Prolonged concurrent hypotension and low bispectral index ('double low') are associated with mortality, serious complications, and prolonged hospitalization after cardiac surgery

SQI-DOANet: electroencephalogram-based deep neural network for estimating signal quality index and depth of anaesthesia

Objective. Monitoring the depth of anaesthesia (DOA) during surgery is of critical importance. However, during surgery electroencephalography (EEG) is usually subject to various disturbances that affect the accuracy of DOA. Therefore, accurately estimating noise in EEG and reliably assessing DOA remains an important challenge. In this paper, we proposed a signal quality index (SQI) network (SQINet) for assessing the EEG signal quality and a DOA network (DOANet) for analyzing EEG signals to precisely estimate DOA. The two networks are termed SQI-DOANet.Approach. The SQINet contained a shallow convolutional neural network to quickly determine the quality of the EEG signal. The DOANet comprised a feature extraction module for extracting features, a dual attention module for fusing multi-channel and multi-scale information, and a gated multilayer perceptron module for extracting temporal information. The performance of the SQI-DOANet model was validated by training and testing the model on the large VitalDB database, with the bispectral index (BIS) as the reference standard.Main results. The proposed DOANet yielded a Pearson correlation coefficient with the BIS score of 0.88 in the five-fold cross-validation, with a mean absolute error (MAE) of 4.81. The mean Pearson correlation coefficient of SQI-DOANet with the BIS score in the five-fold cross-validation was 0.82, with an MAE of 5.66.Significance. The SQI-DOANet model outperformed three compared methods. The proposed SQI-DOANet may be used as a new deep learning method for DOA estimation. The code of the SQI-DOANet will be made available publicly athttps://github.com/YuRui8879/SQI-DOANet.

Association between cumulative duration of deep anesthesia and postoperative acute kidney injury after noncardiac surgeries: a retrospective observational study

BACKGROUND

Bispectral index (BIS) is a processed electroencephalography monitoring tool and is widely used in anesthetic depth monitoring. Deep anesthesia exposure may be associated with multiple adverse outcomes. However, the relationship between anesthetic depth and postoperative acute kidney injury (AKI) remains unclear. We sought to determine the effect of BIS-based deep anesthesia duration on postoperative AKI following noncardiac surgery.

METHODS

This retrospective study used data from the Vital Signs DataBase, including patients undergoing noncardiac surgeries with BIS monitoring. The BIS values were collected every second during anesthesia. Restricted cubic splines and logistic regression were used to assess the association between the cumulative duration of deep anesthesia and postoperative AKI.

RESULTS

4774 patients were eligible, and 129 (2.7%) experienced postoperative AKI. Restricted cubic splines showed that a cumulative duration of BIS < 45 was nonlinearly associated with postoperative AKI (P-overall = 0.033 and P-non-linear = 0.023). Using the group with the duration of BIS < 45 less than 15 min as the reference, ORs of postoperative AKI were 2.59 (95% confidence interval [CI]:0.60 to 11.09, p = 0.200) in the 15-100 min group, and 4.04 (95%CI:0.92 to 17.76, p = 0.064) in the ≥ 100 min group after adjusting for preoperative and intraoperative covariates in multivariable logistic regression.

CONCLUSIONS

The cumulative duration of BIS < 45 was independently and nonlinearly associated with the risk of postoperative AKI in patients undergoing noncardiac surgery.

Near-infrared spectroscopy and processed electroencephalogram monitoring for predicting peri-operative stroke risk in cardiothoracic surgery: An observational cohort study

BACKGROUND

Stroke is a feared complication after cardiothoracic surgery, with an incidence of around 2 to 3%. Anaesthesia and postoperative sedation may obscure clinical symptoms of stroke and thus delay diagnosis and timely intervention.

OBJECTIVES

The objective was to assess the value of intra-operative neuromonitoring and blood pressure monitoring for predicting the occurrence of peri-operative stroke within 3 days after cardiothoracic surgery.

DESIGN

Single-centre retrospective observational cohort study.

SETTING

Academic tertiary care medical centre.

PATIENTS

All consecutive patients with cardiothoracic surgery and intra-operative neuromonitoring admitted postoperatively to the Intensive Care Unit (ICU) between 2008 and 2017.

MAIN OUTCOME MEASURES

The primary endpoint was the occurrence of any stroke confirmed by brain imaging within 3 days postcardiothoracic surgery. Areas under the curve (AUC) of intra-operative mean arterial pressure (MAP), cerebral oxygen saturation (ScO2) and bispectral index (BIS) below predefined thresholds were calculated, and the association with early stroke was tested using logistic regression analyses.

RESULTS

A total of 2454 patients admitted to the ICU after cardiothoracic surgery had complete intra-operative data for ScO2, BIS and MAP and were included in the analysis. In 58 patients (2.4%), a stroke was confirmed. In univariate analysis, a larger AUCMAP greater than 60 mmHg [odds ratio (OR) 1.43; 95% confidence interval (CI), 1.21 to 1.68) and larger AUCBIS<25 (OR 1.51; 95% CI, 1.24 to 1.83) were associated with the occurrence of postoperative stroke while ScO2 less than 50% or greater than 20% reduction from individual baseline was not (OR 0.91; 95% CI, 0.50 to 1.67). After multivariable analysis, AUCBIS<25 (OR 1.45; 95% CI, 1.12 to 1.87) and longer duration of MAP less than 60 mmHg (OR 1.52; 95% CI, 1.02 to 2.27) remained independently associated with stroke occurrence.

CONCLUSION

Cumulative intra-operative BIS values below 25 and longer duration of MAP below 60 mmHg were associated with the occurrence of peri-operative stroke within 3 days after cardiothoracic surgery. Prospective studies are warranted to evaluate a causal relationship between low BIS and stroke to establish whether avoiding intra-operative BIS values below 25 might reduce the incidence of peri-operative stroke.

