Clinical effectiveness and cost-effectiveness of depth of anaesthesia monitoring (E-Entropy, Bispectral Index and Narcotrend): a systematic review and economic evaluation

Skin conductance algesimeter is unreliable during sudden perioperative temperature increases

OBJECTIVES

Pain assessment in anesthetized and non-communicative patients remains a challenge. Clinical signs such as tachycardia, hypertension, sweat and tears, have a low specificity for pain and should therefore ideally be replaced by more specific monitoring techniques. Skin conductance variability has been demonstrated to establish a patients' sensitivity to pain, but may be influenced by temperature changes that leads to profuse sweating. The aim of this pilot study was to test skin conductance changes during sudden temperature changes due to hyperthermic intraperitoneal chemotherapy (HIPEC) perfusation.

METHODS

We investigated skin conductance algesimeter (SCA) in ten consecutive patients undergoing cytoreductive surgery and HIPEC. Results from the SCA was compared to other standard physiological variables at seven time points during the surgical procedure, in particular during the period with hyperthermic intraabdominal perfusion leading to an increase in the patients core temperature.

RESULTS

Nine out of ten patients had an increase in the SCA measurements during the HIPEC phase correlating the increase in temperature.

CONCLUSION

SCA is unreliable to detect increased pain sensation during sudden perioperative temperature changes in adult patients.

Guidelines for reducing the environmental impact of general anaesthesia

OBJECTIVE

To provide guidelines for reducing the environmental impact of general anaesthesia.

DESIGN

A committee of ten experts from SFAR and SF2H and SFPC learned societies was set up. A policy of declaration of competing interests was applied and observed throughout the guideline-writing process. Likewise, it did not benefit from any funding from a company marketing a health product (drug or medical device). The committee followed the GRADE® method (Grading of Recommendations Assessment, Development and Evaluation) to assess the quality of the evidence on which the recommendations were based.

METHODS

We aimed to formulate recommendations according to the GRADE® methodology for three different fields: anaesthesia vapours and gases; intravenous drugs; medical devices and the working environment. Each question was formulated according to the PICO format (Population, Intervention, Comparator, Outcome). The literature review and recommendations were formulated according to the GRADE® methodology.

RESULTS

The experts' work on the synthesis and application of the GRADE® method led to the formulation of 17 recommendations. Since the GRADE® method could not be entirely applied to all of the questions, some of the recommendations were formulated as expert opinions.

CONCLUSION

Based on strong agreement between experts, we produced 17 recommendations designed to guide reducing the environmental impact of general anaesthesia.

[Processed EEG for personalized dosing of anesthetics during general anesthesia]

Electroencephalogram (EEG)-guided anesthesia is indispensable in modern operating rooms and has become established as the standard form of monitoring. Many anesthesiologists rely on processed EEG indices in the hope of averting anesthesia-related complications, such as intraoperative awareness, postoperative delirium and other cognitive complications in their patients. This educational review aims to provide information on the five most prevalent monitors used to guide depth of sedation during general anesthesia. This article elucidates the principles underpinning the application of these monitors where known, which are generally based on power in various EEG frequency bands and on the burst suppression pattern. Convinced that EEG-guided anesthesia has the potential of benefitting many surgical patients, it is felt that many basic principles and shortcomings of processed EEG indices need to be better understood in the clinical practice. After discussing the different monitors and clinically relevant data from the literature, the article gives a short practical guidance on how to critically interpret processed EEG information and troubleshooting of confounded indices in the context of clinical situations.

Comparative analysis of the effect of electromyogram to bispectral index and 95% spectral edge frequency under remimazolam and propofol anesthesia: a prospective, randomized, controlled clinical trial

Background

Bispectral index (BIS), an index used to monitor the depth of anesthesia, can be interfered with by the electromyogram (EMG) signal. The 95% spectral edge frequency (SEF95) also can reflect the sedation depth. Remimazolam in monitored anesthesia care results in higher BIS values than propofol, though in the same sedation level assessed by Modified Observers Assessment of Alertness and Sedation (MOAA/S). Our study aims to illustrate whether EMG is involved in remimazolam causing higher BIS value than propofol preliminarily and to explore the correlations among BIS, EMG, and SEF95 under propofol and remimazolam anesthesia.

Patients and methods

Twenty-eight patients were randomly divided into propofol (P) and remimazolam (RM) groups. Patients in the two groups received alfentanil 10 μg/kg, followed by propofol 2 mg/kg and remimazolam 0.15 mg/kg. Blood pressure (BP), heart rate (HR), and oxygen saturation (SpO2) were routinely monitored. The BIS, EMG, and SEF95 were obtained through BIS VISTATM. The primary outcomes were BIS, EMG, and the correlation between BIS and EMG in both groups. Other outcomes were SEF95, the correlation between BIS and SEF95, and the correlation between EMG and SEF95. And all the statistical and comparative analysis between these signals was conducted with SPSS 26.0 and GraphPad Prism 8.

Results

BIS values, EMG, and SEF95 were significantly higher in the RM group than in the P group (all p < 0.001). There was a strong positive correlation between BIS and EMG in the RM group (r = 0.416). Nevertheless, the BIS in the P group showed a weak negative correlation with EMG (r = -0.219). Both P (r = 0.787) and RM group (r = 0.559) had a reasonably significant correlation coefficient between BIS and SEF95. SEF95 almost did not correlate with EMG in the RM group (r = 0.101).

Conclusion

Bispectral index can be interfered with high EMG intensity under remimazolam anesthesia. However, EMG can hardly affect the accuracy of BIS under propofol anesthesia due to low EMG intensity and a weak negative correlation between EMG and BIS. Moreover, SEF95 may have a great application prospect in predicting the sedation condition of remimazolam.

Meta-Analysis of the Prognostic Value of Narcotrend Monitoring of Different Depths of Anesthesia and Different Bispectral Index (BIS) Values for Cognitive Dysfunction after Tumor Surgery in Elderly Patients

Objective

To study the effect of Narcotrend monitoring on the incidence of early postoperative cognitive dysfunction (POCD) under different bispectral index (BIS) conditions and the effect of different depths of anesthesia on the incidence of POCD.

Methods

We performed a literature search of PubMed, Embase, OVID (database system made by Ovid Technologies, USA), CBM (Chinese Biomedical Literature database), CNKI (China National Knowledge Infrastructure), Wanfang, and VIP databases (full-text database of Chinese sci-tech journals), etc., from the date of the establishment of the database until December 31, 2020. Our meta-analysis was focused on the collection and study of Narcotrend monitoring of different depths of anesthesia. We carefully read the abstracts and full texts of randomized controlled trials on the incidence of POCD in the early postoperative period, and their references were tracked. Data extraction and quality evaluation of the included literature were also performed, and RevMan 5.3 software was used for analysis.

