Association between intraoperative electroencephalographic suppression and postoperative mortality

Processed electroencephalography-guided general anesthesia and norepinephrine requirements: A randomized trial in patients having vascular surgery

STUDY OBJECTIVE

Processed electroencephalography (pEEG) may help clinicians optimize depth of general anesthesia. Avoiding excessive depth of anesthesia may reduce intraoperative hypotension and the need for vasopressors. We tested the hypothesis that pEEG-guided - compared to non-pEEG-guided - general anesthesia reduces the amount of norepinephrine needed to keep intraoperative mean arterial pressure above 65 mmHg in patients having vascular surgery.

DESIGN

Randomized controlled clinical trial.

SETTING

University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

PATIENTS

110 patients having vascular surgery.

INTERVENTIONS

pEEG-guided general anesthesia.

MEASUREMENTS

Our primary endpoint was the average norepinephrine infusion rate from the beginning of induction of anesthesia until the end of surgery.

MAIN RESULT

96 patients were analyzed. The mean ± standard deviation average norepinephrine infusion rate was 0.08 ± 0.04 μg kg-1 min-1 in patients assigned to pEEG-guided and 0.12 ± 0.09 μg kg-1 min-1 in patients assigned to non-pEEG-guided general anesthesia (mean difference 0.04 μg kg-1 min-1, 95% confidence interval 0.01 to 0.07 μg kg-1 min-1, p = 0.004). Patients assigned to pEEG-guided versus non-pEEG-guided general anesthesia, had a median time-weighted minimum alveolar concentration of 0.7 (0.6, 0.8) versus 0.8 (0.7, 0.8) (p = 0.006) and a median percentage of time Patient State Index was <25 of 12 (1, 41) % versus 23 (3, 49) % (p = 0.279).

CONCLUSION

pEEG-guided - compared to non-pEEG-guided - general anesthesia reduced the amount of norepinephrine needed to keep mean arterial pressure above 65 mmHg by about a third in patients having vascular surgery. Whether reduced intraoperative norepinephrine requirements resulting from pEEG-guided general anesthesia translate into improved patient-centered outcomes remains to be determined in larger trials.

Association between sedation during spinal anesthesia and mortality in older patients undergoing hip fracture surgery: A nationwide retrospective cohort study in Japan

STUDY OBJECTIVE

Intraoperative sedation plays an important role in the management of regional anesthesia. Few studies have investigated the association of sedation during spinal anesthesia with postoperative mortality in older patients as a primary outcome. This study aimed to test the hypothesis that sedation during spinal anesthesia increases postoperative mortality in older patients undergoing hip fracture surgery.

DESIGN

Retrospective, cohort study.

SETTING

Acute and subacute care hospitals in Japan.

PATIENTS

Patients aged 65 years and older who received hip fracture surgery under spinal anesthesia between April 2014 and May 2022.

EXPOSURE

Sedation during spinal anesthesia.

MEASUREMENTS

Postoperative in-hospital all-cause mortality within 30 days.

MAIN RESULTS

In total, 25,554 eligible patients were identified. Propensity score matching created 4735 pairs, and baseline patient characteristics were acceptably balanced between the sedation and non-sedation groups. There was no significant difference in 30-day postoperative mortality between the two groups (hazard ratio [95% CIs]: 0.92 [0.59-1.44]).

CONCLUSIONS

There was no association between sedation during hip fracture surgery in older patients under spinal anesthesia and postoperative mortality. However, these results are limited to our population, and further prospective studies are needed to determine the safety of sedation.

EEG-Messung in Narkose

Based on the existing literature, the application of designated, processed EEG-monitors to measure anesthetic depth and the associated clinical implications are explained. EEG-monitors quantify the hypnotic portion of anesthesia, but not the nociceptive properties of anesthetics. Depth of anesthesia monitoring is common practice in many German hospitals and helps to visualize the interindividual variability of anesthetics, especially of propofol. Although deep anesthesia is associated with increased long-term mortality, this relation seems not to be causally related. Nevertheless, depth of anesthesia monitors help to identify patients being especially susceptible to anesthetics. Moreover, they have shown to reduce the incidence of intraoperative awareness and postoperative delirium. The application of processed EEG-monitors to reduce the incidence of postoperative delirium is currently recommended by the European Society of Anaesthesiology and Intensive Care.

EEG pre-burst suppression: characterization and inverse association with preoperative cognitive function in older adults

The most common complication in older surgical patients is postoperative delirium (POD). POD is associated with preoperative cognitive impairment and longer durations of intraoperative burst suppression (BSup) - electroencephalography (EEG) with repeated periods of suppression (very low-voltage brain activity). However, BSup has modest sensitivity for predicting POD. We hypothesized that a brain state of lowered EEG power immediately precedes BSup, which we have termed "pre-burst suppression" (preBSup). Further, we hypothesized that even patients without BSup experience these preBSup transient reductions in EEG power, and that preBSup (like BSup) would be associated with preoperative cognitive function and delirium risk. Data included 83 32-channel intraoperative EEG recordings of the first hour of surgery from 2 prospective cohort studies of patients ≥age 60 scheduled for ≥2-h non-cardiac, non-neurologic surgery under general anesthesia (maintained with a potent inhaled anesthetic or a propofol infusion). Among patients with BSup, we defined preBSup as the difference in 3-35 Hz power (dB) during the 1-s preceding BSup relative to the average 3-35 Hz power of their intraoperative EEG recording. We then recorded the percentage of time that each patient spent in preBSup, including those without BSup. Next, we characterized the association between percentage of time in preBSup and (1) percentage of time in BSup, (2) preoperative cognitive function, and (3) POD incidence. The percentage of time in preBSup and BSup were correlated (Spearman's ρ [95% CI]: 0.52 [0.34, 0.66], p < 0.001). The percentage of time in BSup, preBSup, or their combination were each inversely associated with preoperative cognitive function (β [95% CI]: -0.10 [-0.19, -0.01], p = 0.024; -0.04 [-0.06, -0.01], p = 0.009; -0.04 [-0.06, -0.01], p = 0.003, respectively). Consistent with prior literature, BSup was significantly associated with POD (odds ratio [95% CI]: 1.34 [1.01, 1.78], p = 0.043), though this association did not hold for preBSup (odds ratio [95% CI]: 1.04 [0.95, 1.14], p = 0.421). While all patients had ≥1 preBSup instance, only 20.5% of patients had ≥1 BSup instance. These exploratory findings suggest that future studies are warranted to further study the extent to which preBSup, even in the absence of BSup, can identify patients with impaired preoperative cognition and/or POD risk.

