noxious painful stimulus (LOS) in elderly and young patients, respectively. We hypothesized that the elderly patients will require lower target concentration of both propofol and remifentanil at above two clinical end-points.

METHODS

There were 80 American Society of Anesthesiologists (ASA) physical status I-II unpremedicated patients enrolled in this study, they were divided into elderly group (age ≥65 years, n = 40) and young group (aged 18-64 years, n = 40). Propofol was initially given to a predicted blood concentration of 1.2 μg/ml and thereafter increased by 0.3 μg/ml every 30 s until Observer's Assessment of Alertness and Sedation score was 1. The propofol level was kept constant, and remifentanil was given to provide a predict blood concentration of 2.0 ng/ml, and then increased by 0.3 ng/ml every 30 s until loss of response to a tetanic stimulus. BIS (version 3.22, BIS Quattro sensor) was also recorded.

RESULTS

In elderly group, the propofol effect-site C 50 at LOC of was 1.5 (1.4-1.6) μg/ml, was significantly lower than that of young group, which was 2.2 (2.1-2.3) μg/ml, the remifentanil effect-site C 50 at LOS was 3.5 (3.3-3.7) ng/ml in elderly patients, was similar with 3.7 (3.6-3.8) ng/ml in young patients. Fifty percent of patients lost consciousness at a BIS value of 57.3 (56.4-58.1), was similar with that of young group, which was 55.2 (54.0-56.3).

CONCLUSION

In elderly patients, the predicted blood and effect-site concentrations of propofol at LOC were lower than that of young patients. At same sedation status, predicted blood and effect-site concentrations of remifentanil required at LOS were similar in elderly and young patients. BIS were not affected by age. Low-propofol/high-opioid may be optional TCI strategy for elderly patients.

Comparison of Laryngeal Mask Airway Supreme(TM) Versus Unique(TM) in Edentulous Geriatric Patients

OBJECTIVE

It is more difficult to perform bag-mask ventilation in edentulous patients than in patients with intact dentition. The laryngeal mask airway (LMA) provides a better alternative to the standard face mask if the facial contours of the patient are not suited for the standard face mask. We aimed to compare these two different LMAs in edentulous geriatric patients.

METHODS

Edentulous patients aged ≥65 years of American Society of Anesthesiologists physical status I-III were included in the study. They were randomly assigned to Supreme group (n=30) and Unique group (n=30). Success of first insertion attempt, ease and time of insertion and oropharyngeal leak pressure were recorded.

RESULTS

The success rate of the first insertion attempt was higher in the Supreme group than in the Unique group (86.6 and 73.3%, respectively; p=0.04). Time of insertion was similar (10.04 s and 11.87 s, respectively) and insertion was easy in 90% and 100% of patients, respectively. Oropharyngeal leak pressures were measured as 20.56-cm H2O and 17.10-cm H2O for LMA Supreme™ and LMA Unique™, respectively.

CONCLUSION

The efficacy and safety in both groups were comparable in edentulous geriatric patients during short surgical procedures. Even the success rate of insertion with both was lower than that mentioned in the literature; the success of insertion at the first attempt was superior with the LMA Supreme™ in our edentulous study group.

Bispectral index for improving anaesthetic delivery and postoperative recovery

BACKGROUND

The use of clinical signs may not be reliable in measuring the hypnotic component of anaesthesia. The use of bispectral index (BIS) to guide the dose of anaesthetic may have certain advantages over clinical signs. This is the second update of a review originally published in 2007.

OBJECTIVES

The primary objective of this review focused on whether the incorporation of BIS into the standard practice for management of anaesthesia can reduce the risk of intraoperative awareness, consumption of anaesthetic agents, recovery time and total cost of anaesthesia in surgical patients undergoing general anaesthesia.

SEARCH METHODS

In this updated version, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 1), MEDLINE (1990 to 31 January 2013), EMBASE (1990 to 31 January 2013) and reference lists of articles. Previously, we searched to May 2009.

SELECTION CRITERIA

We included randomized controlled trials comparing BIS with standard practice criteria for titration of anaesthetic agents.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality, extracted data and analysed the data. We contacted study authors for further details.

MAIN RESULTS

We included 36 trials. In studies using clinical signs as standard practice, the results demonstrated a significant effect of the BIS-guided anaesthesia in reducing the risk of intraoperative awareness among surgical patients at high risk for awareness (7761 participants; odds ratio (OR) 0.24, 95% confidence interval (CI) 0.12 to 0.48). This effect was not demonstrated in studies using end tidal anaesthetic gas (ETAG) monitoring as standard practice (26,530 participants; OR 1.13, 95% CI 0.56 to 2.26). BIS-guided anaesthesia reduced the requirement for propofol by 1.32 mg/kg/hr (672 participants; 95% CI -1.91 to -0.73) and for volatile anaesthetics (desflurane, sevoflurane, isoflurane) by 0.65 minimal alveolar concentration equivalents (MAC) (95% CI -1.01 to -0.28) in 985 participants. Irrespective of the anaesthetics used, BIS reduced the following recovery times: time for eye opening (2557 participants; by 1.93 min, 95% CI -2.70 to -1.16), response to verbal command (777 participants; by 2.73 min, 95% CI -3.92 to -1.54), time to extubation (1501 participants; by 2.62 min, 95% CI -3.46 to -1.78), and time to orientation (373 participants; by 3.06 min, 95% CI -3.63 to -2.50). BIS shortened the duration of postanaesthesia care unit stay by 6.75 min (1953 participants; 95% CI -11.20 to -2.31) but did not significantly reduce the time to home readiness (329 participants; -7.01 min, 95% CI -30.11 to 16.09).