Postoperative Application of Dexmedetomidine is the Optimal Strategy to Reduce the Incidence of Postoperative Delirium After Cardiac Surgery: A Network Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Previous pairwise meta-analyses demonstrated the efficacy and safety of dexmedetomidine in preventing postoperative delirium (POD) after cardiac surgery; however, the optimal time of applying dexmedetomidine remains unclear.

OBJECTIVE

This network meta-analysis aimed to determine the optimal time of using dexmedetomidine to reduce the incidence of POD following cardiac surgery.

METHODS

We first retrieved eligible randomized controlled trials (RCTs) from previous meta-analyses, and then an updated search was performed to identify additional RCTs in PubMed, Embase, and the Cochrane library from January 1, 2021 to October 31, 2021. Two authors screened literature, collected data, and evaluated bias risk of eligible studies. Finally, we performed Bayesian network analysis using R version 3.6.1 with the "gemtc" and "rjags" package.

RESULTS

Eighteen studies with 2636 patients were included, and all studies were identified from previous meta-analyses. Results showed that postoperative dexmedetomidine reduced the risk of POD compared with normal saline (NS) (odds ratio [OR], 0.13; 95% credible interval [CrI], 0.03-0.35) and propofol (PRO) (OR, 0.19; 95%CrI, 0.04-0.66). Postoperative dexmedetomidine was associated with a lower incidence of POD compared with perioperative dexmedetomidine (OR, 0.21; 95% CrI, 0.04-0.82). Moreover, postoperative dexmedetomidine had the highest probability of ranking best (90.98%), followed by intraoperative dexmedetomidine (46.83%), PRO (36.94%), perioperative dexmedetomidine (30.85%), and NS (60.02%).

CONCLUSION AND RELEVANCE

Dexmedetomidine reduces the incidence of POD compared with PRO and NS in patients undergoing cardiac surgery, and postoperative application of dexmedetomidine is the optimal time.

Optimization of the target strategy of perioperative infusion therapy based on monitoring data of central hemodynamics in order to prevent complications

Enhanced Recovery After Surgery (ERAS) protocols are increasingly used in the perioperative period around the world. The concept of goal-directed fluid therapy (GDT) is a key element of the ERAS protocols. Inadequate perioperative infusion therapy can lead to a number of complications, including the development of an infectious process, namely surgical site infections, pneumonia, urinary tract infections. Optimal infusion therapy is difficult to achieve with standard parameters (e.g., heart rate, blood pressure, central venous pressure), so there are various methods of monitoring central hemodynamics - from invasive, minimally invasive to non-invasive. The latter are increasingly used in clinical practice. The current evidence base shows that perioperative management, specifically the use of GDT guided by real-time, continuous hemodynamic monitoring, helps clinicians maintain a patient's optimal fluid balance. The manuscript presents the analytical data, which describe the benefits and basic principles of perioperative targeted infusion therapy based on central hemodynamic parameters to reduce the risk of complications.

Open Reimplementation of the BIS Algorithms for Depth of Anesthesia

BACKGROUND

BIS (a brand of processed electroencephalogram [EEG] depth-of-anesthesia monitor) scores have become interwoven into clinical anesthesia care and research. Yet, the algorithms used by such monitors remain proprietary. We do not actually know what we are measuring. If we knew, we could better understand the clinical prognostic significance of deviations in the score and make greater research advances in closed-loop control or avoiding postoperative cognitive dysfunction or juvenile neurological injury. In previous work, an A-2000 BIS monitor was forensically disassembled and its algorithms (the BIS Engine) retrieved as machine code. Development of an emulator allowed BIS scores to be calculated from arbitrary EEG data for the first time. We now address the fundamental questions of how these algorithms function and what they represent physiologically.

METHODS

EEG data were obtained during induction, maintenance, and emergence from 12 patients receiving customary anesthetic management for orthopedic, general, vascular, and neurosurgical procedures. These data were used to trigger the closely monitored execution of the various parts of the BIS Engine, allowing it to be reimplemented in a high-level language as an algorithm entitled ibis. Ibis was then rewritten for concision and physiological clarity to produce a novel completely clear-box depth-of-anesthesia algorithm titled openibis .

RESULTS

The output of the ibis algorithm is functionally indistinguishable from the native BIS A-2000, with r = 0.9970 (0.9970-0.9971) and Bland-Altman mean difference between methods of -0.25 ± 2.6 on a unitless 0 to 100 depth-of-anesthesia scale. This precision exceeds the performance of any earlier attempt to reimplement the function of the BIS algorithms. The openibis algorithm also matches the output of the native algorithm very closely ( r = 0.9395 [0.9390-0.9400], Bland-Altman 2.62 ± 12.0) in only 64 lines of readable code whose function can be unambiguously related to observable features in the EEG signal. The operation of the openibis algorithm is described in an intuitive, graphical form.

CONCLUSIONS

The openibis algorithm finally provides definitive answers about the BIS: the reliance of the most important signal components on the low-gamma waveband and how these components are weighted against each other. Reverse engineering allows these conclusions to be reached with a clarity and precision that cannot be obtained by other means. These results contradict previous review articles that were believed to be authoritative: the BIS score does not appear to depend on a bispectral index at all. These results put clinical anesthesia research using depth-of-anesthesia scores on a firm footing by elucidating their physiological basis and enabling comparison to other animal models for mechanistic research.