Association between mean arterial pressure and sublingual microcirculation during major non-cardiac surgery: Post hoc analysis of a prospective cohort

OBJECTIVE

To test the hypothesis that there is an association between mean arterial pressure (MAP) and sublingual perfusion during major surgery, and perhaps an identifiable harm threshold.

METHODS

This post hoc analysis of a prospective cohort included patients who had elective major non-cardiac surgery with a duration of ≥2 h under general anesthesia. We assessed sublingual microcirculation every 30 min using SDF+ imaging and determined the De Backer score, Consensus Proportion of Perfused Vessels (Consensus PPV), and the Consensus PPV (small). Our primary outcome was the relationship between MAP and sublingual perfusion which was evaluated with linear mixed effects modeling.

RESULTS

A total of 100 patients were included, with MAP ranging between 65 mmHg and 120 mmHg during anesthesia and surgery. Over a range of intraoperative MAPs between 65 and 120 mmHg, there were no meaningful associations between blood pressure and various measures of sublingual perfusion. There were also no meaningful changes in microcirculatory flow over 4.5 h of surgery.

CONCLUSIONS

In patients having elective major non-cardiac surgery with general anesthesia, sublingual microcirculation is well maintained when MAP ranges between 65 and 120 mmHg. It remains possible that sublingual perfusion will be a useful marker of tissue perfusion when MAP is lower than 65 mmHg.

The use of mean circulatory filling pressure analogue for monitoring hemodynamic coherence: A post-hoc analysis of the SPARSE data and proof-of-concept study

BACKGROUND

Dissociation between macrocirculation and microcirculation is often observed in surgical patients.

OBJECTIVE

To test the hypothesis that the analogue of mean circulatory filling pressure (Pmca) can monitor hemodynamic coherence during major non-cardiac surgery.

METHODS

In this post-hoc analysis and proof-of-concept study, we used the central venous pressure (CVP), mean arterial pressure (MAP), and cardiac output (CO) to calculate Pmca. Efficiency of the heart (Eh), arterial resistance (Rart), effective arterial elastance (Ea), venous compartment resistance (Rven), oxygen delivery (DO2), and oxygen extraction ratio (O2ER) were also calculated. Sublingual microcirculation was assessed using SDF + imaging, and the De Backer score, Consensus Proportion of Perfused Vessels (Consensus PPV), and Consensus PPV (small) were determined.

RESULTS

Thirteen patients were included, with a median age of 66 years. Median Pmca was 16 (14.9-18) mmHg and was positively associated with CO [p <  0.001; a 1 mmHg increase in Pmca increases CO by 0.73 L  min - 1 (p <  0.001)], Eh (p <  0.001), Rart (p = 0.01), Ea (p = 0.03), Rven (p = 0.005), DO2 (p = 0.03), and O2ER (p = 0.02). A significant correlation was observed between Pmca and Consensus PPV (p = 0.02), but not with De Backer Score (p = 0.34) or Consensus PPV (small) (p = 0.1).

CONCLUSION

Significant associations exist between Pmca and several hemodynamic and metabolic variables including Consensus PPV. Adequately powered studies should determine whether Pmca can provide real-time information on hemodynamic coherence.

Contribution of intraoperative electroencephalogram suppression to frailty-associated postoperative delirium: mediation analysis of a prospective surgical cohort

BACKGROUND

Frailty is a risk factor for postoperative delirium (POD), and has led to preoperative interventions that have reduced, but not eliminated, the risk. We hypothesised that EEG suppression, another risk factor for POD, mediates some of the frailty risk for POD.

METHODS

A prospective cohort study enrolled patients aged 65 yr or older, scheduled for noncardiac surgery under total intravenous anaesthesia. Frailty was assessed using the FRAIL scale. Cumulative duration of EEG suppression, defined as an amplitude between -5 and 5 μV for >0.5 s during anaesthesia, was measured. POD was diagnosed by either confusion assessment method (CAM), CAM-ICU, or medical records. The severity of POD was assessed using the Delirium Rating Scale - Revised-98 (DRS). Mediation analysis was used to estimate the relationships between frailty, EEG suppression, and severity of POD.

RESULTS

Among 252 enrolled patients, 51 were robust, 129 were prefrail, and 72 were frail. Patients classified as frail had higher duration of EEG suppression than either the robust (19 vs 0.57 s, P<0.001) or prefrail groups (19 vs 3.22 s, P<0.001). Peak delirium score was higher in the frail group than either the robust (17 vs 15, P<0.001) or prefrail groups (17 vs 16, P=0.007). EEG suppression time mediated 24.2% of the frailty-DRS scores association.

CONCLUSION

EEG suppression time mediated a statistically significant portion of the frailty-POD association in older noncardiac surgery patients. Trials directed at reducing EEG suppression time could result in intraoperative interventions to reduce POD in frail patients.

CLINICAL TRIAL REGISTRATION

ChiCTR2000041092 (Chinese Clinical Trial Registry).

Depth of anaesthesia and mortality after cardiac or noncardiac surgery: a systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Recent randomised controlled trials have failed to show a benefit in mortality by using processed electroencephalography (pEEG) to guide lighter anaesthesia. We performed a meta-analysis of mortality data from randomised trials of pEEG monitoring to assess the evidence of any protective effect of pEEG-guided light anaesthesia compared with deep anaesthesia in adults aged ≥18 yr.

METHODS

Our study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. In February 2022, we searched three databases (Cochrane CENTRAL, OVID Medline, EMBASE) for RCTs of pEEG monitoring that provided mortality data at 30 days, 90 days, and/or 1 yr or longer.

RESULTS

We included 16 articles from 12 RCTs with 48 827 total participants. We observed no statistically significant mortality reduction with light anaesthesia compared with deep anaesthesia in patients aged ≥18 yr when all studies were pooled (odds ratio [OR]=0.99; 95% confidence interval (CI), 0.92-1.08). This result did not change significantly when analysing mortality at 30 days, 90 days, 1 yr or longer. We observed no mortality benefit for pEEG monitoring compared with usual care (OR=1.02; 95% CI, 0.89-1.18), targeting higher pEEG index values compared with lower values (OR=0.89; 95% CI, 0.60-1.32), or low pEEG index value alerts compared with no alerts (OR=1.02; 95% CI, 0.41-2.52).

CONCLUSIONS

pEEG-guided lighter anaesthesia does not appear to reduce the risk of postoperative mortality. The absence of a plausible rationale for why deeper anaesthesia should increase mortality has hampered appropriate design of definitive clinical trials.

CLINICAL TRIAL REGISTRATION

CRD42022285195 (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.

