Nociception-guided versus Standard Care during Remifentanil-Propofol Anesthesia: A Randomized Controlled Trial

Effects of goal-directed analgesia using the analgesia nociception index in children undergoing surgery for moyamoya disease: A randomised controlled trial

BACKGROUND

The potential benefits of Analgesia Nociception Index guided intra-operative analgesia on intra-operative opioid consumption remains to be demonstrated in paediatric anaesthesia.

OBJECTIVES

This study aimed to explore the effects of Analgesia Nociception Index guided analgesia on sufentanil consumption during anaesthesia and postoperative pain scores in paediatric patients with moyamoya disease.

DESIGN

A prospective randomised controlled study.

SETTING

Seoul National University Children's Hospital, Seoul, Republic of Korea.

PATIENTS

A total of 40 children scheduled for encephaloduroarteriosynangiosis.

MAIN OUTCOME MEASURES

The primary outcome was total intra-operative sufentanil consumption, and the secondary outcomes included postoperative pain scores and incidence of opioid-related adverse events.

RESULTS

The Analgesia Nociception Index group showed lower intra-operative sufentanil consumption (in μg kg -1  h -1 ) compared with the Standard group (0.30 ± 0.12 and 0.39 ± 0.17, respectively; mean difference, -0.09; 95% confidence interval, -0.19 to 0.00; P  = 0.049). Postoperatively, compared with the Standard group, the Analgesia Nociception Index group reported lower median pain scores at 18 and 24 h and maximum pain within 24 h (1 [0 to 2] vs. 3 [2 to 5]; P  = 0.004, 1 [0 to 2] vs. 3 [1 to 4]; P  = 0.041, and 4 [3 to 5] vs. 5 [4 to 7]; P  = 0.045, respectively), with fewer patients experiencing nausea (3 [15%] vs. 10 [50%], P  = 0.043).

CONCLUSION

The Analgesia Nociception Index guided analgesic protocol can reduce intra-operative sufentanil consumption and postoperative pain within 24 h with fewer nausea symptoms in paediatric patients with moyamoya disease who undergo encephaloduroarteriosynangiosis.

TRIAL REGISTRATION NUMBER

NCT05672212.

Nociception level index variations in ICU: curarized vs non-curarized patients - a pilot study

PURPOSE

Pain is a major physiological stressor that can worsen critical medical conditions in many ways. Currently, there is no reliable monitoring tool which is available for pain monitoring in the deeply sedated ± curarized critically ill patients. This study aims to assess the effectiveness of the multiparameter nociception index (NOL®) in the critical care setting. We compared NOL with traditionally used neurovegetative signs and examined its correlation with sedation depth measured by bispectral index (BIS®) electroencephalographic (EEG) monitoring.

METHODS

This retrospective monocentric cohort study was conducted in a general intensive care unit, including patients who required moderate-to-deep levels of sedation with or without continuous neuromuscular blockade. The performance of NOL was evaluated both in the entire studied population, as well as in two subgroups: curarized and non-curarized patients.

RESULTS

NOL demonstrated greater accuracy than all other indicators in pain detection in the overall population. In the non-curare subgroup, all indices correctly recognized painful stimulation, while in the patients subjected to neuromuscular blocking agent's infusion, only NOL properly identified nociception. In the former group, EEG's relation to nociception was on the border of statistical significance, whereas in the latter BIS showed no correlation with NOL.

CONCLUSION

NOL emerges as a promising device for pain assessment in the critical care setting and exhibits its best performance precisely in the clinical context where reliable pain assessment methods are most lacking. Furthermore, our research confirms the distinction between sedation and analgesia, highlighting the necessity for distinct monitoring instruments to accurately assess them.

Does Nociception Level Index-Guided Opioid Administration Reduce Intraoperative Opioid Consumption? A Systematic Review and Meta-Analysis

BACKGROUND

The nociception level (NOL) index is a quantitative parameter derived from physiological signals to measure intraoperative nociception. The aim of this systematic review and meta-analysis was to evaluate if NOL monitoring reduces intraoperative opioid use compared to conventional therapy (opioid administered at clinician discretion).

METHODS

This meta-analysis comprises randomized clinical trials comparing NOL-guided opioid administration to conventional therapy in adult patients undergoing any type of surgery. A systematic search of PubMed, Scopus, and CENTRAL databases was conducted. The primary outcome was intraoperative opioid consumption and the effect estimate of the NOL index was measured using the standardized mean difference (SMD) where 0.20 is considered a small and 0.80 a large effect size. A random-effects model with Hartung-Knapp-Sidik-Jonkman adjustment was applied to estimate the treatment effect. Heterogeneity was explored clinically and statistically (using the inconsistency I² statistic, prediction intervals, and influence analysis). The quality (certainty) of evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) guidelines methodology.

RESULTS

This review comprised 9 trials (519 patients). The intraoperative opioid SMD (NOL monitoring versus conventional therapy) was -0.26 (95% confidence interval [CI], -0.82 to 0.30; P = .31; low certainty of evidence). We observed substantial clinical (intraoperative opioid regimens) and statistical heterogeneity with the I² statistic being 86% (95% CI, 75%-92%). The prediction interval was between -1.95 and 1.42 indicating where the SMD between NOL and conventional therapy would lie if a similar study were conducted in the future.

CONCLUSIONS

This meta-analysis does not provide evidence supporting the role of NOL monitoring in reducing intraoperative opioid consumption.

What are standard monitoring devices for anesthesia in future?

Monitoring the patient's physiological functions is critical in clinical anesthesia. The latest version of the Japanese Society of Anesthesiologists' Guidelines for Safe Anesthesia Monitoring, revised in 2019, covers various factors, including electroencephalogram monitoring, oxygenation, ventilation, circulation, and muscle relaxation. However, with recent advances in monitoring technologies, the information provided has become more detailed, requiring practitioners to update their knowledge. At a symposium organized by the Journal of Anesthesia in 2023, experts across five fields discussed their respective topics: anesthesiologists need to interpret not only the values displayed on processed electroencephalogram monitors but also raw electroencephalogram data in the foreseeable future. In addition to the traditional concern of preventing hypoxemia, monitoring for potential hyperoxemia and the effects of mechanical ventilation itself will become increasingly important. The importance of using AI analytics to predict hypotension, assess nociception, and evaluate microcirculation may increase. With the recent increase in the availability of neuromuscular monitoring devices in Japan, it is important for anesthesiologists to become thoroughly familiar with the features of each device to ensure its effective use. There is a growing desire to develop and introduce a well-organized, integrated "single screen" monitor.

Effect of nociception level-directed analgesic management on opioid usage in robot-assisted laparoscopic radical prostatectomy: a single-center, single-blinded, randomized controlled trial

PURPOSE

To assess the importance of appropriate opioid administration methods according to nociceptive monitoring.

METHODS

We conducted a randomized controlled trial involving 54 patients who underwent robot-assisted laparoscopic radical prostatectomy at our hospital. Patients were randomly allocated to either receive nociception level (NOL)-directed intraoperative opioid management with a minimum flow of remifentanil (NOL group) or conventional intraoperative analgesic management (control group). The primary outcome was the mean intraoperative remifentanil infusion flow rate (intraoperative remifentanil usage [μg]/ideal body weight [kg]/operation time [min]). The main secondary outcomes were plasma concentrations of three perioperative inflammatory biomarkers (interleukin-6, C-reactive protein [CRP], and cortisol levels) and postoperative pain (Numeric Rating Scale [NRS]) scores 2 h postoperatively and on postoperative days 1, 2, 3, and 7.

RESULTS

Compared with standard analgesia management, NOL-directed analgesic management reduced remifentanil consumption by 20% ( - 0.038; 95% confidence interval, - 0.059 to - 0.017; p = 0.0007). NOL-directed management did not lead to an increase in IL-6, CRP, or cortisol levels compared with conventional analgesic management. Furthermore, this protocol led to improvements in the NRS scores at rest 2 h postoperatively and upon movement up to postoperative day 3.

CONCLUSION

NOL-directed analgesic management reduced remifentanil consumption by 20% and the NRS scores at rest 2 h postoperatively and upon movement up to postoperative day 3 without an increase in inflammatory marker levels.

REGISTRY NUMBER

Japan Registry of Clinical Trials, JRCTs052220034.

Development, Validation, and Comparison of a Novel Nociception/Anti-Nociception Monitor against Two Commercial Monitors in General Anesthesia

In this paper, we present the development and the validation of a novel index of nociception/anti-nociception (N/AN) based on skin impedance measurement in time and frequency domain with our prototype AnspecPro device. The primary objective of the study was to compare the Anspec-PRO device with two other commercial devices (Medasense, Medstorm). This comparison was designed to be conducted under the same conditions for the three devices. This was carried out during total intravenous anesthesia (TIVA) by investigating its outcomes related to noxious stimulus. In a carefully designed clinical protocol during general anesthesia from induction until emergence, we extract data for estimating individualized causal dynamic models between drug infusion and their monitored effect variables. Specifically, these are Propofol hypnotic drug to Bispectral index of hypnosis level and Remifentanil opioid drug to each of the three aforementioned devices. When compared, statistical analysis of the regions before and during the standardized stimulus shows consistent difference between regions for all devices and for all indices. These results suggest that the proposed methodology for data extraction and processing for AnspecPro delivers the same information as the two commercial devices.