Results

In the end, eight articles were included, with a total of 714 patients. The meta-analysis results showed that four articles (255 patients) compared the state of deep anesthesia (BIS 30-40) with conventional anesthesia (BIS 40-60 earlier) after POCD. Also, the incidence of POCD on the first day after deep anesthesia (Narcotrend stage (NTS): negative correlation is currently the most appropriate EEG description; Nd can subdivide the original EEG into six stages and 15 levels (Nd Sg, NTS), namely, A (state of wakefulness) state, B0 B2 (sedated state), C0 C2 (light anesthetic state), D0 D2 (general anesthesia), and E0-E1) was significantly lower than that of conventional anesthesia (NTS DO-D1) (odds ratio (OR) = 0.21, 95% confidence interval (CI): 0.13-0.35, P < 0.00001). Moreover, the incidence of POCD in deep anesthesia (NTS E1) at 7 days after surgery was significantly lower than that of conventional anesthesia (NTS D0) (OR (odds ratio) = 0.45, 95% CI: 0.23-0.91, P=0.03), while the incidence of POCD 7 days after NTS D2 in conventional anesthesia was significantly lower than that of NTS D0 (OR = 0.42, 95% CI: 0.24-0.71, P=0.001). Discussion. Deep anesthesia can reduce the incidence of POCD (OR = 0.40, 95% CI: 0.22-0.73, P=0.002). This meta-analysis included three studies (216 patients) that compared the early postoperative POCD incidence of BIS 40-50 under conventional anesthesia and BIS 50-60; the BIS 40-50 did not significantly reduce the incidence of POCD (OR = 1.11, 95% CI: 0.24-5.24, P=0.9). The incidence of POCD under deep anesthesia with Narcotrend monitoring was lower than that under conventional anesthesia.

Arthroscopic hip surgery compared with personalised hip therapy in people over 16 years old with femoroacetabular impingement syndrome: UK FASHIoN RCT

BACKGROUND

Femoroacetabular impingement syndrome is an important cause of hip pain in young adults. It can be treated by arthroscopic hip surgery or with physiotherapist-led conservative care.

OBJECTIVE

To compare the clinical effectiveness and cost-effectiveness of hip arthroscopy with best conservative care.

DESIGN

The UK FASHIoN (full trial of arthroscopic surgery for hip impingement compared with non-operative care) trial was a pragmatic, multicentre, randomised controlled trial that was carried out at 23 NHS hospitals.

PARTICIPANTS

Participants were included if they had femoroacetabular impingement, were aged ≥ 16 years old, had hip pain with radiographic features of cam or pincer morphology (but no osteoarthritis) and were believed to be likely to benefit from hip arthroscopy.

INTERVENTION

Participants were randomly allocated (1 : 1) to receive hip arthroscopy followed by postoperative physiotherapy, or personalised hip therapy (i.e. an individualised physiotherapist-led programme of conservative care). Randomisation was stratified by impingement type and recruiting centre using a central telephone randomisation service. Outcome assessment and analysis were masked.

MAIN OUTCOME MEASURE

The primary outcome was hip-related quality of life, measured by the patient-reported International Hip Outcome Tool (iHOT-33) 12 months after randomisation, and analysed by intention to treat.

RESULTS

Between July 2012 and July 2016, 648 eligible patients were identified and 348 participants were recruited. In total, 171 participants were allocated to receive hip arthroscopy and 177 participants were allocated to receive personalised hip therapy. Three further patients were excluded from the trial after randomisation because they did not meet the eligibility criteria. Follow-up at the primary outcome assessment was 92% (N = 319; hip arthroscopy, n = 157; personalised hip therapy, n = 162). At 12 months, mean International Hip Outcome Tool (iHOT-33) score had improved from 39.2 (standard deviation 20.9) points to 58.8 (standard deviation 27.2) points for participants in the hip arthroscopy group, and from 35.6 (standard deviation 18.2) points to 49.7 (standard deviation 25.5) points for participants in personalised hip therapy group. In the primary analysis, the mean difference in International Hip Outcome Tool scores, adjusted for impingement type, sex, baseline International Hip Outcome Tool score and centre, was 6.8 (95% confidence interval 1.7 to 12.0) points in favour of hip arthroscopy (p = 0.0093). This estimate of treatment effect exceeded the minimum clinically important difference (6.1 points). Five (83%) of six serious adverse events in the hip arthroscopy group were related to treatment and one serious adverse event in the personalised hip therapy group was not. Thirty-eight (24%) personalised hip therapy patients chose to have hip arthroscopy between 1 and 3 years after randomisation. Nineteen (12%) hip arthroscopy patients had a revision arthroscopy. Eleven (7%) personalised hip therapy patients and three (2%) hip arthroscopy patients had a hip replacement within 3 years.

LIMITATIONS

Study participants and treating clinicians were not blinded to the intervention arm. Delays were encountered in participants accessing treatment, particularly surgery. Follow-up lasted for 3 years.

CONCLUSION

Hip arthroscopy and personalised hip therapy both improved hip-related quality of life for patients with femoroacetabular impingement syndrome. Hip arthroscopy led to a greater improvement in quality of life than personalised hip therapy, and this difference was clinically significant at 12 months. This study does not demonstrate cost-effectiveness of hip arthroscopy compared with personalised hip therapy within the first 12 months. Further follow-up will reveal whether or not the clinical benefits of hip arthroscopy are maintained and whether or not it is cost-effective in the long term.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN64081839.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 16. See the NIHR Journals Library website for further project information.

Systematic review and meta-analysis of the prognostic value of Narcotrend monitoring of different depths of anesthesia and different Bispectral Index (BIS) values for cognitive dysfunction after tumor surgery in elderly patients

Background

To study the effect of Narcotrend monitoring on the incidence of early postoperative cognitive dysfunction (POCD) under different Bispectral Index (BIS) conditions and the effect of different depths of anesthesia on the incidence of POCD.

Methods

We performed a literature search of the PubMed, Embase, OVID (database system made by Ovid Technologies, USA), Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI), VIP Chinese Sci-tech Journals Database, Wanfang Data, etc. from the date of establishment of the database until December 31, 2020.

Results

In the end, eighty articles were included, with a total of 714 patients. The meta-analysis results showed that four articles (255 patients) compared the state of deep anesthesia (BIS 30–40) with conventional anesthesia (BIS 40–60 earlier) after POCD. Also, the incidence of POCD on the first day after deep anesthesia [Narcotrend stage (NTS): negative correlation is currently the most appropriate egg description; Nd can subdivide the original electroencephalogram (EEG) into six stages 15 levels (Nd Sg, NTS), or A (state of wakefulness), state B0–B2 (sedated state), state C0–C2 (light anesthetic state), state D0–D2 (general anesthesia), state E0–E2 (deep anesthesia state), and state F0–F2 (burst suppression state)] was significantly lower than that of conventional anesthesia (NTS D0–D1) [odds ratio (OR) =0.21, 95% confidence interval (CI): 0.13–0.35, P<0.00001]. Moreover, the incidence of POCD in deep anesthesia (NTS E1) at 7 days after surgery was significantly lower than that of conventional anesthesia (NTS D0) (OR =0.45, 95% CI: 0.23–0.91, P=0.03), while the incidence of POCD 7 days after NTS D2 in conventional anesthesia was significantly lower than that of NTS D0 (OR =0.42, 95% CI: 0.24–0.71, P=0.001).

Discussions

POCDs are thought to be the result of a combination of physical defects and precipitating factors in patients with their own physical impairments, and despite potential adverse effects, there is currently no consensus on the incidence of POCDs in patients with tumor, current risk factors, causes, and prevention strategies. Moreover, the level of evidence is low, and the deviation between different studies cannot be ruled out.

A survey of current practices, attitudes and demands of anaesthesiologists regarding the depth of anaesthesia monitoring in China

Background

In this study, we aimed to analyse survey data to explore two different hypotheses; and for this purpose, we distributed an online survey to Chinese anaesthesiologists. The hypothetical questions in this survey include: (1) Chinese anaesthesiologists mainly use the depth of anaesthesia (DoA) monitors to prevent intraoperative awareness and (2) the accuracy of these monitors is the most crucial performance factor during the clinical daily practice of Chinese anaesthesiologists.