Predicting personalised remifentanil effect site concentration for surgical incision using the nociception level index: A prospective calibration and validation study

BACKGROUND

Inadequate antinociception can cause haemodynamic instability. The nociception level (NOL) index measures response to noxious stimuli, but its capacity to predict optimal antinociception is unknown.

OBJECTIVE

To determine if NOL index change to a tetanic stimulus in cardiac and noncardiac surgery patients could predict the required remifentanil concentration for haemodynamic stability at skin incision.

DESIGN

A prospective two-phase cohort study.

SETTING

University hospital.

PATIENTS

Patients undergoing remifentanil-propofol target controlled infusion (TCI) anaesthesia.

INTERVENTIONS

During the calibration phase, investigators evaluated the tetanic stimulus induced NOL index change under standardised TCI remifentanil-propofol anaesthesia during a no-touch period [bispectral index (BIS) between 40 and 60, NOL index under 15]. If the NOL index change was 20 or greater following tetanic stimulation, investigators repeated the tetanus at higher remifentanil concentrations until the response was blunted. Surgeons incised the skin at this remifentanil concentration. The investigators derived a prediction model and in the validation phase calculated, using the NOL response to a single tetanus, the required incision remifentanil concentration for the start of surgery.

MAIN OUTCOME

Haemodynamic stability at incision [i.e. maximum heart rate (HR) < 20% increase from baseline, minimum HR (40 bpm) and mean arterial pressure (MAP) ± <20% of baseline].

RESULTS

During the calibration phase, no patient had hypertension. Two patients had a HR increase slightly greater than 20% (25.4 and 26.7%) within the first 2 min of surgery, but neither of these two patients had a HR above 76 bpm. Two patients were slightly hypotensive after incision (MAP 64 and 73 mmHg). During the validation phase, neither tachycardia nor hypotension occurred, but MAP increased to 21.5% above baseline for one patient.

CONCLUSION

During a no-touch period in patients under steady-state general anaesthesia [propofol effect site concentration (Ce) required for BIS between 40 and 60], the NOL index response to a tetanic stimulus under remifentanil antinociception can be used to personalise remifentanil Ce for the start of surgery and ensure stable haemodynamics.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT03324269.

Relationship of Effective Circulating Volume with Sublingual Red Blood Cell Velocity and Microvessel Pressure Difference: A Clinical Investigation and Computational Fluid Dynamics Modeling

The characteristics of physiologic hemodynamic coherence are not well-investigated. We examined the physiological relationship between circulating blood volume, sublingual microcirculatory perfusion, and tissue oxygenation in anesthetized individuals with steady-state physiology. We assessed the correlation of mean circulatory filling pressure analogue (Pmca) with sublingual microcirculatory perfusion and red blood cell (RBC) velocity using SDF+ imaging and a modified optical flow-based algorithm. We also reconstructed the 2D microvessels and applied computational fluid dynamics (CFD) to evaluate the correlation of Pmca and RBC velocity with the obtained pressure and velocity fields in microvessels from CFD (pressure difference, (Δp)). Twenty adults with a median age of 39.5 years (IQR 35.5−44.5) were included in the study. Sublingual velocity distributions were similar and followed a log-normal distribution. A constant Pmca value of 14 mmHg was observed in all individuals with sublingual RBC velocity 6−24 μm s−1, while a Pmca < 14 mmHg was observed in those with RBC velocity > 24 μm s−1. When Pmca ranged between 11 mmHg and 15 mmHg, Δp fluctuated between 0.02 Pa and 0.1 Pa. In conclusion, the intact regulatory mechanisms maintain a physiological coupling between systemic hemodynamics, sublingual microcirculatory perfusion, and tissue oxygenation when Pmca is 14 mmHg.

Association of Preoperative Basal Inflammatory State, Measured by Plasma suPAR Levels, with Intraoperative Sublingual Microvascular Perfusion in Patients Undergoing Major Non-Cardiac Surgery

It remains unknown whether chronic systemic inflammation is associated with impaired microvascular perfusion during surgery. We evaluated the association between the preoperative basal inflammatory state, measured by plasma soluble urokinase-type plasminogen activator receptor (suPAR) levels, and intraoperative sublingual microcirculatory variables in patients undergoing major non-cardiac surgery. Plasma suPAR levels were determined in 100 non-cardiac surgery patients using the suPARnostic® quick triage lateral flow assay. We assessed sublingual microcirculation before surgical incision and every 30 min during surgery using Sidestream Darkfield (SDF+) imaging and determined the De Backer score, the Consensus Proportion of Perfused Vessels (Consensus PPV), and the Consensus PPV (small). Elevated suPAR levels were associated with lower intraoperative De Backer score, Consensus PPV, and Consensus PPV (small). For each ng mL−1 increase in suPAR, De Backer score, Consensus PPV, and Consensus PPV (small) decreased by 0.7 mm−1, 2.5%, and 2.8%, respectively, compared to baseline. In contrast, CRP was not significantly correlated with De Backer score (r = −0.034, p = 0.36), Consensus PPV (r = −0.014, p = 0.72) or Consensus PPV Small (r = −0.037, p = 0.32). Postoperative De Backer score did not change significantly from baseline (5.95 ± 3.21 vs. 5.89 ± 3.36, p = 0.404), while postoperative Consensus PPV (83.49 ± 11.5 vs. 81.15 ± 11.8, p < 0.001) and Consensus PPV (small) (80.87 ± 13.4 vs. 78.72 ± 13, p < 0.001) decreased significantly from baseline. In conclusion, elevated preoperative suPAR levels were associated with intraoperative impairment of sublingual microvascular perfusion in patients undergoing elective major non-cardiac surgery.

Burst Suppression During General Anesthesia and Postoperative Outcomes: Mini Review

In the last decade, burst suppression has been increasingly studied by many to examine whether it is a mechanism leading to postoperative cognitive impairment. Despite a lack of consensus across trials, the current state of research suggests that electroencephalogram (EEG) burst suppression, duration and EEG emergence trajectory may predict postoperative delirium (POD). A mini literature review regarding evidence about burst suppression impact and susceptibilities was conducted, resulting in conflicting studies. Primarily, studies have used different algorithm values to replace visual burst suppression examination, although many studies have since emerged showing that algorithms underestimate burst suppression duration. As these methods may not be interchangeable with visual analysis of raw data, it is a potential factor for the current heterogeneity between data. Even though additional research trials incorporating the use of raw EEG data are necessary, the data currently show that monitoring with commercial intraoperative EEG machines that use EEG indices to estimate burst suppression may help physicians identify burst suppression and guide anesthetic titration during surgery. These modifications in anesthetics could lead to preventing unfavorable outcomes. Furthermore, some studies suggest that brain age, baseline impairment, and certain medications are risk factors for burst suppression and postoperative delirium. These patient characteristics, in conjunction with intraoperative EEG monitoring, could be used for individualized patient care. Future studies on the feasibility of raw EEG monitoring, new technologies for anesthetic monitoring and titration, and patient-associated risk factors are crucial to our continued understanding of burst suppression and postoperative delirium.