The role of surgical tissue injury and intraoperative sympathetic activation in postoperative immunosuppression after breast-conserving surgery versus mastectomy: a prospective observational study

BACKGROUND

Breast cancer is the second most common cause of death from cancer in women worldwide. Counterintuitively, large population-based retrospective trials report better survival after breast-conserving surgery (BCS) compared to mastectomy, corrected for tumour- and patient variables. More extensive surgical tissue injury and activation of the sympathetic nervous system by nociceptive stimuli are associated with immune suppression. We hypothesized that mastectomy causes a higher expression of plasma damage associated molecular patterns (DAMPs) and more intraoperative sympathetic activation which induce postoperative immune dysregulation. Immune suppression can lead to postoperative complications and affect tumour-free survival.

METHODS

In this prospective observational study, plasma DAMPs (HMGB1, HSP70, S100A8/A9 and S100A12), intraoperative sympathetic activation (Nociception Level (NOL) index from 0 to 100), and postoperative immune function (plasma cytokine concentrations and ex vivo cytokine production capacity) were compared in patients undergoing elective BCS (n = 20) versus mastectomy (n = 20).

RESULTS

Ex vivo cytokine production capacity of TNF, IL-6 and IL-1β was nearly absent in both groups one hour after surgery. Levels appeared recovered on postoperative day 3 (POD3), with significantly higher ex vivo production capacity of IL-1β after BCS (p = .041) compared to mastectomy. Plasma concentration of IL-6 was higher one hour after mastectomy (p = .045). Concentrations of plasma alarmins S100A8/A9 and S100A12 were significantly higher on POD3 after mastectomy (p = .003 and p = .041, respectively). Regression analysis showed a significantly lower percentage of NOL measurements ≤ 8 (absence of nociception) during mastectomy when corrected for norepinephrine equivalents (36% versus 45% respectively, p = .038). Percentage of NOL measurements ≤ 8 of all patients correlated with ex vivo cytokine production capacity of IL-1β and TNF on POD3 (r = .408; p = .011 and r = .500; p = .001, respectively).

CONCLUSIONS

This pilot study revealed substantial early postoperative immune suppression after BCS and mastectomy that appears to recover in the following days. Differences between BCS and mastectomy in release of DAMPs and intraoperative sympathetic activation could affect postoperative immune homeostasis and thereby contribute to the better survival reported after BCS in previous large population-based retrospective trials. These results endorse further exploration of (1) S100 alarmins as potential therapeutic targets in breast cancer surgery and (2) suppression of intraoperative sympathetic activation to substantiate the observed association with postoperative immune dysregulation.

Depth of Anesthesia and Nociception Monitoring: Current State and Vision For 2050

Anesthesia objectives have evolved into combining hypnosis, amnesia, analgesia, paralysis, and suppression of the sympathetic autonomic nervous system. Technological improvements have led to new monitoring strategies, aimed at translating a qualitative physiological state into quantitative metrics, but the optimal strategies for depth of anesthesia (DoA) and analgesia monitoring continue to stimulate debate. Historically, DoA monitoring used patient's movement as a surrogate of awareness. Pharmacokinetic models and metrics, including minimum alveolar concentration for inhaled anesthetics and target-controlled infusion models for intravenous anesthesia, provided further insights to clinicians, but electroencephalography and its derivatives (processed EEG; pEEG) offer the potential for personalization of anesthesia care. Current studies appear to affirm that pEEG monitoring decreases the quantity of anesthetics administered, diminishes postanesthesia care unit duration, and may reduce the occurrence of postoperative delirium (notwithstanding the difficulties of defining this condition). Major trials are underway to further elucidate the impact on postoperative cognitive dysfunction. In this manuscript, we discuss the Bispectral (BIS) index, Narcotrend monitor, Patient State Index, entropy-based monitoring, and Neurosense monitor, as well as middle latency evoked auditory potential, before exploring how these technologies could evolve in the upcoming years. In contrast to developments in pEEG monitors, nociception monitors remain by comparison underdeveloped and underutilized. Just as with anesthetic agents, excessive analgesia can lead to harmful side effects, whereas inadequate analgesia is associated with increased stress response, poorer hemodynamic conditions and coagulation, metabolic, and immune system dysregulation. Broadly, 3 distinct monitoring strategies have emerged: motor reflex, central nervous system, and autonomic nervous system monitoring. Generally, nociceptive monitors outperform basic clinical vital sign monitoring in reducing perioperative opioid use. This manuscript describes pupillometry, surgical pleth index, analgesia nociception index, and nociception level index, and suggest how future developments could impact their use. The final section of this review explores the profound implications of future monitoring technologies on anesthesiology practice and envisages 3 transformative scenarios: helping in creation of an optimal analgesic drug, the advent of bidirectional neuron-microelectronic interfaces, and the synergistic combination of hypnosis and virtual reality.

Effect of nociception level index-guided intra-operative analgesia on early postoperative pain and opioid consumption: a systematic review and meta-analysis

Acute postoperative pain remains a critical treatment priority and has prompted a search for technologies and techniques to assist with intra-operative analgesic monitoring and management. Anaesthetists traditionally rely on clinical judgement to guide intra-operative analgesia, but several emerging technologies such as the nociception level index herald the possibility of routine intra-operative analgesia monitoring. However, the impact of devices like nociception level index on postoperative outcomes has not been proven. We undertook a systematic review and meta-analysis of articles which compared nociception level index-guided analgesia to standard care. The primary outcomes were pain intensity and opioid consumption during the first 60-120 min after surgery. Secondary outcomes were the incidence of postoperative nausea and vomiting and duration of stay in the post-anaesthesia care unit. Ten studies, collectively including 662 patients and published between 2019 and 2023, met inclusion criteria for both the qualitative systematic review and quantitative meta-analysis. Risk of methodological bias was generally low or unclear, and six studies reported a significant conflict of interest relevant to their findings. Our meta-analysis was performed using a random-effects model. It found statistically significant benefits of nociception level index-guided analgesia for early postoperative pain (mean (95%CI) difference -0.46 (-0.88 to -0.03) on an 11-point scale, p = 0.03), and opioid requirement (mean (95%CI) difference -1.04 (-1.94 to -0.15) mg intravenous morphine equivalent, p = 0.02). Our meta-analysis of the current literature finds that nociception level index-guided analgesia statistically significantly reduces reported postoperative pain intensity and opioid consumption but fails to show clinically relevant outcomes. We found no evidence that nociception level index-guided analgesia affected postoperative nausea and vomiting nor duration of stay in the post-anaesthesia care unit.

Generalizability of nociception level as a measure of intraoperative nociceptive stimulation: A retrospective analysis

BACKGROUND

Nociception-guided intraoperative opioid administration might help reduce postoperative pain. A commonly used and validated nociception monitor system is nociception level (NOL), which provides the nociception index, ranging from 0 to 100, with 0 representing no nociception and 100 representing extreme nociception. We tested the hypothesis that NOL responses are similar in men and women given remifentanil and fentanyl, across various types of anesthesia, as a function of American Society of Anesthesiologists physical status designations, and over a range of ages and body morphologies.

METHODS

We conducted a retrospective cohort analysis of trial data from eight prospective NOL validation studies. Among 522 noncardiac surgical patients enrolled in these studies, 447 were included in our analysis. We assessed NOL responses to various noxious and non-noxious stimuli.

RESULTS

The average NOL in response to 315 noxious stimuli was 47 ± 15 (95% CI = 45-49). The average NOL in response to 361 non-noxious stimuli was 10 ± 12 (95% CI = 9-11). NOL responses were similar in men and women, in patients given remifentanil and fentanyl, across various types of anesthesia, as a function of American Society of Anesthesiologists physical status designations, and over a range of ages and body morphologies.

CONCLUSION

Nociception level appears to provide accurate estimates of intraoperative nociception over a broad range of patients and anesthetic conditions.

A randomised controlled trial of the analgesia nociception index for intra-operative remifentanil dose and pain after gynaecological laparotomy

We aimed to investigate the effect of the analgesia nociception index on postoperative pain. We randomly allocated 170 women scheduled for gynaecological laparotomy and analysed results from 159: in 80 women, remifentanil was infused to maintain analgesia nociception indices 50-70; and in 79 women, remifentanil was infused to maintain systolic blood pressure < 120% of baseline values. The primary outcome was the proportion of women with pain scores ≥ 5 (scale 0-10) within 40 min of admission to recovery. The proportion of women with pain scores ≥ 5 was 62/80 (78%) vs. 64/79 (81%), p = 0.73. Mean (SD) doses of fentanyl in recovery were 53.6 (26.9) μg vs. 54.8 (20.8) μg, p = 0.74. Intra-operative remifentanil doses were 0.124 (0.050) μg.kg-1 .min-1 vs. 0.129 (0.044) μg.kg-1 .min-1 , p = 0.55.

EEG-derived pain threshold index-guided versus standard care during propofol-remifentanil anesthesia: A randomized controlled trial

Purpose

The pain threshold index (PTI), a novel index of nociception based on spontaneous EEG wavelet analysis, has been reported to provide reliable accuracy for predicting postoperative pain and hemodynamic reactivity. The present study is aimed to investigate whether PTI-guided analgesia reduces the pain intensity and rate of remedial analgesia in the post-anesthesia care unit (PACU).