Methods

We collected and statistically analysed the response of a total of 12,750 anesthesiologists who were invited to participate in an anonymous online survey. The Chinese Society of Anaesthesiologists (CSA) trial group provided the email address of each anaesthesiologist, and the selection of respondents was random from the computerized system.

Results

The overall response rate was 32.0% (4037 respondents). Only 9.1% (95% confidence interval, 8.2-10.0%) of the respondents routinely used DoA monitors. Academic respondents (91.5, 90.3-92.7%) most frequently used DoA monitoring to prevent awareness, whereas nonacademic respondents (88.8, 87.4-90.2%) most frequently used DoA monitoring to guide the delivery of anaesthetic agents. In total, the number of respondents who did not use a DoA monitor and whose patients experienced awareness (61.7, 57.8-65.6%) was significantly greater than those who used one or several DoA monitors (51.5, 49.8-53.2%). Overall, the crucial performance factor during DoA monitoring was considered by 61.9% (60.4-63.4%) of the respondents to be accuracy. However, most respondents (95.7, 95.1-96.3%) demanded improvements in the accuracy of the monitors for DoA monitoring. In addition, broad application in patients of all ages (86.3, 85.2-87.4%), analgesia monitoring (80.4, 79.2-81.6%), and all types of anaesthetic agents (75.6, 74.3-76.9%) was reported. In total, 65.0% (63.6-66.5%) of the respondents believed that DoA monitors should be combined with EEG and vital sign monitoring, and 53.7% (52.1-55.2%) believed that advanced DoA monitors should include artificial intelligence.

Conclusions

Academic anaesthesiologists primarily use DoA monitoring to prevent awareness, whereas nonacademic anaesthesiologists use DoA monitoring to guide the delivery of anaesthetics. Anaesthesiologists demand high-accuracy DoA monitors incorporating EEG signals, multiple vital signs, and antinociceptive indicators. DoA monitors with artificial intelligence may represent a new direction for future research on DoA monitoring.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01510-7.

Effects of circadian rhythm on Narcotrend index and target-controlled infusion concentration of propofol anesthesia

Background

The effects of circadian rhythms on drug metabolism and efficacy are being increasingly recognized. However, the extent to which they affect general anesthesia remains unclear. This study aims to investigate the effects of circadian rhythms on anesthetic depth and the concentrations of propofol target-controlled infusion (TCI).

Methods

Sixty patients undergoing laparoscopic surgeries were sequentially assigned to four groups. Group ND (n = 15): Propofol TCI with Narcotrend monitor during the day (8:00–18:00), Group NN (n = 15): Propofol TCI with Narcotrend monitor during the night (22:00–5:00), Group CLTD (n = 15): Propofol closed-loop TCI guided by bispectral index (BIS) during the day (8:00–18:00), Group CLTN (n = 15): Propofol closed-loop TCI guided by BIS during the night (22:00–5:00). The Narcotrend index, mean arterial pressure (MAP) and heart rate (HR) were compared between group ND and NN at 7 time points, from 5 min before induction to the end of operation. The propofol TCI concentrations, MAP and HR were compared between group CLTD and CLTN at 7 time points, from 5 min after induction to the end of operation.

Results

The Narcotrend index, MAP, and HR in group NN were lower than those in group ND from the beginning of mechanical ventilation to the end of operation (p < 0.05). The propofol TCI concentrations in group CLTN were lower than those in group CLTD from the beginning of operation to the end of operation (p < 0.05).

Conclusion

Circadian rhythms have a significant effect on the depth of anesthesia and drug infusion concentrations during propofol TCI. When using general anesthesia during night surgery, the propofol infusion concentration should be appropriately reduced compared to surgery during the day.

Trial registration

The present study was registered on the ClinicalTrials.gov website (NCT02440269) and approved by the Medical Ethics Committee of Southwest Hospital of Third Military Medical University (ethics lot number: 2016 Research No. 93). All patients provided informed written consent to participate in the study.

Rapid arousal from anaesthesia after reversal of deep rocuronium-induced neuromuscular block with sugammadex in a neuroradiological procedure

We describe the case of a 42-year-old man undergoing elective embolisation of an arteriovenous malformation at the level of the right posterior cerebral artery under propofol anaesthesia. We used the SedLine Brain Function Monitor (Masimo) to titrate the anaesthetic depth with propofol. At the end of the procedure, the patient aroused from anaesthesia very rapidly after the reversal of deep neuromuscular block with sugammadex, despite still significant calculated doses of propofol at the effect site. This rapid arousal was monitored using the SedLine Brain Function Monitor.

Comparison of adequacy of anaesthesia monitoring with standard clinical practice monitoring during routine general anaesthesia: An international, multicentre, single-blinded randomised controlled trial

BACKGROUND

Previous studies have suggested that monitoring the levels of both hypnosis and antinociception could reduce periods of inadequate anaesthesia. However, the evidence regarding associated benefits of this monitoring is still limited.

OBJECTIVE

The primary objective of this study was to confirm that guidance of anaesthesia by depth of hypnosis and antinociception monitoring decreases the number of inadequate anaesthesia events in comparison with standard clinical practice.

DESIGN

A multicentre, single-blinded, randomised controlled trial.

SETTING

The study was conducted in four European University hospitals in four different countries between December 2013 and November 2016.

PATIENTS

The study population consisted of a total of 494 adult patients undergoing elective surgery requiring tracheal intubation.

INTERVENTIONS

The patients were allocated to one of two groups. The first group was treated using Entropy for depth of hypnosis and surgical pleth index to determine depth of antinociception (adequacy of anaesthesia group; AoA group). The second group was monitored using standard monitoring alone (control group). Anaesthesia was conducted with target-controlled infusions of propofol and remifentanil.

MAIN OUTCOME MEASURES

The primary outcome of the study was the number of total unwanted events for example signs of inadequately light or unintentionally deep anaesthesia.

RESULTS

Evidence of inadequate anaesthesia had an incidence of around 0.7 events per patient in both groups with no difference between groups (P = 0.519). In the AoA group, the overall consumption of propofol was significantly reduced (6.9 vs. 7.5 mg kg h, P = 0.008) in comparison with the control group. The consumption of remifentanil was equal in both groups. The times to emergence [8.0 vs. 9.6 min (P = 0.005)] and full recovery in the postanaesthesia care unit (P = 0.043) were significantly shorter in the AoA group. No differences were seen in postoperative pain scores or in the use of analgesics.

CONCLUSION

In the current study, the guidance of total intravenous anaesthesia by Entropy and surgical pleth index in comparison with standard monitoring alone was not able to validate reduction of unwanted anaesthesia events. However, there was a reduction in the use of propofol, and shorter times for emergence and time spent in the postanaesthesia care unit.

TRIAL REGISTRATION

at ClinicalTrials.gov NCT01928875.

Sub-chronic exposure to morphine alters general anesthetic potency by differentially regulating the expression of neurotransmitter receptor subunits in mice

BACKGROUND

Sub-chronic exposure to morphine can increase the potency of propofol but decrease the potency of ketamine by unknown mechanisms. The present study was designed to investigate the effects of sub-chronic exposure to morphine on the expression of neurotransmitter receptor subunits, which might contribute to the potency changes of ketamine and propofol in vivo.

METHODS

Sub-chronic exposure to morphine was established by administering subcutaneous injections of morphine for 5 consecutive days. The median effective dose (ED₅₀) of ketamine and/or propofol was measured on day 1, day 3, day 7 and day 15, after the last morphine dosage. Mice in the sham group received an equal volume of normal saline. The expressions of N-methyl D-aspartate (NMDA) receptor and γ-aminobutyric acid A (GABA_A) receptor subunits in the forebrain were measured. Knockdown or overexpression of a subunit was used to determine the causality between the change in anesthetic potency and the expression of an identified receptor subunit.