Persistent Depletion of Neuroprotective Factors Accompanies Neuroinflammatory, Neurodegenerative, and Vascular Remodeling Spectra in Serum Three Months after Non-Emergent Cardiac Surgery

We hypothesized that the persistent depletion of neuroprotective markers accompanies neuroinflammation and neurodegeneration in patients after cardiac surgery. A total of 158 patients underwent elective heart surgery with their blood collected before surgery (t_baseline) and 24 h (t_24hr), seven days (t_7d), and three months (t_3m) post-surgery. The patients’ serum was measured for markers of neurodegeneration (τau, τaup181–183, amyloid β1-40/β2-42, and S100), atypical neurodegeneration (KLK6 and NRGN), neuro-injury (neurofilament light/heavy, UC-HL, and GFAP), neuroinflammation (YKL-40 and TDP-43), peripheral nerve damage (NCAM-1), neuroprotection (apoE4, BDNF, fetuin, and clusterin), and vascular smoldering inflammation (C-reactive protein, CCL-28 IL-6, and IL-8). The mortality at 28 days, incidence of cerebrovascular accidents (CVA), and functional status were followed for three months. The levels of amyloid β1-40/β1-42 and NF-L were significantly elevated at all time points. The levels of τau, S100, KLK6, NRGN, and NCAM-1 were significantly elevated at 24 h. A cluster analysis demonstrated groupings around amyloids, KLK6, and NCAM-1. YKL-40, but not TDP-43, was significantly elevated across all time points. BDNF, apoE4, fetuin, and clusterin levels were significantly diminished long-term. IL-6 and IL-8 levles returned to baseline at t_3m. The levels of CRP, CCL-28, and Hsp-70 remained elevated. At 3 months, 8.2% of the patients experienced a stroke, with transfusion volume being a significant variable. Cardiac-surgery patients exhibited persistent peripheral and neuronal inflammation, blood vessel remodeling, and the depletion of neuroprotective factors 3 months post-procedure.

Comparing propofol anaesthesia guided by Bispectral Index monitoring and frontal EEG wave analysis with standard monitoring in laparoscopic surgery: protocol for the 'EEG in General Anaesthesia - More Than Only a Bispectral Index' Trial, a multicentre, double-blind, randomised controlled trial

INTRODUCTION

The use of Bispectral Index (BIS) monitors for assessing depth of sedation has led to a reduction in both the incidence of awareness and anaesthetic consumption in total intravenous anaesthesia. However, these monitors are vulnerable to artefacts. In addition to the processed number, the raw frontal electroencephalogram (EEG) can be displayed as a curve on the same monitor. Anaesthesia practitioners can learn to interpret the EEG in a short tutorial and may be quicker and more accurate thanBIS in assessing anaesthesia depth by recognising EEG patterns. We hypothesise that quality of recovery (QoR) in patients undergoing laparoscopic surgery is better, if propofol is titrated by anaesthesia practitioners able to interpret the EEG.

METHODS AND ANALYSIS

This is a multicentre, double-blind (patients and outcome assessors) randomised controlled trial taking place in four Swiss hospitals. Patients aged 18 years or older undergoing laparoscopic procedures with general anaesthesia using propofol and anaesthesia practitioners with more than 2 years experience will be eligible. The primary study outcome is the difference in QoR 24 hours after surgery. Secondary outcomes are propofol consumption, incidence of postoperative nausea and vomiting (PONV) and postoperative delirium.QoR and propofol consumption are compared between both groups using a two-sample t-test. Fisher's exact test is used to compare the incidences of PONV and delirium. A total of 200 anaesthesia practitioners (and 200 patients) are required to have an 80% chance of detecting the minimum relevant difference for the QoR-15 as significant at the 5% level assuming a SD of 20.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from all responsible ethics committees (lead committee: Ethikkommission Nordwest- und Zentralschweiz, 16 January 2021). The findings of the trial will be published in a peer-reviewed journal, presented at international conferences, and may lead to a change in titrating propofol in clinical practice.

TRIAL REGISTRATION NUMBER

www.

CLINICALTRIALS

gov:NCT04105660.

Effectiveness of the advisory display SmartPilot® view in the assessment of anesthetic depth in low risk gynecological surgery patients: a randomized controlled trial

Background

Assessment of appropriate anesthetic depth is crucial to prevent harm to patients. Unnecessary deep anesthesia can be harmful, potentially causing acute renal failure, myocardial injury, delirium, and an increased mortality rate. Conversely, too light anesthesia combined with muscle relaxants can result in intraoperative patient awareness and lead to serious psychological trauma. This trial aimed to ascertain the effectiveness of the advisory display SmartPilot® View (SPV), as a supplemental measure in the assessment of anesthetic depth in low risk gynecological surgery patients. The hypothesis was that the use of the SPV would increase the precision of assessment, and result in a higher mean arterial pressure.

Methods

This trial used a randomized, controlled, single-blind design with a homogeneous sample. Patients undergoing minor, low risk gynecological surgery were randomly assigned to two groups: a test group wherein current standards were supplemented with the advisory display SPV and a control group assessed using only the current standards. Female patients aged between 18 and 75 years with American Society of Anesthesiologists Physical Status Classification System scores of 1–3 undergoing planned general anesthesia using the total intravenous anesthetic method, combining propofol and remifentanil, were included. The exclusion criteria included a body mass index ≥ 35 kg/m², a history of alcoholism, drug intake affecting propofol and remifentanil dynamics, and inability to consent. The independent sample t-test and chi-square test or Fisher’s exact test were used to assess the statistical significance of differences between the two groups.

Results

A total of 114 patients were included in the analysis (test group n = 58, control group n = 56). No significant differences in the mean arterial pressure, heart rate, bispectral index, extubation delay, or post-anesthesia care unit stay were found between groups.

Conclusions

The addition of the advisory display SmartPilot® View to current standards in the evaluation of anesthetic depth had no significant effect on the outcome.

Trial registration

The trial was registered on January 16th 2019 with ClinicalTrials.gov (ref: NCT03807271).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01593-w.

Quo Vadis Anesthesiologist? The Value Proposition of Future Anesthesiologists Lies in Preserving or Restoring Presurgical Health after Surgical Insult

This Special Issue of the Journal of Clinical Medicine is devoted to anesthesia and perioperative care [...].

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.