Methods

A total of 122 females undergoing elective gynecologic surgeries had been randomized to receive either PTI-guided analgesia (PTI group) or standard clinical care (control group). Remifentanil administration in the PTI group was guided by PTI to maintain the value between 40 and 65, while that in the control group was guided by hemodynamic changes. The primary outcome was remedial analgesia rate in the PACU. The postoperative pain scores, intraoperative remifentanil requirements, opioid-related adverse events and perioperative serum stress hormone concentrations between the two groups were also compared.

Findings

It was found that 23 of 58 patients (40%) in the control group and 8 of 58 patients (14%) in the PTI group needed remedial analgesia. The relative risk of receiving remedial analgesia was 2.88 (95% CI, 1.40-5.89, P = 0.002) in the control group. Sufentanil consumption in the PACU (μg) was lower in the PTI group (P = 0.002) than in the control group. Remifentanil and propofol consumption, opioid-related adverse events between these two groups were comparable.

Implications

PTI-guided analgesia during gynaecologic operations resulted in 25.87% less remedial analgesia. However, studies with different PTI thresholds and larger, more diverse populations should be conducted to further demonstrate the clinical effectiveness of PTI.

Pharmacodynamic mechanism-based interaction model for the haemodynamic effects of remifentanil and propofol in healthy volunteers

BACKGROUND

Propofol and remifentanil are frequently combined for the induction and maintenance of general anaesthesia. Both propofol and remifentanil cause vasodilation and potentially reduce arterial BP. We aimed to develop a mechanism-based model that characterises the haemodynamic interactions between remifentanil and propofol.

METHODS

Data from two clinical trials in healthy volunteers were analysed using remifentanil-alone, propofol-alone, and combination groups. We evaluated remifentanil effects on haemodynamics using a previously developed mechanism-based haemodynamic model of propofol. The interaction between propofol and remifentanil was explored using the principles of the general pharmacodynamic interaction (GPDI) model.

RESULTS

Remifentanil alone increased the dissipation rate of total peripheral resistance by 50% at 3.0 ng ml-1. Additionally, the dissipation rates of HR and stroke volume were attenuated by 4.8% and 4.9% per 1 ng ml-1 increase in remifentanil concentration, respectively. The maximal effect of propofol alone in decreasing the production rate of total peripheral resistance was 78%, which decreased to 32% when combined with remifentanil 4 ng ml-1. The effects of remifentanil on HR and stroke volume were attenuated by propofol with maximum decreases of 11.9% and 21.2%, respectively. Goodness-of-fit plots and prediction-corrected visual predictive check plots showed good predictive performance of the models.

CONCLUSIONS

The structure of the previous mechanism-based haemodynamic model for propofol was able to describe the effects of remifentanil alone on haemodynamic variables. The GPDI model provided a good framework for characterising the pharmacodynamic interaction between remifentanil and propofol on haemodynamic properties.

CLINICAL TRIAL REGISTRATION

NCT02043938; NCT03143972.

Influence of Intraoperative Nociception during Hip or Knee Arthroplasty with Supplementary Regional Anaesthesia on Postoperative Pain and Opioid Consumption

Background and Objectives: Early postoperative mobilization is central for postoperative outcomes after lower extremity joint replacement surgery. By providing adequate pain control, regional anaesthesia plays an important role for postoperative mobilization. It was the objective of this study to investigate the use of the nociception level index (NOL) to determine the effect of regional anaesthesia in hip or knee arthroplasty patients undergoing general anaesthesia with additional peripheral nerve block. Materials and Methods: Patients received general anaesthesia, and continuous NOL monitoring was established before anaesthesia induction. Depending on the type of surgery, regional anaesthesia was performed with a Fascia Iliaca Block or an Adductor Canal Block. Results: For the final analysis, 35 patients remained, 18 with hip and 17 with knee arthroplasty. We found no significant difference in postoperative pain between hip or knee arthroplasty groups. NOL increase at the time of skin incision was the only parameter associated with postoperative pain measured using a numerical rating scale (NRS > 3) after 24 h in movement (-12.3 vs. +119%, p = 0.005). There was no association with intraoperative NOL values and postoperative opioid consumption, nor was there an association between secondary parameters (bispectral index, heart rate) and postoperative pain levels. Conclusions: Intraoperative NOL changes may indicate regional anaesthesia effectiveness and could be associated with postoperative pain levels. This remains to be confirmed in a larger study.

Analgesic Efficacy of Erector Spinae Plane Block in Pediatric Abdominal Surgery: Guidance with Conventional Method and NOL: Case Series

Background

Erector spinae plane (ESP) block is a regional anesthesia technique that blocks both somatic and visceral nerve fibers. Despite its high analgesic potential, its mechanism of action is not yet fully understood. The ultrasound-guided ESP block, which can be easily performed, makes important contributions to the control of intraoperative pain in pediatric patients undergoing abdominal surgery. The follow-up of pain in the intraoperative period is usually done by evaluating the changes in hemodynamic parameters. Due to physiological differences in pediatric patients, it is more difficult to do this with only hemodynamic changes than in adult patients. Aim: The NOL® (Nociception Level) monitor calculates the nociception/pain score by evaluating many parameters through a proprietary algorithm. Our primary aim was to demonstrate the effectiveness of ESP block with an advanced pain monitor in this patient group; our secondary aim was to investigate the necessity of pain monitors in the pediatric patient group.

Methods

In this case series, we applied intraoperative NOL® monitoring in addition to standard monitoring (ECG, SpO2, heart rate, EtCO₂) in pediatric patients (16 cases) who were scheduled for abdominal surgery and underwent ESP block.

Results

Considering the hemodynamic data, NOL values, postoperative pain scores, side effects, and complications, it was concluded that ESP block can be used safely in this patient group. Although the hemodynamic data and the NOL® index were compatible with each other after a nociceptive stimulus, the NOL index was less affected by other variables and gave the clinician clearer information about pain.

Artificial Intelligence for Perioperative Medicine: Perioperative Intelligence

The anesthesiologist's role has expanded beyond the operating room, and anesthesiologist-led care teams can deliver coordinated care that spans the entire surgical experience, from preoperative optimization to long-term recovery of surgical patients. This expanded role can help reduce postoperative morbidity and mortality, which are regrettably common, unlike rare intraoperative mortality. Postoperative mortality, if considered a disease category, will be the third leading cause of death just after heart disease and cancer. Rapid advances in technologies like artificial intelligence provide an opportunity to build safe perioperative practices. Artificial intelligence helps by analyzing complex data across disparate systems and producing actionable information. Using artificial intelligence technologies, we can critically examine every aspect of perioperative medicine and devise innovative value-based solutions that can potentially improve patient safety and care delivery, while optimizing cost of care. In this narrative review, we discuss specific applications of artificial intelligence that may help advance all aspects of perioperative medicine, including clinical care, education, quality improvement, and research. We also discuss potential limitations of technology and provide our recommendations for successful adoption.

Nociception Level Index-Guided Intraoperative Analgesia for Improved Postoperative Recovery: A Randomized Trial

BACKGROUND

Nociception is the physiological response to nociceptive stimuli, normally experienced as pain. During general anesthesia, patients experience and respond to nociceptive stimuli by increasing blood pressure and heart rate if not controlled by preemptive analgesia. The PMD-200 system from Medasense (Ramat Gan, Israel) evaluates the balance between nociceptive stimuli and analgesia during general anesthesia and generates the nociception level (NOL) index from a single finger probe. NOL is a unitless index ranging from 0 to 100, with values exceeding 25 indicating that nociception exceeds analgesia. We aimed to demonstrate that titrating intraoperative opioid administration to keep NOL <25 optimizes intraoperative opioid dosing. Specifically, we tested the hypothesis that pain scores during the initial 60 minutes of recovery are lower in patients managed with NOL-guided fentanyl than in patients given fentanyl per clinical routine.

METHODS

We conducted a randomized, single-center trial of patients having major abdominal open and laparoscopic surgeries. Patients were randomly assigned 1:1 to intraoperative NOL-guided fentanyl administration or fentanyl given per clinical routine. The primary outcome was pain score (0-10 verbal response scale) at 10-minute intervals during the initial 60 minutes of recovery. Our secondary outcome was a measure of adequate analgesia, defined as a pain score <5, assessed separately at each interval.

RESULTS

With a planned maximum sample size of 144, the study was stopped for futility after enrolling 72 patients from November 2020 to October 2021. Thirty-five patients were assigned to NOL-guided analgesic dosing and 37 to routine care. Patients in the NOL group spent significantly less time with a NOL index >25 (median reduction [95% confidence interval {CI}] of 14 [4-25] minutes) were given nearly twice as much intraoperative fentanyl (median [quartiles] 500 [330, 780] vs 300 [200, 330] µg), and required about half as much morphine in the recovery period (3.3 [0, 8] vs 7.7 [0, 13] mg). However, in the primary outcome analysis, NOL did not reduce pain scores in the first 60 minutes after awakening, assessed in a linear mixed effects model with mean (standard error [SE]) of 4.12 (0.59) for NOL and 4.04 (0.58) for routine care, and estimated difference in means of 0.08 (-1.43, 1.58), P = .895.

CONCLUSIONS

More intraoperative fentanyl was given in NOL-guided patients, but NOL guidance did not reduce initial postoperative pain scores.

