Does nociception monitor-guided anesthesia affect opioid consumption? A systematic review of randomized controlled trials

Comparison of surgical pleth index-guided analgesia versus conventional analgesia technique in general anesthesia surgeries: A systematic review and meta-analysis

OBJECTIVE

The objective of this study is to investigate whether the use of surgical pleth index (SPI)-guided intraoperative analgesia can result in a reduction in opioid consumption, intraoperative circulatory fluctuations, and the incidence of postoperative adverse reactions when compared to conventional analgesia techniques.

METHODS

A comprehensive literature search was conducted in PubMed, Embase, Web of Science, and the Cochrane Library from the inception of these databases to November 2024. The objective was to identify randomized controlled trials that compared the use of SPI-guided analgesia with conventional analgesia practices in adult patients who underwent general anesthesia. The primary outcome was the intraoperative consumption of opioids, while intraoperative circulatory fluctuations, postoperative opioid consumption, pain scores, and adverse events served as secondary outcomes. Standardized mean differences (SMDs), weighted mean differences (WMDs) or pooled risk ratios (RRs) along with the corresponding 95 % confidence intervals (CIs) were employed for analysis.

RESULTS

Fourteen studies were included in our meta-analysis. The pooled results indicated no significant difference in intraoperative opioid consumption between the SPI-guided analgesia group and the control group (SMD = 0.16, 95 % CI: -0.15 to 0.47, p = 0.33). However, SPI-guided analgesia was found to reduce intraoperative propofol dosage (SMD = -0.31, 95 % CI: -0.54 to -0.08, p = 0.008), prevent intraoperative tachycardia (RR = 0.50, 95 % CI: 0.30 to 0.85, p = 0.011), and significantly shorten the eye-opening time (WMD = -1.89, 95 % CI: -2.47 to -1.31, p < 0.001). No statistically significant differences were observed in extubation time, postoperative nausea and vomiting, pain scores, or postoperative opioid consumption.

CONCLUSIONS

Compared to the conventional analgesia group, SPI-guided analgesia does not reduce intraoperative opioid consumption in adult patients undergoing general anesthesia.

TRIAL REGISTRATION

The protocol for this meta-analysis has been registered in PROSPERO (CRD42024611690).

Reliability of nociceptive monitors vs. standard practice during general anesthesia: a prospective observational study

BACKGROUND

Inadequate or excessive nociceptive control during general anesthesia can result in significant adverse outcomes. Using traditional clinical variables, such as heart rate, systolic blood pressure, and respiratory rate, to assess and manage nociceptive responses is often insufficient and could lead to overtreatment with both anesthetics and opioids. This study evaluated the feasibility and effectiveness of three nociception monitoring techniques Nociception Level Index (NOL), Skin Conductance Algesimeter (SCA) and heart rate monitoring in patients undergoing image-guided, minimally invasive abdominal interventions under general anesthesia.

METHOD

This prospective observational study collected data from 2022 to 2024. All patients were anesthetized according to the department's routine, and predetermined events were recorded. Two commercially available nociception monitors, the PMD-200 from Medasense (NOL) and PainSensor from MedStorm (SCA), were used, and their data were collected along with various hemodynamic parameters. The three nociception monitoring techniques were compared during predetermined events.

RESULT

A total of 49 patients were included in this study. NOL and SCA demonstrated higher responsiveness than HR for all events except for skin incision. The comparison of the values above and below the threshold for each nociceptive stimulus showed significance for all measurements using the SCA and NOL. However, using HR as a surrogate for nociception with a threshold of a 10% increase from baseline, the difference was significant only at skin incision. There was no variation in the peak values attributable to differences in patients' age. Weight was a significant predictor of the peak NOL values.

CONCLUSION

NOL and SCA demonstrated superior sensitivity and responsiveness to nociceptive stimuli compared to HR, effectively detecting significant changes in nociceptive thresholds across various stimuli, although responses during skin incision showed no such advantage.

