Processed Electroencephalogram Monitoring and Postoperative Delirium: A Systematic Review and Meta-analysis

Incidence of Concurrent Cerebral Desaturation and Electroencephalographic Burst Suppression in Cardiac Surgery Patients

BACKGROUND

Increased intraoperative electroencephalographic (EEG) burst suppression is associated with postoperative delirium. Cerebral desaturation is considered as one of the factors associated with burst suppression. Our study investigates the association between cerebral desaturation and burst suppression by analyzing their concurrence. Additionally, we aim to examine their association with cardiac surgical phases to identify potential for targeted interventions.

METHODS

We retrospectively analyzed intraoperative 1-minute interval observations in 51 patients undergoing cardiac surgery. Processed EEG and cerebral oximetry were collected, with the anesthesiologists blinded to the information. The associations between cerebral desaturation (defined as a 10% decrease from baseline) and burst suppression, as well as with phase of cardiac surgery, were analyzed using the Generalized Logistic Mixed Effect Model. The results were presented as odds ratio and 95% confidence intervals (CIs). A value of P < .05 was considered statistically significant.

RESULTS

The odds of burst suppression increased 1.5 times with cerebral desaturation (odds ratio [OR], 1.52, 95% CI, 1.11-2.07; P = .009). Compared to precardiopulmonary bypass (pre-CPB), the odds of cerebral desaturation were notably higher during CPB (OR, 22.1, 95% CI, 12.4-39.2; P < .001) and post-CPB (OR, 18.2, 95% CI, 12.2-27.3; P < .001). However, the odds of burst suppression were lower during post-CPB (OR, 0.69, 95% CI, 0.59-0.81; P < .001) compared to pre-CPB. Compared to pre-CPB, the odds of concurrent cerebral desaturation and burst suppression were notably higher during CPB (OR, 52.3, 95% CI, 19.5-140; P < .001) and post-CPB (OR, 12.7, 95% CI, 6.39-25.2; P < .001). During CPB, the odds of cerebral desaturation (OR, 6.59, 95% CI, 3.62-12; P < .001) and concurrent cerebral desaturation and burst suppression (OR, 10, 95% CI, 4.01-25.1; P < .001) were higher in the period between removal of aortic cross-clamp and end of CPB. During the entire surgery, the odds of burst suppression increased 8 times with higher inhalational anesthesia concentration (OR, 7.81, 95% CI, 6.26-9.74; P < .001 per 0.1% increase).

CONCLUSIONS

Cerebral desaturation is associated with intraoperative burst suppression during cardiac surgery, most significantly during CPB, especially during the period between the removal of the aortic cross-clamp and end of CPB. Further exploration with simultaneous cerebral oximetry and EEG monitoring is required to determine the causes of burst suppression. Targeted interventions to address cerebral desaturation may assist in mitigating burst suppression and consequently enhance postoperative cognitive function.

Electroencephalogram monitoring during anesthesia and critical care: a guide for the clinician

Perioperative anesthetic, surgical and critical careinterventions can affect brain physiology and overall brain health. The clinical utility of electroencephalogram (EEG) monitoring in anesthesia and intensive care settings is multifaceted, offering critical insights into the level of consciousness and depth of anesthesia, facilitating the titration of anesthetic doses, and enabling the detection of ischemic events and epileptic activity. Additionally, EEG monitoring can aid in predicting perioperative neurocognitive disorders, assessing the impact of systemic insults on cerebral function, and informing neuroprognostication. This review provides a comprehensive overview of the fundamental principles of electroencephalography, including the foundations of processed and quantitative electroencephalography. It further explores the characteristic EEG signatures associated wtih anesthetic drugs, the interpretation of the EEG data during anesthesia, and the broader clinical benefits and applications of EEG monitoring in both anesthetic practice and intensive care environments.

Anesthesia-induced electroencephalogram oscillations and perioperative outcomes in older adults undergoing cardiac surgery

BACKGROUND

Electroencephalogram oscillations during general anesthesia may change as a function of cognitive and physical health. This study aimed to characterize associations between anesthesia-induced oscillations and postoperative outcomes in cardiac surgery patients over 60 years.

METHODS

This was a prespecified secondary data analysis from the Minimizing Intensive Care Unit Dysfunction with Dexmedetomidine-induced Sleep (MINDDS) study. Participants were admitted from home for elective cardiac surgery with cardiopulmonary bypass. The primary outcome was postoperative delirium obtained using the Confusion Assessment Method. Secondary outcomes were non-home discharge and 30-day readmission. The exposure of interest was alpha power measured during the maintenance phase of isoflurane-general anesthesia. Confounding cognitive and physical health variables were collected.

RESULTS

Of 394 participants in the MINDDS study, 302 had analyzable electroencephalograms. The incidence of postoperative delirium was 11.1 %. Odds of postoperative delirium decreased by 14 % for every decibel increase in alpha power (OR 0.86, 95 % CI: 0.78 to 0.95; P = 0.004). This finding was not significant in adjusted analysis (ORadj 0.92, 95 % CI: 0.81 to 1.03; P = 0.154). Non-home discharge setting findings were not associated with alpha power. The odds of 30-day readmission decreased by 20 % for every decibel increase in alpha power (ORadj 0.80, 95 % CI: 0.71 to 0.91; P < 0.001). Findings were conserved in exploratory and sensitivity analyses.

CONCLUSIONS

In this study anesthesia-induced oscillations were associated with postoperative outcomes; however, these were not independently associated with delirium or discharge disposition after considering preoperative cognitive and physical health. These oscillations were robustly associated with 30-day readmission however, which may help anesthesiologists identify high-risk patients, offering benefits beyond the operating room.

CLINICAL TRIAL REGISTRATION

Registration Number: NCT02856594.

Prevention and management of postoperative delirium in adult patients: a best practice implementation project

OBJECTIVE

To describe the process of implementing evidence-based best practices to improve the prevention and management of Postoperative Delirium in the Post-Anesthesia Care Unit.

METHOD

Report on an evidence implementation project applying the JBI based on the audit and feedback process, with a structured approach to identifying and managing barriers in accordance with recommended clinical practices. Medical records, electronic nursing record systems, and staff interviews were used to assess compliance rates.

RESULTS

In the baseline audit, a zero compliance rate was found in most criteria in relation to the best evidence. Following this phase, interprofessional training was carried out, a validated tool was provided to identify patients at risk of delirium, and changes were made to the electronic nursing records system. In the first follow-up audit, there was an increase in the compliance rate in four of the nine criteria audited. Four criteria achieved 100% compliance in the second follow-up audit.

CONCLUSION

Best practices were implemented that contributed to improving the prevention and management of Postoperative Delirium. Subsequent to new training and re-auditing after one year, an increase in adherence to best practices was observed.

Modulating delirium through stimulation (MoDeSt): study protocol for a randomized, double-blind, sham-controlled trial assessing the effect of postoperative transcranial electrical stimulation on delirium incidence

BACKGROUND

Postoperative delirium (POD) is the most common neurological adverse event among elderly patients undergoing surgery. POD is associated with an increased risk for postoperative complications, long-term cognitive decline, an increase in morbidity and mortality as well as extended hospital stays. Delirium prevention and treatment options are currently limited. This study will evaluate the effect of transcranial electrical stimulation (tES) on the incidence of POD.

METHODS

We will perform a randomized, double-blind, sham-controlled trial using single-session postoperative application of tES in the recovery room in 225 patients (> 65 years) undergoing elective major surgery. Patients will be randomly allocated (ratio 1:1:1) to one of three study groups: (1) alpha-tACS over posterior parietal cortex [2 mA, 20 min], (2) anodal tDCS over left dorsolateral prefrontal cortex [2 mA, 20 min], (3) sham [2 mA, 30 s]. Delirium will be screened twice daily with the 3-min diagnostic interview Confusion Assessment Method (3D-CAM) in the 5 days following surgery. The primary outcome is the incidence of POD defined as at least one positive screening during the five first postoperative days compared between tACS and sham groups. Secondary outcomes include delirium severity, duration, phenotype, postoperative pain, postoperative nausea and vomiting, electroencephalographic (EEG) markers, and fluid biomarkers.

DISCUSSION

If effective, tES is a novel, easily applicable, non-invasive method to prevent the occurrence of POD. The comprehensive neurophysiological and biofluid assessments for markers of (neuro-)inflammation and neurodegeneration will shed light on the pathomechanisms behind POD and further elucidate the (after-)effects of tES. The potential implications for the postoperative recovery comprise enhanced patient safety, neurocognitive outcome, perioperative manageability but also reduced healthcare costs.

