Correlation between incremental remifentanil doses and the Nociception Level (NOL) index response after intraoperative noxious stimuli

Using the nociception level index to compare the intraoperative antinociceptive effect of propofol and sevoflurane during clinical and experimental noxious stimulus in patients under general anesthesia

STUDY

Propofol and sevoflurane are two anesthetic agents widely used to induce and maintain general anesthesia (GA). Their intrinsic antinociceptive properties remain unclear and are still debated.

OBJECTIVE

To determine whether propofol presents stronger antinociceptive properties than sevoflurane using intraoperative clinical and experimental noxious stimulations and evaluating postoperative pain outcomes.

DESIGN

A prospective randomized monocentric trial.

SETTING

Perioperative care.

PATIENTS

60 adult patients with ASA status I to III who underwent elective abdominal laparoscopic surgery under GA were randomized either in propofol or sevoflurane group to induce and maintain GA.

INTERVENTIONS

We used clinical and experimental noxious stimulations (intubation, tetanic stimulation) to assess the antinociceptive properties of propofol and sevoflurane in patients under GA and monitored using the NOL index, BIS index, heart rate, and mean arterial blood pressure.

MEASUREMENTS

We measured the difference in the NOL index alterations after intubation and tetanic stimulation during either intravenous anesthesia (propofol) or inhaled anesthesia (sevoflurane). We also intraoperatively measured the NOL index and remifentanil consumption and recorded postoperative pain scores and opioid consumption in the post-anesthesia care unit. Intraoperative management was standardized by targeting similar values of depth of anesthesia (BIS index), hemodynamic (HR and MAP), NOL index values (below the threshold of 20), same multimodal analgesia and type of surgery.

MAIN RESULTS

We found the antinociceptive properties of propofol and sevoflurane similar. The only minor difference was after tetanic stimulation: the delta NOL was higher in the sevoflurane group (39 ± 13 for the propofol group versus 47 ± 15 for sevoflurane; P = 0.04). Intraoperative and postoperative pain outcomes and opioid consumption were similar between groups.

CONCLUSIONS

Despite a precise intraoperative experimental and clinical protocol using the NOL index, propofol does not provide a higher level of antinociception during anesthesia or analgesia after surgery when compared to sevoflurane. Anesthesiologists may prefer propofol over sevoflurane to reduce PONV or anesthesia-related pollution, but not for superior antinociceptive properties.

Analysis of the Effects of Epidural Anesthesia on the Nociception Level Index (NOL®) during Abdominal Surgery

Background: The NOL® system (PMD-200™ Nociception Level Monitor; Medasense Ltd., Ramat Gan, Israel) is used for the real-time detection of physiological nociception in anesthetized patients by assessing the parameters indicative of sympathetic activity, such as photoplethysmography, skin conductance, peripheral temperature, and accelerometry, which are quantified into the NOL®-Index. This index is more sensitive than traditional clinical parameters in estimating pain and stress responses. While its effectiveness in general anesthesia is well documented, its efficacy in epidural anesthesia needs further investigation. Methods: This retrospective study analyzed NOL®-Index dynamics compared to conventional parameters after epidural administration of bupivacaine. Following ethics committee approval, 119 NOL® measurements were retrospectively analyzed after thoracic epidural catheter administration in 40 patients undergoing abdominal and urological surgery. The NOL-Index® was assessed at 0, 1, 3, and 5 min post application and compared to heart rate, blood pressure, and bispectral index dynamics. Results: This study showed a significant decrease in the NOL®-Index post-local-anesthetic administration with better sensitivity than classical clinical parameters (0 min = 38 ± 11; 1 min = 22 ± 13*; 3 min = 17 ± 11*; 5 min = 12 ± 10*). Higher doses of local anesthetics led to a significant, dose-dependent decrease in NOL®-Index (low dose, 5 min = 15 ± 10*; high dose, 5 min = 8 ± 8*). Conclusions: This study is the first to demonstrate the effectiveness of the NOL®-Index in measuring nociceptive effects following epidural administration, highlighting its potential superiority over conventional parameters and its sensitivity to dose variations.

Current perioperative nociception monitoring and potential directions

Perioperative nociception-antinociception balance is essential for the prevention of adverse postoperative events. Estimating the nociception level helps optimize intraoperative management. In the past two decades, various nociception monitoring devices have been developed for the identification of intraoperative nociception. However, each type of nociception monitoring device has advantages and disadvantages, limiting their clinical application in particular patients and settings. Therefore, this review aimed to summarize the information on nociceptor monitoring in current clinical settings, explore each technique's particularities, and possible future directions to provide a reference for clinicians and researchers.