Nociception level response to calibrated stimulations in children: First assessment of the nociception level index in pediatric anesthesia

INTRODUCTION

Intraoperative monitoring of nociception has made great progress in adult anesthesia. However, pediatric data are scarce. The Nociception Level (NOL) is one of the most recent indexes of nociception. Its originality is that it provides a multiparametric assessment of nociception. In adults, NOL monitoring allowed lower perioperative opioid requirements, hemodynamic stability, and qualitative postoperative analgesia. So far, the NOL has never been used in children. Our objective was to validate the ability of NOL to provide a quantitative assessment of nociception in anesthetized children.

METHODS

In 5-12 years old children anesthetized with sevoflurane and alfentanil (10 µg kg^-1), before surgical incision, we performed three standardized tetanic stimulations (5 s, 100 Hz) of different intensities (10-30-60 mA) in a randomized order. NOL, heart rate, blood pressure and Analgesia-Nociception Index variations were assessed after each stimulation.

RESULTS

Thirty children were included. Data were analyzed with a covariance pattern linear mixed regression model. NOL increased after the stimulations (p < 0.05 at each intensity). NOL response was influenced by stimulation intensity (p < 0.001). Heart rate and blood pressure were barely modified by the stimulations. Analgesia-Nociception Index decreased after the stimulations (p < 0.001 at each intensity). Analgesia-Nociception index response was not influenced by stimulation intensity (p = 0.064). NOL and Analgesia-Nociception Index responses were significantly correlated (Pearson r = 0.47; p < 0.001).

CONCLUSIONS

NOL allows a quantitative assessment of nociception under anesthesia in 5-12 years-old children. This study provides a solid basis for all future investigations on NOL monitoring in pediatric anesthesia.

REGISTRATION

NCT05233449.

Effects of remifentanil on brain responses to noxious stimuli during deep propofol sedation

BACKGROUND

The safety of anaesthesia has improved as a result of better control of anaesthetic depth. However, conventional monitoring does not inform on the nature of nociceptive processes during unconsciousness. A means of inferring the quality of potentially painful experiences could derive from analysis of brain activity using neuroimaging. We have evaluated the dose effects of remifentanil on brain response to noxious stimuli during deep sedation and spontaneous breathing.

METHODS

Optimal data were obtained in 26 healthy subjects. Pressure stimulation that proved to be moderately painful before the experiment was applied to the thumbnail. Functional MRI was acquired in 4-min periods at low (0.5 ng ml^-1), medium (1 ng ml^-1), and high (1.5 ng ml^-1) target plasma concentrations of remifentanil at a stable background infusion of propofol adjusted to induce a state of light unconsciousness.

RESULTS

At low remifentanil doses, we observed partial activation in brain areas processing sensory-discriminative and emotional-affective aspects of pain. At medium doses, relevant changes were identified in structures highly sensitive to general brain arousal, including the brainstem, cerebellum, thalamus, auditory and visual cortices, and the frontal lobe. At high doses, no significant activation was observed.

CONCLUSIONS

The response to moderately intense focal pressure in pain-related brain networks is effectively eliminated with safe remifentanil doses. However, the safety margin in deep sedation-analgesia would be narrowed in minimising not only nociceptive responses, but also arousal-related biological stress.

Prediction of acute postoperative pain based on intraoperative nociception level (NOL) index values: the impact of machine learning-based analysis

The relationship between intraoperative nociception and acute postoperative pain is still not well established. The nociception level (NOL) Index (Medasense, Ramat Gan, Israel) uses a multiparametric approach to provide a 0-100 nociception score. The objective of the ancillary analysis of the NOLGYN study was to evaluate the ability of a machine-learning aglorithm to predict moderate to severe acute postoperative pain based on intraoperative NOL values. Our study uses the data from the NOLGYN study, a randomized controlled trial that evaluated the impact of NOL-guided intraoperative administration of fentanyl on overall fentanyl consumption compared to standard of care. Seventy patients (ASA class I-III, aged 18-75 years) scheduled for gynecological laparoscopic surgery were enrolled. Variables included baseline demographics, NOL reaction to incision or intubation, median NOL during surgery, NOL time-weighted average (TWA) above or under manufacturers' recommended thresholds (10-25), and percentage of surgical time spent with NOL > 25 or < 10. We evaluated different machine learning algorithms to predict postoperative pain. Performance was assessed using cross-validated area under the ROC curve (CV-AUC). Of the 66 patients analyzed, 42 (63.6%) experienced moderate to severe pain. NOL post-intubation (42.8 (31.8-50.6) vs. 34.8 (25.6-41.3), p = 0.05), median NOL during surgery (13 (11-15) vs. 11 (8-13), p = 0.027), percentage of surgical time spent with NOL > 25 (23% (18-18) vs. 20% (15-24), p = 0.036), NOL TWA < 10 (2.54 (2.1-3.0) vs. 2.86 (2.48-3.62), p = 0.044) and percentage of surgical time spent with NOL < 10 (41% (36-47) vs. 47% (40-55), p = 0.022) were associated with moderate to severe PACU pain. Corresponding ROC AUC for the prediction of moderate to severe PACU pain were 0.65 [0.51-0.79], 0.66 [0.52-0.81], 0.66 [0.52-0.79], 0.65 [0.51-0.79] and 0.67 [0.53-0.81]. Penalized logistic regression achieved the best performance with a 0.753 (0.718-0.788) CV-AUC. Our results, even if limited by the small number of patients, suggest that acute postoperative pain is better predicted by a multivariate machine-learning algorithm rather than individual intraoperative nociception variables. Further larger multicentric trials are highly recommended to better understand the relationship between intraoperative nociception and acute postoperative pain.Trial registration Registered on ClinicalTrials.gov in October 2018 (NCT03776838).

Nociception Control of Bilateral Single-Shot Erector Spinae Plane Block Compared to No Block in Open Heart Surgery-A Post Hoc Analysis of the NESP Randomized Controlled Clinical Trial

Background and Objectives: The erector spinae plane block (ESPB) is an analgesic adjunct demonstrated to reduce intraoperative opioid consumption within a Nociception Level (NOL) index-directed anesthetic protocol. We aimed to examine the ESPB effect on the quality of intraoperative nociception control evaluated with the NOL index. Materials and Methods: This is a post hoc analysis of the NESP (Nociception Level Index-Directed Erector Spinae Plane Block in Open Heart Surgery) randomized controlled trial. Eighty-five adult patients undergoing on-pump cardiac surgery were allocated to group 1 (Control, n = 43) and group 2 (ESPB, n = 42). Both groups received general anesthesia. Preoperatively, group 2 received bilateral single-shot ESPB (1.5 mg/kg/side 0.5% ropivacaine mixed with dexamethasone 8 mg/20 mL). Until cardiopulmonary bypass (CPB) was initiated, fentanyl administration was individualized using the NOL index. The NOL index was compared at five time points: pre-incision (T1), post-incision (T2), pre-sternotomy (T3), post-sternotomy (T4), and pre-CPB (T5). On a scale from 0 (no nociception) to 100 (extreme nociception), a NOL index > 25 was considered an inadequate response to noxious stimuli. Results: The average NOL index across the five time points in group 2 to group 1 was 12.78 ± 0.8 vs. 24.18 ± 0.79 (p < 0.001). The NOL index was significantly lower in the ESPB-to-Control group at T2 (12.95 ± 1.49 vs. 35.97 ± 1.47), T3 (13.28 ± 1.49 vs. 24.44 ± 1.47), and T4 (15.52 ± 1.49 vs. 34.39 ± 1.47) (p < 0.001) but not at T1 and T5. Compared to controls, significantly fewer ESPB patients reached a NOL index > 25 at T2 (4.7% vs. 79%), T3 (0% vs. 37.2%), and T4 (7.1% vs. 79%) (p < 0.001). Conclusions: The addition of bilateral single-shot ESPB to general anesthesia during cardiac surgery improved the quality of intraoperative nociception control according to a NOL index-based evaluation.

Nociception level index variations in patients with complex regional pain syndrome: a pilot study

The nociception level index (NOL) is a multi-parameter index that incorporates changes in autonomic parameters to evaluate nociception, with more painful stimuli causing more pronounced index variations. How this nociception monitor relates to the pain experience is uncertain, and patients with chronic pain may respond differently to acute pain due to alterations in pain processing. The goal of this pilot study was to evaluate NOL index variations after a painful physiotherapy exercise in patients with upper limb complex regional pain syndrome. Baseline NOL indexes were recorded using a finger probe (PMD-200™ Monitor, Medasense, Israel) and patient reported baseline pain scores using an 11-point numeric rating scale (NRS). Patients then performed a painful physiotherapy exercise and NOL index and pain scores were again recorded. The same procedure and recordings were repeated after a stellate ganglion block. Data were analyzed using a paired Student T test and a P value < 0.05 was considered statistically significant. Twenty patients (12/20 female, 10/20 right-sided) were included in this study. Patients reported moderate baseline pain (4.0 ± 2.7) despite having a low baseline NOL index (7.66 ± 5.76 out of 100). NRS and NOL index scores increased significantly during exercise, both before and after the block. The NOL index increased significantly when patients reported increased pain, indicating that it could eventually be useful in the objective assessment of acute pain in the chronic pain patients. However, NOL index was not able to reflect pain levels at rest, before the painful stimulation, in this chronic pain population. Further studies are needed to better assess NOL index utility at rest and to confirm these findings in this specific chronic pain population.