TRIAL REGISTRATION

German Clinical Trial Registry DRKS00033703. Registered on February 23, 2024.

Neural oscillations and memory: unraveling the mechanisms of anesthesia-induced amnesia

General anesthesia is a widely used medical practice, affecting more than 300 million patients annually. Despite its ubiquity, the underlying mechanisms through which anesthetic agents induce amnesia remain poorly understood. This review explores the impact of general anesthetics on memory function, with a particular focus on the role of neural oscillations in anesthesia-induced memory suppression. Neural oscillations, such as theta, gamma, delta oscillations, slow oscillations (SO), spindles, and sharp wave ripples (SWR), are critical for memory formation and consolidation. Various anesthetics modulate these oscillations in ways that affect memory, even at subanesthetic concentrations. We highlight recent findings on the molecular and electrophysiological mechanisms by which general anesthetics influence memory-related neural oscillations, including the inhibition of synaptic plasticity, alterations in spike-timing-dependent plasticity (STDP), and disruption of cross-frequency couplings like theta-gamma and SO-spindle-SWR. Additionally, the review addresses the significance of age in anesthesia-related memory loss, with elderly patients being particularly vulnerable to long-term cognitive decline. Electrophysiological techniques, such as Electroencephalography (EEG); and advanced neuromodulation techniques, such as chemogenetics, and optogenetics, have provided insights into the neural dynamics underpinning anesthesia-induced amnesia, yet the causal relationship between EEG rhythms and memory impairment remains to be fully elucidated. This review underscores the importance of further research into the interaction between anesthesia, neural oscillations, and memory. Understanding these mechanisms will not only advance theoretical knowledge of general anesthesia but also aid in the development of safer anesthetic strategies to mitigate postoperative cognitive dysfunction, especially in high-risk populations.

Early processed electroencephalography for the monitoring of deeply sedated mechanically ventilated critically ill patients

BACKGROUND

Deep sedation may be indicated in the intensive care unit (ICU) for the management of acute organ failure, but leads to sedative-induced delirium. Whether processed electroencephalography (p-EEG) is useful in this setting is unclear.

AIM

To describe the PSI index in deeply sedated critically ill patients with acute organ failure, and to examine a potential association between low PSI values and ICU delirium. [Correction added on 16 October 2024, after first online publication: Aim subsection in Abstract has been added on this version.] METHODS: We conducted a single-centre observational study of non-neurological ICU patients sedated according to a standardized guideline of deep sedation (Richmond Agitation Sedation Scale [RASS] between -5 and -4) during the acute phase of respiratory and/or cardio-circulatory failure. The SedLine (Masimo Incorporated, Irvine, California) was used to monitor the Patient State Index (PSI) (ranging from 0 to 100, <25 = very deep sedation and >50 = light sedation to full awareness) during the first 72 h of care. Delirium was assessed with the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU).

RESULTS

The median duration of PSI monitoring was 43 h. Patients spent 49% in median of the total PSI monitoring duration with a PSI <25. Patients with delirium (n = 41/97, 42%) spent a higher percentage of total monitored time with PSI <25 (median 67% [19-91] vs. 47% [12.2-78.9]) in non-delirious patients (p .047). After adjusting for the cumulative dose of analgesia and sedation, increased time spent with PSI <25 was associated with higher delirium (odds ratio 1.014; 95% CI 1.001-1.027, p = .036).

CONCLUSIONS

A clinical protocol of deep sedation targeted to RASS at the acute ICU phase may be associated with prolonged EEG suppression and increased delirium. Whether PSI-targeted sedation may help reducing sedative dose and delirium deserves further clinical investigation.

RELEVANCE TO CLINICAL PRACTICE

Patients requiring deep sedation are at high risk of being over-sedated and developing delirium despite the application of an evidence-based sedation guideline. Development of early objective measures are essential to improve sedation management in these critically ill patients.

Comparing Bispectral Index Monitoring vs Clinical Assessment for Deep Sedation in the ICU: Effects on Delirium Reduction and Sedative Drug Doses-A Randomized Trial

BACKGROUND

Sedative overdoses pose a risk of delirium among patients in the ICU, with potential mitigation through the use of a processed EEG monitor (the bispectral index [BIS]) to guide depth of sedation.

RESEARCH QUESTION

Can BIS-guided deep sedation (Richmond Agitation Sedation Scale [RASS] score, -4 or -5) reduce sedative dosage and increase delirium-free and coma-free (DFCF) days?

STUDY DESIGN AND METHODS

A randomized controlled trial was conducted in a tertiary mixed ICU, enrolling patients requiring deep sedation for > 8 h. Patients were assigned randomly to either the clinical assessment (CA) or BIS groups (BIS range, 40-60). Both groups used a BIS sensor, whereas the CA group's screen remained covered. After deep sedation, BIS sensors were removed, and delirium was assessed twice daily by researchers masked to the randomization. The primary outcome was the number of DFCF days within 14 days after deep sedation. Additionally, we compared doses of sedative drugs and BIS values during deep sedation.

RESULTS

Ninety-nine patients were included in the study. We found no significant difference in DFCF days (P = .1) between CA and BIS arms, but propofol doses were significantly lower in the BIS group (CA group, 1.77 mg/kg/h [95% CI, 1.60-1.93] vs BIS group, 1.44 mg/kg/h [95% CI, 1.04-1.83]; P = .03). During deep sedation, the CA group spent 46% of the total hours (95% CI, 35%-57%) with BIS values of < 40, whereas the BIS group spent 32% (95% CI, 25%-40%; P = .03). Subgroup analysis focusing on patients sedated for > 24 h revealed an increase in DFCF days in the BIS group (CA group: median, 1 day [interquartile range, 0-9 days] vs BIS group: median, 8 days [interquartile range, 0-13 days]; P = .04).

INTERPRETATION

In this study, BIS-guided deep sedation did not improve DFCF days, but did reduce sedative drug use. In patients requiring sedation for > 24 h, it showed an improvement in DFCF days.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT03840577; URL: www.

CLINICALTRIALS

gov.

Intraoperative electroencephalogram features related to frailty in older patients: an exploratory prospective observational study

Frailty is an independent risk factor for the increased incidence of postoperative delirium (POD). To date, the effect of frailty on intraoperative electroencephalogram (EEG) changes remains unexplored. The present study, an exploratory analysis of a prospective cohort study, aimed to investigate the differences in EEG characteristics between frail and robust patients. This prospective observational study was conducted between December 2020 and November 2021. The preoperative frailty status was assessed using the FRAIL scale. The patients' baseline (before anesthesia) and intraoperative EEG data were collected using a brain function monitor. Finally, 20 robust and 26 frail older patients scheduled for elective spinal surgery or transurethral prostatectomy under propofol-based general anesthesia were included in the final analysis. Baseline and intraoperative EEG spectrogram and power spectra were compared between the frail and robust groups. No differences were observed in baseline EEG between the frail and robust groups. When the intraoperative EEG spectral parameters were compared, the alpha peak frequency (10.56 ± 0.49 vs. 10.14 ± 0.36 Hz, P = 0.002) and alpha peak, delta, theta, alpha, and beta powers were lower in the frail group. After adjusting for age, Charlson Comorbidity Index (CCI), and mini-mental state examination (MMSE) score, the FRAIL score was still negatively associated with total, delta, theta, alpha, and beta powers. Frail patients had reduced EEG (0-30 Hz) power after the induction of propofol-based general anesthesia. After adjusting for age, CCI, and MMSE score, frail patients still showed evidence of reduced δ, θ, α, and β power.

Electroencephalographic spectrogram-guided total intravenous anesthesia using dexmedetomidine and propofol prevents unnecessary anesthetic dosing during craniotomy: a propensity score-matched analysis

BACKGROUND

The bispectral index (BIS) may be unreliable to gauge anesthetic depth when dexmedetomidine is administered. By comparison, the electroencephalogram (EEG) spectrogram enables the visualization of the brain response during anesthesia and may prevent unnecessary anesthetic consumption.

METHODS

This retrospective study included 140 adult patients undergoing elective craniotomy who received total intravenous anesthesia using a combination of propofol and dexmedetomidine infusions. Patients were equally matched to the spectrogram group (maintaining the robust EEG alpha power during surgery) or the index group (maintaining the BIS score between 40 and 60 during surgery) based on the propensity score of age and surgical type. The primary outcome was the propofol dose. Secondary outcome was the postoperative neurological profile.