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 the Location of Tetanic Stimulation on Autonomic Responses: A Randomized Cross-Over Pilot Study

Background

Tetanic stimuli are used as standardized noxious inputs to investigate nociception. Previous studies have applied tetanic stimuli to various anatomical locations without validating that the resulting physiological responses were independent of the location where tetanic stimuli were applied. Our aim was to investigate the effects of three anatomical tetanic stimulus application sites on physiological variables reflecting autonomic nervous system responses as measured by photoplethysmography (PPG).

Methods

Under general anesthesia, a five second, 100 hertz, 70 milliamp tetanic stimulus was applied to the ulnar nerve, medial side of the tibia, and thorax (T5 dermatome) (N=12). The effect of tetanic stimuli on PPG-derived variables (AC, DC, and ACDC) and pulse rate at each stimulus location was determined using repeated-measures analysis of variance (ANOVA) followed by Dunnett's post hoc test. Maximum tetanic stimulus-induced changes in PPG-derived variables and pulse rates were compared among the three stimulus locations using ANOVA.

Results

AC and ACDC values of PPG decreased, and the DC values of PPG increased in response to tetanic stimuli-induced vasoconstriction at each location (p<0.001 for all). The maximum changes in the AC, ACDC, and DC values did not differ between locations (p=NS). There were no significant changes in pulse rate (p=NS).

Conclusion

The results showed that tetanic stimulation at either of these three locations provides the same autonomic nervous system responses, as measured by PPG.

Clinical Trial Registration

ClinicalTrials.gov; NCT03648853.

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.

The Validity of Vital Signs for Pain Assessment in critically Ill Adults: A Narrative Review

OBJECTIVES

Pain assessment in the intensive care unit (ICU) is challenging because many patients are unable to self-report or exhibit pain-related behaviors. In such situations, vital signs (VS) through continuous monitoring are alternative cues for pain assessment. This review aimed to describe the reliability and validity of VS for ICU pain assessment.

DESIGN

Narrative review of the literature.

DATA SOURCES

Medline, Embase, CINAHL, Cochrane.

REVIEW/ANALYSIS METHODS

A narrative review was conducted with a comprehensive search in four databases. Search terms included VS, pain assessment, and ICU.

RESULTS

Out of 1,359 results, 30 studies from 17 countries were included. Heart rate, blood pressure, and respiratory rate were most used for ICU pain assessment. Assessments were performed at rest before procedures, during nociceptive and non-nociceptive procedures, and after procedures. Increases in respiratory rate were clinically significant by more than 25% during nociceptive procedures (e.g., endotracheal suctioning, turning) compared with rest/pre-procedures in five studies. Correlations of VS with self-reported pain (reference standard measure) and behavioral pain scores (alternative measure) were absent or weak.

CONCLUSIONS

VS are not valid indicators for ICU pain assessment. Increases of respiratory rate may be a cue for the detection of pain. However, fluctuations in respiratory rate can be influenced by opioids or controlled ventilation mode. Our results dissuade the use of VS for pain assessment because of the lack of association with ICU pain reference standards. Other physiologic measures of pain in critically ill adults should be explored.

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 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.

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.

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.

Impact of Processed Electroencephalography in Cardiac Surgery: A Retrospective Analysis

OBJECTIVE

The use of brain function monitoring with processed electroencephalography (pEEG) during cardiac surgery is gaining interest for the optimization of hypnotic agent delivery during the maintenance of anesthesia. The authors sought to determine whether the routine use of pEEG-guided anesthesia is associated with a reduction of hemodynamic instability during cardiopulmonary bypass (CPB) separation and subsequently reduces vasoactive and inotropic requirements in the intensive care unit.

DESIGN

This is a retrospective cohort study based on an existing database.

SETTING

A single cardiac surgical center.

PARTICIPANTS

Three hundred patients undergoing cardiac surgery, under CPB, between December 2013 and March 2020.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

One hundred and fifty patients had pEEG-guided anesthesia, and 150 patients did not have a pEEG-guided anesthesia. Multiple logistic regression demonstrated that pEEG-guided anesthesia was not associated with a successful CPB separation (p = 0.12). However, the use of pEEG-guided anesthesia reduced by 57% the odds of being in a higher category for vasoactive inotropic score compared to patients without pEEG (odds ratio = 0.43; 95% confidence interval: 0.26-0.73; p = 0.002). Duration of mechanical ventilation, fluid balance, and blood losses were also reduced in the pEEG anesthesia-guided group (p < 0.003), but there were no differences in organ dysfunction duration and mortality.