TRIAL REGISTRATION

Clinical trial - NCT05218551.

Comparison of different monitors for measurement of nociception during general anaesthesia: a network meta-analysis of randomised controlled trials

BACKGROUND

To avoid underdosing or overdosing of analgesic medications, a variety of nociception monitors that use distinct techniques have been developed to quantify nociception during general anaesthesia. Although prior meta-analyses have examined the behaviour of nociception monitors vs standard care protocols, they did not include the potentially valuable data for monitor-to-monitor comparisons. In order to capture these data fully and compare the behaviour of these monitors, we conducted a systematic search and network meta-analysis.

METHODS

We performed a Bayesian network meta-analysis on data obtained from a systematic search within PubMed, Embase, Web of Science, Cochrane Library, and EmCare databases. The search was aimed to detect relevant RCTs on the use of nociception monitoring versus standard care or versus other nociception devices(s) during general anaesthesia in adult patients. The primary endpoint was intraoperative opioid consumption, for which we calculated the standardised mean difference (SMD) of morphine equivalents (MEs). Secondary endpoints included postoperative opioid consumption and nausea or vomiting, extubation time, postoperative pain score, and time to discharge readiness. The risk of bias was assessed using the revised Cochrane Risk of Bias tool for randomised trials (RoB 2.0).

RESULTS

Thirty-eight RCTs, including 3412 patients and studying five different types of nociception monitors, were included in the analyses: Nociception Level Monitor (NOL), Analgesia Nociception Index (ANI), Surgical Plethysmographic Index (SPI), Pupillometry (pupillary pain index [PPI] or pupil dilation reflex [PDR]), and the beat-by-beat cardiovascular depth of anaesthesia index (CARDEAN). Pupillometry showed a significant reduction in intraoperative opioid consumption compared with standard care (SMD -2.44 ME; 95% credible interval [CrI] -4.35 to -0.52), and compared with SPI (SMD -2.99 ME; 95% CrI -5.15 to -0.81). With respect to monitors other than pupillometry, no significant differences in opioid consumption were detected in comparison with standard care or other monitors. Pupillometry was associated with a longer time to discharge readiness from the PACU, whereas NOL was associated with shorter extubation times. No relevant differences in other secondary outcomes were found.

CONCLUSIONS

Apart from pupillometry, no monitors demonstrated a significant effect on intraoperative opioid consumption. Secondary outcomes indicate limited clinical benefit for patients when using these monitors.

Intraoperative pharmacologic opioid minimisation strategies and patient-centred outcomes after surgery: a scoping review

BACKGROUND

Postoperative patient-centred outcome measures are essential to capture the patient's experience after surgery. Although a large number of pharmacologic opioid minimisation strategies (i.e. opioid alternatives) are used for patients undergoing surgery, it remains unclear which strategies are most promising in terms of patient-centred outcome improvements. This scoping review had two main objectives: (1) to map and describe evidence from clinical trials assessing the patient-centred effectiveness of pharmacologic intraoperative opioid minimisation strategies in adult surgical patients, and (2) to identify promising pharmacologic opioid minimisation strategies.

METHODS

We searched MEDLINE, Embase, CENTRAL, Web of Science, and CINAHL databases from inception to February 2023. We included trials investigating the use of opioid minimisation strategies in adult surgical patients and reporting at least one patient-centred outcome. Study screening and data extraction were conducted independently by at least two reviewers.

RESULTS

Of 24,842 citations screened for eligibility, 2803 trials assessed the effectiveness of intraoperative opioid minimisation strategies. Of these, 457 trials (67,060 participants) met eligibility criteria, reporting at least one patient-centred outcome. In the 107 trials that included a patient-centred primary outcome, patient wellbeing was the most frequently used domain (55 trials). Based on aggregate findings, dexmedetomidine, systemic lidocaine, and COX-2 inhibitors were promising strategies, while paracetamol, ketamine, and gabapentinoids were less promising. Almost half of the trials (253 trials) did not report a protocol or registration number.