Electroencephalographic Burst-Suppression, Perioperative Neuroprotection, Postoperative Cognitive Function, and Mortality: A Focused Narrative Review of the Literature

Burst-suppression is an electroencephalographic pattern that results from a diverse array of pathophysiological causes and/or metabolic neuronal suppression secondary to the administration of anesthetic medications. The purpose of this review is to provide an overview of the physiological mechanisms that underlie the burst-suppression pattern and to present in a comprehensive way the available evidence both supporting and in opposition to the clinical use of this electroencephalographic pattern as a therapeutic measure in various perioperative settings.

Current trends in anesthetic depth and antinociception monitoring: an international survey

Current trends in anesthetic depth (i.e., hypnosis) and antinociception monitoring are unclear. We thus aimed to determine contemporary perspectives on monitoring these components of anesthesia during general anesthesia. Participants received and responded anonymously to an internet-based international survey supported by the European Society of Anaesthesiology and Intensive Care. Comparisons, when applicable, were carried out using Chi² analysis or Fischer's exact test. A total of 564 respondents, predominantly from Europe (80.1%), participated. There was a strong participation from Belgium (11.5%). A majority (70.9%) of anesthetists considered hypnotic monitoring important on most occasions to always. In contrast, a majority (62.6%) never or only occasionally considered antinociception monitoring important. This difference in the perceived importance of anesthetic depth versus antinociception monitoring was significant (p < 0.0001). A majority of respondents (70.1%) believed that guiding hypnosis and antinociception using these monitors would improve patient care on most occasions to always. Nonetheless, a substantial number of participants were unsure if hypnotic (23%) or antinociception (32%) monitoring were recommended and there was a lack of knowledge (58%) of any published algorithms to titrate hypnotic and/or antinociceptive drugs based on the information provided by the monitors. In conclusion, current trends in European academic centers prioritize anesthesia depth over antinociception monitoring. Despite an agreement among respondents that applying strategies that optimize anesthetic depth and antinociception could improve outcome, there remains a lack of knowledge of appropriate algorithms. Future studies and recommendations should focus on clarifying goal-directed anesthetic strategies and determine their impact on perioperative patient outcome.

Association Between Burst-Suppression Latency and Burst-Suppression Ratio Under Isoflurane or Adjuvant Drugs With Isoflurane Anesthesia in Mice

The same doses of anesthesia may yield varying depths of anesthesia in different patients. Clinical studies have revealed a possible causal relationship between deep anesthesia and negative short- and long-term patient outcomes. However, a reliable index and method of the clinical monitoring of deep anesthesia and detecting latency remain lacking. As burst-suppression is a characteristic phenomenon of deep anesthesia, the present study investigated the relationship between burst-suppression latency (BSL) and the subsequent burst-suppression ratio (BSR) to find an improved detection for the onset of intraoperative deep anesthesia. The mice were divided young, adult and old group treated with 1.0% or 1.5% isoflurane anesthesia alone for 2 h. In addition, the adult mice were pretreated with intraperitoneal injection of ketamine, dexmedetomidine, midazolam or propofol before they were anesthetized by 1.0% isoflurane for 2 h. Continuous frontal, parietal and occipital electroencephalogram (EEG) were acquired during anesthesia. The time from the onset of anesthesia to the first occurrence of burst-suppression was defined as BSL, while BSR was calculated as percentage of burst-suppression time that was spent in suppression periods. Under 1.0% isoflurane anesthesia, we found a negative correlation between BSL and BSR for EEG recordings obtained from the parietal lobes of young mice, from the parietal and occipital lobes of adult mice, and the occipital lobes of old mice. Under 1.5% isoflurane anesthesia, only the BSL calculated from EEG data obtained from the occipital lobe was negatively correlated with BSR in all mice. Furthermore, in adult mice receiving 1.0% isoflurane anesthesia, the co-administration of ketamine and midazolam, but not dexmedetomidine and propofol, significantly decreased BSL and increased BSR. Together, these data suggest that BSL can detect burst-suppression and predict the subsequent BSR under isoflurane anesthesia used alone or in combination with anesthetics or adjuvant drugs. Furthermore, the consistent negative correlation between BSL and BSR calculated from occipital EEG recordings recommends it as the optimal position for monitoring burst-suppression.

Heterogeneous impact of hypotension on organ perfusion and outcomes: a narrative review

Arterial blood pressure is the driving force for organ perfusion. Although hypotension is common in acute care, there is a lack of accepted criteria for its definition. Most practitioners regard hypotension as undesirable even in situations that pose no immediate threat to life, but hypotension does not always lead to unfavourable outcomes based on experience and evidence. Thus efforts are needed to better understand the causes, consequences, and treatments of hypotension. This narrative review focuses on the heterogeneous underlying pathophysiological bases of hypotension and their impact on organ perfusion and patient outcomes. We propose the iso-pressure curve with hypotension and hypertension zones as a way to visualize changes in blood pressure. We also propose a haemodynamic pyramid and a pressure-output-resistance triangle to facilitate understanding of why hypotension can have different pathophysiological mechanisms and end-organ effects. We emphasise that hypotension does not always lead to organ hypoperfusion; to the contrary, hypotension may preserve or even increase organ perfusion depending on the relative changes in perfusion pressure and regional vascular resistance and the status of blood pressure autoregulation. Evidence from RCTs does not support the notion that a higher arterial blood pressure target always leads to improved outcomes. Management of blood pressure is not about maintaining a prespecified value, but rather involves ensuring organ perfusion without undue stress on the cardiovascular system.

Effect of electroencephalography-guided anesthesia on neurocognitive disorders in elderly patients undergoing major non-cardiac surgery: A trial protocol The POEGEA trial (POncd Elderly GEneral Anesthesia)

Introduction

The number of elderly patients undergoing major surgery is rapidly increasing. They are particularly at risk of developing postoperative neurocognitive disorders (NCD). Earlier studies suggested that processed electroencephalographic (EEG) monitors may reduce the incidence of postoperative NCD. However, none of these studies controlled for intraoperative nociception levels or personalized blood pressure targets. Their results remain unclear if the reduction in the incidence of postoperative NCD relates to avoidance of any electroencephalographic pattern suggesting excessive anesthesia depth.