CONCLUSION

During cardiac surgery, pEEG-guided anesthesia allowed a reduction in the use of inotropic or vasoactive agents at arrival in the intensive care unit. However, it did not facilitate weaning from CPB compared to a group where pEEG was unavailable. A pEEG-guided anesthetic management could promote early vasopressor weaning after cardiac surgery.

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.

[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.

Description of the validity of the Analgesia Nociception Index (ANI) and Nociception Level Index (NOL) for nociception assessment in anesthetized patients undergoing surgery: a systematized review

Maintaining optimum analgesia in anesthetized patients is challenging due to the inability to self-report pain or exhibit pain-related behaviours. The Analgesia Nociception Index (ANI) (based on heart rate variability [HRV]) and the Nociception Level Index (NOL) (based on HRV, photoplethysmography, skin conductance, and temperature) both include HRV and provide continuous index monitoring for nociception assessment. The research question was: "What are the validation strategies of the NOL and ANI for nociception assessment in anesthetized patients?". The objectives were to describe and analyze the validation strategies and results. A systematized review was conducted using a comprehensive search with keywords under three concepts (nociception/pain, ANI/NOL, and validity) in four databases. A quality assessment using an adapted GRADE approach for measurement tools, and a risk of bias assessment using QUADAS-2 tool were performed by two reviewers. Out of 525 results, 15 validation studies were included. Strategies included hypothesis testing, discriminative, and criterion validation. Significant changes in ANI/NOL values were found in response to nociceptive stimuli at different opioid concentrations (hypothesis testing). Higher ANI/NOL values were observed during nociceptive stimuli (discriminative). AUCs ranging from 0.83 to 0.99 were obtained to detect nociceptive stimuli (criterion). Both technologies performed superiorly in detecting nociceptive stimuli compared to individual monitoring of HR and blood pressure. Although the aforementioned validation strategies are deemed appropriate, in the absence of a gold standard, criterion validation findings should be interpreted with caution. Moreover, reliability could be examined using test-retest with consistent ANI/NOL values during a stable time-interval.

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.

[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.

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

Introduction

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

Objective

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

Material and methods

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

Study registration

NCT04825847 on ClinicalTrials.gov.

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.

A randomized controlled trial comparing nociception level (NOL) index, blood pressure, and heart rate responses to direct laryngoscopy versus videolaryngoscopy for intubation: the NOLint project

PURPOSE

The effect of direct laryngoscopy using a Macintosh blade (MAC) vs GlideScope™ videolaryngoscopy using a Spectrum LoPro blade (GVL) on nociceptive stimulation has not been quantitatively studied. This study used the new nociception level (NOL) index to compare the nociceptive response induced by GVL or MAC during laryngoscopy with or without intubation.

METHODS

Patients underwent two laryngoscopies at four-minute intervals (L1, L2), one with GVL and the other with MAC (first randomization). A third laryngoscopy (L3) followed by tracheal intubation was performed four minutes after L2 (GVL or MAC, second randomization). Nociception was quantitatively assessed by NOL and standard hemodynamic parameters (heart rate [HR] and mean arterial pressure). For the crossover design, blade comparisons accounted for sequence and blade type. A possible carryover effect between laryngoscopies was assessed.

RESULTS

In the 50 patients randomized, there was no carryover effect from one laryngoscopy to the next for all analyzed parameters. Nociception level index peak values were higher with MAC than GVL. Analysis of ΔNOL showed a lower nociceptive response with GVL for L1+L2 combined. Mean peak NOL values were significantly higher after L3+intubation than after L1+L2, for both GVL and MAC groups. Analysis of ΔHR values did not show a significant difference between GVL and MAC for any laryngoscopy.

CONCLUSION

Laryngoscopy alone with GVL induces less nociception than with MAC. The NOL was more sensitive than HR at detecting nociceptive responses to MAC vs GVL. Additionally, and irrespective of which technique/blade was used, the combination of laryngoscopy + tracheal intubation produced a much greater nociceptive response than the laryngoscopy alone.