RESULTS

After sub-chronic exposure of mice to morphine, the expression of NMDA receptor 1 (NR1) was most elevated in the forebrain on day 1 (P < 0.0001 vs. sham). In contrast, the expression of GABA_A receptor β3 (GABA_ARβ3) gradually decreased to its lowest level on day 7 (P = 0.005 vs. sham) in the forebrain. Regression analysis revealed that the expression of NR1 in the forebrain was relevant to the increased ED₅₀ of ketamine (P = 0.0002), while the expression of GABA_ARβ3 in the forebrain was relevant to the decreased ED₅₀ of propofol (P = 0.0051) after morphine exposure. Knockdown expression of NR1 in the forebrain reversed the elevated ED₅₀ of ketamine after morphine treatment. Overexpression of GABA_ARβ3 in the forebrain increased the ED₅₀ of propofol to the sham-level after morphine treatment.

CONCLUSIONS

Sub-chronic exposure to morphine can differentially modulate the expressions of NR1 and GABA_ARβ3 in mice, which may contribute to the changes in ED₅₀ of ketamine and propofol in vivo.

Polyspikes and Rhythmic Polyspikes During Volatile Induction of General Anesthesia With Sevoflurane Result in Bispectral Index Variations

BACKGROUND

Although electroencephalography (EEG)-based indices may show artifactual values, raw EEG signal is seldom used to monitor the depth of volatile induction of general anesthesia (VIGA). The current analysis aimed to identify whether bispectral index (BIS) variations reliably reflect the actual depth of general anesthesia during presence of different types of epileptiform patterns (EPs) in EEGs during induction of general anesthesia.

METHODS

Sixty patients receiving either VIGA with sevoflurane using increasing concentrations (group VIMA) or vital capacity (group VCRII) technique or intravenous single dose of propofol (group PROP) were included. Monitoring included facial electromyography (fEMG), fraction of inspired sevoflurane (FiAA), fraction of expired sevoflurane (FeAA), minimal alveolar concentration (MAC) of sevoflurane, BIS, standard EEG, and hemodynamic parameters.

RESULTS

In the PROP group no EPs were observed. During different stages of VIGA with sevoflurane in the VIMA and VCRII groups, presence of polyspikes and rhythmic polyspikes in patients' EEGs resulted in artifactual BIS values indicating a false awareness/wakefulness from anesthesia, despite no concomitant change of FiAA, FeAA, and MAC of sevoflurane. Periodic epileptiform discharges did not result in aberrant BIS values.

CONCLUSION

Our results suggest that raw EEG correlate it with values of BIS, FiAA, FeAA, and MAC of sevoflurane during VIGA. It seems that because artifactual BIS values indicating false awareness/wakefulness as a result of presence of polyspikes and rhythmic polyspikes in patients' EEGs may be misleading to an anesthesiologist, leading to unintentional administration of toxic concentration of sevoflurane in ventilation gas.

Neuromonitoring during general anesthesia in non-neurologic surgery

Cerebral complications are common in perioperative settings even in non-neurosurgical procedures. These include postoperative cognitive dysfunction or delirium as well as cerebrovascular accidents. During surgery, it is essential to ensure an adequate degree of sedation and analgesia, and at the same time, to provide hemodynamic and respiratory stability in order to minimize neurological complications. In this context, the role of neuromonitoring in the operating room is gaining interest, even in the non-neurolosurgical population. The use of multimodal neuromonitoring can potentially reduce the occurrence of adverse effects during and after surgery, and optimize the administration of anesthetic drugs. In addition to the traditional focus on monitoring hemodynamic and respiratory systems during general anesthesia, the ability to constantly monitor the activity and maintenance of brain homeostasis, creating evidence-based protocols, should also become part of the standard of care: in this challenge, neuromonitoring comes to our aid. In this review, we aim to describe the role of the main types of noninvasive neuromonitoring such as those based on electroencephalography (EEG) waves (EEG, Entropy module, Bispectral Index, Narcotrend Monitor), near-infrared spectroscopy (NIRS) based on noninvasive measurement of cerebral regional oxygenation, and Transcranial Doppler used in the perioperative settings in non-neurosurgical intervention. We also describe the advantages, disadvantage, and limitation of each monitoring technique.

High Incidence of Burst Suppression during Propofol Sedation for Outpatient Colonoscopy: Lessons Learned from Neuromonitoring

Background

Although anesthesia providers may plan for moderate sedation, the depth of sedation is rarely quantified. Using processed electroencephalography (EEG) to assess the depth of sedation, this study investigates the incidence of general anesthesia with variable burst suppression in patients receiving propofol for outpatient colonoscopy. The lessons learned from neuromonitoring can then be used to guide institutional best sedation practice.

Methods

This was a prospective observational study of 119 outpatients undergoing colonoscopy at Thomas Jefferson University Hospital (TJUH). Propofol was administered by CRNAs under anesthesiologists' supervision. The Patient State Index (PSi™) generated by the Masimo SedLine® Brain Root Function monitor (Masimo Corp., Irvine, CA) was used to assess the depth of sedation. PSi data correlating to general anesthesia with variable burst suppression were confirmed by neuroelectrophysiologists' interpretation of unprocessed EEG.

Results

PSi values of <50 consistent with general anesthesia were attained in 118/119 (99.1%) patients. Of these patients, 33 (27.7%) attained PSi values <25 consistent with variable burst suppression. The 118 patients that reached PSi <50 spent a significantly greater percentage (53.1% vs. 42%) of their case at PSi levels <50 compared to PSi levels >50 (p=0.001). Mean total propofol dose was significantly correlated to patient PSi during periods of PSi <25 (R=0.406, p=0.021).

Conclusion

Although providers planned for moderate to deep sedation, processed EEG showed patients were under general anesthesia, often with burst suppression. Anesthesiologists and endoscopists may utilize processed EEG to recognize their institutional practice patterns of procedural sedation with propofol and improve upon it.

A two-step surgery and a multidisciplinary approach in a centenarian patient with an acute presentation of right colon cancer

Background

As surgery remains the cornerstone of colorectal cancer (CRC) treatment, the number of older patients presented for colorectal resection is rapidly increasing. Nevertheless, the choice to operate an oldest-old patient still remain challenging and requires a careful assessment of risk to benefit ratio in order to guarantee appropriate surgical strategies and perioperative management.

Case presentation

A centenarian patient, acutely admitted to the emergency department, was diagnosed with an ileus caused by stenosing ascending colon cancer with abnormal distension of the right colon at high risk of perforation. Facing with this complex clinical scenario, a lateral decompressive cecostomy as alternative surgical procedure, was performed in local anesthesia in order to avoid the stressful event of an emergency surgery. Thereafter, the patient was admitted to the surgical ward and followed by a geriatrician who performed a comprehensive geriatric assessment (CGA) and daily clinical evaluations. This integrated plan of care was mainly focused on rehabilitation, nutritional interventions and therapeutic reconciliation, maximizing patient’s clinical conditions and performance status. Then, the second surgical step, the radical colon surgery with curative intent and bowel continuity reestablishment was performed, demonstrating to be feasible and safety also in a very advanced age patient in term of prolonged survival and preservation of an adequate quality of life.

Conclusions

This is the first case-report that illustrates a successful two step surgery for CRC in a centenarian patient thanks to a multidisciplinary based approach, overwhelming the mere concept of chronological age.