Effect of NOciception Level-Directed analgesic management on Opioid usage in Robot-assisted laparoscopic radical prostatectomy (NOLDOR): study protocol for a single-centre single-blinded randomised controlled trial

Background

The nociception level (NOL) index discriminates noxious stimuli during surgery with high sensitivity and specificity. Although some studies have reported that a NOL-directed opioid protocol reduces intraoperative opioid consumption, one study implied that it might cause an unintended increase in the stress response. Therefore, we designed a study to investigate the effects of the NOL-directed opioid protocol and measure inflammatory biomarkers.

Methods

This single-centre RCT will enrol 54 patients undergoing robot-assisted laparoscopic radical prostatectomy. Eligible patients will be randomly allocated to receive (i) NOL-directed intraoperative opioid management (NOL group) or (ii) conventional intraoperative analgesic management (control group). The remifentanil infusion rate will be determined solely using the NOL index during surgery in the NOL group. The primary outcome will be the mean intraoperative remifentanil infusion rate. Secondary outcomes will include the plasma concentrations of three perioperative inflammatory biomarkers (interleukin-6, C-reactive protein, and cortisol) and the variation in the NOL index at the start of pneumoperitoneum and with postural changes.

Conclusions

This study is expected to accumulate evidence on the effects of NOL-directed analgesic opioid protocol and provide additional evidence regarding the variability of stress responses and the character of the NOL index.

Clinical trial registration

JRCTs052220034.

Nociception Level Index-Directed Erector Spinae Plane Block in Open Heart Surgery: A Randomized Controlled Clinical Trial

Background and Objectives: The erector spinae plane block (ESPB) is a multimodal opioid-sparing component, providing chest-wall analgesia of variable extent, duration, and intensity. The objective was to examine the ESPB effect on perioperative opioid usage and postoperative rehabilitation when used within a Nociception Level (NOL) index-directed anesthetic protocol. Materials and Methods: This prospective, randomized, controlled, open-label study was performed in adult patients undergoing on-pump cardiac surgery in a single tertiary hospital. Eighty-three adult patients who met eligibility criteria were randomly allocated to group 1 (Control, n = 43) and group 2 (ESPB, n = 40) and received general anesthesia with NOL index-directed fentanyl dosing. Preoperatively, group 2 also received bilateral single-shot ultrasound-guided ESPB (1.5 mg/kg/side 0.5% ropivacaine mixed with dexamethasone 8 mg/20 mL). Postoperatively, both groups received intravenous paracetamol (1 g every 6 h). Morphine (0.03 mg/kg) was administered for numeric rating scale (NRS) scores ≥4. Results: The median (IQR, 25th−75th percentiles) intraoperative fentanyl and 48 h morphine dose in group 2-to-group 1 were 1.2 (1.1−1.5) vs. 4.5 (3.8−5.5) µg·kg−1·h−1 (p < 0.001) and 22.1 (0−40.4) vs. 60.6 (40−95.7) µg/kg (p < 0.001). The median (IQR) time to extubation in group 2-to-group 1 was 90 (60−105) vs. 360 (285−510) min (p < 0.001). Two hours after ICU admission, 87.5% of ESPB patients were extubated compared to 0% of controls (p < 0.001), and 87.5% were weaned off norepinephrine compared to 46.5% of controls (p < 0.001). The median NRS scores at 0, 6, 12, 24, and 48 h after extubation were significantly decreased in group 2. There was no difference in opioid-related adverse events and length of stay. Conclusions: NOL index-directed ESPB reduced intraoperative fentanyl by 73.3% and 48 h morphine by 63.5%. It also hastened the extubation and liberation from vasopressor support and improved postoperative analgesia.

Effects of Dexmedetomidine and Propofol on Postoperative Analgesia and the Cellular Immune Function of Patients Undergoing Radical Gastrectomy for Gastric Cancer

In order to optimize the anesthesia scheme and improve the effect of surgical treatment, the effects of dexmedetomidine and propofol on postoperative analgesia and cellular immune function of patients undergoing radical gastrectomy for gastric cancer have been analyzed. A total of 86 patients admitted to our hospital from March 2021 to March 2022 who received laparoscopic radical gastritis were selected. The combined dexmedetomidine group (n = 43) and the control group (n = 43) are grouped by the random number table method, respectively. Anesthesia induction regimens of dexmedetomidine combined with propofol and conventional propofol are treated, and the changes in serum stress index, immune function index, analgesia score, and pain score are observed. The results show that the postoperative stress response, analgesic effect, and immune function of patients receiving dexmedetomidine combined with propofol anesthesia are significantly better than those receiving conventional anesthesia, and the incidence of postoperative complications in the dexmedetomidine combined group is significantly lower than that in the control group. The results demonstrate that dexmedetomidine combined with propofol anesthesia intervention has high security in undergoing radical gastrectomy for gastric cancer.

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.

Nociception monitors vs. standard practice for titration of opioid administration in general anesthesia: A meta-analysis of randomized controlled trials

Background

Nociception monitors are being increasingly used during surgery, but their effectiveness in guiding intraoperative opioid administration is still uncertain. This meta-analysis of randomized controlled trials (RCTs) aimed to compare the effectiveness of nociception monitors vs. standard practice for opioid administration titration during general anesthesia.

Methods

We searched the electronic databases of PubMed, EMBASE, Cochrane Library, Clinical Trial, and Web of Science from inception up to August 1, 2021, to identify relevant articles, and extracted the relevant data. Intraoperative opioid administration, extubation time, postoperative pain score, postoperative opioid consumption and postoperative nausea and vomiting (PONV) were compared between patients receiving nociception monitoring guidance and patients receiving standard management. The standardized mean difference (SMD), with 95% confidence interval (CI), was used to assess the significance of differences. The risk ratio (RR), with 95% CI, was used to assess the difference in incidence of PONV. Heterogeneity among the included trials was evaluated by the I² test. RevMan 5.3 software was used for statistical analysis.

Results

A total of 21 RCTs (with 1957 patients) were included in the meta-analysis. Intraoperative opioid administration was significantly lower in patients receiving nociception monitor-guided analgesia than in patients receiving standard management (SMD, −0.71; 95% CI, −1.07 to −0.36; P < 0.001). However, pain scores and postoperative opioid consumption were not significantly higher in the former group. Considerable heterogeneity was found among the studies (92%). Extubation time was significantly shorter (SMD, −0.22; 95% CI, −0.41 to −0.03; P = 0.02) and the incidence of PONV significantly lower (RR, 0.78; 95% CI, 0.61 to 1.00; P = 0.05) in patients receiving nociception monitoring guidance.

Conclusions

Intraoperative nociception monitoring guidance may reduce intraoperative opioid administration and appears to be a viable strategy for intraoperative titration of opioids.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=273619, identifier: CRD42019129776.

Reduced postoperative pain in patients receiving nociception monitor guided analgesia during elective major abdominal surgery: a randomized, controlled trial

The Nociception Level index (NOL™) is a multiparameter index, based on artificial intelligence for the monitoring of nociception during anesthesia. We studied the influence of NOL-guided analgesia on postoperative pain scores in patients undergoing major abdominal surgery during sevoflurane/fentanyl anesthesia. This study was designed as a single-center, prospective randomized, controlled study. After Institutional Review Board approval and written informed consent, 75 ASA 1–3 adult patients undergoing major abdominal surgery, were randomized to NOL-guided fentanyl dosing (NOL) or standard care (SOC) and completed the study. The sevoflurane target MAC range was 0.8–1.2. In the NOL-guided group (N = 36), when NOL values were > 25 for at least 1 min, a weight adjusted fentanyl bolus was administered. In the control group (N = 39) fentanyl administration was based on hemodynamic indices and clinician judgement. After surgery, pain, was evaluated using the Numerical Rating Scale (NRS) pain scale, ranging from 0 to 10, at 15 min intervals for 180 min or until patient discharge from the PACU. Median postoperative pain scores reported were 3.0 [interquartile range 0.0–5.0] and 5.0 [3.0–6.0] at 90 min in NOL-guided and control groups respectively (Bootstrap corrected actual difference 1.5, 95% confidence interval 0.4–2.6). There was no difference in postoperative morphine consumption or intraoperative fentanyl consumption. Postoperative pain scores were significantly improved in nociception level index-guided patients. We attribute this to more objective fentanyl dosing when timed to actual nociceptive stimuli during anesthesia, contributing to lower levels of sympathetic activation and surgical stress. Clinicaltrials.gov identifier: NCT03970291 date of registration May 31, 2019.

Quantitative assessment of a pediatric nociception monitor in children under sevoflurane anesthesia

INTRODUCTION

Intraoperative monitoring of nociception has recently made substantial progress in adult anesthesia. In contrast, pediatric data are scarce. Newborn-Infant Parasympathetic Evaluation (NIPE index, Mdoloris Medical Systems, Loos, France) is the first nociception index specifically designed for young children. It is a dimensionless index comprised between 0 and 100. Two previous studies suggested that NIPE could indeed 'detect' nociception in anesthetized children. The objective of our study was to investigate if NIPE allowed to detect and to provide a quantitative assessment of nociception in children.

METHODS

Children were anesthetized with sevoflurane, and received a bolus of alfentanil (10 µg/kg before intubation). Before surgical incision, each participant received three tetanic stimulations (5 s, 100 Hertz) with a 5 min interval, in a randomized order: 10, 30 and 60 milliamps. NIPE and heart rate variations were assessed after each stimulation.