TRIAL REGISTRATION

www.clinicaltrials.gov (NCT03277872); registered 29 August 2017.

Face transplantation: anesthesia and other organizational considerations

In 2005, the first facial vascularized composite allotransplant was performed in France. In May 2018, our team at Maisonneuve-Rosemont Hospital, Montreal, Quebec, had the privilege to participate in the first facial transplant in Canada. Interdisciplinary collaboration, coordination, and communication formed the cornerstone of this medical undertaking and, ultimately, its success. This report details the anesthetic and organizational considerations of our experience.

Assessing the antinociceptive effect of nitrous oxide to tetanic stimulation in anaesthetised patients with new intra-operative nociception monitors: An observational study

BACKGROUND

Nitrous oxide (N2O) has been used since the 19th century for its analgesic, antinociceptive and anxiolytic effects during surgical procedures in awake and anaesthetised patients. However, quantification of noxious stimuli that occur under general anaesthesia is a constant challenge for anaesthesiologists, and recently two new indices have been developed to assess intra-operative nociception.

OBJECTIVE

The aim of this study was to quantify with new indices as well as with more classical clinical parameters the antinociceptive effect of N2O during general anaesthesia.

DESIGN

Prospective, open label, patient-blinded, observational and descriptive trial.

SETTING

Single-centre academic hospital.

PARTICIPANTS

Forty American Society of Anesthesiologists' physical status 1 to 3 patients undergoing general anaesthesia for elective abdominal surgery via laparotomy were recruited.

MAIN OUTCOMES MEASURES

Intra-operative pain was assessed using a standardised electrical stimulation of the forearm (tetanic stimulation at 70 mA, 100 Hz for 30 s), at 0, 25 and 50% inhaled N2O/O2. Heart rate (HR), mean arterial blood pressure, bispectral index, the analgesia nociception index and the nociception level (NOL) index were used to evaluate intra-operative nociception before and after each standardised tetanic stimulation.

RESULTS

There was a 16% reduction of the analgesia nociception index reaction, a 31% reduction of the NOL reaction and a 51% reduction of the HR reaction to a standardised electrical tetanic nociceptive stimulation during administration of 50% N2O. Administration of 50 or 25% inhaled N2O produced the same quality of antinociception based on HR and NOL index analyses. HR and the NOL index were the best parameters to identify the antinociceptive effect of intra-operatively administered N2O.

CONCLUSION

In anaesthetised patients, our study demonstrated clinically significant antinociceptive properties of N2O. Our results showed that low concentrations of N2O (25%) are as effective as higher concentrations (50%) to achieve a significant antinociceptive effect. These findings may help decrease negative effects of using higher concentrations of N2O, including its side effects and its environmental pollution.

TRIAL REGISTRATION

ClinicalTrials.gov registration identifier: NCT02701478.

Nociception level index: do intra-operative values allow the prediction of acute postoperative pain?

Nociception Level Index (NOL) guided analgesia has previously been found to correlate with noxious stimuli during surgery. It was aim of this study to investigate the relationship between intra-operative NOL and acute postoperative pain. After IRB approval, 80 patients scheduled for non-emergency surgery were enrolled. NOL data were recorded from induction of anaesthesia until the end of surgery. After admission to the postoperative acute care unit (PACU), pain scores (numeric rating scale [NRS, 0-10] were obtained 5-minutely for 15 min. NOL data of 74 patients were analyzed. Receiver-operating curve (ROC) analysis identified the NOL reaction to the knife to skin incision (median NOL within 60 s post knife to skin) vs. the median NOL during surgery vs. NOL at the end of surgery to have the highest correlation coefficient (ρ = 0.3; P = 0.01) as well as the highest area under the ROC curve (AUC 0.68; P = 0.01) for the prediction of moderate-severe pain in PACU. A NOL > 20 after skin incision predicted moderate-severe postoperative pain with the highest combined sensitivity (73%) and specificity (58%). A NOL < 10 after skin incision excluded moderate-severe pain in PACU with a negative predictive value of 83%. The NOL reaction to skin incision, but not NOL during surgery appears to allow the exclusion and, to a lesser degree the prediction of moderate-severe pain in PACU. The results may also strengthen the manufacturers recommendation of an intraoperative NOL range of 10-25.Australian New Zealand Clinical Trials Registry: ACTRN12619001596190.