Permutation entropy in intraoperative ECoG of brain tumour patients in awake tumour surgery- a robust parameter to separate consciousness from unconsciousness

Awake craniotomies represent an essential opportunity in the case of lesions in eloquent areas. Thus, optimal surveillance of the patient during different stages of sedation, as well as the detection of seizure activity during brain surgery, remains difficult, as skin electrodes for electroencephalographic (EEG) analysis are not applicable in most cases. We assessed the applicability of ECoG to monitor different stages of sedation, as well as the influence of different patient characteristics, such as tumour volume, size, entity, and age or gender on permutation entropy (PeEn). We conducted retrospective analysis of the ECoG data of 16 patients, who underwent awake craniotomies because of left-sided brain tumours at our centre between 2014 and 2016. PeEn could be easily calculated and compared using frontal and parietal cortical electrodes. A comparison of PeEn scores showed significantly higher values in awake patients than in patients under anaesthesia (p ≤ 0.004) and significantly higher ones in the state of transition than under general anaesthesia (p = 0.023). PeEn scores in frontal and parietal leads did not differ significantly, making them both applicable for continuous surveillance during brain surgery. None of the following clinical characteristics showed significant correlation with PeEn scores: tumour volume, WHO grade, first or recurrent tumour, gender, and sex. Being 50 years or older led to significantly lower values in parietal leads but not in frontal leads. ECoG and a consecutive analysis of PeEn are feasible and suitable for the continuous surveillance of patients during awake craniotomies. Hence, the analysis is not influenced by patients' clinical characteristics.

Electroencephalography and Brain Oxygenation Monitoring in the Perioperative Period

Maintaining brain function and integrity is a pivotal part of anesthesiological practice. The present overview aims to describe the current role of the 2 most frequently used monitoring methods for evaluation brain function in the perioperative period, ie, electroencephalography (EEG) and brain oxygenation monitoring. Available evidence suggests that EEG-derived parameters give additional information about depth of anesthesia for optimizing anesthetic titration. The effects on reduction of drug consumption or recovery time are heterogeneous, but most studies show a reduction of recovery times if anesthesia is titrated along processed EEG. It has been hypothesized that future EEG-derived indices will allow a better understanding of the neurophysiological principles of anesthetic-induced alteration of consciousness instead of the probabilistic approach most often used nowadays.Brain oxygenation can be either measured directly in brain parenchyma via a surgical burr hole, estimated from the venous outflow of the brain via a catheter in the jugular bulb, or assessed noninvasively by near-infrared spectroscopy. The latter method has increasingly been accepted clinically due to its ease of use and increasing evidence that near-infrared spectroscopy-derived cerebral oxygen saturation levels are associated with neurological and/or general perioperative complications and increased mortality. Furthermore, a goal-directed strategy aiming to avoid cerebral desaturations might help to reduce these complications. Recent evidence points out that this technology may additionally be used to assess autoregulation of cerebral blood flow and thereby help to titrate arterial blood pressure to the individual needs and for bedside diagnosis of disturbed autoregulation.

Cost-Effectiveness Research in Anesthesiology

Perioperative interventions aimed at decreasing costs and improving outcomes have become increasingly popular in recent years. Anesthesiologists are often faced with a choice among different treatment strategies with little data available on the comparative cost-effectiveness. We performed a systematic review of the English language literature between 1980 and 2014 to identify cost-effectiveness analyses of anesthesiology and perioperative medicine interventions. We excluded interventions related to critical care or pediatric anesthesiology, and articles on interventions not normally ordered or performed by anesthesiologists. Of the >5000 cost-effectiveness analyses published to date, only 28 were applicable to anesthesiology and perioperative medicine and met inclusion criteria. Multidisciplinary interventions were the most cost-effective overall; 8 of 8 interventions were "dominant" (improved outcomes, reduced cost) or cost-effective, including accelerated, standardized perioperative recovery pathways, and perioperative delirium prevention bundles. Intraoperative measures were dominant in 3 of 5 cases, including spinal anesthesia for benign abdominal hysterectomy. With regard to prevention of perioperative infection, methicillin-resistant Staphylococcus aureus (MRSA) decolonization was dominant or cost-effective in 2 of 2 studies. Three studies assessing various antibiotic prophylaxis regimens had mixed results. Autologous blood donation was not found to be cost-effective in 5 of 7 studies, and intraoperative cell salvage therapy was also not cost-effective in 2 of 2 reports. Overall, there remains a paucity of cost-effectiveness literature in anesthesiology, particularly relating to intraoperative interventions and multidisciplinary perioperative interventions. Based on the available studies, multidisciplinary perioperative optimization interventions such as accelerated, standardized perioperative recovery pathways, and perioperative delirium prevention bundles tended to be most cost-effective. Our review demonstrates that there is a need for more rigorous cost-effective analyses in many areas of anesthesiology and that anesthesiologists should continue to lead collaborative, multidisciplinary efforts in perioperative medicine.

Joint consensus on anesthesia in urologic and gynecologic robotic surgery: specific issues in management from a task force of the SIAARTI, SIGO, and SIU

INTRODUCTION

Proper management of patients undergoing robotic-assisted urologic and gynecologic surgery must consider a series of peculiarities in the procedures for anesthesiology, critical care medicine, respiratory care, and pain management. Although the indications for robotic-assisted urogynecologic surgeries have increased in recent years, specific guidance documents are still lacking.

EVIDENCE ACQUISITION

A multidisciplinary group including anesthesiologists, gynecologists, urologists, and a clinical epidemiologist systematically reviewed the relevant literature and provided a set of recommendations and unmet needs on peculiar aspects of anesthesia in this field.

EVIDENCE SYNTHESIS

Nine core contents were identified, according to their requirements in urogynecologic robotic-assisted surgery: patient position, pneumoperitoneum and ventilation strategies, hemodynamic variations and fluid therapy, neuromuscular block, renal surgery and prevention of acute kidney injury, monitoring the Department of anesthesia, postoperative delirium and cognitive dysfunction, prevention of postoperative nausea and vomiting, and pain management in endometriosis.

CONCLUSIONS

This consensus document provides guidance for the management of urologic and gynecologic patients scheduled for robotic-assisted surgery. Moreover, the identified unmet needs highlight the requirement for further prospective randomized studies.

Anesthesia depth monitoring using alternative placement of entropy sensors: a prospective study

Spectral entropy is based on analysis of variations in electroencephalography and frontal electromyography, and is a safe and reliable method for anesthesia depth monitoring. However, standard frontal positioning of entropy electrodes in patients undergoing cardiac surgery is sometimes challenging. The present study aimed to compare standard entropy sensor placement with an alternative (infraorbital) site. This prospective study included 20 patients who underwent cardiovascular surgery at the authors' center. Monitoring was performed with standard and alternative entropy electrode positions from patient admission to surgery to transfer to the intensive care unit. Data were recorded every 15 s; all data were analyzed and compared using Bland-Altman, scatter plot with Pearson correlation coefficient, and sensitivity/specificity analyses. Overall, 20,784 pairs of response entropy (RE) and state entropy (SE) indexes were collected. Bland-Altman analysis revealed a mean difference in RE of 0.37 (95% LOA - 7.09, 7.88) and SE 0.69 (95% LOA - 5.95, 7.31); with 3.46% (720/20,784) RE and 3.40% (706/10,790) SE values lying outside of the limits of agreement. Correlation analysis revealed strong positive correlation in both cases: RE, r = 0.983, p < 0.05; SE, r = 0.984; p < 0.05. Sensitivity/specificity analysis revealed 98.1% sensitivity, 93.3% specificity and 97.1% test efficiency for RE, and 99.2%, 95.1% and 98.5% for SE, respectively. Infraorbital entropy sensor placement in patients undergoing cardiovascular surgery is reliable and effective. The strong positive correlation between the two methods of registration enables alternative entropy measurement when frontal placement is not possible.