Objective

The objective of this trial is to investigate–in patients ≥ 70 years old undergoing major non-cardiac surgery–the effect of EEG-guided anesthesia on postoperative NCD while controlling for intraoperative nociception, personalized blood pressure targets, and using detailed information provided by the EEG monitor (including burst suppression ratio, density spectral array, and raw EEG waveform).

Material and methods

This prospective, randomized, controlled trial will be conducted in a single Canadian university hospital. Patients ≥ 70 years old undergoing elective major non-cardiac surgery will be included in the trial. The administration of sevoflurane will be adjusted to maintain a BIS index value between 40 and 60, to keep a Suppression Ratio (SR) at 0%, to keep a direct EEG display without any suppression time and a spectrogram with most of the EEG wave frequency within the alpha, theta, and delta frequencies in the EEG-guided group. In the control group, sevoflurane will be administered to achieve an age-adjusted minimum alveolar concentration of [0.8–1.2]. In both groups, a nociception monitor will guide intraoperative opioid administration, individual blood pressure targets will be used, and cerebral oximetry used to tailor intraoperative hemodynamic management. The primary endpoint will be the incidence of NCD at postoperative day 1, as evaluated by the Montreal Cognitive Assessment (MoCA). Secondary endpoints will include the incidence of postoperative NCD at different time points and the evaluation of cognitive trajectories up to 90 days after surgery among EEG-guided and control groups.

Study registration

NCT04825847 on ClinicalTrials.gov.

Effects of depth of neuromuscular blockade on the BIS-guided propofol requirement: A randomized controlled trial

BACKGROUND

Deep neuromuscular blockade is considered beneficial for improving the surgical space condition during laparoscopic surgery. Adequacy of the surgical space condition may affect the anesthetists' decision regarding titration of depth of anesthesia. We investigated whether deep neuromuscular blockade reduces the propofol requirement under bispectral index monitoring compared to moderate neuromuscular blockade.

METHODS

Adult patients undergoing elective laparoscopic colorectal surgery were randomly allocated to a moderate or deep group. A train-of-four count of 1-2 in the moderate group, and a post-tetanic count of 1-2 in the deep group, were maintained by continuous infusion of rocuronium. The induction and maintenance of anesthesia were achieved by target-controlled infusion of propofol and remifentanil. The dose of propofol was adjusted to maintain the bispectral index in the range of 40-50. The remifentanil dose was titrated to maintain the systolic blood pressure to within 20% of the ward values.

RESULTS

A total of 82 patients were included in the analyses. The mean±SD dose of propofol was 7.54 ± 1.66 and 7.42 ± 1.01 mg·kg-1·h-1 in the moderate and deep groups, respectively (P = .104). The mean±SD dose of remifentanil was 4.84 ± 1.74 and 4.79 ± 1.77 μg kg-1 h-1 in the moderate and deep groups, respectively (P = .688). In comparison to the moderate group, the deep group showed significantly lower rates of intraoperative patient movement (42.9% vs 22.5%, respectively, P = .050) and additional neuromuscular blocking agent administration (76% vs 53%, respectively, P = .007). Postoperative complications, including pulmonary complications, wound problems and reoperation, were not different between the two groups.

CONCLUSION

Deep neuromuscular blockade did not reduce the bispectral index-guided propofol requirement compared to moderate neuromuscular blockade during laparoscopic colon surgery, despite reducing movement of the patient and the requirement for a rescue neuromuscular blocking agent.

TRIAL REGISTRATION

Clinicaltrials.gov (NCT03890406).

Effect of electroencephalogram-guided anaesthesia administration on 1 yr mortality: 1 yr follow-up of a randomised clinical trial

BACKGROUND

Intraoperative EEG suppression duration has been associated with postoperative delirium and mortality. In a clinical trial testing anaesthesia titration to avoid EEG suppression, the intervention did not decrease the incidence of postoperative delirium, but was associated with reduced 30 day mortality. The present study evaluated whether the EEG-guided anaesthesia intervention continued to be associated with reduced 1 yr mortality.

METHODS

This manuscript reports 1 yr follow-up of patients from a single-centre RCT, including a post-hoc secondary outcome (1 yr mortality) in addition to pre-specified secondary outcomes. The trial included patients aged 60 yr or older undergoing surgery with general anaesthesia between January 2015 and May 2018. Patients were randomised to receive EEG-guided anaesthesia or usual care. The previously reported primary outcome was postoperative delirium. The outcome of the current study was all-cause 1 yr mortality.

RESULTS

Of the 1232 patients enrolled, 614 patients were randomised to EEG-guided anaesthesia and 618 patients to usual care. One year mortality was 57/591 (9.6%) in the guided group and 62/601 (10.3%) in the usual-care group. No significant difference in mortality was observed (adjusted absolute risk difference, -0.7%; 99.5% confidence interval, -5.8% to 4.3%; P=0.68).

CONCLUSIONS

An EEG-guided anaesthesia intervention aiming to decrease duration of EEG suppression during surgery did not significantly decrease 1 yr mortality. These findings, in the context of other studies, do not provide supportive evidence for EEG-guided anaesthesia to prevent intermediate term postoperative death.

CLINICAL TRIAL REGISTRATION

NCT02241655.

Does electroencephalographic burst suppression still play a role in the perioperative setting?

With the widespread use of electroencephalogram [EEG] monitoring during surgery or in the Intensive Care Unit [ICU], clinicians can sometimes face the pattern of burst suppression [BS]. The BS pattern corresponds to the continuous quasi-periodic alternation between high-voltage slow waves [the bursts] and periods of low voltage or even isoelectricity of the EEG signal [the suppression] and is extremely rare outside ICU and the operative room. BS can be secondary to increased anesthetic depth or a marker of cerebral damage, as a therapeutic endpoint [i.e., refractory status epilepticus or refractory intracranial hypertension]. In this review, we report the neurophysiological features of BS to better define its role during intraoperative and critical care settings.