Development of a random forest model for hypotension prediction after anesthesia induction for cardiac surgery

BACKGROUND

Hypotension after the induction of anesthesia is known to be associated with various adverse events. The involvement of a series of factors makes the prediction of hypotension during anesthesia quite challenging.

AIM

To explore the ability and effectiveness of a random forest (RF) model in the prediction of post-induction hypotension (PIH) in patients undergoing cardiac surgery.

METHODS

Patient information was obtained from the electronic health records of the Second Affiliated Hospital of Hainan Medical University. The study included patients, ≥ 18 years of age, who underwent cardiac surgery from December 2007 to January 2018. An RF algorithm, which is a supervised machine learning technique, was employed to predict PIH. Model performance was assessed by the area under the curve (AUC) of the receiver operating characteristic. Mean decrease in the Gini index was used to rank various features based on their importance.

RESULTS

Of the 3030 patients included in the study, 1578 (52.1%) experienced hypotension after the induction of anesthesia. The RF model performed effectively, with an AUC of 0.843 (0.808-0.877) and identified mean blood pressure as the most important predictor of PIH after anesthesia. Age and body mass index also had a significant impact.

CONCLUSION

The generated RF model had high discrimination ability for the identification of individuals at high risk for a hypotensive event during cardiac surgery. The study results highlighted that machine learning tools confer unique advantages for the prediction of adverse post-anesthesia events.

Dexmedetomidine reduces the incidence of postoperative delirium after cardiac surgery: a meta-analysis of randomized controlled trials

Background

The role of dexmedetomidine in preventing postoperative delirium (POD) after cardiac surgery remains controversial because of several recent trials with negative results. We aimed to perform an updated meta-analysis of randomized controlled trials (RCTs) to clarify this controversy.

Methods

RCTs investigating the perioperative administration of dexmedetomidine in cardiac surgery were retrieved from PubMed, Web of Science, and the Cochrane library until August,27,2020. Two researchers independently screened the literature, collected the data and evaluated the bias risk of the included studies. The meta-analysis was performed with the RevMan 5.3.

Results

A total of 15 studies including 2813 patients were included in the study. A pooled result showed that dexmedetomidine could reduce the risk of POD in adult population underwent cardiac surgery (OR 0.56, 95%CI 0.36–0.89, P = 0.0004, I² = 64%). The subgroup analysis demonstrated that the protective effect of dexmedetomidine was only present in the patients injected with dexmedetomidine after surgery but not from the start of surgery, in the adult patients without specific age limitation but not in the elderly, and in the studies in comparison with other sedatives but not with placebo. There were no statistical differences when analyzing the secondary outcomes including hypotension (OR 1.13; 95% CI 0.54–2.37, P < 0.00001, I² = 85%), bradycardia (OR 1.72; 95% CI 0.84–3.53, P = 0.04, I² = 58%) and atrial fibrillation (OR 0.87; 95% CI 0.70–1.08, P = 0.43, I² = 0).

Conclusions

Dexmedetomidine can reduce the incidence of POD compared to other sedatives and opioids after cardiac surgery in adult patients. The proper population and timing for perioperative use of dexmedetomidine after cardiac surgery remain to be further investigated.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01370-1.

Bispectral index monitoring of the clinical effects of propofol closed-loop target-controlled infusion: Systematic review and meta-analysis of randomized controlled trials

BACKGROUND

To investigate whether closed-loop systems under bispectral index anesthesia depth monitoring can reduce the intraoperative propofol dosage.

METHODS

All randomized controlled trials (RCTs) on reducing propofol dosage under closed-loop systems were collected, and the literature was screened out, the abstracts and full texts were carefully read, and the references were tracked, data extraction and quality evaluation were conducted on the included research, and the RevMan5.3 software was used for meta-analysis. The main results were propofol and the incidence of adverse reactions such as hypertensive hypotension and postoperative cognitive dysfunction. A total of 879 cases were included in 8 articles, including 450 occurrences in the closed-loop system group and 429 cases in the open-loop system group.

RESULTS

Compared with manual control, closed-loop systems under bispectral index anesthesia depth monitoring reduced the dose of propofol (MD: -0.62, 95% CI: -1.08--0.16, P = .008), with heterogeneity (I2 = 80%). Closed-loop systems significantly reduced the incidence of abnormal blood pressure (MD: -0.02, 95%CI: -0.05-0.01, P = .15, I2 = 74%) and postoperative cognitive dysfunction (MD: -0.08, 95% CI: -0.14 -0.01, P = .02, I2 = 94%).

CONCLUSION

Bispectral index monitoring of propofol closed-loop target-controlled infusion system can reduce the amount of propofol, reduce the incidence of adverse reactions such as hypertensive or hypotension and postoperative cognitive dysfunction.

Simulation of operating room crisis management - hypotension training for pre-clinical students

BACKGROUND

Simulation training is an essential criterion for medical staff. The majority of residents are trained in operating room crisis management (ORCM), but only a few pre-clinical anesthesia undergraduate students are trained. Anesthesia methodology and technology were studied by the anesthesia undergraduate students in theory, but they were not able to practically resolve all clinical problems scientifically and reasonably. Consequently, there is a need to apply their competencies and bring together their technology knowledge practically. The crisis management of operating room emergencies was a method of choice applied and used over time. Here, we designed the scenarios for comprehensive crisis management to train anesthesia undergraduate students. We tried to establish or identify the problems which occurred during attempts to implement these scenarios.

METHODS

Anesthesia undergraduate students initially examined the basic theory, fundamental practice techniques, and case studies before the simulation training program. Subsequently, they participated in comprehensive ORCM training. Training outcomes were evaluated through different viewpoints: understanding the subject, crisis management, nontechnical skills, and a user experience evaluation.

RESULTS

Anesthesia undergraduate students performed significantly better with completion of ORCM, indicated by higher scores in all four tests (P < 0.001), as well as clinical crisis management (P = 0.0016) and nontechnical skills (P = 0.0002). Following the simulation, the students described the experience as helpful in "combining theoretical knowledge with clinical practice", helpful with memorization, and in "promoting understanding of the subject," while "learning clinical logic authentically" and "inspiring learning interests."