Equipment failure of intravenous syringe pump detected by increase in Narcotrend stage: A case report

RATIONALE

Awareness is the recovery of consciousness during general anesthesia. It occurs when patients under general anesthesia receive inadequate anesthetic medications to maintain unconsciousness during surgery. Equipment failure is a common cause of intraoperative awareness.

PATIENT CONCERNS

A 16-year-old boy, 85 kg in weight, was admitted to our hospital for thyroglossal cystectomy under general anesthesia. Six minutes after the intubation, we noted that the Narcotrend index indicated a condition of light anesthesia and the patient was observed to be in tears.

DIAGNOSIS

Improper positioning of the syringe fixing clamp on the CP700TCI infusion pump caused equipment failure and light anesthesia.

INTERVENTIONS

Bolus of 50 mg propofol and 2 mg midazolam were administered manually by syringe, and inhalation of 2% sevoflurane was supplemented. Infusion pump was replaced.

OUTCOMES

The Narcotrend index of the patient returned to state of deep anesthesia following manual administration of the anesthetic medications. Following the surgery, the patient had an uneventful recovery, and did not present with evidence of awareness.

LESSONS

Users of the CP700TCI syringe pump should pay attention to the position of the syringe fixing clamp. Anesthesiologists should check all the equipment according to a defined checklist prior to anesthesia. Narcotrend monitor could help to detect light anesthesia and prevent potential awareness.

Adverse postoperative cognitive disorders: a national survey of portuguese anesthesiologists

Background and objectives

Postoperative delirium and postoperative cognitive dysfunction are some of the most common complications in older surgical patients and are associated with adverse outcomes. The aim of this study was to evaluate portuguese anesthesiologists’ perspectives and knowledge about adverse postoperative cognitive disorders, and routine clinical practice when caring for older surgical patients.

Methods

We used a prospective online survey with questions using a Likert scale from 1 to 5 (completely disagree to completely agree), or yes/no/don’t know answer types. Potential participants were portuguese anesthesiologists working in hospitals affiliated with the portuguese national health system and private hospitals.

Results

We analyzed 234 surveys (17.7% of total potential respondents). The majority believed that the risk of cognitive side effects should be considered when choosing the type of anesthesia (87.6%) and that preoperative cognitive function should be routinely assessed (78.6%). When caring for an agitated and confused patient postoperatively, 62.4% would first administer an analgesic and 11.1% an anxiolytic. Protocols to screen and manage postoperative cognitive disorders are rarely used. Nearly all respondents believe that postoperative delirium and postoperative cognitive dysfunction are neglected areas in anesthesiology.

Conclusions

Overall, participants perceive postoperative cognitive disorders as important adverse outcomes following surgery and anesthesia are aware of the main risk factors for their development but may lack information on prevention and management of postoperative delirium. The majority of hospitals do not have protocols regarding preoperative cognitive assessment, diagnosis, management or follow-up of patients with delirium and postoperative cognitive dysfunction.

Neuromonitoring in the ambulatory anesthesia setting: a pro-con discussion

PURPOSE OF REVIEW

Various neurologically focused monitoring modalities such as processed electroencephalography (pEEG), tissue/brain oxygenation monitors (SbO2), and even somatosensory evoked responses have been suggested as having the potential to improve the well tolerated and effective delivery of care in the setting of outpatient surgery. The present article will discuss the pros and cons of such monitors in this environment.

RECENT FINDINGS

There is a paucity of evidence from rigorous, well designed clinical trials demonstrating that the routine use of any neuromonitoring technique in an ambulatory surgery setting leads to meaningful cost savings or a reduction in morbidity or mortality.

SUMMARY

The use of advanced neuromonitoring techniques (primarily pEEG) may be considered reasonable in two instances: for the prevention of intraoperative awareness during the administration of total intravenous anesthesia coupled with the use of a neuromuscular blocking drug, and for the prevention of relative drug overdose (and possibly postoperative delirium) in the elderly.

[Adverse postoperative cognitive disorders: a national survey of portuguese anesthesiologists]

BACKGROUND AND OBJECTIVES

Postoperative delirium and postoperative cognitive dysfunction are some of the most common complications in older surgical patients and are associated with adverse outcomes. The aim of this study was to evaluate portuguese anesthesiologists' perspectives and knowledge about adverse postoperative cognitive disorders, and routine clinical practice when caring for older surgical patients.

METHODS

We used a prospective online survey with questions using a Likert scale from 1 to 5 (completely disagree to completely agree), or yes/no/don't know answer types. Potential participants were portuguese anesthesiologists working in hospitals affiliated with the portuguese national health system and private hospitals.

RESULTS

We analyzed 234 surveys (17.7% of total potential respondents). The majority believed that the risk of cognitive side effects should be considered when choosing the type of anesthesia (87.6%) and that preoperative cognitive function should be routinely assessed (78.6%). When caring for an agitated and confused patient postoperatively, 62.4% would first administer an analgesic and 11.1% an anxiolytic. Protocols to screen and manage postoperative cognitive disorders are rarely used. Nearly all respondents believe that postoperative delirium and postoperative cognitive dysfunction are neglected areas in anesthesiology.

CONCLUSIONS

Overall, participants perceive postoperative cognitive disorders as important adverse outcomes following surgery and anesthesia are aware of the main risk factors for their development but may lack information on prevention and management of postoperative delirium. The majority of hospitals do not have protocols regarding preoperative cognitive assessment, diagnosis, management or follow-up of patients with delirium and postoperative cognitive dysfunction.

Cost-effectiveness of anesthesia maintained with sevoflurane or propofol with and without additional monitoring: a prospective, randomized controlled trial

Background

We compared cost-effectiveness of anesthesia maintained with sevoflurane or propofol with and without additional monitoring, in the clinical setting of ear-nose-throat surgery.

Methods

One hundred twenty adult patients were randomized to four groups. In groups SEVO and SEVO+ anesthesia was maintained with sevoflurane, in group SEVO+ with additional bispectral index (BIS) and train-of-four (TOF) monitoring. In groups PROP and PROP+ anesthesia was maintained with propofol, in group PROP+ with additional BIS and TOF monitoring.

Results

Total cost of anesthesia per hour was greater in group SEVO+ compared to SEVO [€ 19.95(8.53) vs. 12.15(5.32), p <  0.001], and in group PROP+ compared to PROP (€ 22.11(8.08) vs. 13.23(4.23), p <  0.001]. Time to extubation was shorter in group SEVO+ compared to SEVO [11.1(4.7) vs. 14.5(3.9) min, p = 0.002], and in PROP+ compared to PROP [12.6(5.4) vs. 15.2(4.7) min, p <  0.001]. Postoperatively, arterial blood pressure returned to its initial values sooner in groups SEVO+ and PROP+.

Conclusions

Our study demonstrated that the use of BIS and TOF monitoring decreased the total cost of anesthesia drugs and hastened postoperative recovery. However, in our circumstances, these were associated with higher disposables costs. Detailed cost analysis and further investigations are needed to identify patient populations who would benefit most from additional monitoring.

Trial registration

ClinicalTrials.gov, NCT02920749. Retrospectively registered (date of registration September 2016).