RESULTS

Patients in the spectrogram group received significantly less propofol (1585 ± 581 vs. 2314 ± 810 mg, P < 0.001). Fewer patients in the spectrogram group exhibited delayed emergence (1.4% vs. 11.4%, P = 0.033). The postoperative delirium profile was similar between the groups (profile P = 0.227). Patients in the spectrogram group exhibited better in-hospital Barthel's index scores changes (admission state: 83.6 ± 27.6 vs. 91.6 ± 17.1; discharge state: 86.4 ± 24.3 vs. 85.1 ± 21.5; group-time interaction P = 0.008). However, the incidence of postoperative neurological complications was similar between the groups.

CONCLUSIONS

EEG spectrogram-guided anesthesia prevents unnecessary anesthetic consumption during elective craniotomy. This may also prevent delayed emergence and improve postoperative Barthel index scores.

Intraoperative monitoring of the central and peripheral nervous systems: a narrative review

The central and peripheral nervous systems are the primary target organs during anaesthesia. At the time of the inception of the British Journal of Anaesthesia, monitoring of the central nervous system comprised clinical observation, which provided only limited information. During the 100 yr since then, and particularly in the past few decades, significant progress has been made, providing anaesthetists with tools to obtain real-time assessments of cerebral neurophysiology during surgical procedures. In this narrative review article, we discuss the rationale and uses of electroencephalography, evoked potentials, near-infrared spectroscopy, and transcranial Doppler ultrasonography for intraoperative monitoring of the central and peripheral nervous systems.

Preoperative mild cognitive impairment as a risk factor of postoperative cognitive dysfunction in elderly patients undergoing spine surgery

Introduction

Any persistent degree of cognitive impairment in older adults is a concern as it can progress to dementia. This study aimed to determine the incidence and risk factors for early postoperative cognitive dysfunction (POCD) in elderly patients undergoing spine surgery.

Methods

Patients were enrolled from a previous prospective observational study after screening for normal cognitive function using the Mini Mental State Examination (MMSE). Cognitive function was evaluated before surgery and at 1 week, month, and year post-surgery using MMSE and Montreal Cognitive Assessment scores (MoCA). Mild cognitive impairment (MCI) was determined using the MoCA scores adjusted for age. POCD was defined as a drop of three or more points on the MMSE 1 week post-surgery. Multivariate logistic analysis was performed to identify POCD risk factors.

Results

A total of 427 patients were included. Eighty-five (20%) had pre-existing MCI. The MCI group showed lower MoCA scores at each time point (baseline, 1 week after surgery, 1 month after surgery, 1 year after surgery) compared to the non-MCI group. Those in the MCI group had a higher rate of admission to intensive care unit after surgery, postoperative delirium, and POCD 1 week post-surgery, than those in the non-MCI group (16.5% vs. 6.7%, p = 0.008; 27.1% vs. 15.8%, p = 0.024; and 18.8% vs. 8.2%, p < 0.001, respectively). Among them, 10.3% were assessed for POCD on postoperative day 7 and self-reported poor social roles and physical functioning 1 week postoperatively.

Conclusion

Preoperative MCI was seen in ~20% of surgical patients aged >70 years. POCD was seen in ~20% of patients with pre-existing MCI, and ~ 10% of those without. Benzodiazepine use, significant comorbidities, pre-existing MCI, and depressive tendencies were risk factors for POCD.

Pro-Con Debate: Electroencephalography-Guided Anesthesia for Reducing Postoperative Delirium

Postoperative delirium (POD) has significant implications on morbidity, mortality, and health care expenditures. Monitoring electroencephalography (EEG) to adjust anesthetic management has gained interest as a strategy to mitigate POD. In this Pro-Con commentary article, the pro side supports the use of EEG to reduce POD, citing an empiric reduction in POD with processed EEG (pEEG)-guided general anesthesia found in several studies and recent meta-analysis. The Electroencephalography Guidance of Anesthesia to Alleviate Geriatric Syndromes (ENGAGES) trial is the exception to this, and issues with methods and achieved depths are discussed. Meanwhile, the Con side advocates that the use of EEG to reduce POD is not yet certain, citing that there is a lack of evidence that associations between anesthetic depth and POD represent causal relationships. The Con side also contends that the ideal EEG signatures to guide anesthetic titration are currently unknown, and the potential benefits of reduced anesthesia levels may be outweighed by the risks of potentially insufficient anesthetic administration. As the public health burden of POD increases, anesthesia clinicians will be tasked to consider interventions to mitigate risk such as EEG. This Pro-Con debate will provide 2 perspectives on the evidence and rationales for using EEG to mitigate POD.

Incidence change of postoperative delirium after implementation of processed electroencephalography monitoring during surgery: a retrospective evaluation study

BACKGROUND

Postoperative delirium (POD) is a common complication in the elderly, which is associated with poor outcomes after surgery. Recognized as predisposing factors for POD, anesthetic exposure and burst suppression during general anesthesia can be minimized with intraoperative processed electroencephalography (pEEG) monitoring. In this study, we aimed to evaluate whether implementation of intraoperative pEEG-guided anesthesia is associated with incidence change of POD.

METHODS

In this retrospective evaluation study, we analyzed intravenous patient-controlled analgesia (IVPCA) dataset from 2013 to 2017. There were 7425 patients using IVPCA after a noncardiac procedure under general anesthesia. Patients incapable of operating the device independently, such as cognitive dysfunction or prolonged sedation, were declined and not involved in the dataset. After excluding patients who opted out within three days (N = 110) and those with missing data (N = 24), 7318 eligible participants were enrolled. Intraoperative pEEG has been implemented since July 2015. Participants having surgery after this time point had intraoperative pEEG applied before induction until full recovery. All related staff had been trained in the application of pEEG-guided anesthesia and the assessment of POD. Patients were screened twice daily for POD within 3 days after surgery by staff in the pain management team. In the first part of this study, we compared the incidence of POD and its trend from 2013 January-2015 July with 2015 July-2017 December. In the second part, we estimated odds ratios of risk factors for POD using multivariable logistic regression in case-control setting.

RESULTS

The incidence of POD decreased from 1.18 to 0.41% after the administration of intraoperative pEEG. For the age group ≧ 75 years, POD incidence decreased from 5.1 to 1.56%. Further analysis showed that patients with pEEG-guided anesthesia were associated with a lower odd of POD (aOR 0.33; 95% CI 0.18-0.60) than those without after adjusting for other covariates.

CONCLUSIONS

Implementation of intraoperative pEEG was associated with a lower incidence of POD within 3 days after surgery, particularly in the elderly. Intraoperative pEEG might be reasonably considered as part of the strategy to prevent POD in the elder population.

TRIAL REGISTRATION

Not applicable.

Long-term survival in older patients given propofol or sevoflurane anaesthesia for major cancer surgery: follow-up of a multicentre randomised trial

BACKGROUND

Experimental evidence indicates that i.v. anaesthesia might reduce cancer recurrence compared with volatile anaesthesia, but clinical information is observational only. We therefore tested the primary hypothesis that propofol-based anaesthesia improves survival over 3 or more years after potentially curative major cancer surgery.

METHODS

This was a long-term follow-up of a multicentre randomised trial in 14 tertiary hospitals in China. We enrolled 1228 patients aged 65-90 yr who were scheduled for major cancer surgery. They were randomised to either propofol-based i.v. anaesthesia or to sevoflurane-based inhalational anaesthesia. The primary endpoint was overall survival after surgery. Secondary endpoints included recurrence-free and event-free survival.

RESULTS

Amongst subjects randomised, 1195 (mean age 72 yr; 773 [65%] male) were included in the modified intention-to-treat analysis. At the end of follow-up (median 43 months), there were 188 deaths amongst 598 patients (31%) assigned to propofol-based anaesthesia compared with 175 deaths amongst 597 patients (29%) assigned to sevoflurane-based anaesthesia; adjusted hazard ratio 1.02; 95% confidence interval (CI): 0.83-1.26; P=0.834. Recurrence-free survival was 223/598 (37%) in patients given propofol anaesthesia vs 206/597 (35%) given sevoflurane anaesthesia; adjusted hazard ratio 1.07; 95% CI: 0.89-1.30; P=0.465. Event-free survival was 294/598 (49%) in patients given propofol anaesthesia vs 274/597 (46%) given sevoflurane anaesthesia; adjusted hazard ratio 1.09; 95% CI 0.93 to 1.29; P=0.298.

CONCLUSIONS

Long-term survival after major cancer surgery was similar with i.v. and volatile anaesthesia. Propofol-based iv. anaesthesia should not be used for cancer surgery with the expectation that it will improve overall or cancer-specific survival.

CLINICAL TRIAL REGISTRATIONS

ChiCTR-IPR-15006209; NCT02660411.