Brain Aging and Anesthesia

Herein, the authors review the neuroanatomical and the neurophysiological aspects of the normal aging evolution based on the recent literature and briefly describe the difference between physiological and pathological brain aging, with consideration of the currently recommended anesthesia management of older patients. The population of elderly patients is growing drastically with advances in medicine that have prolonged the life span. One of the direct consequence has been a significant increase in the request for anesthesia care for older patients despite the type of surgery (cardiac vs noncardiac and mainly orthopedic). Because the brain of this category of patients undergoes a specific triple influence (immune, metabolic, and inflammatory), some particular physiological, anatomical, and structural modifications must be taken into account because they expose these patients more specifically to postoperative cognitive disturbances. To prevent type of adverse outcome, a better knowledge and understanding of these neurosciences must be promoted. The strategies developed to prevent such adverse outcomes include the determination and detection of significant at-risk patients and improvement in the titration of anesthesia to reduce exposure of anesthesia to these patients through an adapted anesthesia-induced unconsciousness that avoids, as much as possible, the risk of toxic overdose with an overly deep brain depression. To accomplish this, the unprocessed electroencephalogram (EEG) and its spectrogram may represent a significant improvement in monitoring, first by allowing for the rapid recognition of repetitive or persistent EEG suppression by the on-line reading of the raw EEG trace and second by allowing for the accurate determination of the adequate anesthetic-induced state, obtained in general in this category of patients by substantially lowered doses of anesthetic agents. This represents a new methodology for anesthesia titration that is adjusted on a more case-by-case basis and is related to the physiology of individual patients. A better understanding of aging-induced brain transformations remains the key regarding the improvement of the anesthetic management of the always growing population of elderly patients. The promotion of the unprocessed EEG may represent the best method of preventing the risk of anesthetic toxicity, including postoperative cognitive dysfunctions.

The cumulative duration of bispectral index less than 40 concurrent with hypotension is associated with 90-day postoperative mortality: a retrospective study

BACKGROUND

The relationship between intraoperative low bispectral index (BIS) values and poor clinical outcomes has been controversial. Intraoperative hypotension is associated with postoperative complication. The purpose of this study was to investigate the influence of intraoperative low BIS values and hypotension on postoperative mortality in patients undergoing major abdominal surgery.

METHODS

This retrospective study analyzed 1862 cases of general anesthesia. We collected the cumulative time of BIS values below 20 and 40 as well as electroencephalographic suppression and documented the incidences in which these states were maintained for at least 5 min. Durations of intraoperative mean arterial pressures (MAP) less than 50 mmHg were also recorded. Multivariable logistic regression was used to evaluate the association between suspected risk factors and postoperative mortality.

RESULTS

Ninety-day mortality and 180-day mortality were 1.5 and 3.2% respectively. The cumulative time in minutes for BIS values falling below 40 coupled with MAP falling below 50 mmHg was associated with 90-day mortality (odds ratio, 1.26; 95% confidence interval, 1.04-1.53; P = .019). We found no association between BIS related values and 180-day mortality.

CONCLUSIONS

The cumulative duration of BIS values less than 40 concurrent with MAP less than 50 mmHg was associated with 90-day postoperative mortality, not 180-day postoperative mortality.

Acute continuous nocturnal light exposure decreases BSR under sevoflurane anesthesia in C57BL/6J mice: possible role of differentially spared light-sensitive pathways under anesthesia

Brain responses to external stimuli such as light are preserved under general anesthesia. In nocturnal animals, acute light exposure can induce sleep, and acute dark can increase wakefulness. This study aims to investigate the effect of acute continuous nocturnal light exposure (ACNLE) on burst-suppression patterns under sevoflurane anesthesia using electroencephalogram (EEG) monitoring in mice. We set the initial sevoflurane dose to 2.0% and increased it by 0.5% every 20 min until it reached 4.0%. Burst-suppression ratio (BSR), EEG power and quantitative burst analysis were used to assess the effects of ACNLE on burst suppression patterns under sevoflurane anesthesia. Blood serum corticosterone measurement and c-Fos immunofluorescent staining of the suprachiasmatic nucleus (SCN) and ventrolateral preoptic nucleus (VLPO) were used to demonstrate the biological consequence induced by ACNLE. Compared to darkness, ACNLE caused significant changes in EEG power and decrease of BSR at 2.5%, 3.0% and 3.5% sevoflurane. ACNLE was also associated with an increase in burst duration and burst frequency as well as a decrease in burst maximum peak-to-peak amplitude and burst power in the beta (15-25 Hz) and gamma (25-80 Hz) bands. ACNLE increased the concentration of serum corticosterone and the expression of c-Fos in the SCN, while not changed c-Fos expression in the VLPO. These results demonstrated that ACNLE influences the BSR under sevoflurane anesthesia, possibly by activating light-sensitive nonvisual pathways including SCN and increasing of peripheral serum corticosterone levels.

Impact of hypotension on cerebral perfusion during general anesthesia induction: A prospective observational study in adults

INTRODUCTION

During anesthesia, decreases in mean arterial pressure (MAP) are common but the impact on possible cerebral hypoperfusion remains a matter of debate. We evaluated cerebral perfusion in patients with or without cardiovascular comorbidities (Hi-risk vs Lo-risk) during induction of general anesthesia and during hypotensive episodes.

METHODS

Patients scheduled for neuroradiology procedure using standardized target-controlled Propofol-Remifentanil infusion were prospectively included. Monitoring included Transcranial Doppler (TCD) measuring mean blood velocity of the middle cerebral artery (Vm), Bispectral Index with burst suppression ratio (SR) and cerebral Near-Infrared Spectroscopy (NIRS). Hypotensive episodes were treated with a 10 µg bolus of Norepinephrine.

RESULTS

Eighty-one patients were included, 37 Hi-risk and 44 Lo-risk. During induction of anesthesia, MAP and Vm decreased in all patients, with greater changes observed in Hi-risk patients compared to Lo-risk patients (-34 [38-29]% vs -17 [25-8]%, P < .001 and -39 [45-29]% vs -28 [34-19]%, P < .01 respectively). In Hi-risk patients, the MAP-decrease correlated with the Vm-decrease (r = .48, P < .01), and was associated with more frequent occurrences of SR (21 vs 5 patients, P < .01 for Hi-risk vs Lo-risk). For the MAP-increase induced by norepinephrine, the Vm-increase was greater in Hi-risk than in Lo-risk patients (+15 [8-21]% vs +4 [1-11]%, P < .01). During induction and norepinephrine boluses, NIRS values did not follow acute changes of Vm.

CONCLUSION

Our results showed that Hi-risk patients had a higher decrease in MAP and Vm, and a higher occurrence of SR during induction of anesthesia than Lo-risk patients. Correction of MAP with norepinephrine increased Vm mainly in Hi-rik patients.