CONCLUSIONS

Researchers should prioritise and include patient-centred outcomes in the assessment of opioid minimisation strategy effectiveness. We identified three potentially promising pharmacologic intraoperative opioid minimisation strategies that should be further assessed through systematic reviews and multicentre trials. Findings from our scoping review may be influenced by selective outcome reporting bias.

STUDY REGISTRATION

OSF - https://osf.io/7kea3.

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.

The association of hemodynamic parameters and clinical demographic variables with acute postoperative pain in female oncological breast surgery patients: A retrospective cohort study

OBJECTIVES

Appropriate administration of intraoperative analgesia is an essential factor in care and reasonable recovery times. Inappropriate intraoperative analgesia puts the patient at risk of acute postoperative pain (APOP). The absence of an objective standard for intraoperative nociceptive monitoring complicates pain care. Heart rate (HR) and mean arterial blood pressure (MABP) have been suggested as useful parameters during general anesthesia for nociceptive monitoring. However, studies focusing on whether intraoperative heart rate variability (HRv) and mean arterial blood pressure variability (MABPv) during general anesthesia can accurately monitor nociception in patients have remained inconclusive. The current study aimed to (1) identify the association of intraoperative heart rate and blood pressure variability in patients undergoing low-risk surgery with the incidence of APOP in the immediate postoperative setting and (2) evaluate the associations of clinical demographic factors with the incidence of APOP.

METHODS

A retrospective observational cohort study was conducted. The outcome was moderate-to-severe APOP, defined as a numeric rating scale score of ≥ 4. HRv, MABPv, and potential confounders, such as age, body mass index, duration of surgery, smoking, depression, preoperative use of analgesics, and type of surgery, were used as independent variables.

RESULTS

Data from 764 female oncological breast surgery patients were analyzed. No statistically significant association of HRv and MABPv with APOP was found. Lower age was associated with higher odds of APOP (odds ratio [OR] 0.978, p = 0.001). Increased length of surgery (OR 1.013, p = 0.022) and a history of depression were associated with increased odds of APOP (OR 2.327, p = 0.010). The subtype of surgery was statistically significantly associated with APOP (p = 0.006).

CONCLUSIONS

Our results suggest that heart rate and blood pressure variability intraoperatively, in female patients undergoing low-risk surgery, are not associated with, and thus not predictive of, APOP in the immediate postoperative setting.

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.

Mechanisms inherent in acute-to-chronic pain after surgery - risk, diagnostic, predictive, and prognostic factors

PURPOSE OF REVIEW

Pain is an expected consequence of a surgery, but it is far from being well controlled. One major complication of acute pain is its risk of persistency beyond healing. This so-called chronic post-surgical pain (CPSP) is defined as new or increased pain due to surgery that lasts for at least 3 months after surgery. CPSP is frequent, underlies a complex bio-psycho-social process and constitutes an important socioeconomic challenge with significant impact on patients' quality of life. Its importance has been recognized by its inclusion in the eleventh version of the ICD (International Classification of Diseases).

RECENT FINDINGS

Evidence for most pharmacological and non-pharmacological interventions preventing CPSP is inconsistent. Identification of associated patient-related factors, such as psychosocial aspects, comorbidities, surgical factors, pain trajectories, or biomarkers may allow stratification and selection of treatment options based on underlying individual mechanisms. Consequently, the identification of patients at risk and implementation of individually tailored, preventive, multimodal treatment to reduce the risk of transition from acute to chronic pain is facilitated.

SUMMARY

This review will give an update on current knowledge on mechanism-based risk, prognostic and predictive factors for CPSP in adults, and preventive and therapeutic approaches, and how to use them for patient stratification in the future.