CONCLUSIONS

This research indicates that ORCM could be implemented as a useful learning tool for pre-clinical anesthesia undergraduate students. The ORCM could be an excellent training method to help improve students' professional competence in crisis management and nontechnical skills, integrating the knowledge and technology of the field of anesthesiology.

Relationship between blood pressure stability and mortality in cardiac surgery patients: retrospective cohort study

Performance measurement variables can be applied in clinical practice to evaluate hemodynamic instability. This study aimed to evaluate the relationship between the performance measurement of mean arterial pressure during cardiac surgery using cardiopulmonary bypass and postoperative mortality. A retrospective cohort study of patients who underwent cardiac surgery requiring cardiopulmonary bypass between 2013 and 2016 was conducted. The median performance error (MDPE) and median absolute performance error (MDAPE) were calculated using the preoperative mean arterial pressure as a reference, and intraoperative mean arterial pressures as measured values. Multivariable logistic regression analyses were performed using performance measurement variables to predict 30-day mortality. Overall survival according to performance measurement variables was evaluated using Cox proportional hazard models and Kaplan-Meier survival curves were generated to compare survival probability. Among 1203 patients, 110 (9.1%) died after surgery, and the 30-day mortality rate was 2.3% (28/1203). After adjusting for confounders, MDPE and MDAPE were significant mean arterial pressure derived predictors of 30-day mortality and overall survival. Intraoperative hypotension measured by performance measurement variables was independently associated with 30-day and overall mortality after cardiac surgery requiring cardiopulmonary bypass. Kaplan-Meier survival curves showed lower survival probability in patients with higher MDAPE during the pre- and post- cardiopulmonary bypass periods (P < 0.001 by log-rank test). Intraoperative hypotension measured by performance measurement variables was independently associated with 30-day and overall mortality after cardiac surgery requiring CPB. We propose that performance measurement variables are useful for quantifying the degree of intraoperative hypotension and predicting survival following cardiac surgery.Trial registration: ClinicalTrials.gov, identifier: NCT03785132.

Use of the Hypotension Prediction Index During Cardiac Surgery

OBJECTIVE

The hypotension prediction index (HPI) is a novel parameter developed by Edwards Lifesciences (Irvine, CA) that is obtained through an algorithm based on arterial pressure waveform characteristics. Past studies have demonstrated its accuracy in predicting hypotensive events in noncardiac surgeries. The authors aimed to evaluate the use of the HPI in cardiac surgeries requiring cardiopulmonary bypass (CPB).

DESIGN

Prospective cohort feasibility study.

SETTING

Single university medical center.

PARTICIPANTS

Sequential adult patients undergoing elective cardiac surgeries requiring CPB between October 1, 2018, and December 31, 2018.

INTERVENTIONS

HPI monitor was connected to the patient's arterial pressure transducer. Anesthesiologists and surgeons were blinded to the monitor output.

MEASUREMENTS AND MAIN RESULTS

HPI values and hypotensive events were recorded before and after CPB. The primary outcomes were the area under the curve (AUC) of the receiver operating characteristic curve, sensitivity, and specificity of HPI predicting hypotension. The AUC, sensitivity, and specificity for HPI lead time to hypotension five minutes before the event were 0.90 (95% confidence interval [CI]: 0.853-0.949), 84% (95% CI: 77.7-90.5), and 84% (95% CI: 70.9-96.8), respectively. Ten minutes before the event AUC, sensitivity, and specificity for HPI lead time to hypotension were 0.83 (95% CI: 0.750-0.905), 79% (95% CI: 69.8-88.1), and 74% (95% CI: 58.8-89.6), respectively. Fifteen minutes before the hypotensive event AUC, sensitivity, and specificity for HPI lead time to hypotension were 0.83 (95% CI: 0.746-0.911), 79% (95% CI: 68.4-89.0), and 74% (95% CI: 58.8-89.6), respectively.

CONCLUSION

HPI predicted hypotensive episodes during cardiac surgeries with a high degree of sensitivity and specificity.

Outcomes of individualized goal-directed therapy based on cerebral oxygen balance in high-risk patients undergoing cardiac surgery: A randomized controlled trial

STUDY OBJECTIVE

To investigate whether optimizing individualized goal-directed therapy (GDT) based on cerebral oxygen balance in high-risk surgical patients would reduce postoperative morbidity.

DESIGN

This was a prospective, randomized, controlled study.

SETTING

The study was performed in the First Affiliated Hospital of Anhui Medical University, Hefei, China, from April 2017 to July 2018.

PATIENTS

146 high-risk adult patients undergoing valve replacements or coronary artery bypass surgery with cardiopulmonary bypass (CPB) were enrolled.

INTERVENTION

Patients were randomized to an individualized GDT group or usual care group. Individualized GDT was targeted to achieve the following goals: A less than 20% decline in the regional cerebral oxygen saturation (rScO₂) level from baseline; a less than 20% decline in the mean arterial pressure (MAP) from baseline, as well as a bispectral index (BIS) of 45-60 before and after CPB and 40-45 during CPB.

MEASUREMENTS

The primary outcome was a composite endpoint of 30-day mortality and major postoperative complications.

MAIN RESULTS

128 completed the trial and were included in the modified intention-to-treat analysis. Early morbidity was similar between the GDT (25 [39%] of 65 patients) and usual care groups (33 [53%] of 63 patients) (relative risk 0.73, 95% CI 0.50-1.08; P = 0.15). Secondary analysis showed that 75 (59%) of 128 patients achieved individual targets (irrespective of intervention) and sustained less morbidity (relative risk 3.41, 95% CI 2.19-5.31; P < 0.001).