Impact of chronic treatment by β1-adrenergic antagonists on Nociceptive-Level (NOL) index variation after a standardized noxious stimulus under general anesthesia: a cohort study

During the perioperative period, nociception control is certainly one of the anesthesiologist's main objectives when assuming care of a patient. There exists some literature demonstrating that the nociceptive stimuli experienced during surgery are responsible for peripheral and central sensitization phenomena, which can in turn lead to persistent postsurgical pain. An individualized approach to the evaluation and treatment of perioperative nociception is beneficial in order to avoid the sensitization phenomena that leads to prolonged postoperative pain and to minimize the consumption of opiates and their adverse effects. In terms of sensitivity, specificity, and positive/negative predictive values when compared to heart rate (HR) and mean arterial pressure (MAP), recent literature has shown that the NOL variation (ΔNOL) is the best index to distinguish noxious from non-noxious stimuli. Chronic treatment with β1-adrenergic antagonists may constitute a limitation to the use of the NOL index. β1-adrenergic antagonists induce a depressive action on the heart rate, which results in a limitation of its variability after a noxious stimulus. Since heart rate and heart rate variability are two parameters integrated into the NOL index, the validity of the NOL index in a population of patients receiving β1-adrenergic antagonists has not yet been determined. Our study sought to explore the NOL index, the BIS, and the heart rate variation in a group of patients under chronic treatment with β1-adrenergic antagonists submitted to standardized noxious stimulus under general anesthesia. We then compared those results to a control group of patients from our previous study (CJA group) that received no β1-adrenergic antagonist chronic treatment. The patients in this study were subjected to a standardized anesthetic protocol from induction up to 3 min after a standardized tetanic stimulus to the ulnar nerve at a frequency of 100 Hz and an amperage of 70 mA, for a duration of 30 s. Data were electronically recorded to obtain NOL, BIS, and heart rate values every 5 s for the duration of the protocol. The NOL maximal mean value reached after noxious stimulation was not different between our two cohorts (CJA: 30(14) versus BETANOL: 36(14) (p = 0.12)). There was no statistically significant difference between our cohorts in regards of the NOL AUC representing the variation of the NOL over a 180 s period (CJA: 595(356) versus BETANOL: 634(301) (p = 0.30)). However, a repeated measurement ANCOVA identified slight statistically significant differences between our cohorts in the peak of variation of the NOL index between 20 and 65 s after noxious stimulation, the NOL index of the cohort of beta-blocked patients being higher than the CJA patients. Moreover, the time to reach the maximum value was not different (CJA: 73(37) versus BETANOL: 63(41) (p = 0.35)). NOL sensitivity and specificity to detect a noxious stimulus under general anesthesia were similar in patients taking beta-blockers or not, and were better than those of heart rate and Bispectral index (AUC NOL 0.97, CI(0.92-1), versus AUC BIS 0.78, CI(0.64-0.89) and AUC HR 0.66, CI(0.5-0.8)). In conclusion, the NOL index is a reliable monitor to assess nociception in a population of patients under chronic beta-blocker therapy. Patients under such therapy achieve similar maximal NOL values over a 180 s period after a standardized noxious stimulus and the NOL variation over time, represented by the AUC is not significantly different from a cohort of non-beta-blocked patients. Whether the patient takes beta-blockers or not, sensitivity of the NOL index is greater than that seen for BIS index or heart rate to detect an experimental noxious stimulus under general anesthesia.

Nociception level-guided opioid administration in radical retropubic prostatectomy: a randomised controlled trial

BACKGROUND

This RCT investigated the effect of opioid titration by three different nociception monitoring devices or clinical signs during general anaesthesia.

METHODS

Ninety-six patients undergoing radical retropubic prostatectomy with propofol/remifentanil anaesthesia were randomised into one of four groups to receive remifentanil guided by one of three nociception monitoring devices (surgical pleth index [SPI], pupillary pain index [PPI], or nociception level [NOL]) or by clinical judgement (control). Intraoperative remifentanil requirement was the primary endpoint, whereas recovery parameters and stress hormone levels were secondary endpoints.