Joint consensus on abdominal robotic surgery and anesthesia from a task force of the SIAARTI and SIC

Minimally invasive surgical procedures have revolutionized the world of surgery in the past decades. While laparoscopy, the first minimally invasive surgical technique to be developed, is widely used and has been addressed by several guidelines and recommendations, the implementation of robotic-assisted surgery is still hindered by the lack of consensus documents that support healthcare professionals in the management of this novel surgical procedure. Here we summarize the available evidence and provide expert opinion aimed at improving the implementation and resolution of issues derived from robotic abdominal surgery procedures. A joint task force of Italian surgeons, anesthesiologists and clinical epidemiologists reviewed the available evidence on robotic abdominal surgery. Recommendations were graded according to the strength of evidence. Statements and recommendations are provided for general issues regarding robotic abdominal surgery, operating theatre organization, preoperative patient assessment and preparation, intraoperative management, and postoperative procedures and discharge. The consensus document provides evidence-based recommendations and expert statements aimed at improving the implementation and management of robotic abdominal surgery.

Unusual elevation in Entropy but not in PSI during general anesthesia: a case report

Background

EEG monitoring is useful for determining an adequate level of anesthesia. However it is sometimes interfered by various reasons. We describe a case in which we successfully confirmed the adequate depth of anesthesia by monitoring the patient state index (PSI), which was computed from the SedLine monitor data in Root (Masimo) during general anesthesia. Our case showed unusual elevations in entropy, but not in PSI.

Case presentation

A 34-year-old woman was scheduled for emergency surgery for a left tibial open fracture and a right femoral closed fracture, which were sustained during a traffic accident. Forty-five minutes after intubation, the response entropy abruptly increased up to 100 and state entropy to 91. Despite the absence of other abnormal events, the entropy data led to two types of incorrect decisions. The first was owing to the effect of the EMG and the second was misleading during the surgeon’s hammering. However, PSI from the SedLine monitor seemed to be less influenced by the same events.

Conclusions

In this report, we suggest that the PSI, derived from new-generation SedLine (Root, Masimo) may be a useful parameter for clinically determining the level of sedation. The use of two monitoring devices with different EEG algorithms might be helpful for determining the anesthetic depth and making decisions.

Electronic supplementary material

The online version of this article (10.1186/s12871-018-0486-8) contains supplementary material, which is available to authorized users.

Neurophysiological assessment of brain dysfunction in critically ill patients: an update

The aim of this review was to provide up-to-date information about the usefulness of clinical neurophysiology testing in the management of critically ill patients. Evoked potentials (EPs) and electroencephalogram (EEG) are non-invasive clinical neurophysiology tools that allow an objective assessment of the central nervous system's function at the bedside in intensive care unit (ICU). These tests are quite useful in diagnosing cerebral complications, and establishing the vital and functional prognosis in ICU. EEG keeps a particularly privileged importance in detecting seizures phenomena such as subclinical seizures and non-convulsive status epilepticus. Quantitative EEG (QEEG) analysis techniques commonly called EEG Brain mapping can provide obvious topographic displays of digital EEG signals characteristics, showing the potential distribution over the entire scalp including filtering, frequency, and amplitude analysis and color mapping. Evidences of usefulness of QEEG for seizures detection in ICU are provided by several recent studies. Furthermore, beyond detection of epileptic phenomena, changes of some QEEG panels are early warning indicators of sedation level as well as brain damage or dysfunction in ICU. EPs offer the opportunity for assessing brainstem's functional integrity, as well as subcortical and cortical brain areas. A multimodal use, combining EEG and various modalities of EPs is recommended since this allows a more accurate functional exploration of the brain and helps caregivers to tailor therapeutic measures according to neurological worsening trends and to anticipate the prognosis in ICU.

Standards of anesthesiology practice during neuroradiological interventions

Interventional radiology is a rapidly growing discipline with an expanding variety of indications and techniques in pediatric and adult patients. Accordingly, the number of procedures during which monitoring either under sedation or under general anesthesia is needed is increasing. In order to ensure high-quality care as well as patient comfort and safety, implementation of anes-thesiology practice guidelines in line with institutional radiology practice guidelines is paramount [1]. However, practice guidelines are no substitute for lack of communi-cation between specialties. Interdisciplinary indications within neurosciences call for efficient co-operation among radiology, neurology, neurosurgery, vascular surgery, anesthesiology and intensive care. Anesthesia team and intensive care personnel should be informed early and be involved in coordinated planning so that optimal results can be achieved under minimized risks and pre-arranged complication management.

Consciousness fluctuation during general anesthesia: a theoretical approach to anesthesia awareness and memory modulation

With anesthesia awareness as a model of study we debate the both fascinating and dangerous phenomenon called consciousness fluctuation that takes place during surgical anesthesia. In accordance with current scientific knowledge this paradox is the consequence of our limits in both precise knowledge of anesthesia mechanisms and our inability to accurately assess the level of anesthesia with brain monitoring. We also focus on the relationships between memory and anesthesia, as well as the possibility of interfering with memory during general anesthesia.

Spectral entropy monitoring for adults and children undergoing general anaesthesia

BACKGROUND

Anaesthetic drugs during general anaesthesia are titrated according to sympathetic or somatic responses to surgical stimuli. It is now possible to measure depth of anaesthesia using electroencephalography (EEG). Entropy, an EEG-based monitor can be used to assess the depth of anaesthesia using a strip of electrodes applied to the forehead, and this can guide intraoperative anaesthetic drug administration.

OBJECTIVES

The primary objective of this review was to assess the effectiveness of entropy monitoring in facilitating faster recovery from general anaesthesia. We also wanted to assess mortality at 24 hours, 30 days, and one year following general anaesthesia with entropy monitoring.The secondary objectives were to assess the effectiveness of the entropy monitor in: preventing postoperative recall of intraoperative events (awareness) following general anaesthesia; reducing the amount of anaesthetic drugs used; reducing cost of the anaesthetic as well as in reducing time to readiness to leave the postanaesthesia care unit (PACU).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 10), MEDLINE via Ovid SP (1990 to September 2014) and EMBASE via Ovid SP (1990 to September 2014). We reran the search in CENTRAL, MEDLINE via Ovid SP and EMBASE via Ovid SP in January 2016. We added one potential new study of interest to the list of 'Studies awaiting Classification' and we will incorporate this study into the formal review findings during the review update.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) conducted in adults and children (aged greater than two years of age), where in one arm entropy monitoring was used for titrating anaesthesia, and in the other standard practice (increase in heart rate, mean arterial pressure, lacrimation, movement in response to noxious surgical stimuli) was used for titrating anaesthetic drug administration. We also included trials with an additional third arm, wherein another EEG monitor, the Bispectral index (BIS) monitor was used to assess anaesthetic depth.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Two review authors independently extracted details of trial methodology and outcome data from trials considered eligible for inclusion. All analyses were made on an intention-to-treat basis. We used a random-effect model where there was heterogeneity. For assessments of the overall quality of evidence for each outcome that included pooled data from RCTs, we downgraded evidence from 'high quality' by one level for serious (or by two for very serious) study limitations (risk of bias, indirectness of evidence, serious inconsistency, imprecision of effect or potential publication bias).