CONCLUSIONS

In high-risk patients undergoing cardiac surgery, individualized GDT therapy did not yield better outcomes, however, the achievement of preoperative individual targets may be associated with less morbidity.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT03103633. Registered on 1 April 2017.

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.

The Impact of Suprarenal Cross-Clamping on Kidney Function in Patients Undergoing Retroperitoneal Abdominal Aortic Aneurysm Repair following an Enhanced Recovery Protocol

BACKGROUND

The retroperitoneal approach (RP) is a well-established procedure for juxtarenal and infrarenal (IR) abdominal aortic aneurysm (AAA) repair when an endovascular option is not available. The aim of this study is to compare the effect of suprarenal (SR) and IR aortic clamping on postoperative renal function following an Enhanced Recovery Protocol (ERP). Since there are no defined guidelines within aortic surgery, we focused our attention on the role of fluid and vasopressor administration in the development of postoperative acute kidney injury (AKI).

METHODS

This is a single-center retrospective cohort study on 140 RP aortic aneurysm repair patients operated between 2009 and 2019. Patients were divided in 2 groups: 24 had SR clamping and 116 IR clamping. Since 2009, at our institution all patients have followed an Enchanced Recovery Program which has been implemented as standard care for patients undergoing open AAA repair.

RESULTS

The 2 groups were well matched for baseline characteristics, preoperative renal function, and comorbidity. There was an increased need for intraoperative fluids (P = 0.015), and vasopressors (P = 0.002) in the SR group compared to the IR group. Patients in the SR group showed a higher trend of postoperative AKI as opposed to the control group (37.5% vs. 19.8%), although this event was not statistically significant (P = 0.106). Acute Kidney Injury Network stage III requiring temporary dialysis occurred in only 3 patients who all belonged to the IR group. Conversely, stage I and II with a 2- or 3-fold increase in postoperative creatinine were more frequent in the SR group. However, these normalized before discharge in all cases. To the best of our knowledge, none of the above required permanent dialysis.

CONCLUSIONS

The results from this study show that SR clamping during RP juxtarenal aortic aneurysm repair does not have an adverse effect on postoperative renal function in the short term. However, patients undergoing SR clamping require greater fluid and vasopressor usage, in contrast with the restrictive fluid therapy established by traditional protocols. This could be an important benchmark for future implementation of ERPs in vascular surgery, especially in open procedures requiring visceral clamping.

Anesthetic Management Using Multiple Closed-loop Systems and Delayed Neurocognitive Recovery: A Randomized Controlled Trial

BACKGROUND

Cognitive changes after anesthesia and surgery represent a significant public health concern. We tested the hypothesis that, in patients 60 yr or older scheduled for noncardiac surgery, automated management of anesthetic depth, cardiac blood flow, and protective lung ventilation using three independent controllers would outperform manual control of these variables. Additionally, as a result of the improved management, patients in the automated group would experience less postoperative neurocognitive impairment compared to patients having standard, manually adjusted anesthesia.

METHODS

In this single-center, patient-and-evaluator-blinded, two-arm, parallel, randomized controlled, superiority study, 90 patients having noncardiac surgery under general anesthesia were randomly assigned to one of two groups. In the control group, anesthesia management was performed manually while in the closed-loop group, the titration of anesthesia, analgesia, fluids, and ventilation was performed by three independent controllers. The primary outcome was a change in a cognition score (the 30-item Montreal Cognitive Assessment) from preoperative values to those measures 1 week postsurgery. Secondary outcomes included a battery of neurocognitive tests completed at both 1 week and 3 months postsurgery as well as 30-day postsurgical outcomes.

RESULTS

Forty-three controls and 44 closed-loop patients were assessed for the primary outcome. There was a difference in the cognition score compared to baseline in the control group versus the closed-loop group 1 week postsurgery (-1 [-2 to 0] vs. 0 [-1 to 1]; difference 1 [95% CI, 0 to 3], P = 0.033). Patients in the closed-loop group spent less time during surgery with a Bispectral Index less than 40, had less end-tidal hypocapnia, and had a lower fluid balance compared to the control group.

CONCLUSIONS

Automated anesthetic management using the combination of three controllers outperforms manual control and may have an impact on delayed neurocognitive recovery. However, given the study design, it is not possible to determine the relative contribution of each controller on the cognition score.

Intraoperative Blood Pressure Variability Predicts Postoperative Mortality in Non-Cardiac Surgery-A Prospective Observational Cohort Study

Little is known about the clinical importance of blood pressure variability (BPV) during anesthesia in non-cardiac surgery. We sought to investigate the impact of intraoperative BPV on postoperative mortality in non-cardiac surgery subjects, taking into account patient- and procedure-related variables. This prospective observational study covered 835 randomly selected patients who underwent gastrointestinal (n = 221), gynecological (n = 368) and neurosurgical (n = 246) procedures. Patient’s and procedure’s risks were assessed according to the validated tools and guidelines. Blood pressure (systolic, SBP, and diastolic, DBP) was recorded in five-minute intervals during anesthesia. Mean arterial pressure (MAP) was assessed. Individual coefficients of variation (Cv) were calculated. Postoperative 30-day mortality was considered the outcome. Median SBP_Cv was 11.2% (IQR 8.4–14.6), DBP_Cv was 12.7% (IQR 9.8–16.3) and MAP_Cv was 10.96% (IQR 8.26–13.86). Mortality was 2%. High SBP_Cv (i.e., ≥11.9%) was associated with increased mortality by 4.5 times (OR = 4.55; 95% CI 1.48–13.93; p = 0.008). High DBP_Cv (i.e., ≥22.4%) was associated with increased mortality by nearly 10 times (OR = 9.73; 95% CI 3.26–28.99; p < 0.001). High MAP_Cv (i.e., ≥13.6%) was associated with increased mortality by 3.5 times (OR = 3.44; 95% CI 1.34–8.83; p = 0.01). In logistic regression, it was confirmed that the outcome was dependent on both SBPV and DBPV, after adjustment for perioperative variables, with AUCSBP_Cv = 0.884 (95% CI 0.859–0.906; p < 0.001) and AUCDBP_Cv = 0.897 (95% CI 0.873–0.918; p < 0.001). Therefore, intraoperative BPV may be considered a prognostic factor for the postoperative mortality in non-cardiac surgery, and DBPV seems more accurate in outcome prediction than SBPV.