Prediction of blood pressure changes during surgical incision using the minimum evoked current of vascular stiffness value under sevoflurane anesthesia

Necessary and sufficient opioids should be administered for safe and stable anesthesia. However, opioid sensitivity varies among individuals. We previously reported that sympathetic responses to nociceptive stimuli under propofol anesthesia could be predicted by measuring the minimum evoked current of the vascular stiffness value (MECK). However, this result has only been proven under propofol anesthesia. We propose that MECK could be used under anesthesia with a volatile anesthetic. Thirty patients undergoing laparotomy with sevoflurane anesthesia received 0.7 minimum alveolar concentration (MAC) sevoflurane and intravenous remifentanil at a constant concentration of 2 ng/mL, followed by tetanic stimulation, to measure MECK. After tetanic stimulation, the same anesthetic conditions were maintained, and the rate of change in systolic blood pressure (ROCBP) during the skin incision was measured. The correlation coefficient between the MECK and ROCBP during skin incision under sevoflurane anesthesia was R =  - 0.735 (P < 0.01), similar to that in a previous study with propofol (R =  - 0.723). Thus, a high correlation was observed. The slope of the linear regression equation was - 0.27, similar to that obtained in the study on propofol (- 0.28). These results suggest that, as with propofol anesthesia, MECK can be used as a predictive index for ROCBP under 0.7 MAC sevoflurane anesthesia.Clinical trial registration: Registry, University hospital Medical Information Network; registration number, UMIN000047425; principal investigator's name, Noboru Saeki; date of registration, April 8, 2022.

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.

Parametric Modeling and Deep Learning for Enhancing Pain Assessment in Postanesthesia

OBJECTIVE

The problem of reliable and widely accepted measures of pain is still open. It follows the objective of this work as pain estimation through post-surgical trauma modeling and classification, to increase the needed reliability compared to measurements only.

METHODS

This article proposes (i) a recursive identification method to obtain the frequency response and parameterization using fractional-order impedance models (FOIM), and (ii) deep learning with convolutional neural networks (CNN) classification algorithms using time-frequency data and spectrograms. The skin impedance measurements were conducted on 12 patients throughout the postanesthesia care in a proof-of-concept clinical trial. Recursive least-squares system identification was performed using a genetic algorithm for initializing the parametric model. The online parameter estimates were compared to the self-reported level by the Numeric Rating Scale (NRS) for analysis and validation of the results. Alternatively, the inputs to CNNs were the spectrograms extracted from the time-frequency dataset, being pre-labeled in four intensities classes of pain during offline and online training with the NRS.

RESULTS

The tendency of nociception could be predicted by monitoring the changes in the FOIM parameters' values or by retraining online the network. Moreover, the tissue heterogeneity, assumed during nociception, could follow the NRS trends. The online predictions of retrained CNN have more specific trends to NRS than pain predicted by the offline population-trained CNN.

CONCLUSION

We propose tailored online identification and deep learning for artefact corrupted environment. The results indicate estimations with the potential to avoid over-dosing due to the objectivity of the information.

SIGNIFICANCE

Models and artificial intelligence (AI) allow objective and personalized nociception-antinociception prediction in the patient safety era for the design and evaluation of closed-loop analgesia controllers.

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.

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.

Intraoperative pharmacologic opioid minimisation strategies and patient-centred outcomes after surgery: a scoping review protocol

INTRODUCTION

For close to a century opioid administration has been a standard of care to complement anaesthesia during surgery. Considering the worldwide opioid epidemic, this practice is now being challenged and there is a growing use of systemic pharmacological opioid minimising strategies. Our aim is to conduct a scoping review that will examine clinical trials that have evaluated the impact of intraoperative opioid minimisation strategies on patient-centred outcomes and identify promising strategies.