Protocol for the Effectiveness of an Anesthesiology Control Tower System in Improving Perioperative Quality Metrics and Clinical Outcomes: the TECTONICS randomized, pragmatic trial

Introduction: Perioperative morbidity is a public health priority, and surgical volume is increasing rapidly. With advances in technology, there is an opportunity to research the utility of a telemedicine-based control center for anesthesia clinicians that assess risk, diagnoses negative patient trajectories, and implements evidence-based practices. Objectives: The primary objective of this trial is to determine whether an anesthesiology control tower (ACT) prevents clinically relevant adverse postoperative outcomes including 30-day mortality, delirium, respiratory failure, and acute kidney injury. Secondary objectives are to determine whether the ACT improves perioperative quality of care metrics including management of temperature, mean arterial pressure, mean airway pressure with mechanical ventilation, blood glucose, anesthetic concentration, antibiotic redosing, and efficient fresh gas flow. Methods and analysis: We are conducting a single center, randomized, controlled, phase 3 pragmatic clinical trial. A total of 58 operating rooms are randomized daily to receive support from the ACT or not. All adults (eighteen years and older) undergoing surgical procedures in these operating rooms are included and followed until 30 days after their surgery. Clinicians in operating rooms randomized to ACT support receive decision support from clinicians in the ACT. In operating rooms randomized to no intervention, the current standard of anesthesia care is delivered. The intention-to-treat principle will be followed for all analyses. Differences between groups will be presented with 99% confidence intervals; p-values <0.005 will be reported as providing compelling evidence, and p-values between 0.05 and 0.005 will be reported as providing suggestive evidence. Registration: TECTONICS is registered on ClinicalTrials.gov, NCT03923699; registered on 23 April 2019.

Anaesthetic depth and complications after major surgery: an international, randomised controlled trial

BACKGROUND

An association between increasing anaesthetic depth and decreased postoperative survival has been shown in observational studies; however, evidence from randomised controlled trials is lacking. Our aim was to compare all-cause 1-year mortality in older patients having major surgery and randomly assigned to light or deep general anaesthesia.

METHODS

In an international trial, we recruited patients from 73 centres in seven countries who were aged 60 years and older, with significant comorbidity, having surgery with expected duration of more than 2 h, and an anticipated hospital stay of at least 2 days. We randomly assigned patients who had increased risk of complications after major surgery to receive light general anaesthesia (bispectral index [BIS] target 50) or deep general anaesthesia (BIS target 35). Anaesthetists also nominated an appropriate range for mean arterial pressure for each patient during surgery. Patients were randomly assigned in permuted blocks by region immediately before surgery, with the patient and assessors masked to group allocation. The primary outcome was 1-year all-cause mortality. The trial is registered with the Australian New Zealand Clinical Trials Registry, ACTRN12612000632897, and is closed to accrual.

FINDINGS

Patients were enrolled between Dec 19, 2012, and Dec 12, 2017. Of the 18 026 patients screened as eligible, 6644 were enrolled, randomly assigned to treatment or control, and formed the intention-to-treat population (3316 in the BIS 50 group and 3328 in the BIS 35 group). The median BIS was 47·2 (IQR 43·7 to 50·5) in the BIS 50 group and 38·8 (36·3 to 42·4) in the BIS 35 group. Mean arterial pressure was 3·5 mm Hg (4%) higher (median 84·5 [IQR 78·0 to 91·3] and 81·0 [75·4 to 87·6], respectively) and volatile anaesthetic use was 0·26 minimum alveolar concentration (30%) lower (0·62 [0·52 to 0·73] and 0·88 [0·74 to 1·04], respectively) in the BIS 50 than the BIS 35 group. 1-year mortality was 6·5% (212 patients) in the BIS 50 group and 7·2% (238 patients) in the BIS 35 group (hazard ratio 0·88, 95% CI 0·73 to 1·07, absolute risk reduction 0·8%, 95% CI -0·5 to 2·0). Grade 3 adverse events occurred in 954 (29%) patients in the BIS 50 group and 909 (27%) patients in the BIS 35 group; and grade 4 adverse events in 265 (8%) and 259 (8%) patients, respectively. The most commonly reported adverse events were infections, vascular disorders, cardiac disorders, and neoplasms.

INTERPRETATION

Among patients at increased risk of complications after major surgery, light general anaesthesia was not associated with lower 1-year mortality than deep general anaesthesia. Our trial defines a broad range of anaesthetic depth over which anaesthesia may be safely delivered when titrating volatile anaesthetic concentrations using a processed electroencephalographic monitor.

FUNDING

Health Research Council of New Zealand; National Health and Medical Research Council, Australia; Research Grant Council of Hong Kong; National Institute for Health and Research, UK; and National Institutes of Health, USA.

Misuse of Regression Adjustment for Additional Confounders Following Insufficient Propensity Score Balancing

After propensity score (PS) matching, inverse probability weighting, and stratification or regression adjustment for PS, one may compare different exposure groups with or without further covariate adjustment. In the former case, although a typical application uses the same set of covariates in the PS and the stratification post-PS balancing, several studies adjust for additional confounders in the stratification while ignoring the covariates that have been balanced by the PS. We show the bias arising from such partial adjustments for distinct sets of confounders by PS and regression or stratification. Namely, the stratification or regression after PS balancing causes imbalance in the confounders that have been balanced by the PS if PS-balanced confounders are ignored. We empirically illustrate the bias in the Rotterdam Tumor Bank, in which strong confounders distort the association between chemotherapy and recurrence-free survival. If additional covariates are adjusted for after PS balancing, the covariate sets conditioned in PS should be again adjusted for, or PS should be reestimated by including the additional covariates to avoid bias owing to covariate imbalance.

Determination of the minimal alveolar concentration of sevoflurane associated with isoelectric electroencephalogram in children: A prospective, randomized, double-blind study

OBJECTIVE

We investigated the minimal alveolar concentration (MAC) of sevoflurane associated with the occurrence of isoelectric electroencephalogram in 50% of children under steady-state conditions (MAC IE). The MAC IE was determined in 100% oxygen and with the addition of 50% nitrous oxide or after the injection of fentanyl.

METHODS

Seventy-two children (ASA I or II, age 3-8 years) undergoing elective surgery were allocated to one of three groups: in 100% oxygen (group O₂ ), in 50% oxygen and 50% nitrous oxide (group N₂ O), or in 100% oxygen with a bolus of 3 μg/kg fentanyl (group FENTANYL). The state of isoelectric EEG was considered as significant when a burst suppression ratio of 100% lasted for >1 minute. The MAC IE was determined by the Dixon's up-and-down method after a 15-minute period with a stable endtidal concentration of sevoflurane. The concentration of sevoflurane was determined by the electroencephalogram of the previous patient: increase of 0.2% if isoelectric EEG were absent or decrease of 0.2% if isoelectric EEG were present.