Changes in dynamic arterial elastance induced by volume expansion and vasopressor in the operating room: a prospective bicentre study

BACKGROUND

Dynamic arterial elastance (Eadyn), defined as the ratio between pulse pressure variations and stroke volume variations, has been proposed to assess functional arterial load. We evaluated the evolution of Eadyn during volume expansion and the effects of neosynephrine infusion in hypotensive and preload-responsive patients.

METHODS

In this prospective bicentre study, we included 56 mechanically ventilated patients in the operating room. Each patient had volume expansion and neosynephrine infusion. Stroke volume and stroke volume variations were obtained using esophageal Doppler, and pulse pressure variations were measured through the arterial line. Pressure response to volume expansion was defined as an increase in mean arterial pressure (MAP) ≥ 10%.

RESULTS

Twenty-one patients were pressure responders to volume expansion. Volume expansion induced a decrease in Eadyn (from 0.69 [0.58-0.85] to 0.59 [0.42-0.77]) related to a decrease in pulse pressure variations more pronounced than the decrease in stroke volume variations. Baseline and changes in Eadyn after volume expansion were related to age, history of arterial hypertension, net arterial compliance and effective arterial elastance. Eadyn value before volume expansion > 0.65 predicted a MAP increase ≥ 10% with a sensitivity of 76% (95% CI 53-92%) and a specificity of 60% (95% CI 42-76%). Neosynephrine infusion induced a decrease in Eadyn (from 0.67 [0.48-0.80] to 0.54 [0.37-0.68]) related to a decrease in pulse pressure variations more pronounced than the decrease in stroke volume variations. Baseline and changes in Eadyn after neosynephrine infusion were only related to heart rate.

CONCLUSION

Eadyn is a potential sensitive marker of arterial tone changes following vasopressor infusion.

Feasibility of closed-loop titration of norepinephrine infusion in patients undergoing moderate- and high-risk surgery

BACKGROUND

Vasopressor agents are used to prevent intraoperative hypotension and ensure adequate perfusion. Vasopressors are usually administered as intermittent boluses or manually adjusted infusions, but this practice requires considerable time and attention. We have developed a closed-loop vasopressor (CLV) controller to correct hypotension more efficiently. Here, we conducted a proof-of-concept study to assess the feasibility and performance of CLV control in surgical patients.

METHODS

Twenty patients scheduled for elective surgical procedures were included in this study. The goal of the CLV system was to maintain MAP within 5 mm Hg of the target MAP by automatically adjusting the rate of a norepinephrine infusion using MAP values recorded continuously from an arterial catheter. The primary outcome was the percentage of time that patients were hypotensive, as defined by a MAP of 5 mm Hg below the chosen target. Secondary outcomes included the total dose of norepinephrine, percentage of time with hypertension (MAP>5 mm Hg of the chosen target), raw percentage "time in target" and Varvel performance criteria.

RESULTS

The 20 subjects (median age: 64 years [52-71]; male (35%)) underwent elective surgery lasting 154 min [124-233]. CLV control maintained MAP within ±5 mm Hg of the target for 91.6% (85.6-93.3) of the intraoperative period. Subjects were hypotensive for 2.6% of the intraoperative period (range, 0-8.4%). Additional performance criteria for the controller included mean absolute performance error of 2.9 (0.8) and mean predictive error of 0.5 (1.0). No subjects experienced major complications.

CONCLUSIONS

In this proof of concept study, CLV control minimised perioperative hypotension in subjects undergoing moderate- or high-risk surgery. Further studies to demonstrate efficacy are warranted.

TRIAL REGISTRY NUMBER

NCT03515161 (ClinicalTrials.gov).

Triple-low Alerts Do Not Reduce Mortality

EDITOR’S PERSPECTIVE

What We Already Know about This Topic

Intraoperative triple-low events (mean arterial pressure less than 75 mmHg, Bispectral Index less than 45, and minimum alveolar fraction of anesthetic less than 0.8) have been found to be associated with increased risk of mortality

What This Article Tells Us That Is New

A randomized electronic alert of triple-low events to treating clinicians did not reduce 90-day mortality

The alerts minimally influenced clinician responses, assessed as vasopressor administration or reduction in end-tidal volatile anesthetic partial pressure, and there was no association between response to alerts and mortality

Triple-low events predict mortality but do not appear to be causally related

Background

Triple-low events (mean arterial pressure less than 75 mmHg, Bispectral Index less than 45, and minimum alveolar fraction less than 0.8) are associated with mortality but may not be causal. This study tested the hypothesis that providing triple-low alerts to clinicians reduces 90-day mortality.

Methods

Adults having noncardiac surgery with volatile anesthesia and Bispectral Index monitoring were electronically screened for triple-low events. Patients having triple-low events were randomized in real time, with clinicians either receiving an alert, “consider hemodynamic support,” or not. Patients were blinded to treatment. Helpful responses to triple-low events were defined by administration of a vasopressor within 5 min or a 20% reduction in end-tidal volatile anesthetic concentration within 15 min.

Results

Of the qualifying patients, 7,569 of 36,670 (20%) had triple-low events and were randomized. All 7,569 were included in the primary analysis. Ninety-day mortality was 8.3% in the alert group and 7.3% in the nonalert group. The hazard ratio (95% CI) for alert versus nonalert was 1.14 (0.96, 1.35); P = 0.12, crossing a prespecified futility boundary. Clinical responses were helpful in about half the patients in each group, with 51% of alert patients and 47% of nonalert patients receiving vasopressors or having anesthetics lowered after start of triple low (P &lt; 0.001). There was no relationship between the response to triple-low events and adjusted 90-day mortality.