METHODS AND ANALYSIS

Our scoping review will follow the framework developed by Arksey and O'Malley. We will search MEDLINE, Embase, CENTRAL, Web of Science and CINAHL from their inception approximately in March 2023. We will include randomised controlled trials, assessing the impact of systemic intraoperative pharmacologic opioid minimisation strategies on patient-centred outcomes. We define an opioid minimisation strategy as any non-opioid drug with antinociceptive properties administered during the intraoperative period. Patient-centred outcomes will be defined and classified based on the consensus definitions established by the Standardised Endpoints in Perioperative Medicine initiative (StEP-COMPAC group) and informed by knowledge users and patient partners. We will use a coproduction approach involving interested parties. Our multidisciplinary team includes knowledge users, patient partners, methodologists and knowledge user organisations. Knowledge users will provide input on methods, outcomes, clinical significance of findings, implementation and feasibility. Patient partners will participate in assessing the relevance of our design, methods and outcomes and help to facilitate evidence translation. We will provide a thorough description of available clinical trials, compare their reported patient-centred outcome measures with established recommendations and identify promising strategies.

ETHICS AND DISSEMINATION

Ethics approval is not required for the review. Our scoping review will inform future research including clinical trials and systematic reviews through identification of important intraoperative interventions. Results will be disseminated through a peer-reviewed publication, presentation at conferences and through our network of knowledge user collaborators.

REGISTRATION

Open Science Foundation (currently embargoed).

Relationship between ANI and qNOX and between MAC and qCON during outpatient laparoscopic cholecystectomy using remifentanil and desflurane without muscle relaxants: a prospective observational preliminary study

This study was designed to investigate qCON and qNOX variations during outpatient laparoscopic cholecystectomy using remifentanil and desflurane without muscle relaxants and compare these indices with ANI and MAC. Adult patients undergoing outpatient laparoscopic cholecystectomy were included in this prospective observational study. Maintenance of anesthesia was performed using remifentanil targeted to ANI 50-80 and desflurane targeted to MAC 0.8-1.2 without muscle relaxants. The ANI, qCON and qNOX and desflurane MAC values were collected at different time-points and analyzed using repeated measures ANOVA. The relationship between ANI and qNOX and between qCON and MAC were analyzed by linear regression. The ANI was comprised between 50 and 80 during maintenance of anesthesia. Higher values of qNOX and qCON were observed at induction and extubation than during all other time-points where they were comprised between 40 and 60. A poor but significant negative linear relationship (r² = 0.07, p < 0.001) was observed between ANI and qNOX. There also was a negative linear relationship between qCON and MAC (r² = 0.48, p < 0.001) and between qNOX and remifentanil infusion rate (r² = 0.13, p < 0.001). The linear mixed-effect regression correlation (r²) was 0.65 for ANI-qNOX and 0.96 for qCON-MAC. The qCON and qNOX monitoring seems informative during general anesthesia using desflurane and remifentanil without muscle relaxants in patients undergoing ambulatory laparoscopic cholecystectomy. While qCON correlated with MAC, the correlation of overall qCON and ANI was poor but significant. Additionally, the qNOX weakly correlated with the remifentanil infusion rate. This observational study suggests that the proposed ranges of 40-60 for both indexes may correspond to adequate levels of hypnosis and analgesia during general anesthesia, although this should be confirmed by further research.

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.

Intraoperative Assessment of Surgical Stress Response Using Nociception Monitor under General Anesthesia and Postoperative Complications: A Narrative Review

We present a narrative review focusing on the new role of nociception monitor in intraoperative anesthetic management. Higher invasiveness of surgery elicits a higher degree of surgical stress responses including neuroendocrine-metabolic and inflammatory-immune responses, which are associated with the occurrence of major postoperative complications. Conversely, anesthetic management mitigates these responses. Furthermore, improper attenuation of nociceptive input and related autonomic effects may induce increased stress response that may adversely influence outcome even in minimally invasive surgeries. The original role of nociception monitor, which is to assess a balance between nociception caused by surgical trauma and anti-nociception due to anesthesia, may allow an assessment of surgical stress response. The goal of this review is to inform healthcare professionals providing anesthetic management that nociception monitors may provide intraoperative data associated with surgical stress responses, and to inspire new research into the effects of nociception monitor-guided anesthesia on postoperative complications.