RESULTS

The mean [95% confidence interval {CI}] remifentanil administration rate differed between the groups: control 0.34 (0.32-0.37), SPI 0.46 (0.38-0.55), PPI 0.07 (0.06-0.08), and NOL 0.16 (0.12-0.21) μg kg^-1 min^-1(P<0.001). Intraoperative cessation of remifentanil administration occurred in different numbers (%) of patients: control 0 (0%), SPI 1 (4.3%), PPI 18 (75.0%), and NOL 11 (47.8%); P=0.002. The area under the curve analyses indicated differences in cumulative cortisol levels (mg L^-1 min^-1) amongst the groups: control 37.9 (33.3-43.1), SPI 38.6 (33.8-44.2), PPI 72.1 (63.1-82.3), and NOL 54.4 (47.6-62.1) (mean [95% CI]). Pairwise group comparison results were as follows: control vs SPI, P=0.830; control vs PPI, P<0.001; control vs NOL, P=0.001; SPI vs PPI, P<0.001; SPI vs NOL, P=0.002; and PPI vs NOL, P=0.009.

CONCLUSIONS

The nociception monitoring devices and clinical signs reflect the extent of nociception differently, leading to dissimilar doses of remifentanil. Very low remifentanil doses were associated with an increase and higher remifentanil doses were accompanied by a decrease in serum cortisol concentrations. Use of nociception monitoring devices for guiding intra-operative opioid dosing needs further validation.

CLINICAL TRIAL REGISTRATION

NCT03380949.

Comparison of Three Normalization Methods in Monitoring Analgesic Depth with Photoplethysmographic Diastolic Interval

The purpose of the present study was to investigate the ability of three different normalization methods, namely root mean square (RMS) value, mean value, and maximum which referred to pulse beat interval (PBI), based on photoplethysmographic diastolic interval (DI) in response to laryngeal mask airway (LMA) insertion under various remifentanil concentrations during general anesthesia. Sixty patients were randomly allocated to one of the four groups to receive a possible remifentanil effect-compartment target concentration (Ce_remi) of 0, 1, 3, or 5 ng/ml, and an effect-compartment target controlled infusion of propofol to maintain the state entropy (SE) at 40~60. Three normalized measures DI_RMS, DI_Mean, and DIPBI were compared with the DI values without normalization. Before LMA insertion, only DI showed a considerable correlation with remifentanil concentrations. DI_RMS and DI_Mean performed better than DI in discriminating 'insufficient' concentrations (0 and 1 ng/ml) from 'sufficient' concentrations (3 and 5 ng/ml). DIRMS was superior to all other variables in grading analgesic depth after nociceptive event occurred with PK value of 0.836. These results demonstrate that the normalization using RMS value, compared to using mean value and maximum, seems to provide a more effective approach for signal pre-processing.

Effect of Laryngeal Mask Airway Insertion on Parameters Derived From Catacrotic Phase of Photoplethysmography Under Different Concentrations of Remifentanil

BACKGROUND

Some parameters have been extracted from photoplethysmography (PPG) with a good relativity with nociception, but without encouraging results in qualifying the balance of nociception-anti-nociception (NAN). The features of PPG have not been thoroughly depicted and more prospective univariate parameters deserve to be explored. The aim of this study was to investigate the ability of parameters derived from catacrotic phase of PPG to grade the level of analgesia.

METHODS

45 patients with ASA I or II were randomized to receive a remifentanil effect-compartment target controlled infusion (Ceremi) of 0, 1, or 3 ng/ml, and a propofol effect-compartment target controlled infusion to maintain an acceptable level of hypnosis with state entropy (SE) at 40~60. Laryngeal mask airway (LMA) insertion was applied as a noxious stimulus. Five diastole-related parameters, namely diastolic interval (DI), diastolic slope (DS), the minimum slope during catacrotic phase (DSmin), the interval between DSmin and its nearest trough (DTI), and area difference ratio (ADR), were extracted. Pulse beat interval (PBI) was calculated as a reference parameter.

RESULTS

LMA insertion elicited a significant variation in all parameters except ADR during Ceremi of 0 and 1 ng/ml. Compared to PBI (prediction probability ([Formula: see text]) = 0.796), the parameters of DI, DS, and DTI presented a better consistence with the level of anti-nociceptive medication, with [Formula: see text] of 0.825, 0.822, and 0.822 respectively.

CONCLUSION

The features extracted from catacrotic phase of PPG, including DI, DS, and DTI, could provide a promising potential to qualify the balance of NAN.