Delirium in older patients given propofol or sevoflurane anaesthesia for major cancer surgery: a multicentre randomised trial

BACKGROUND

Delirium is a common and disturbing postoperative complication that might be ameliorated by propofol-based anaesthesia. We therefore tested the primary hypothesis that there is less delirium after propofol-based than after sevoflurane-based anaesthesia within 7 days of major cancer surgery.

METHODS

This multicentre randomised trial was conducted in 14 tertiary care hospitals in China. Patients aged 65-90 yr undergoing major cancer surgery were randomised to either propofol-based anaesthesia or to sevoflurane-based anaesthesia. The primary endpoint was the incidence of delirium within 7 postoperative days.

RESULTS

A total of 1228 subjects were enrolled and randomised, with 1195 subjects included in the modified intention-to-treat analysis (mean age 71 yr; 422 [35%] women); one subject died before delirium assessment. Delirium occurred in 8.4% (50/597) of subjects given propofol-based anaesthesia vs 12.4% (74/597) of subjects given sevoflurane-based anaesthesia (relative risk 0.68 [95% confidence interval {CI}: 0.48-0.95]; P=0.023; adjusted relative risk 0.59 [95% CI: 0.39-0.90]; P=0.014). Delirium reduction mainly occurred on the first day after surgery, with a prevalence of 5.4% (32/597) with propofol anaesthesia vs 10.7% (64/597) with sevoflurane anaesthesia (relative risk 0.50 [95% CI: 0.33-0.75]; P=0.001). Secondary endpoints, including ICU admission, postoperative duration of hospitalisation, major complications within 30 days, cognitive function at 30 days and 3 yr, and safety outcomes, did not differ significantly between groups.

CONCLUSIONS

Delirium was a third less common after propofol than sevoflurane anaesthesia in older patients having major cancer surgery. Clinicians might therefore reasonably select propofol-based anaesthesia in patients at high risk of postoperative delirium.

CLINICAL TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR-IPR-15006209) and ClinicalTrials.gov (NCT02662257).

Frailty: the perioperative and anesthesia challenges of an emerging pandemic

Frailty is a complex and multisystem biological process characterized by reductions in physiological reserve. It is an increasingly common phenomena in the surgical population, and significantly impacts postoperative recovery. In this review, we will discuss the pathophysiology of frailty, as well as preoperative, intraoperative, and postoperative considerations for frailty care. We will also discuss the different models of postoperative care, including enhanced recovery pathways, as well as elective critical care admission. With discoveries of new effective interventions, and advances in healthcare information technology, optimized pathways could be developed to provide the best care possible that meets the challenges of perioperative frailty.

Postoperative delirium: identifying the patient at risk and altering the course: A narrative review

Postoperative delirium (POD) is a common neurocognitive syndrome seen in older patients after major surgery. POD is linked to longer stays in hospital and intensive care, a greater incidence of postoperative complications, worse functional outcome, and higher mortality. Researchers have not yet fully elucidated the exact pathophysiology of POD. Several risk factors that contribute to the development of POD have been identified, such as advanced age, cardiac or hip surgery, preoperative cognitive decline or delirium, disturbances in brain levels of neurotransmitters and information processing, oxidative stress and neuro-inflammation. Identifying patients at risk for POD enables a more precise and efficient allocation of medical resources and facilitates POD prevention and management. The present review addresses how to identify patients at risk of POD and summarizes the currently available evidence and best-practice recommendations for peri-operative management and prevention of POD.

Depth of anesthesia, temperature, and postoperative delirium in children and adolescents undergoing cardiac surgery

BACKGROUND

After pediatric cardiosurgical interventions, postoperative delirium can occur, which can be associated with undesirable consequences during and after the hospital stay. It is therefore important to avoid any factors causing delirium as far as possible. Electroencephalogram (EEG) monitoring can be used during anesthesia to individually adjust dosages of hypnotically acting drugs. It is necessary to gain knowledge about the relationship between intraoperative EEG and postoperative delirium in children.

METHODS

In a dataset comprising 89 children (53 male, 36 female; median age: 0.99 (interquartile range: 0.51, 4.89) years) undergoing cardiac surgery involving use of a heart-lung machine, relationships between depth of anesthesia as measured by EEG (EEG index: Narcotrend Index (NI)), sevoflurane dosage, and body temperature were analyzed. A Cornell Assessment of Pediatric Delirium (CAP-D) score ≥ 9 indicated delirium.

RESULTS

The EEG could be used in patients of all age groups for patient monitoring during anesthesia. In the context of induced hypothermia, EEG monitoring supported individually adjusted sevoflurane dosing. The NI was significantly correlated with the body temperature; decreasing temperature was accompanied by a decreasing NI. A CAP-D score ≥ 9 was documented in 61 patients (68.5%); 28 patients (31.5%) had a CAP-D < 9. Delirious patients with an intubation time ≤ 24 h showed a moderate negative correlation between minimum NI (NImin) and CAP-D (rho = -0.41, 95% CI: -0.70 - -0.01, p = 0.046), i.e., CAP-D decreased with increasing NImin. In the analysis of all patients' data, NImin and CAP-D showed a weak negative correlation (rho = -0.21, 95% CI: -0.40 - 0.01, p = 0.064). On average, the youngest patients had the highest CAP-D scores (p = 0.002). Patients with burst suppression / suppression EEG had a longer median intubation time in the intensive care unit than patients without such EEG (p = 0.023). There was no relationship between minimum temperature and CAP-D score.

CONCLUSIONS

The EEG can be used to individually adjust sevoflurane dosing during hypothermia. Of the patients extubated within 24 h and classified as delirious, patients with deeper levels of anesthesia had more severe delirium symptoms than patients with lighter levels of anesthesia.

Density Spectral Array Enables Precise Sedation Control for Supermicrosurgical Lymphaticovenous Anastomosis: A Retrospective Observational Cohort Study

Supermicrosurgical lymphaticovenous anastomosis (LVA) is a minimally invasive surgical technique that creates bypasses between lymphatic vessels and veins, thereby improving lymphatic drainage and reducing lymphedema. This retrospective single-center study included 137 patients who underwent non-intubated LVA in southern Taiwan. A total of 119 patients were enrolled and assigned to two study groups: the geriatric (age ≥ 75 years, n = 23) and non-geriatric groups (age < 75 years, n = 96). The primary outcome was to investigate and compare the arousal and maintenance of the propofol effect-site concentration (Ce) using an electroencephalographic density spectral array (EEG DSA) in both groups. The results showed that the geriatric group required less propofol (4.05 [3.73-4.77] mg/kg/h vs. 5.01 [4.34-5.92] mg/kg/h, p = 0.001) and alfentanil (4.67 [2.53-5.82] μg/kg/h vs. 6.68 [3.85-8.77] μg/kg/h, p = 0.047). The median arousal Ce of propofol among the geriatric group (0.6 [0.5-0.7] μg/mL) was significantly lower than that in patients aged ≤ 54 years (1.3 [1.2-1.4] μg/mL, p < 0.001), 55-64 years (0.9 [0.8-1.0] μg/mL, p < 0.001), and <75 years (0.9 [0.8-1.2] μg/mL, p < 0.001). In summary, the combined use of EEG DSA provides the objective and depth of adequate sedation for extensive non-intubated anesthesia in late-elderly patients who undergo LVA without perioperative complications.

Processed electroencephalography-guided general anaesthesia to reduce postoperative delirium: a systematic review and meta-analysis

BACKGROUND

Postoperative delirium (POD) is the most common serious postoperative complication in older adults. It has uncertain aetiology, limited preventative strategies, and poor long-term outcomes. This updated systematic review and meta-analysis aimed to estimate the effect of processed electroencephalography (pEEG)-guided general anaesthesia during surgery on POD incidence.

METHODS

We performed a systematic review and meta-analysis by searching OVID MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL) electronic databases. Studies of adult patients having general anaesthesia for any surgery where pEEG was used and POD was an outcome measure were included. Full-text reports of RCTs published from database inception until August 28, 2021, were included. Trials were excluded if sedation rather than general anaesthesia was administered, or the setting was intensive care. The primary outcome was POD assessed by validated tools. The study was prospectively registered with PROSPERO.

RESULTS

Nine studies, which included 4648 eligible subjects, were identified. The incidence of POD in the pEEG-guided general anaesthesia or lighter pEEG target group was 19.0% (440/2310) compared with 23.3% (545/2338) in the usual care or deeper pEEG target group (pooled odds ratio=0.78; 95% confidence interval, 0.60-1.00; P=0.054). Significant heterogeneity was detected (I²=53%).