Does surgical plethysmographic index-guided analgesia affect opioid requirement and extubation time? A systematic review and meta-analysis

Purpose

This meta-analysis of all relevant clinical trials investigated surgical plethysmographic index (SPI)-guided analgesia’s efficacy under general anesthesia for perioperative opioid requirement and emergence time after anesthesia.

Methods

PubMed, Embase, Web of Science, and Cochrane Library were searched up to January 2022 to identify clinical trials comparing SPI-guided and conventional clinical practice for patients who underwent general anesthesia. With the random-effects model, we compared intraoperative opioid consumption, emergence time, postoperative pain, analgesia requirement, and incidence of postoperative nausea and vomiting (PONV).

Results

Thirteen randomized controlled trials (RCTs) (n = 1314) met our selection criteria. The overall pooled effect sizes of all RCTs indicated that SPI-guided analgesia could not significantly reduce opioid consumption during general anesthesia. SPI-guided analgesia accompanied with hypnosis monitoring could decrease intraoperative opioid consumption (standardized mean difference [SMD] − 0.31, 95% confidence interval [CI] − 0.63 to 0.00) more effectively than SPI without hypnosis monitoring (SMD 1.03, 95% CI 0.53–1.53), showing a significant difference (p < 0.001). SPI-guided analgesia could significantly shorten the emergence time, whether assessed by extubation time (SMD − 0.36, 95% CI − 0.70 to − 0.03, p < 0.05, I² = 67%) or eye-opening time (SMD − 0.40, 95% CI − 0.63 to − 0.18, p < 0.001, I² = 54%). SPI-guided analgesia did not affect the incidence of PONV, postoperative pain, and analgesia management.

Conclusion

SPI-guided analgesia under general anesthesia could enhance recovery after surgery without increasing the postoperative complication risk. However, it did not affect intraoperative opioid requirement. Notably, SPI-guided analgesia with hypnosis monitoring could effectively reduce intraoperative opioid requirement.

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.

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.

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.

General anesthetic techniques for enhanced recovery after surgery: Current controversies

General anesthesia technique can influence not only immediate postoperative outcomes, but also long-term outcomes beyond hospital stay (e.g., readmission after discharge from hospital). There is lack of evidence regarding superiority of total intravenous anesthesia over inhalation anesthesia with regards to postoperative outcomes even in high-risk population including cancer patients. Optimal balanced general anesthetic technique for enhance recovery after elective surgery in adults includes avoidance of routine use preoperative midazolam, avoidance of deep anesthesia, use of opioid-sparing approach, and minimization of neuromuscular blocking agents and appropriate reversal of residual paralysis. Given that the residual effects of drugs used during anesthesia can increase postoperative morbidity and delay recovery, it is prudent to use a minimal number of drug combinations, and the drugs used are shorter-acting and administered at the lowest possible dose. It is imperative that the discerning anesthesiologist consider whether each drug used is really necessary for accomplishing perioperative goals.

"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.

Monitoring nociception and awareness during palliative sedation: A systematic review

BACKGROUND

Providing unawareness and pain relief are core elements of palliative sedation. In addition to clinical scales, nociception and electroencephalogram-based depth of sedation monitoring are used to assess the level of consciousness and analgesia during sedation in intensive care units and during procedures.

AIM

To determine whether reported devices impact the outcomes of palliative sedation.

DESIGN

Systematic review and narrative synthesis of research published between January 2000 and December 2020.

DATA SOURCES

Embase, Google Scholar, PubMed, CENTRAL, and the Cochrane Library. All reports describing the use of any monitoring device to assess the level of consciousness or analgesia during palliative sedation were screened for inclusion. Data concerning safety and efficacy were extracted. Patient comfort was the primary outcome of interest. Articles reporting sedation but that did not meet guidelines of the European Association for Palliative Care were excluded.