AUTHORS' CONCLUSIONS

BIS-guided anaesthesia can reduce the risk of intraoperative awareness in surgical patients at high risk for awareness in comparison to using clinical signs as a guide for anaesthetic depth. BIS-guided anaesthesia and ETAG-guided anaesthesia may be equivalent in protection against intraoperative awareness but the evidence for this is inconclusive. In addition, anaesthesia guided by BIS kept within the recommended range improves anaesthetic delivery and postoperative recovery from relatively deep anaesthesia.

Evolution of electroencephalogram signal analysis techniques during anesthesia

Biosignal analysis is one of the most important topics that researchers have tried to develop during the last century to understand numerous human diseases. Electroencephalograms (EEGs) are one of the techniques which provides an electrical representation of biosignals that reflect changes in the activity of the human brain. Monitoring the levels of anesthesia is a very important subject, which has been proposed to avoid both patient awareness caused by inadequate dosage of anesthetic drugs and excessive use of anesthesia during surgery. This article reviews the bases of these techniques and their development within the last decades and provides a synopsis of the relevant methodologies and algorithms that are used to analyze EEG signals. In addition, it aims to present some of the physiological background of the EEG signal, developments in EEG signal processing, and the effective methods used to remove various types of noise. This review will hopefully increase efforts to develop methods that use EEG signals for determining and classifying the depth of anesthesia with a high data rate to produce a flexible and reliable detection device.

Monitoring the depth of anaesthesia

One of the current challenges in medicine is monitoring the patients’ depth of general anaesthesia (DGA). Accurate assessment of the depth of anaesthesia contributes to tailoring drug administration to the individual patient, thus preventing awareness or excessive anaesthetic depth and improving patients’ outcomes. In the past decade, there has been a significant increase in the number of studies on the development, comparison and validation of commercial devices that estimate the DGA by analyzing electrical activity of the brain (i.e., evoked potentials or brain waves). In this paper we review the most frequently used sensors and mathematical methods for monitoring the DGA, their validation in clinical practice and discuss the central question of whether these approaches can, compared to other conventional methods, reduce the risk of patient awareness during surgical procedures.

Bispectral index for improving anaesthetic delivery and postoperative recovery

BACKGROUND

The use of clinical signs may not be reliable to measure the hypnotic component of anaesthesia. The use of bispectral index to guide the dose of anaesthetics may have certain advantages over clinical signs.

OBJECTIVES

The objective of this review was to assess whether bispectral index (BIS) reduced anaesthetic use, recovery times, recall awareness and cost.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 2), MEDLINE (1990 to May 2007), EMBASE (1990 to May 2007) and reference lists of articles.

SELECTION CRITERIA

We included randomized controlled trials comparing BIS with clinical signs (CS) in titrating anaesthetic agents.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality, extracted data and analysed the data. We contacted study authors for further details.

MAIN RESULTS

We included 20 studies with 4056 participants. Seven recent trials are still awaiting assessment. BIS-guided anaesthesia reduced the requirement for propofol by 1.30 mg/kg/hr (578 participants; 95% confidence interval (CI) -1.97 to -0.62) and for volatile anaesthetics (desflurane, sevoflurane, isoflurane) by 0.17 minimal alveolar concentration equivalents (MAC) (689 participants; 95% CI -0.27 to -0.07). Irrespective of the anaesthetic, BIS reduced the recovery times: time for eye opening by 2.43 min (996 participants; 95% CI -3.60 to -1.27), response to verbal command by 2.28 min (717 participants; 95% CI -3.47 to -1.09), time to extubation by 3.05 min (1057 participants; 95% CI -3.98 to -2.11) and orientation by 2.46 min (316 participants; 95% CI -3.21 to -1.71). BIS shortened the duration of postanaesthesia care unit stay by 6.83 min (584 participants; 95% CI -12.08 to -1.58) but did not reduce time to home readiness (329 participants; 95% CI -30.11 to 16.09). The BIS-guided anaesthesia significantly reduced the incidence of intraoperative recall awareness in surgical patients with high risk of awareness (OR 0.20, 95% CI 0.05 to 0.79).

AUTHORS' CONCLUSIONS

Anaesthesia guided by BIS within the recommended range (40 to 60) could improve anaesthetic delivery and postoperative recovery from relatively deep anaesthesia. In addition, BIS-guided anaesthesia has a significant impact on reduction of the incidence of intraoperative recall in surgical patients with high risk of awareness.