CONCLUSIONS

Our primary analysis demonstrated a highly sensitive result with a pooled analysis of trials in which the intervention group adhered to manufacturer's recommended guidelines, showing reduced incidence of POD with pEEG guidance. High clinical heterogeneity limits inferences from this and any future meta-analyses.

CLINICAL TRIAL REGISTRATION

CRD42020199404 (PROSPERO).

Protocol for the electroencephalography guidance of anesthesia to alleviate geriatric syndromes (ENGAGES-Canada) study: A pragmatic, randomized clinical trial

Background:  There is some evidence that electroencephalography guidance of general anesthesia can decrease postoperative delirium after non-cardiac surgery.  There is limited evidence in this regard for cardiac surgery.  A suppressed electroencephalogram pattern, occurring with deep anesthesia, is associated with increased incidence of postoperative delirium (POD) and death.  However, it is not yet clear whether this electroencephalographic pattern reflects an underlying vulnerability associated with increased incidence of delirium and mortality, or whether it is a modifiable risk factor for these adverse outcomes. Methods:  The Electroe ncephalography Guidance of Anesthesia to Alleviate Geriatric Syndromes ( ENGAGES-Canada) is an ongoing pragmatic 1200 patient trial at four Canadian sites.  The study compares the effect of two anesthetic management approaches on the incidence of POD after cardiac surgery.  One approach is based on current standard anesthetic practice and the other on electroencephalography guidance to reduce POD. In the guided arm, clinicians are encouraged to decrease anesthetic administration, primarily if there is electroencephalogram suppression and secondarily if the EEG index is lower than the manufacturers recommended value (bispectral index (BIS) or WAVcns below 40 or Patient State Index below 25).  The aim in the guided group is to administer the minimum concentration of anesthetic considered safe for individual patients.  The primary outcome of the study is the incidence of POD, detected using the confusion assessment method or the confusion assessment method for the intensive care unit; coupled with structured delirium chart review.  Secondary outcomes include unexpected intraoperative movement, awareness, length of intensive care unit and hospital stay, delirium severity and duration, quality of life, falls, and predictors and outcomes of perioperative distress and dissociation. Discussion:  The ENGAGES-Canada trial will help to clarify whether or not using the electroencephalogram to guide anesthetic administration during cardiac surgery decreases the incidence, severity, and duration of POD. Registration: ClinicalTrials.gov ( NCT02692300) 26/02/2016.

Protocol for the electroencephalography guidance of anesthesia to alleviate geriatric syndromes (ENGAGES-Canada) study: A pragmatic, randomized clinical trial

Background:  There is some evidence that electroencephalography guidance of general anesthesia can decrease postoperative delirium after non-cardiac surgery.  There is limited evidence in this regard for cardiac surgery.  A suppressed electroencephalogram pattern, occurring with deep anesthesia, is associated with increased incidence of postoperative delirium (POD) and death.  However, it is not yet clear whether this electroencephalographic pattern reflects an underlying vulnerability associated with increased incidence of delirium and mortality, or whether it is a modifiable risk factor for these adverse outcomes. Methods:  The Electroe ncephalography Guidance of Anesthesia to Alleviate Geriatric Syndromes ( ENGAGES-Canada) is an ongoing pragmatic 1200 patient trial at four Canadian sites.  The study compares the effect of two anesthetic management approaches on the incidence of POD after cardiac surgery.  One approach is based on current standard anesthetic practice and the other on electroencephalography guidance to reduce POD. In the guided arm, clinicians are encouraged to decrease anesthetic administration, primarily if there is electroencephalogram suppression and secondarily if the EEG index is lower than the manufacturers recommended value (bispectral index (BIS) or WAVcns below 40 or Patient State Index below 25).  The aim in the guided group is to administer the minimum concentration of anesthetic considered safe for individual patients.  The primary outcome of the study is the incidence of POD, detected using the confusion assessment method or the confusion assessment method for the intensive care unit; coupled with structured delirium chart review.  Secondary outcomes include unexpected intraoperative movement, awareness, length of intensive care unit and hospital stay, delirium severity and duration, quality of life, falls, and predictors and outcomes of perioperative distress and dissociation. Discussion:  The ENGAGES-Canada trial will help to clarify whether or not using the electroencephalogram to guide anesthetic administration during cardiac surgery decreases the incidence, severity, and duration of POD. Registration: ClinicalTrials.gov ( NCT02692300) 26/02/2016.

Decreased Electroencephalographic Alpha Power During Anesthesia Induction Is Associated With EEG Discontinuity in Human Infants

BACKGROUND

Electroencephalogram (EEG) discontinuity can occur at high concentrations of anesthetic drugs, reflecting suppression of electrocortical activity. This EEG pattern has been reported in children and reflects a deep state of anesthesia. Isoelectric events on the EEG, a more extreme degree of voltage suppression, have been shown to be associated with worse long-term neurologic outcomes in neonates undergoing cardiac surgery. However, the clinical significance of EEG discontinuities during pediatric anesthesia for noncardiac surgery is not yet known and merits further research. In this study, we assessed the incidence of EEG discontinuity during anesthesia induction in neurologically normal infants and the clinical factors associated with its development. We hypothesized that EEG discontinuity would be associated with sevoflurane-induced alpha (8-12 Hz) power during the period of anesthesia induction in infants.

METHODS

We prospectively recorded 26 channels of EEG during anesthesia induction in an observational cohort of 54 infants (median age, 7.6 months; interquartile range [IQR] [4.9-9.8 months]). We identified EEG discontinuity, defined as voltage amplitude <25 microvolts for >2 seconds, and assessed its association with sevoflurane-induced alpha power using spectral analysis and multivariable logistic regression adjusting for clinically important variables.

RESULTS

EEG discontinuity was observed in 20 of 54 subjects (37%), with a total of 25 discrete events. Sevoflurane-induced alpha power in the posterior regions of the head (eg, parietal or occipital regions) was significantly lower in the EEG discontinuity group (midline parietal channel on the electroencephalogram, International 10-20 System [Pz]; 8.3 vs 11.2 decibels [dBs]; P = .004), and this association remained after multivariable adjustment (adjusted odds ratio [aOR] = 0.51 per dB increase in alpha power [95% CI, 0.30-0.89]; P = .02). There were no differences in the baseline (unanesthetized) EEG between groups in alpha power or power in any other frequency band.

CONCLUSIONS

We demonstrate that EEG discontinuity is common during anesthesia induction and is related to the level of sevoflurane-induced posterior alpha power, a putative marker of cortical-thalamic circuit development in the first year of life. This association persisted even after adjusting for age and propofol coadministration. The fact that this difference was only observed during anesthesia and not in the baseline EEG suggests that otherwise hidden brain circuit properties are unmasked by general anesthesia. These neurophysiologic markers observed during anesthesia may be useful in identifying patients who may have a greater chance of developing discontinuity.

Bispectral Index (BIS) Monitoring and Postoperative Delirium in Elderly Patients Undergoing Surgery: A Systematic Review and Meta-Analysis With Trial Sequential Analysis

OBJECTIVE

To examine the effect of bispectral index (BIS)-guided anesthesia on the incidence of postoperative delirium (POD) in elderly patients undergoing surgery.

DESIGN

A systematic review, meta-analysis, and trial sequential analysis (TSA).

SETTING

In the operating room, postoperative anesthesia care units (PACU), and ward.

PARTICIPANTS

Elderly patients (>60 years old) undergoing surgery.

INTERVENTIONS

The EMBASE, MEDLINE, and CENTRAL databases were searched systematically from their inception until December 2020 for randomized controlled trials comparing BIS and usual care or blinded BIS.

MEASUREMENTS AND MAIN RESULTS

Ten trials (N = 3,891) were included for quantitative meta-analysis. In comparison to the control group, there was no significant difference in the incidence of POD in elderly patients randomized to BIS-guided anesthesia (odds ratio [OR] 0.71, 95% CI 0.47-1.08, I² = 76%, p = 0.11, level of evidence = very low, TSA = inconclusive). The authors' review demonstrated that elderly patients with BIS-guided anesthesia were significantly associated with a lower incidence of postoperative cognitive dysfunction (POCD) (OR 0.64, 95% CI 0.46-0.88, p = 0.006), extubation time (mean difference [MD] -3.38 minutes, 95% CI -4.38 to -2.39, p < 0.00001), time to eye opening (MD -2.17 minutes, 95% CI -4.21 to -0.14, p = 0.04), and time to discharge from the PACU (MD -10.77 minutes, 95% CI -11.31 to - 10.23, p < 0.00001).

CONCLUSION

The authors' meta-analysis demonstrated that BIS-guided anesthesia was not associated with a reduced incidence of POD, but it was associated with a reduced incidence of POCD and improved recovery parameters.