RESULTS

Six reports of five studies were identified. Four of these were case series and two were case reports. Together, these six reports involved a total of 67 sedated adults. Methodological quality was assessed fair to good. Medication regimens were adjusted to bispectral index monitoring values in two studies, which found poor correlation between monitoring values and observational scores. In another study, high nociception index values, representing absence of pain, were used to detect opioid overdosing. Relatives and caregivers found the procedures feasible and acceptable.

[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.

Impact of opioid-free anaesthesia on postoperative nausea, vomiting and pain after gynaecological laparoscopy - A randomised controlled trial

STUDY OBJECTIVE

Opioid-free anaesthesia may enhance postoperative recovery by reducing opioid-related side effects such as nausea, hyperalgesia or tolerance. The objective was to investigate the impact of multimodal opioid-free general anaesthesia on postoperative nausea, vomiting, pain and morphine consumption compared to the traditional opioid-based approach.

DESIGN

This study was conducted as a prospective parallel-group randomised controlled trial.

SETTING

Perioperative Care.

PATIENTS

152 adult women undergoing elective inpatient gynaecological laparoscopy.

INTERVENTIONS

Patients were randomly assigned for opioid-free anaesthesia (Group OF) with dexmedetomidine, esketamine and sevoflurane or to have opioid-based anaesthesia (Group C) with sufentanil and sevoflurane.

MEASUREMENTS

Primary outcome was the occurrence of nausea within 24 h after surgery. Patients were assessed for the incidence and severity of PONV, postoperative pain and morphine consumption and recovery characteristics.

MAIN RESULTS

Patients in both groups had comparable clinical and surgical data. 69.7% of patients in the control group and 68.4% of patients in the opioid-free group met the primary endpoint (OR 1.06, 95% Confidence Interval (CI) (0.53; 2.12) p = 0.86). The incidence of clinically important PONV defined by the PONV impact scale was 8.1% (Group C) vs 10.5% (OF); p = 0.57). Antiemetic requirements, pain scores and morphine consumption were equivalent in both groups. Postoperative sedation was significantly increased in group OF (p < 0.001), and the median length of stay at the post-anaesthesia care unit was 69.0 min (46.5-113.0) vs 50.0 (35.3-77.0) minutes in the control group (p < 0.001).

CONCLUSIONS

Opioid-free multimodal general anaesthesia is feasible but did not decrease the incidence of PONV, or reduce pain scores and morphine consumption compared to an opioid-containing anaesthetic regimen.

Median Effective Dose of Lidocaine for the Prevention of Pain Caused by the Injection of Propofol Formulated with Medium- and Long-Chain Triglycerides Based on Lean Body Weight

OBJECTIVE

To determine the median effective dose (ED50) of prophylactic intravenous lidocaine for the prevention of propofol medium-chain triglyceride/long-chain triglyceride (MCT/LCT) emulsion injection pain.

DESIGN

Prospective trial, Dixon up-and-down sequential method.

SETTING

Operating room of a single hospital.

PATIENTS

Thirty patients aged 18-65 years with American Society of Anesthesiologists (ASA) status I or II who were scheduled for elective surgery under general anesthesia (GA) were included.

INTERVENTIONS

The initial dose of prophylactic lidocaine before propofol MCT/LCT emulsion injection was set at 0.5 mg/kg lean body weight (LBW). The lidocaine dose was adjusted according to the degree of patients' injection pain using the Dixon up-and-down sequential method.

MEASUREMENTS

The ED50 and 95% confidence intervals (CIs) of lidocaine were calculated using the Dixon-Massey formula. Vital signs and adverse effects were recorded. In the postanesthesia care unit (PACU), patients were asked if they recalled feeling any injection pain with visual analog scale (VAS) evaluation.

RESULTS

The ED50 of lidocaine for the prevention of propofol MCT/LCT emulsion injection pain was 0.306 mg/kg LBW (95% CI, 0.262-0.357 mg/kg LBW). No adverse reactions to lidocaine occurred. In the PACU, 90.9% of patients who experienced injection pain recalled this pain (VAS score, 2.8±1.8).