RESULTS

Thirty children (2.4±1.6 years) were included. Mean delay between alfentanil and the first stimulation was 19±4 min. Mean baseline NIPE was 75±10. NIPE variation after the stimulations was significant at 10, 30 and 60 mA (linear mixed regression model, p<0.001). The intensity of stimulation significantly influenced the amplitude of NIPE variation (linear mixed regression model p<0.001), but had no statistically significant effect on heart rate variation (p=0.52).

DISCUSSION

NIPE might allow a quantitative assessment of nociception in young children in these anesthetic conditions. This study provides a basis for future research investigating the potential benefits of NIPE-guided intraoperative analgesia in pediatric anesthesia.

TRIAL REGISTRATION NUMBER

NCT04381637.

Effect of combined intraoperative use of the Nociception Level (NOL) and bispectral (BIS) indexes on desflurane administration

BACKGROUND

Currently, nociception monitors are not part of standard anaesthesia care. We investigated whether combined intraoperative nociception (NOL index) and anaesthesia (BIS index) monitoring during general anaesthesia would reduce anaesthetics consumption and enhance intraoperative safety and postoperative recovery when compared to standard of care monitoring (SOC).

METHODS

In this randomised study, we included 60 patients undergoing colonic surgery under desflurane/remifentanil anaesthesia and epidural analgesia. Patients received either standard monitoring or combined BIS + NOL index monitoring. In the monitored group, remifentanil infusion was titrated to achieve a NOL index below 20. Desflurane was adjusted to BIS values (45-55). In the SOC group, remifentanil and desflurane were titrated on vital signs and MAC. The primary outcome was intraoperative desflurane consumption.

RESULTS

Fifty-five patients were analysed. Desflurane administration was reduced in the monitored group from 0.25 ± 0.05 to 0.20 ± 0.06 mL kg^-1 h^-1 (p < 0.001). The cumulative time with a BIS under 40 was significantly higher in the SOC group with a median time of 12.6 min (95% CI: 0.6-80.0) versus 2.0 min (95% CI: 0.3-5.83) (p = 0.023). Time for extubation was significantly shorter in the monitored group: 4.4 min (95% CI: 2.4-4.9) versus 6.28 min (95% IC: 5.0-8.2) (p = 0.003). We observed no differences in remifentanil or phenylephrine requirements during anaesthesia or in postoperative outcome measures, such as postoperative pain, opioid consumption, neurocognitive recovery.

CONCLUSION

Combined intraoperative monitoring of anaesthesia and nociception during colonic surgery resulted in less desflurane consumption and quicker extubation time compared to standard clinical care monitoring.

Monitoring of analgesia level during general anesthesia in children

PURPOSE OF REVIEW

Monitoring of intraoperative nociception has made substantial progress in adult anesthesia during the last 10 years. Several monitors have been validated and their use has been associated with intraoperative or postoperative benefits in the adult population. In pediatric anesthesia, less data are available. However, several recent publications have assessed the performance of nociception monitors in children, and investigated their potential benefits in this context. This review will describe the main validated intraoperative nociception monitors, summarize adult findings and describe the available pediatric data.

RECENT FINDINGS

Six intraoperative nociception indices were included in this review. Among them, four have shown promising results in children: Surgical Pleth Index (GE-Healthcare, Helsinki, Finland), Analgesia-Nociception Index (Mdoloris Medical Systems, Loos, France), Newborn-Infant Parasympathetic Evaluation (Mdoloris Medical Systems), and Pupillometry (IDMED, Marseille, France). The relevance of Skin Conductance (MedStorm innovations, AS, Oslo, Norway) under general anesthesia could not be established. Finally, the Nociception Level (Medasense, Ramat Gan, Israel) still requires to be investigated in children.

SUMMARY

To date, four monitors may provide a relevant assessment of intraoperative nociception in children. However, the potential clinical benefits associated with their use to guide analgesia remain to be demonstrated.

Identification of the intraoperative antinociceptive effect of intravenous fentanyl using the Nociception Level (NOL) index versus clinical parameters in patients undergoing gynecological laparoscopic surgery: A secondary analysis of the NOLGYN study

BACKGROUND

While we typically assess nociception balance during general anaesthesia through clinical parameters such as heart rate (HR) and mean arterial pressure (MAP) variation, these parameters are not specific to nociception.

OBJECTIVE

We hypothesized that using the Nociception Level (NOL) index to assess the analgesic effect of a fentanyl bolus would be superior to standard clinical parameters.

DESIGN

Ancillary study of the NOLGYN study, a randomized controlled trial comparing intraoperative NOL-guided administration of fentanyl (NOL group) versus standardized care (SC group).

SETTING

University hospital in Montréal, Canada between November 2018, and December 2019.

PATIENTS

Women undergoing gynecological laparoscopic surgery.

INTERVENTION

In our evaluation of intraoperative nociception, we analyzed the analgesic effect of fentanyl using three parameters: MAP, HR, and the Nociception Level (NOL) index. All fentanyl injection events were extracted from the database.

MAIN OUTCOME MEASURE

The primary endpoint was the difference between values before and after each injection.

RESULTS

The median of the NOL index before fentanyl injection was 30.5 (IQR 19.4 to 40.7) versus 18.9 (IQR 11.5 to 27.4) after (P < 0.001). The median of MAP was 106.4 mmHg (IQR 99.9 to 113.4) before injection versus 103.2 mmHg (IQR 97.5 to 110.7) after (P < 0.001). The median of HR before injection was 74.2 (IQR 64.2 to 83.8) versus 72.4 (IQR 63.4 to 81.3) after (P < 0.001).

CONCLUSIONS

The NOL index, HR, and MAP all statistically discriminated the analgesic effect of fentanyl but only the NOL index proved clinically relevant to identify the analgesic effect of one fentanyl injection.

TRIAL REGISTRATION

www.

CLINICALTRIALS

gov (NCT03776838) registered in October 2018.

Different perspectives for monitoring nociception during general anesthesia

Safe anesthesia is achieved using objective methods that estimate the patient’s state during different phases of surgery. A patient’s state under anesthesia is characterized by three major aspects, which are linked to the main effects produced by each of the families of anesthetic agents administered: hypnosis, analgesia, and muscular relaxation.

While quantification techniques designed to assess muscular relaxation under neuromuscular blocking agents have a relatively long history with a high degree of standardization and understanding (e.g., the train-of-four), the knowledge and techniques used to the depth of hypnosis assessment suffer from a lesser degree in both standardization and interpretation due to brain complexity.

The problem of standardization and interpretation in the analgesia and nociception assessment increases since it involves more systems, the central nervous system, and the autonomic nervous system.

This helps to explain why there are multiple a priori valid approaches to develop nociception monitoring from different interpretations and physiological bases of noxious stimuli processing. Thus, in this review, the current monitoring technologies clinically available for estimating a patient’s nociception under general anesthesia are described.

Analgesia Nociception Index-Guided Remifentanil versus Standard Care during Propofol Anesthesia: A Randomized Controlled Trial

The clinical benefits to be expected from intraoperative nociception monitors are currently under investigation. Among these devices, the Analgesia Nociception-Index (ANI) has shown promising results under sevoflurane anesthesia. Our study investigated ANI-guided remifentanil administration under propofol anesthesia. We hypothesized that ANI guidance would result in reduced remifentanil consumption compared with standard management. This prospective, randomized, controlled, single-blinded, bi-centric study included women undergoing elective gynecologic surgery under target-controlled infusion of propofol and remifentanil. Patients were randomly assigned to an ANI or Standard group. In the ANI group, remifentanil target concentration was adjusted by 0.5 ng mL⁻¹ steps every 5 min according to the ANI value. In the Standard group, remifentanil was managed according to standard practice. Our primary objective was to compare remifentanil consumption between the groups. Our secondary objectives were to compare the quality of anesthesia, postoperative analgesia and the incidence of chronic pain. Eighty patients were included. Remifentanil consumption was lower in the ANI group: 4.4 (3.3; 5.7) vs. 5.8 (4.9; 7.1) µg kg⁻¹ h⁻¹ (difference = −1.4 (95% CI, −2.6 to −0.2), p = 0.0026). Propofol consumption was not different between the groups. Postoperative pain scores were low in both groups. There was no difference in morphine consumption 24 h after surgery. The proportion of patients reporting pain 3 months after surgery was 18.8% in the ANI group and 30.8% in the Standard group (difference = −12.0 (95% CI, −32.2 to 9.2)). ANI guidance resulted in lower remifentanil consumption compared with standard practice under propofol anesthesia. There was no difference in short- or long-term postoperative analgesia.

[Does NoL monitoring affect opioid consumption during da Vinci prostatectomy?]

BACKGROUND

Administration of opioids to suppress pain plays a major role in modern anesthesia. Measuring depth of hypnosis and neuromuscular recovery are already well established, and devices for pain monitoring are available. Nonetheless pain monitoring is rare in clinical practice. Recently, the pain monitoring device PMD200 (Medasense Biometrics™ , Israel) was introduced. It non-invasively measures heart rate, heart rate variability, skin resistance, resistance variability, temperature and movement to calculate a nociception level (NoL) index. The NoL index range starts at zero, which is equivalent to being painless, and goes up to a value of 100. The validity and reliability of NoL monitoring is the content of current studies.