RESULTS

The MAC IE in group O₂ (MAC IE_O2 ) was 5.30 (5.12-5.48)% (median [95% CI]). The MAC IE in group N₂ O (MAC IE_N2O ) was 5.83 (5.67-5.99)%. The MAC IE in group FENTANYL (MAC IE_FENTANYL ) was 5.37 (5.21-5.53)%, which was close to MAC IE_O2 .

CONCLUSION

The MAC IE of sevoflurane calculated in 100% O₂ was 5.30% in children. Addition of 50% N₂ O modestly increased MAC IE of sevoflurane, while 3 μg/kg fentanyl had no effect on MAC IE of sevoflurane.

Stepped wedge cluster randomised controlled trial to assess the effectiveness of an optimisation strategy for general anaesthesia on postoperative morbidity and mortality in elderly patients (the OPTI-AGED study): a study protocol

INTRODUCTION

Elderly patients constitute an increasingly large proportion of the high-risk surgical group. In adult patients, several specific intraoperative approaches such as cardiac output-guided haemodynamic therapy, depth of anaesthesia monitoring (DAM) or lung-protective ventilation (LPV) are designed to reduce postoperative mortality and surgical complications. However, none of these approaches has been specifically performed in the elderly, and no evaluation of a multimodal optimisation strategy for general anaesthesia has been achieved in this population.

AIMS

The objective of this study is to assess, in high-risk patients aged 75 years and over undergoing high-risk surgery, the effectiveness of combined optimisation of anaesthesia involving goal-directed haemodynamic therapy (GDHT), LPV and electroencephalographic DAM on postoperative morbidity and mortality. The primary outcome of the study is a composite criterion associating major postoperative complications and mortality occurring within the 30 first postoperative days. The secondary outcomes are 1-year postoperative autonomy and mortality.

METHODS AND ANALYSIS

This prospective, randomised, controlled, multicentre trial using a stepped wedge cluster design will be conducted in 27 French university centres. Patients aged 75 years and over, undergoing femoral head fractures and major intraperitoneal or vascular elective surgeries will be included after informed consent. They will benefit from usual care in the 'control group' and from a combined optimisation of general anaesthesia involving GDHT, LPV and DAM in the 'optimisation group'. The cluster's crossover will be unidirectional, from control to optimisation, and randomised. Data will be recorded at inclusion, the day of surgery, 7 days, 30 days and 1year postoperatively and collected into a hosted electronic case report form. The primary outcome of the study is a composite criterion associating major postoperative complications and mortality occurring within the 30 first postoperative days. The secondary outcomes are 1- year postoperative autonomy and mortality.

ETHICS AND DISSEMINATION

This protocol was approved by the ethics committee Sud-Est 1 and the French regulatory agency. The finding of the trial will be disseminated through peer-reviewed journals and conferences TRIAL REGISTRATION NUMBER: NCT02668250; Pre-results.

Using machine learning techniques to develop forecasting algorithms for postoperative complications: protocol for a retrospective study

INTRODUCTION

Mortality and morbidity following surgery are pressing public health concerns in the USA. Traditional prediction models for postoperative adverse outcomes demonstrate good discrimination at the population level, but the ability to forecast an individual patient's trajectory in real time remains poor. We propose to apply machine learning techniques to perioperative time-series data to develop algorithms for predicting adverse perioperative outcomes.

METHODS AND ANALYSIS

This study will include all adult patients who had surgery at our tertiary care hospital over a 4-year period. Patient history, laboratory values, minute-by-minute intraoperative vital signs and medications administered will be extracted from the electronic medical record. Outcomes will include in-hospital mortality, postoperative acute kidney injury and postoperative respiratory failure. Forecasting algorithms for each of these outcomes will be constructed using density-based logistic regression after employing a Nadaraya-Watson kernel density estimator. Time-series variables will be analysed using first and second-order feature extraction, shapelet methods and convolutional neural networks. The algorithms will be validated through measurement of precision and recall.

ETHICS AND DISSEMINATION

This study has been approved by the Human Research Protection Office at Washington University in St Louis. The successful development of these forecasting algorithms will allow perioperative healthcare clinicians to predict more accurately an individual patient's risk for specific adverse perioperative outcomes in real time. Knowledge of a patient's dynamic risk profile may allow clinicians to make targeted changes in the care plan that will alter the patient's outcome trajectory. This hypothesis will be tested in a future randomised controlled trial.

Effect of anesthesia depth on postoperative clinical outcome in patients with supratentorial tumor (DEPTH): study protocol for a randomized controlled trial

INTRODUCTION

Recent studies have shown that deep anaesthesia is associated with poor outcomes. However, no randomised controlled trials have been conducted to test the causality in patients undergoing brain tumour resection.

METHODS AND ANALYSIS

DEPTH is a multicenter, randomised, parallel-group, blind trial. The depth of general anaesthesia will be monitored using the bispectral index (BIS). Patients elected for supratentorial tumour resection will be randomly allocated to the deep or the light anaesthesia group in which the target BIS value is 35 or 50, respectively. BIS will be maintained at the target value for more than 90% of the total anaesthesia period. The primary outcome is the disability-free survival rate at postoperative 30 days and 1 year. The secondary outcomes are the mortality and morbidity within 30 days after surgery.

ETHICS APPROVAL AND DISSEMINATION

Ethical approval has been granted by the Medical Ethics Committee of Beijing Tiantan Hospital, Capital Medicine University. The reference number is KY2016-059-02. The results of this study will be disseminated through presentations at scientific conferences and publication in scientific journals.

TRIAL REGISTRATION

NCT03033693.

Advances in awareness monitoring technologies

PURPOSE OF REVIEW

Initial studies suggested that the use of processed electroencephalogram technology could significantly decrease the incidence of unintended intraoperative awareness events during general anesthesia. Subsequent work has cast doubts on these findings. This review will examine the current state of awareness monitoring.

RECENT FINDINGS

Recently published randomized controlled trials examining the use of the bispectral index during general anesthesia have not been able to show superiority over other forms of monitoring depth of anesthesia, such as end-tidal anesthetic-agent concentration. Additionally, there is current interest in utilizing the unprocessed electroencephalogram to ascertain depth of anesthesia and recent studies have demonstrated its use in preventing postoperative delirium.

SUMMARY

Although awareness monitors such as the bispectral index monitor may have benefit in patients in whom volatile anesthetic agents must be minimized - such as in hemodynamically unstable patients, or patients undergoing total intravenous anesthesia - these monitors do not appear to be useful for all patients.