Conclusions

Real-time alerts to triple-low events did not lead to a reduction in 90-day mortality, and there were fewer responses to alerts than expected. However, similar mortality with and without responses suggests that there is no strong relationship between responses to triple-low events and mortality.

Association of Low Blood Pressure, Low Bispectral Index and Low Minimum Alveolar Concentration of Anaesthetic during Surgery with Postoperative 30-day Mortality: A Systemic Review and Meta-Analysis

Objective

The triple low state [low mean arterial pressure, low bispectral index (BIS) and a low minimum alveolar concentration (MAC)] fraction of anaesthetic during surgery) has been a controversial subject of interest in clinical practise. Previous retrospective studies have produced different conclusions on the association between a triple low state and postoperative 30-day mortality. This study was a systematic review of previous studies on the effects of the triple low state on postoperative 30-day mortality and a meta-analysis with a sample size larger than that of previous studies.

Methods

After searching for relevant articles in the PubMed database as on 27 March 2017, we included studies that compared postoperative 30-day mortality between triple low and non-triple low groups. The identified articles were subjected to an initial screening using keywords 'low bispectral index', 'intraoperative hypotension' and 'low minimum alveolar concentration' according to the PRISMA Flow diagram (2009). After a full-text review, appropriate studies were finally included in our meta-analysis. All statistical analyses were performed using the R programme 3.3.2 and meta packages.

Results

Three retrospective cohort studies were included in the meta-analysis. The total number of subjects in the triple low and non-triple low groups was 29,402 and 17,428, respectively; the sample size was 46,830. We derived a hazard ratio (HR) of 1.09 [95% confidence interval (CI), 1.07-1.11)] for the fixed effect model and of 1.30 (95% CI, 1.04-1.07) for the random effect model. In the analysis of heterogeneity among the three studies, I2=95% was obtained (P<0.01). Thus, the values obtained from the random effect model were used; HR was 1.30 for the triple low group, indicating a 30% increase in the overall 30-day mortality.

Conclusion

The present study demonstrated that patients exposed to the triple low state exhibit higher 30-day mortality rates than those not exposed to the triple low state.

Intraoperative electroencephalogram suppression at lower volatile anaesthetic concentrations predicts postoperative delirium occurring in the intensive care unit

BACKGROUND

Postoperative delirium is a common complication associated with increased morbidity and mortality. A recently-reported association between intraoperative electroencephalogram suppression and postoperative delirium might be mediated in some patients by a heightened sensitivity to volatile anaesthetics.

METHODS

This retrospective cohort study included 618 elective surgery patients with planned intensive care unit admission, who also received intraoperative electroencephalogram monitoring and had delirium assessments documented in the medical record. Sensitivity to volatile anaesthetics was assessed using a mixed effects model predicting the likelihood of electroencephalogram suppression at each time point based on the current end-tidal anaesthetic concentration. Patients with a random intercept above the population median (electroencephalogram suppression at lower anaesthetic concentrations) were classified as having heightened sensitivity to volatile anaesthetics. Delirium was defined as a positive Confusion Assessment Method for the Intensive Care Unit assessment anytime in the first five postoperative days.

RESULTS

Postoperative delirium was observed in 162 of 618 patients (26%). Patients who experienced electroencephalogram suppression at lower volatile anaesthetic concentrations had a higher incidence of postoperative delirium [109/309 (35%)] than other patients [53/309 (17%)] [unadjusted odds ratio 2.63; 95% confidence interval (CI), 1.81-3.84, P<0.001]. This association remained significant after adjusting for patient characteristics, surgical variables, and duration of electroencephalogram suppression (adjusted odds ratio 2.13; 95% CI 1.24-3.65, P=0.006).

CONCLUSIONS

These data support the hypothesis that patients with electroencephalogram suppression at lower volatile anaesthetic concentrations have an increased incidence of postoperative delirium. Such patients appear to exhibit a phenotype of anaesthetic sensitivity, which might predispose them to adverse cognitive outcomes.

The EC90 of remifentanil for blunting cardiovascular responses to head fixation for neurosurgery under total intravenous anesthesia with propofol and remifentanil based on bispectral index monitoring: estimation with the biased coin up-and-down sequential method

Background

Head fixation can induce hemodynamic instability. Remifentanil is commonly used with propofol for total intravenous anesthesia (TIVA) during neurosurgery. This study investigated the 90% effective concentration (EC₉₀) of remifentanil for blunting of cardiovascular responses to head fixation during neurosurgery via bispectral index (BIS) monitoring.

Methods

Fifty patients undergoing neurosurgery requiring head fixation were enrolled. This study was performed using the biased coin up-and-down design sequential method (BCD). After tracheal intubation, the effect-site target concentration (Ce) of remifentanil was adjusted to achieve hemodynamic stability and reset to the level preoperatively assigned to each patient, according to the BCD method, approximately 10 min before head fixation. Baseline hemodynamic values were recorded before head fixation. An ineffective response was defined as a case with a > 20% increase in hemodynamic values from baseline. Otherwise, the response was determined to be effective. The EC₉₀ of remifentanil was calculated as a modified isotonic estimator.

Results

Forty-three patients completed this study. The EC₉₀ of remifentanil for blunting cardiovascular responses to head fixation was estimated to be 6.48 ng/mL (95% CI, 5.94–6.83 ng/mL).

Conclusions

Adjustment of the Ce of remifentanil to approximately 6.5 ng/mL before head fixation could prevent noxious cardiovascular responses in 90% of neurosurgical ASA I-II patients aged 20 to 65 years old during propofol target-controlled infusion titrated to maintain BIS between 40 and 50.

Trial registration

ClinicalTrials.gov Identifier NCT01489137, retrospectively registered 5 December 2011.