The effects of anesthesia methods and anesthetics on postoperative delirium in the elderly patients: A systematic review and network meta-analysis

STUDY OBJECTIVE

Postoperative delirium (POD) is one of the serious postoperative complications in elderly patients, which is always related to long-term mortality. Anesthesia is often considered a risk factor for POD. This systematic review and network meta-analysis (NMA) aimed to assess the impact of different anesthesia methods and anesthetics on POD.

MEASUREMENTS

We searched for studies published in PubMed, Embase, Web of Science, Scopus, and Cochrane Library (CENTRAL) from inception to 18 March 2022. RevMan 5.3 and CINeMA 2.0.0 were used to assess the risk of bias and confidence. Data analysis using STATA 17.0 and R 4.1.2. STATA 17.0 was used to calculate the surface under the cumulative ranking curve (SUCRA) and provide network plots with CINeMA 2.0.0. NMA was performed with R 4.1.2 software gemtc packages in RStudio.

MAIN RESULTS

This NMA included 19 RCTs with 5,406 patients. In the pairwise meta-analysis results, only regional anesthesia (RA) with general anesthesia (GA) vs. GA (Log OR: -1.08; 95% CI: -1.54, -0.63) were statistically different in POD incidence. In the NMA results, there was no statistical difference between anesthesia methods, and psoas compartment block (PCB) with bupivacaine was superior to the desflurane, propofol, sevoflurane, and spinal anesthesia with bupivacaine of POD occurrence.

CONCLUSION

Our study indicated that RA and GA had no significant effect on POD, and there was no difference between anesthesia methods. Pairwise meta-analysis showed that, except for RA with GA vs. GA, the rest of the results were not statistically different. Besides, PCB with bupivacaine may benefit to reduce POD incidence.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/dis play_record.php?ID=CRD42022319499, identifier PROSPERO 2022 CRD42022319499.

Effect of Preoperative Oral Saline Administration on Postoperative Delirium in Older Persons: A Randomized Controlled Trial

Objective

Postoperative delirium (POD) seriously affects recovery of older persons, increasing their mortality rate after surgery. We aimed to evaluate preoperative oral saline administration on postoperative delirium in older persons undergoing spinal decompression.

Design

A randomised controlled trial in a large tertiary hospital.

Setting and Participants

A total of 76 older persons (≧65 years old) undergoing spinal surgery from May 2020 to January 2021.

Methods

Older persons (65–83 years old) who underwent elective spinal canal decompression were randomly grouped into either the control group (n = 38) or the intervention group (n = 38). The control group was forbidden from drinking 8 hours prior to the operation while the intervention group was administered 5 mL·kg⁻¹ of normal saline 2 hours before anesthesia. Hemodynamic indicators, diagnostic biomarkers, preoperative mini-mental status scores, and intraoperative fluid dynamics were recorded at baseline and at various postoperative timepoints. Subjects were then scored for POD and postoperative pain.

Results

S100β protein was lowered in S₁ (F_S1 = 12.289, P <0.001) and S₂ (F_S2 = 12.440, P <0.001) in the intervention group while mean arterial blood pressure (F_T1= 42.997, P<0.001) and heart rate (F_T1= 8.974, P=0.004) were increased. The Ln c-reactive protein of the intervention group was lowered 1 day postoperatively (F_S2 = 6.305, P = 0.014). The incidence of postoperative delirium in the control group was higher than in the intervention group (27.8% vs 8.3%, χ² = 4.547, P = 0.033).

Conclusion

Preoperative oral saline can reduce the incidence of postoperative delirium in older persons by minimizing perioperative hemodynamic fluctuations and central nervous system damage.

The absence of dominant alpha-oscillatory EEG activity during emergence from delta-dominant anesthesia predicts neurocognitive impairment- results from a prospective observational trial

STUDY OBJECTIVE

Postoperative neurocognitive disorders (PND) are common complications after surgery under general anesthesia. In our aging society the incidence of PND will increase. Hence, interdisciplinary efforts should be taken to minimize the occurrence of PND. Electroencephalographic (EEG) monitoring of brain activity during anesthesia or emergence from anesthesia is a promising tool to identify patients at risk. We therefore investigated whether we could identify specific EEG signatures during emergence of anesthesia that are associated with the occurrence of PND.

DESIGN AND PATIENTS

We performed a prospective observational investigation on 116 patients to evaluate the EEG features during emergence from general anesthesia dominated by slow delta waves in patients with and without delirium in the postoperative care unit (PACU-D) as assessed by the CAM-ICU and the RASS.

MAIN RESULTS

During emergence both the frontal and global EEG of patients with PACU-D were significantly different from patients without PACU-D. PACU-D patients had lower relative alpha power and reduced fronto-parietal alpha coherence.

CONCLUSIONS

With our analysis we show differences in EEG features associated with anesthesia emergence in patients with and without PACU-D. Frontal and global EEG alpha-band features could help to identify patients with PACU-D.

CLINICAL TRIAL NUMBER

NCT03287401.

Electroencephalogram Features of Perioperative Neurocognitive Disorders in Elderly Patients: A Narrative Review of the Clinical Literature

Postoperative neurocognitive disorder (PND) is a common postoperative complication, particularly in older patients. Electroencephalogram (EEG) monitoring, a non-invasive technique with a high spatial-temporal resolution, can accurately characterize the dynamic changes in brain function during the perioperative period. Current clinical studies have confirmed that the power density of alpha oscillation during general anesthesia decreased with age, which was considered to be associated with increased susceptibility to PND in the elderly. However, evidence on whether general anesthesia under EEG guidance results in a lower morbidity of PND is still contradictory. This is one of the reasons that common indicators of the depth of anesthesia were limitedly derived from EEG signals in the frontal lobe. The variation of multi-channel EEG features during the perioperative period has the potential to highlight the occult structural and functional abnormalities of the subcortical-cortical neurocircuit. Therefore, we present a review of the application of multi-channel EEG monitoring to predict the incidence of PND in older patients. The data confirmed that the abnormal variation in EEG power and functional connectivity between distant brain regions was closely related to the incidence and long-term poor outcomes of PND in older adults.

Perioperative Brain Health in the Older Adult: A Patient Safety Imperative

While people 65 years of age and older represent 16% of the population in the United States, they account for >40% of surgical procedures performed each year. Maintaining brain health after anesthesia and surgery is not only important to our patients, but it is also an increasingly important patient safety imperative for the specialty of anesthesiology. Aging is a complex process that diminishes the reserve of every organ system and often results in a patient who is vulnerable to the stress of surgery. The brain is no exception, and many older patients present with preoperative cognitive impairment that is undiagnosed. As we age, a number of changes occur in the human brain, resulting in a patient who is less resilient to perioperative stress, making older adults more susceptible to the phenotypic expression of perioperative neurocognitive disorders. This review summarizes the current scientific and clinical understanding of perioperative neurocognitive disorders and recommends patient-centered, age-focused interventions that can better mitigate risk, prevent harm, and improve outcomes for our patients. Finally, it discusses the emerging topic of sleep and cognitive health and other future frontiers of scientific inquiry that might inform clinical best practices.

Targeted Interventions to Increase Blood Pressure and Decrease Anaesthetic Concentrations Reduce Intraoperative Burst Suppression: A Randomised, Interventional Clinical Trial

Background

It has been suggested that intraoperative electroencephalographic (EEG) burst suppression (BSupp) may be associated with post-operative neurocognitive disorders in the elderly, and EEG-guided anaesthesia may help to reduce BSupp. Despite of this suggestion, a standard treatment does not exist, as we have yet to fully understand the phenomenon and its underlying pathomechanism. This study was designed to address two underlying phenomena—cerebral hypoperfusion and individual anaesthetic overdose.

Objectives

We aimed to demonstrate that targeted anaesthetic interventions—treating intraoperative hypotension and/or reducing the anaesthetic concentration—reduce BSupp.

Methods

We randomly assigned patients to receive EEG-based interventions during anaesthesia or EEG-blinded standard anaesthesia. If BSupp was detected, defined as burst suppression ratio (BSR) > 0, the primary intervention aimed to adjust the mean arterial blood pressure to patient baseline (MAP intervention) followed by reduction of anaesthetic concentration (MAC intervention).

Results

EEG-based intervention significantly reduced total cumulative BSR, BSR duration, and maximum BSR. MAP intervention caused a significant MAP increase at the end of a BSR > 0 episode compared to the control group. Coincidentally, the maximum BSR decreased significantly; in 55% of all MAP interventions, the BSR decreased to 0% without any further action. In the remaining events, additional MAC intervention was required.