OBJECTIVE

We tested the hypothesis if the use of the PMD200 significantly reduces opioid consumption during da Vinci prostatectomy.

MATERIAL AND METHODS

A total of 50 male patients were included in this randomized, single blinded study. Exclusion criteria were arrhythmia because the pain monitoring device requires a sinus rhythm for reliable results. Patients received a weight-adjusted sufentanil bolus (0.3 µg/kg ideal body weight) during induction of anesthesia. Additionally, they received 10 µg of sufentanil before skin incision. Both groups received total intravenous anesthesia with propofol and continuous muscle relaxation through cis-atracurium. In the control group (CONT; n = 26), a standardized sufentanil bolus of 10 µg were administered by common criteria (heart rate/blood pressure increase, lacrimation, gut feeling) at the anesthesiologist's discretion. In the intervention group (INT; n = 24), patients received the standardized sufentanil bolus when the NoL index was above 25 for 2 min, which corresponds to the manufacturer's recommendation. The NoL index and bolus administrations were recorded for every patient. In the control group, the display of the pain monitor showing the NoL index was not visible for the anesthesiologist. Postoperatively, pain/nausea scores and piritramide consumption were taken every 10 min for 1h in the recovery room. None of the patients had prior chronic pain with long-term use of painkillers. Statistics were done using Mann-Whitney U‑test, Kolmogorov-Smirnov test and Levene test.

RESULTS

Sufentanil bolus administrations, normalized for duration of surgery, were not significantly lower in the intervention group (p = 0.065). We noticed a significant difference in variation of opioid administrations (p = 0.033). Sufentanil boluses per hour in the INT were normally distributed (p = 0.2), whereas in CONT they were not (p = 0.003). Postoperative data like nausea, opioid consumption and pain scale showed no differences between groups.

CONCLUSION

The use of PMD200 did not significantly reduce cumulative opioid consumption. Following on we must reject the initial hypothesis. The difference in sufentanil bolus variances may point to an individualized antinociceptive therapy when NoL monitoring is used. We suppose patients with high opioid demands are detected and patients with low opioid demands did not receive unnecessary opioids. This assumption is only true if the PMD200 measures the entity pain. Further studies with more participants during surgery with higher tissue damage could lead to more convincing data and conclusions.

Exploration of a Multi-Parameter Technology for Pain Assessment in Postoperative Patients After Cardiac Surgery in the Intensive Care Unit: The Nociception Level Index (NOL)TM

Introduction

The aim of this study was to explore the use of a multi-parameter technology, the Nociception Level (NOL) index (Medasense Biometrics Ltd, Ramat Gan, Israel), for pain assessment in postoperative awake patients after cardiac surgery during non-nociceptive and nociceptive procedures in the intensive care unit (ICU).

Materials and Methods

A prospective cohort repeated-measures design was used. Patients were included if they were in the ICU after undergoing cardiac surgery and if they could self-report their pain. A non-invasive probe was placed on the patient’s finger for the continuous monitoring of the NOL index. Patients’ self-reports of pain and anxiety (0–10 Numeric Rating Scale or NRS), and behavioral scores with the Critical-Care Pain Observation Tool (CPOT) were obtained before and during a non-nociceptive procedure (ie, non-invasive blood pressure [NIBP] using cuff inflation), and before, during and after a nociceptive procedure (ie, chest tube removal [CTR]) for a total of five time points. Non-parametric tests were used to compare scores at different time points, and receiver operating characteristic curve analysis was performed.

Results

Fifty-four patients were included in the analysis. The NOL index, pain and anxiety scores were significantly higher during CTR compared to rest and NIBP (p < 0.001). During CTR, the NOL was associated with self-reported pain intensity and unpleasantness but not with anxiety and CPOT scores. The NOL showed a modest performance in detecting pain (NRS ≥1 and ≥5) in this sample with sensitivity and specificity ranging from 61% to 85%.

Conclusion

The NOL index was able to discriminate between a non-nociceptive and a nociceptive procedure and was associated with self-reported pain. Further validation testing of the NOL is necessary in a heterogeneous sample of ICU patients.

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.

Changes in the Nociception Level Index During Surgical Resection of Paragangliomas: A Case Report

Nociception is the detection of noxious stimulation by the nervous system. The PMD-200 monitor is a validated, emerging technology for intraoperative monitoring using the nociception level (NOL) index. We describe a pediatric case of an open resection of paraganglionic masses during which episodic increases in NOL index and blood pressure coincided with tumor manipulation, presumably due to a catecholamine surge. Since the patient was under stable and adequate analgesia, the increases in NOL index likely reflected the physiologic effects of tumor handling rather that the presence of a true noxious stimulus. Clinicians should consider this limitation when using this monitor.

The impact of bolus versus continuous infusion of intravenous ketamine on bispectral index variations and desflurane administration during major surgery: The KETABIS study

BACKGROUND

Although ketamine, a NMDA-receptor antagonist, tends to increase the bispectral index (BIS), it remains a widely used analgesic whenever administered in low doses during major surgery.

OBJECTIVE

The objective of this study was to compare the impact of intravenous ketamine (given either as a continuous infusion or as a bolus) on BIS and to compare desflurane administration and postoperative outcomes between the groups.

DESIGN

Prospective, randomised, parallel-group, open-label study.

SETTING

University hospital, operating room.

PARTICIPANTS

Fifty patients, scheduled for major abdominal surgery.

INTERVENTIONS AND MAIN OUTCOMES MEASURES

Patients were randomised into two groups: ketamine by intravenous continuous infusion - group (KI) and ketamine by i.v. bolus - group (KB). In the KI group, ketamine at a rate of 0.25 mg kg-1 h-1 was commenced at skin incision (T0) and maintained at this rate for the duration of surgery. In group KB, a ketamine bolus of 0.25 mg kg-1was administered at T0 and repeated every hour. The difference in BIS between the groups was compared from T0 onwards. The amount of desflurane administered to keep BIS within the usual recommended range (40-60) was compared, as were the doses of phenylephrine and remifentanil. Postoperative pain and recovery outcomes were also assessed.

RESULTS

After T0, the BIS increased significantly from baseline in group KB compared with group KI: the rise in BIS was 20 ± 8 vs. 11 ± 6, respectively (P = 0.0001). The between-group mean difference (95% confidence interval (CI), was 9 (5 to 13). In group KB, desflurane administration significantly increased for the first 15 min after T0: 6.3 ± 1.8 vs. 3.8 ± 1.3 ml (P < 0.0001) with a mean intergroup group difference (95% CI) of 2.4 (1.5 to 3.4) ml. There was no difference in desflurane administration when considering the full hour from T0 to T60 min: 16 ± 9 vs. 15 ± 5 ml (P = 0.63) with a mean intergroup difference (95% CI) of 1 (-3 to 5) ml. After surgery, pain scores, opioid consumption, incidence of nausea and vomiting and recovery scores were similar between groups.

CONCLUSION

Compared with a continuous ketamine infusion, a ketamine bolus significantly increased the BIS after T0. In order to keep the BIS below 60, significantly more desflurane was administered from T0 to T15 min in group KB. To prevent such higher desflurane administration and its related atmospheric pollution, our results suggest administering intra-operative intravenous ketamine as an infusion rather than a bolus.

TRIAL REGISTRATION

Clinicaltrials.gov registration identifier: NCT03781635.

"Impact of Nociception Level (NOL) index intraoperative guidance of fentanyl administration on opioid consumption, postoperative pain scores and recovery in patients undergoing gynecological laparoscopic surgery. A randomized controlled trial"

STUDY OBJECTIVE

The Nociception Level (NOL) index uses a multiparametric approach to measure the balance between sympathetic and parasympathetic systems activity. Recently, a strong correlation between the NOL index response to nociceptive stimuli and the level of opioid analgesia during surgery was reported. Others observed that intraoperative doses of remifentanil and sufentanil were reduced when the NOL index was used. So far, no study has evaluated the impact of NOL-guided fentanyl antinociception in laparoscopic gynecological surgery. The primary hypothesis of this present study was to evaluate whether intraoperative NOL-guided fentanyl administration would reduce intra-operative opioid consumption. Secondary hypotheses were to assess whether this would lead to lower postoperative opioid consumption and pain scores, as well as improved postoperative outcomes.

SETTING

University hospital, operating room.

PATIENTS

70 adult patients, ASA 1-3, scheduled for total laparoscopic hysterectomy.

INTERVENTIONS

Patients were randomized into 2 groups: SOC (standardization of care) and NOL (using the NOL index to guide the administration of fentanyl). The depth of anesthesia was monitored with BIS™. Intraoperative fentanyl boluses were administered based on heart rate and mean arterial pressure variations in the SOC group, and NOL index for the NOL group.

MEASUREMENTS

Fentanyl total intraoperative dose administered was collected and also averaged per hour. Pain scores and hydromorphone consumption were assessed in the post-anesthesia care unit and up to 24 h.

MAIN RESULTS

Sixty-six patients completed the study, 33 in each group. Total intraoperative fentanyl administration was not different between the two groups (217 (70) in the NOL group vs 280 (210) in the SOC group (P = 0.11)). Nevertheless, intraoperative fentanyl administration per hour was reduced by 25% in the NOL-guided group compared to the SOC group: 81 (24) vs 108 (66) μg.h^-1, respectively (P = 0.03). Hydromorphone consumption and pain scores in the post-anesthesia care unit and at 24 h were not significantly different between the two groups.