Photoplethysmography-derived approximate entropy and sample entropy as measures of analgesia depth during propofol-remifentanil anesthesia

The ability to monitor the physiological effect of the analgesic agent is of interest in clinical practice. Nonstationary changes would appear in photoplethysmography (PPG) during the analgesics-driven transition to analgesia. The present work studied the properties of nonlinear methods including approximate entropy (ApEn) and sample entropy (SampEn) derived from PPG responding to a nociceptive stimulus under various opioid concentrations. Forty patients with ASA I or II were randomized to receive one of the four possible remifentanil effect-compartment target concentrations (Ce_remi) of 0, 1, 3, and 5 ng·ml^-1 and a propofol effect-compartment target-controlled infusion to maintain the state entropy (SE) at 50 ± 10. Laryngeal mask airway (LMA) insertion was applied as a standard noxious stimulation. To optimize the performance of ApEn and SampEn, different coefficients were carefully evaluated. The monotonicity of ApEn and SampEn changing from low Ce_remi to high Ce_remi was assessed with prediction probabilities (P_K). The result showed that low Ce_remi (0 and 1 ng·ml^-1) could be differentiated from high Ce_remi (3 and 5 ng·ml^-1) by ApEn and SampEn. Depending on the coefficient employed in algorithm: ApEn with k = 0.15 yielded the largest P_K value (0.875) whereas SampEn gained its largest P_K of 0.867 with k = 0.2. Thus, PPG-based ApEn and SampEn with appropriate k values have the potential to offer good quantification of analgesia depth under general anesthesia.

Dexmedetomidine Compared to Remifentanil Infusion as Adjuvant to Sevoflurane Anesthesia during Laparoscopic Sleeve Gastrectomy

Objectives

Evaluation of postoperative (PO) analgesic effects of intraoperative (IO) Dexmedetomidine (DEX) compared to remifentanil (REMI) infusions during sevoflurane anesthesia for laparoscopic gastric sleeve surgery.

Patients and Methods

One hundred and thirty-two patients with body mass index >35 kg.m^-2 and ASA Grades II or III were randomly divided into group R received REMI infusion (6-18 μg.kg^-1.h^-1) and Group D received DEX infusion (0.2-0.5 μg.kg^-1.h^-1) after tracheal intubation till before stoppage of inhalational anesthetic. Heart rate and mean arterial pressure were noninvasively monitored during and after surgery. Emergence time, time until postanesthetic care unit transfer, and total operating room (OR) time was recorded. PO shoulder-tip pain and wound pain scores were recorded and rescue analgesia was provided as 50 mg pethidine intramuscular injection. Occurrence of PO nausea and vomiting (PONV) and frequency of the need for antiemetic therapy were recorded. Primary study outcome was the ability of the study infusions to reduce consumption of PO pethidine down to one dose during 24-hr PO.

Results

IO use of REMI or DEX infusion allowed hemodynamic control to surgical stresses with nonsignificant difference between both infusions. REMI infusion insured significantly rapid recovery and short OR times but required larger volume of sevoflurane during surgery and proper PO follow-up for pain and PONV. DEX infusion significantly improved control of PO pain with a larger number of patient requested rescue analgesia only once, reduced the dose of PO analgesia, reduced the frequency of PONV, and the need for antiemetic therapy.

Conclusion

REMI or DEX infusion as IO adjuvant to general anesthesia is appropriate option to achieve hemodynamic control of surgical stresses and to improve perioperative outcomes. REMI infusion may be preferred for its induced rapid recovery and short OR time, whereas DEX infusion may be chosen for its improved control of PO pain and reduction of PO analgesia and frequency of PONV.

Pain monitor: reality or fantasy in ambulatory patients

PURPOSE OF REVIEW

In an unconscious patient, there can be significant challenges to monitoring nociception and proper dosing of analgesic medications. The traditional measures of intraoperative nociception have poor sensitivity and specificity with little predictive value in postoperative outcomes such as postoperative pain, opioid-induced side effects, length of stay or incidence of opioid use disorder. To date, several monitoring modalities are in development to establish objective measures of the balance between nociception and analgesia with the goal of guiding anesthesiologists and improve patient outcomes. In this review, some of the most promising monitoring modalities are discussed with the most recent findings.

RECENT FINDINGS

Multiple modalities are beginning to demonstrate utility compared with traditional care. Most, but not all, of these studies show decreased intraoperative opioid use and some show lower pain scores and opioid requirements in the postanesthesia care unit.

SUMMARY

Recent evidence points to promising efficacy for these monitoring modalities; however, this field is in its infancy. More investigation is required to demonstrate differences in outcome compared with traditional care, and these differences need to be of sufficient import to achieve widespread adoption.