Conclusion

Our results show that targeted interventions (MAC/MAP) reduce total cumulative amount, duration, and maximum BSR > 0 in the elderly undergoing general anaesthesia. Haemodynamic intervention already interrupted or reduced BSupp, strengthening the current reflections that hypotension-induced cerebral hypoperfusion may be seen as potential pathomechanism of intraoperative BSupp.

Clinical Trial Registration

NCT03775356 [ClinicalTrials.gov], DRKS00015839 [German Clinical Trials Register (Deutsches Register klinischer Studien, DRKS)].

Neuroinflammation in perioperative neurocognitive disorders: From bench to the bedside

The perioperative neurocognitive disorders (PNDs) are one of the most common complications in elderly patients characterized by various forms of cognitive decline after anesthesia and surgery. Although the etiology for PNDs remained unclear, neuroinflammation has been characterized as one of the major causes, especially in the elderly patients. The activation of glial cells including microglia and astrocytes plays a significant role in the inflammatory responses in central nerve system (CNS). Although carefully designed, clinical studies on PNDs showed controversial results. Meanwhile, preclinical studies provided evidence from various levels, including behavior performance, protein levels, and gene expression. In this review, we summarize high‐quality studies and recent advances from both clinical and preclinical studies and provide a broad view from the onset of PNDs to its potential therapeutic targets. Future studies are needed to investigate the signaling pathways in PNDs for prevention and treatment, as well as the relationship of PNDs and future neurocognitive dysfunction.

Related Factors and Treatment of Postoperative Delirium in Old Adult Patients: An Integrative Review

“Postoperative delirium” is defined as delirium occurring in the hospital up to one week after a procedure or before discharge (whichever occurs first) that meets the DSM-5 diagnostic criteria. Objectives: To describe the risk factors related to this pathology and identify effective non-pharmacological forms of treatment. An integrative review of the available literature was performed. The search results considered included all quantitative studies published between 2011 and 2019 in both English and Spanish. A total of 117 studies were selected. Advanced age was identified as the principal risk factor for postoperative delirium. Nursing interventions appear to be the key to preventing or reducing the seriousness of delirium after an anaesthetic episode. The aetiology of postoperative delirium remains unknown, and no treatment exists to eliminate this pathology. The role of nursing staff is fundamental in the prevention, diagnosis, and management of the pathology.

The raw and processed electroencephalogram in modern anesthesia practice: a brief primer on select clinical applications

The evidence supporting the intraoperative use of processed electroencephalography (pEEG) monitoring to guide anesthetic delivery is growing rapidly. This article reviews the key features of electroencephalography (EEG) waveforms and their clinical implications in select patient populations and anesthetic techniques. The first patient topic reviewed is the vulnerable brain. This term has emerged as a description of patients who may exhibit increased sensitivity to anesthetics and/or may develop adverse neurocognitive effects following anesthesia. pEEG monitoring of patients who are known to have or are suspected of having vulnerable brains, with focused attention on the suppression ratio, alpha band power, and pEEG indices, may prove useful. Second, pEEG monitoring along with vigilant attention to anesthetic delivery may minimize the risk of intraoperative awareness when administering a total intravenous anesthesia in combination with a neuromuscular blockade. Third, we suggest that processed EEG monitoring may play a role in anesthetic and resuscitative management when adverse changes in blood pressure occur. Fourth, pEEG monitoring can be used to better identify anesthesia requirements and guide anesthetic titration in patients with known or suspected substance use.

Processed Multiparameter Electroencephalogram-Guided General Anesthesia Management Can Reduce Postoperative Delirium Following Carotid Endarterectomy: A Randomized Clinical Trial

Background: Patients undergoing carotid endarterectomy (CEA) for severe carotid stenosis are vulnerable to postoperative delirium, a complication frequently associated with poor outcome. This study investigated the impact of processed electroencephalogram (EEG)-guided anesthesia management on the incidence of postoperative delirium in patients undergoing CEA. Methods: This single-center, prospective, randomized clinical trial on 255 patients receiving CEA under general anesthesia compared the outcomes of patient state index (PSI) monitoring [SEDLine Brain Function Monitor (Masimo, Inc, Irvine, CA)] (standard group, n = 128) with PSI combined with density spectral array(DSA) -guided monitoring (intervention group, n = 127) to reduce the risk of intraoperative EEG burst suppression. All patients were monitored by continuous transcranial Doppler ultrasound (TCD) and near-infrared spectroscopy (NIRS) to avoid perioperative cerebral hypoperfusion or hyperperfusion. According to the surgical process, EEG suppression time was calculated separately for three stages: S1 (from anesthesia induction to carotid artery clamping), S2 (from clamping to declamping), and S3 (from declamping to the end of surgery). The primary outcome was incidence of postoperative delirium according to the Confusion Assessment Method algorithm during the first 3 days post-surgery, and secondary outcomes were other neurologic complications and length of hospital stay. Results: There were no episodes of cerebral hypoperfusion or hyperperfusion according to TCD and NIRS monitoring in either group during surgery. The incidence of postoperative delirium within 3 days post-surgery was significantly lower in the intervention group than the standard group (7.87 vs. 28.91%, P < 0.01). In the intervention group, the total EEG suppression time and the EEG suppression time during S2 and S3 were shorter (Total, 0 "0" vs. 0 "1.17" min, P = 0.04; S2, 0 "0" vs. 0 "0.1" min, P < 0.01; S3, 0 "0" vs. 0 "0" min, P = 0.02). There were no group differences in incidence of neurologic complications and length of postoperative hospital stay. Conclusion: Processed electroencephalogram-guided general anesthesia management, consisting of PSI combined with DSA monitoring, can significantly reduce the risk of postoperative delirium in patients undergoing CEA. Patients, especially those exhibiting hemodynamic fluctuations or receiving surgical procedures that disrupt cerebral perfusion, may benefit from the monitoring of multiple EEG parameters during surgery. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03622515.

Anaesthesia for the elderly: a narrative review

As octogenarians in the operation room are no longer an exemption but the norm, perioperative management needs to be adopted to meet the special requirements of this group of patients. Anaesthesia does not need to be re-invented to fit the elderly. However, as elderly patients are among those most affected by adverse postoperative outcomes, the same diligence that is as a matter of course exercised in anaesthesiologic care of the youngest patients needs to be exercised for the eldest as well. Aging is associated with characteristic physiologic changes and an overall reduction in compensation width. However, the individual relevance of these changes varies distinctly. A comprehensive preoperative assessment is therefore essential to identify those at high risk. Maintaining functionality and preventing cognitive decline are central elements of perioperative care for frail elders, often only requiring unspectacular, but effective adjustments to established routine care processes. This review focuses on current recommendations in the perioperative anaesthesiologic management of elderly patients with a view towards assisting clinical anaesthesiologists in implementing respective structures in their setting and adjusting care pathways to meet the needs of this vulnerable but growing group of patients and improve their postoperative outcome.

The Impact of Monitoring Depth of Anesthesia and Nociception on Postoperative Cognitive Function in Adult Multiple Trauma Patients

Background and Objectives: Patients with traumatic injuries have often been excluded from studies that have attempted to pinpoint modifiable factors to predict the transient disturbance of the cognitive function in the postoperative settings. Anesthetists must be aware of the high risk of developing postoperative delirium and cognitive dysfunction (POCD) in patients undergoing emergency surgery. Monitoring the depth of anesthesia in order to tailor anesthetic delivery may reduce this risk. The primary aim of this study was to improve the prevention strategies for the immediate POCD by assessing anesthetic depth and nociception during emergency surgery. Material and Methods: Of 107 trauma ASA physical status II-IV patients aged over 18 years undergoing emergency noncardiac surgery, 95 patients were included in a prospective randomized study. Exclusion criteria were neurotrauma, chronic use of psychoactive substances or alcohol, impaired preoperative cognitive function, pre-existing psychopathological symptoms, or expected surgery time less than 2 h. Entropy and Surgical Pleth Index (SPI) values were constantly recorded for one group during anesthesia. POCD was assessed 24 h, 48 h, and 72 h after surgery using the Neelon and Champagne (NEECHAM) Confusion Scale. Results: Although in the intervention group, fewer patients experienced POCD episodes in comparison to the control group, the results were not statistically significant (p < 0.08). The study showed a statistically significant inverse correlation between fentanyl and the NEECHAM Confusion Scale at 24 h (r = -0.32, p = 0.0005) and 48 h (r = -0.46, p = 0.0002), sevoflurane and the NEECHAM Confusion Scale at 24 h (r = -0.38, p = 0.0014) and 48 h (r = -0.52, p = 0.0002), and noradrenaline and POCD events in the first 48 h (r = -0.46, p = 0.0013 for the first 24 h, respectively, and r = -0.46, p = 0.0002 for the next 24 h). Conclusions: Entropy and SPI monitoring during anesthesia may play an important role in diminishing the risk of developing immediate POCD after emergency surgery.