CONCLUSION

NOL-guided analgesia allowed for a 22% reduction of the total amount of intraoperative fentanyl which was not significant. Nevertheless, results reported a significant reduction by 25% in the doses of fentanyl averaged per hour of surgery and administered in the NOL-guided group compared with the standardized practice in laparoscopic gynecological surgery. The pain measured postoperatively was similar in the two groups while the average postoperative consumption of opioids to achieve the same level of pain scores in post-anesthesia care unit and at 24 h was not significantly reduced. Further larger multicenter studies centered towards postoperative outcomes are needed.

Relationship between pre-incision Pupillary Pain Index and post-incision heart rate and pupillary diameter variation in children

BACKGROUND

The Pupillary Pain Index is a recent pupillometric index designed to assess the level of analgesia under general anesthesia in children and adults. If analgesia is inadequate, acute nociceptive stimuli such as skin incision may induce significant hemodynamic disturbances.

AIMS

Our aim was to investigate the potential relationship between pre-incision Pupillary Pain Index and heart rate increase following skin incision in children.

METHODS

This was a prospective, non-randomized, registered pilot study. We included children undergoing surgery under general anesthesia. Pupillary Pain Index was assessed 2 min before skin incision. Then, heart rate maximal variation (Δ_HR ) and pupillary diameter maximal variation (Δ_PD ) in the minute following incision were recorded. Spearman coefficient was calculated to characterize the relationship between Pupillary Pain Index and Δ_HR or Δ_PD . Using receiver operating characteristic curve analysis, we also studied the predictive value of pre-incision Pupillary Pain Index for heart rate and pupillary diameter reactivity.

RESULTS

53 patients were included (10 ± 4 years, 40 ± 19 kg). There was a modest correlation between pre-incision Pupillary Pain Index and Δ_HR (Spearman rs = 0.35 [0.05-0.57], p = .011), and between pre-incision Pupillary Pain Index and Δ_PD (Spearman rs = 0.54 [0.33-0.71], p < .001). Regarding the predictive value of Pupillary Pain Index for heart rate or pupillary diameter reactivity, the corresponding areas under the receiver operating characteristic curves were 0.90 [0.82-0.99] and 0.78 [0.65-0.93], respectively. A threshold of Pupillary Pain Index <3 predicted the absence of heart rate reactivity at incision with a good performance (negative predictive value = 1).

CONCLUSIONS

In children, pre-incision Pupillary Pain Index was moderately correlated with post-incision nociception. Pre-incision Pupillary Pain Index had good predictive performances for heart rate or pupillary diameter reactivity to skin incision. Pre-incision Pupillary Pain Index <3 might predict the absence of heart rate reaction to incision.

[Nociception monitoring : Method for intraoperative opioid control?]

The intraoperative dosing of opioids is a challenge in routine anesthesia as the potential effects of intraoperative overdosing and underdosing are not completely understood. In recent years an increasing number of monitors were approved, which were developed for the detection of intraoperative nociception and therefore should enable a better control of opioid titration. The nociception monitoring devices use either continuous hemodynamic, galvanic or thermal biosignals reflecting the balance between parasympathetic and sympathetic activity, measure the pupil dilatation reflex or the nociceptive flexor reflex as a reflexive response to application of standardized nociceptive stimulation. This review article presents the currently available nociception monitors. Most of these monitoring devices detect nociceptive stimulations with higher sensitivity and specificity than changes in heart rate, blood pressure or sedation depth monitoring devices. There are only few studies on the effect of opioid titration guided by nociception monitoring and the possible postoperative benefits of these devices. All nociception monitoring techniques are subject to specific limitations either due to perioperative confounders (e.g. hypovolemia) or special accompanying medical conditions (e.g. muscle relaxation). There is an ongoing discussion about the clinical relevance of nociceptive stimulation in general anesthesia and the effect on patient outcome. Initial results for individual monitor systems show a reduction in opioid consumption and in postoperative pain level. Nevertheless, current evidence does not enable the routine use of nociception monitoring devices to be recommended as a clear beneficial effect on long-term outcome has not yet been proven.

Intraoperative Nociception Monitoring

Nociception refers to the process of encoding and processing noxious stimuli. Its monitoring can have potential benefits. Under anesthesia, nociceptive signals are continuously generated to cause involuntary effects on the autonomic nervous system, reflex movement, and stress response. Most available systems depend on the identification and measurement of these indirect effects to indicate nociception-antinociception balance. Despite advances in monitoring technology and availability, their limitations presently override their benefits. Hence, their utility and applicability in present-day anesthesia care is uncertain. Future technologies might allow automated closed-loop multimodal anesthesia systems, which includes the components of hypnosis and analgesic balance for a patient.

Spontaneous breathing for managing analgesia during balanced anesthesia with remifentanil and desflurane: a prospective, single center randomized controlled trial

The main goal of anesthesiology is to achieve the best level of analgesia and a fast recovery of consciousness following anesthesia. The preservation of spontaneous breathing during general anesthesia with anesthetic gases is practiced by many anesthetists. However, very few studies have dealt with these positive properties of volatile anesthetics such as sevoflurane or desflurane. Remifentanil is a very short half-life opiate that combines sufficient intra-operative analgesia with a fast post-operative recovery time. We tested the hypothesis that spontaneous breathing can reduce overdosing with remifentanil during desflurane anesthesia. In this prospective, single center, multiple anesthetist study, 30 patients were randomized into two groups (volume-controlled ventilation mode and spontaneous breathing). The spontaneous breathing group showed a significantly lower post-operative pain level than the volume-controlled ventilation mode group. Furthermore, less remifentanil as well as less piritramide was needed in the spontaneous breathing group compared with volume-controlled ventilation mode. It was possible to achieve spontaneous breathing in all patients with 0.6 minimum alveolar concentration desflurane, in order to control the remifentanil rate and prevent an overdose. All spontaneous breathing patients had low intra- and post-operative pain levels and the need for analgesics was equal to or lower than that in the volume-controlled ventilation mode group. By reducing the intra-operative amount of opiates, both the post-operative pain and the amount of post-operative analgesia required can be reduced. A balanced anesthesia with spontaneous intra-operative breathing is needed to determine the required amount of opiates. This study was approved by the Ethic Committee of the Ruhr-University of Bochum (approval No. 2435) in September, 2004.

Effect of dexmedetomidine on Nociception Level Index-guided remifentanil antinociception: A randomised controlled trial

BACKGROUND

The effect of dexmedetomidine on Nociception Level Index-guided (Medasense, Israel) antinociception to reduce intra-operative opioid requirements has not been previously investigated.

OBJECTIVE

We aimed to determine if low-dose dexmedetomidine would reduce remifentanil requirements during Nociception Level Index-guided antinociception without increasing complications associated with dexmedetomidine.

DESIGN

Double-blind randomised controlled trial.

SETTING

Two university teaching hospitals in Brussels, Belgium.

PATIENTS

American Society of Anesthesiologists 1 and 2 patients (n = 58) undergoing maxillofacial or cervicofacial surgery under propofol--remifentanil target-controlled infusion anaesthesia.

INTERVENTIONS

A 30 min infusion of dexmedetomidine, or equal volume of 0.9% NaCl, was infused at 1.2 μg kg-1 h-1 immediately preceding induction and then decreased to 0.6 μg kg-1 h-1 until 30 min before ending surgery. Nociception Level Index and frontal electroencephalogram guided the remifentanil and propofol infusions, respectively.

MAIN OUTCOMES

The primary outcome was the remifentanil requirement. Other outcomes included the propofol requirement, cardiovascular status and postoperative outcome.

RESULTS

Mean ± SD remifentanil (3.96 ± 1.95 vs. 4.42 ± 2.04 ng ml-1; P = 0.0024) and propofol (2.78 ± 1.36 vs. 3.06 ± 1.29 μg ml-1; P = 0.0046) TCI effect site concentrations were lower in the dexmedetomidine group at 30 min postincision and remained lower throughout surgery. When remifentanil (0.133 ± 0.085 vs. 0.198 ± 0.086 μg kg-1 min-1; P = 0.0074) and propofol (5.7 ± 2.72 vs. 7.4 ± 2.80 mg kg-1 h-1; P = 0.0228) requirements are represented as infusion rates, this effect became statistically significant at 2 h postincision.

CONCLUSION

In ASA 1 and 2 patients receiving Nociception Level Index-guided antinociception, dexmedetomidine decreases intra-operative remifentanil requirements. Combined frontal electroencephalogram and Nociception Level Index monitoring can measure dexmedetomidine's hypnotic and opioid-sparing effects during remifentanil-propofol target-controlled infusion anaesthesia.

TRIAL REGISTRATIONS

Clinicaltrials.gov: NCT03912740, EudraCT: 2018-004512-22.

Analgesia Nociception Index (ANI) and ephedrine: a dangerous liasion

The Analgesia Nociception Index is a dimensionless scale derived from the heart rate variability; by analyzing the heart rate variability oscillations, it reflects the activity of the sympathetic and parasympathetic nervous systems and ultimately helps to evaluate the Nociception-Antinociception balance during anesthesia and surgery. Drugs like ephedrine affect the heart rate variability inducing artifacts in the ANI readings which should be taken into account in the clinical practice and in clinical research.