MAIN RESULTS

We included 11 RCTs (962 participants). Eight RCTs (762 participants) were carried out on adults (18 to 80 years of age), two (128 participants) involved children (two to 16 years) and one RCT (72 participants) included patients aged 60 to 75 years. Of the 11 included studies, we judged three to be at low risk of bias, and the remaining eight RCTs at unclear or high risk of bias.Six RCTs (383 participants) estimated the primary outcome, time to awakening after stopping general anaesthesia, which was reduced in the entropy as compared to the standard practice group (mean difference (MD) -5.42 minutes, 95% confidence interval (CI) -8.77 to -2.08; moderate quality of evidence). We noted heterogeneity for this outcome; on performing subgroup analysis this was found to be due to studies that included participants undergoing major, long duration surgeries (off-pump coronary artery bypass grafting, major urological surgery). The MD for time to awakening with four studies on ambulatory procedures was -3.20 minutes (95% CI -3.94 to -2.45). No trial reported the second primary outcome, mortality at 24 hours, 30 days, and one year with the use of entropy monitoring.Eight trials (797 participants) compared the secondary outcome, postoperative recall of intraoperative events (awareness) in the entropy and standard practice groups. Awareness was reported by only one patient in the standard practice group, making meaningful estimation of benefit of entropy monitoring difficult; moderate quality of evidence.All 11 RCTs compared the amount of anaesthetic agent used between the entropy and standard practice groups. Six RCTs compared the amount of propofol, four compared the amount of sevoflurane and one the amount of isoflurane used between the groups. Analysis of three studies (166 participants) revealed that the MD of propofol consumption between the entropy group and control group was -11.56 mcg/kg/min (95% CI -24.05 to 0.92); low quality of evidence. Analysis of another two studies (156 participants) showed that the MD in sevoflurane consumption in the entropy group compared to the control group was -3.42 mL (95% CI -6.49 to -0.35); moderate quality of evidence.No trial reported on the secondary outcome of the cost of general anaesthesia.Three trials (170 participants) estimated MD in time to readiness to leave the PACU of the entropy group as compared to the control group (MD -5.94 minutes, 95% CI -16.08 to 4.20; low quality of evidence). Heterogeneity was noted, which was due to the difference in anaesthetic technique (propofol-based general anaesthesia) in one study. The remaining two studies had used volatile-based general anaesthesia. The MD in time to readiness to leave the PACU was -4.17 minutes (95% CI -6.84 to -1.51) with these two studies.

AUTHORS' CONCLUSIONS

The evidence as regards time to awakening, recall of intraoperative awareness and reduction in inhalational anaesthetic agent use was of moderate quality. The quality of evidence of as regards reduction in intravenous anaesthetic agent (propofol) use, as well as time to readiness to leave the PACU was found to be of low quality. As the data are limited, further studies consisting of more participants will be required for ascertaining benefits of entropy monitoring.Further studies are needed to assess the effect of entropy monitoring on focal issues such as short-term and long-term mortality, as well as cost of general anaesthesia.

Acute alcohol intoxication and bispectral index monitoring

BACKGROUND

Bispectral index (BIS) monitoring is commonly used to decrease the risk of awareness during anaesthesia. We aimed to determine the relationship between blood alcohol concentration and brain function (as measured by BIS) in healthy adults.

METHODS

In this prospective observational study, 21 anaesthetic registrars self-regulated alcohol consumption over a 3-h period. Expired alcohol concentration (breathalyser) and BIS measurements were performed hourly for 4 h. A venous blood alcohol sample was taken at the conclusion of the study period.

RESULTS

The main outcome measures were the correlation between blood alcohol and brain function as measured by BIS and the change in BIS from baseline (∆BIS) at 4 h. The median number of standard drinks consumed was 9.1 (IQR 7.7-12.3), range 5.4-17. At 4 h, there was a moderate inverse correlation between BIS and blood alcohol (r = -0.49, P = 0.029) and between ∆BIS and blood alcohol (r = -0.46, P =0.043).

CONCLUSION

In healthy young adults, we found a moderate correlation between venous blood alcohol concentration and BIS. This suggests that acute alcohol consumption can decrease BIS. This information may be relevant when providing anaesthesia to intoxicated patients who require urgent or time-critical surgery, although certain limitations of this study should be kept in mind.

Perioperative management in order to minimise postoperative delirium and postoperative cognitive dysfunction: Results from a Swedish web-based survey

Cognitive side-effects such as emergence agitation (EA), postoperative delirium (POD) and postoperative cognitive dysfunction (POCD) are not infrequently complicating the postoperative care especially in elderly and fragile patients. The aim of the present survey was to gain insight regarding concern and interest in prevention and treatment strategies for postoperative delirium and dysfunction, and the use of EEG-based depth-of-anaesthesia monitoring possibly reducing the risk for cognitive side effects among anaesthesia personnel.

METHODS

A web-based validated questionnaire was sent to all Swedish anaesthesiologists and nurse anaesthetists during summer 2013. The questionnaire consisted of 3 sections, subjective preferences, routines and practices related to the perioperative handling of EA, POD, POCD.

RESULTS

The response rate was 52%. Cardiovascular/pulmonary risks where assessed as importance by 98, 97% of responders while 69% considered the risk of neurocognitive side-effects important. When asked explicitly around cognitive side-effects 89%, 37% and 44% assessed awareness, POC and POD respectively of importance. EEG-based depth-of-anaesthesia monitors were used in 50% of hospitals. The responders were not convinced about the benefits of such monitors even in at-risk patients. Structured protocols for the management of postoperative cognitive side-effects were available only in few hospitals.

CONCLUSION

Swedish anaesthesia personnel are concerned about the risk of postoperative cognitive side-effects but are more concerned about cardiovascular/pulmonary risks, pain, PONV and the rare event of awareness. Most respondents were not convinced about the use of depth-of-anaesthesia monitors. There is a need to improve knowledge around risk factors, prevention and management of postoperative cognitive side effects.

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.

Using bispectral index and cerebral oximetry to guide hemodynamic therapy in high-risk surgical patients

High-risk surgery represents 12.5% of cases but contributes 80% of deaths in the elderly population. Reduction in morbidity and mortality by the use of intervention strategies could result in thousands of lives being saved and savings of up to £400m per annum in the UK. This has resulted in the drive towards goal-directed therapy and intraoperative flow optimization of high-risk surgical patients being advocated by authorities such as the National Institute of Health and Care Excellence and the Association of Anaesthetists of Great Britain and Ireland.Conventional intraoperative monitoring gives little insight into the profound physiological changes occurring as a result of anesthesia and surgery. The build-up of an oxygen debt is associated with a poor outcome and strategies have been developed in the postoperative period to improve outcomes by repayment of this debt. New monitoring technologies such as minimally invasive cardiac output, depth of anesthesia and cerebral oximetry can minimize oxygen debt build-up. This has the potential to reduce complications and lessen the need for postoperative optimization in high-dependency areas.Flow monitoring has thus emerged as essential during intraoperative monitoring in high-risk surgery. However, evidence suggests that current optimization strategies of deliberately increasing flow to meet predefined targets may not reduce mortality.Could the addition of depth of anesthesia and cerebral and tissue oximetry monitoring produce a further improvement in outcomes?Retrospective studies indicate a combination of excessive depth of anesthesia hypotension and low anesthesia requirement results in increased mortality and length of hospital stay.Near infrared technology allows assessment and maintenance of cerebral and tissue oxygenation, a strategy, which has been associated with improved outcomes. The suggestion that the brain is an index organ for tissue oxygenation, especially in the elderly, indicates a role for this technology in the intraoperative period to assess the adequacy of oxygen delivery and reduce the build-up of an oxygen debt.The aim of this article is to make the case for depth of anesthesia and cerebral oximetry alongside flow monitoring as a strategy for reducing oxygen debt during high-risk surgery and further improve outcomes in high-risk surgical patients.