Prevention of postoperative delirium through the avoidance of potentially inappropriate medications in a geriatric surgical patient

We demonstrate the utility of risk stratification for postoperative delirium in geriatric patients and show that postoperative delirium can be prevented in high-risk patients when potentially inappropriate medications (PIMs) (medications that are best avoided in older adults) are avoided. In this case, a 65-year-old woman underwent two debridement procedures with similar presurgical risk for postoperative delirium. There was no risk stratification or preoperative cognitive assessment in the first procedure, she received PIMs and developed postoperative delirium. In the second procedure, PIMs were intentionally avoided and postoperative delirium did not occur. This case supports recent recommendations from the European Society of Anaesthesiology, the American Society of Anesthesiologists and the American Geriatrics Society that providers assess a patient's cognitive function and delirium risk profile preoperatively to appropriately guide perioperative management.

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

The Poincaré plot obtained from electroencephalography (EEG) has been used to evaluate the depth of anesthesia. A standalone EEG Analyzer application was developed; raw EEG signals obtained from a bispectral index (BIS) monitor were analyzed using an on-line monitoring system. Correlations between Poincaré plot parameters and other measurements associated with anesthesia depth were evaluated during emergence from inhalational general anesthesia. Of the participants, 20 were adults anesthetized with sevoflurane (adult_{_SEV}), 20 were adults anesthetized with desflurane (adult_{_DES}), and 20 were pediatric patients anesthetized with sevoflurane (ped_{_SEV}). EEG signals were preprocessed through six bandpass digital filters (f0: 0.5–47 Hz, f1: 0.5–8 Hz, f2: 8–13 Hz, f3: 13–20 Hz, f4: 20–30 Hz, and f5: 30–47 Hz). The Poincaré plot-area ratio (PP_AR = PP_{A_fx}/PP_{A_f0}, fx = f1∼f5) was analyzed at five frequency ranges. Regardless of the inhalational anesthetic used, there were strong linear correlations between the logarithm of PP_AR at f5 and BIS (R² = 0.67, 0.79, and 0.71, in the adult_{_SEV}, adult_{_DES}, and ped_{_SEV} groups, respectively). As an additional observation, a part of EMG activity at the gamma range of 30–47 Hz probably influenced the calculations of BIS and PP_{AR_f5} with a non-negligible level. The logarithm of PP_AR in the gamma band was most sensitive to state changes during the emergence process and could provide a new non-proprietary parameter that correlates with changes in BIS during measurement of anesthesia depth.

Adult Emergence Agitation: A Veteran-Focused Narrative Review

Emergence agitation (EA) is a self-limited state of psychomotor excitement during awakening from general anesthesia. EA is confined to the emergence period as consciousness is restored, which sharply distinguishes it from other postoperative delirium states. Sporadic episodes of EA may become violent with the potential for harm to both patients and caregivers, but the long-term consequences of such events are not fully understood. Current literature on EA in adults is limited to small-scale studies with inconsistent nomenclature, variable time periods that define emergence, a host of different surgical populations, and conflicting diagnostic criteria. Therefore, true incidence rates and risk factors are unknown. In adult noncardiac surgery, the incidence of EA is approximately 19%. Limited data suggest that young adults undergoing otolaryngology operations with volatile anesthetic maintenance may be at the highest risk for EA. Currently suggested EA mechanisms are theoretical but might reflect underblunted sympathetic activation in response to various internal (eg, flashbacks or anxiety) or external (eg, surgical pain) stimuli as consciousness returns. Supplemental dexmedetomidine and ketamine may be utilized for EA prevention. Compared to the civilian population, military veterans may be more vulnerable to EA due to high rates of posttraumatic stress disorder (PTSD) manifesting as violent flashbacks; however, confirmatory data are limited. Nonetheless, expert military medical providers suggest that use of patient-centered rapport tactics, PTSD trigger identification and avoidance, and grounding measures may alleviate hyperactive emergence phenomena. Future research is needed to better characterize EA in veterans and validate prophylactic measures to optimize care for these patients. This narrative review provides readers with an important framework to distinguish EA from delirium. Furthermore, we summarize current knowledge of EA risk factors, mechanisms, and adult management strategies and specifically revisit them in the context of veteran perioperative health. The anesthesiology care team is ideally positioned to further explore EA and develop effective prevention and treatment protocols.

Anesthetic Management of Asleep and Awake Craniotomy for Supratentorial Tumor Resection

Understanding how anesthetics impact cerebral physiology, cerebral blood flow, brain metabolism, brain relaxation, and neurologic recovery is crucial for optimizing anesthesia during supratentorial craniotomies. Intraoperative goals for supratentorial tumor resection include maintaining cerebral perfusion pressure and cerebral autoregulation, optimizing surgical access and neuromonitoring, and facilitating rapid, cooperative emergence. Evidence-based studies increasingly expand the impact of anesthetic care beyond immediate perioperative care into both preoperative optimization and minimizing postoperative consequences. New evidence is needed for neuroanesthesia's role in neurooncology, in preventing conversion from acute to chronic pain, and in decreasing risk of intraoperative ischemia and postoperative delirium.

Intraoperative monitoring parameters and postoperative delirium: Results of a prospective cross-sectional trial

Postoperative delirium (PODE) can be associated with severe clinical complications; therefore, preventive measures are important. The objective of this trial was to elucidate whether haemodynamic or electroencephalographic (EEG) monitoring parameters during general anaesthesia or sevoflurane dosage correlate with the incidence of PODE. In addition, sevoflurane dosages and EEG stages during the steady state of anaesthesia were analyzed in patients of different ages.Eighty adult patients undergoing elective abdominal surgery received anaesthesia with sevoflurane and sufentanil according to the clinical routine. Anaesthesiologists were blinded to the EEG. Haemodynamic parameters, EEG parameters, sevoflurane dosage, and occurrence of PODE were analyzed.Thirteen patients (4 out of 33 women, 9 out of 47 men) developed PODE. Patients with PODE had a greater mean arterial pressure (MAP) variance (267.26 (139.40) vs 192.56 (99.64) mmHg2, P = .04), had a longer duration of EEG burst suppression or suppression (27.09 (45.32) vs 5.23 (10.80) minutes, P = .03), and received higher minimum alveolar sevoflurane concentrations (MAC) (1.22 (0.22) vs 1.09 (0.17), P = .03) than patients without PODE. MAC values were associated with wide ranges of EEG index values representing different levels of hypnosis.The results suggest that, in order to prevent PODE, a great variance of MAP, higher doses of sevoflurane, and deep levels of anaesthesia should be avoided. Titrating sevoflurane according to end-tidal gas monitoring and vital signs can lead to unnecessarily deep or light hypnosis. Intraoperative EEG monitoring may help to prevent PODE.

BIS index monitoring and perioperative neurocognitive disorders in older adults: a systematic review and meta-analysis

BACKGROUND AND AIMS

Perioperative neurocognitive disorders (PND) are common in elderly patients after surgery. It has been reported that BIS-guided anesthesia potentially influenced the occurrence of PND. Therefore, we conducted this systematic review and meta-analysis to explore the associations between bispectral index (BIS) monitoring and PND.

METHODS

Two researchers independently searched for relevant randomized controlled trials (RCTs) in PubMed, EMBASE, and the Cochrane Library (CENTRAL) using keywords related to the BIS and PND from inception to April 22, 2019. Odds ratios (OR) with 95% CI were calculated using a random effects model.

RESULTS

Nine RCTs involving 4023 participants aged 60 years or older were included into this meta-analysis. BIS-guided anesthesia was not associated with lower incidence of POD (random effects; OR: 0.69; 95% CI 0.48, 1.01), delayed neurocognitive recovery (DNR) at 1 day, 7 days (random effects; OR: 0.14; 95% CI 0.02, 1.23; random effects; OR: 0.97; 95% CI 0.57, 1.63), and postoperative neurocognitive disorder (NCD) at 90 days and 1 year after surgery in older adults (random effects; OR:0.72; 95% CI 0.52, 1.00; random effects; OR: 0.26; 95% CI 0.03, 2.47).

CONCLUSIONS

No definite evidence demonstrated that BIS-guided anesthesia decreased the incidence of POD, DNR and postoperative NCD in older patients. More homogeneous RCTs assessing the efficacy of BIS monitoring on reducing the occurrence of these perioperative cognitive disorders are needed.