CONCLUSIONS

Prophylactic intravenous lidocaine (0.306 mg/kg LBW) effectively prevented propofol MCT/LCT emulsion injection pain in 50% of patients scheduled for elective surgery under GA with no adverse reaction occurring.

Perioperative Opioid Administration

Opioids form an important component of general anesthesia and perioperative analgesia. Discharge opioid prescriptions are identified as a contributor for persistent opioid use and diversion. In parallel, there is increased enthusiasm to advocate opioid-free strategies, which include a combination of known analgesics and adjuvants, many of which are in the form of continuous infusions. This article critically reviews perioperative opioid use, especially in view of opioid-sparing versus opioid-free strategies. The data indicate that opioid-free strategies, however noble in their cause, do not fully acknowledge the limitations and gaps within the existing evidence and clinical practice considerations. Moreover, they do not allow analgesic titration based on patient needs; are unclear about optimal components and their role in different surgical settings and perioperative phases; and do not serve to decrease the risk of persistent opioid use, thereby distracting us from optimizing pain and minimizing realistic long-term harms.

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.

Prediction of reactivity during tracheal intubation by pre-laryngoscopy tetanus-induced ANI variation

The ANI is a nociception monitor based on the high frequency parts of heart rate variability. Tracheal intubation may induce potentially deleterious hemodynamic disturbances or motor reactions if analgesia is inadequate. We investigated whether ANI modification generated by a standardized moderate short tetanic stimulation performed before laryngoscopy could predict hemodynamic or somatic reactions to subsequent intubation. We designed a prospective, interventional, monocentric, pilot study. Regional ethics board approved the study, written informed consent was obtained from each participant. Before laryngoscopy, under steady-state total intravenous anaesthesia with propofol and remifentanil, the ulnar nerve was stimulated with a 5 s tetanus (70 mA, 50 Hz). After another steady-state period, orotracheal intubation was performed. ANI variation, hemodynamic parameters and somatic reactions associated with tetanus and intubation were collected. To assess the predictability of hemodynamic or somatic reaction during laryngoscopy by tetanus-induced ANI variation, we calculated the area under the corresponding Receiver Operating Characteristic curve (AUCROC) and the 95% confidence intervals. Thirty-five patients were analyzed. ANI decreased by 21 ± 17 after tetanus. Regarding the ability of tetanus-induced ANI variation to predict hemodynamic or somatic reactions during subsequent intubation, the AUCROCs [95% CI] were 0.61 [0.41-0.81] and 0.52 [0.31-0.72] respectively. ANI varied after a short moderate tetanic stimulation performed before laryngoscopy but this variation was not predictive of a hemodynamic or somatic reaction during intubation.Trial registration NCT04354311, April 20th 2020, retrospectively registered.

Pupillometry pain index decreases intraoperative sufentanyl administration in cardiac surgery: a prospective randomized study

Pupillometry has proven effective for the monitoring of intraoperative analgesia in non-cardiac surgery. We performed a prospective randomized study to evaluate the impact of an analgesia-guided pupillometry algorithm on the consumption of sufentanyl during cardiac surgery. Fifty patients were included prior to surgery. General anesthesia was standardized with propofol and target-controlled infusions of sufentanyl. The standard group consisted of sufentanyl target infusion left to the discretion of the anesthesiologist. The intervention group consisted of sufentanyl target infusion based on the pupillary pain index. The primary outcome was the total intraoperative sufentanyl dose. The total dose of sufentanyl was lower in the intervention group than in the control group and (55.8 µg [39.7–95.2] vs 83.9 µg [64.1–107.0], p = 0.04). During the postoperative course, the cumulative doses of morphine (mg) were not significantly different between groups (23 mg [15–53] vs 24 mg [17–46]; p = 0.95). We found no significant differences in chronic pain at 3 months between the 2 groups (0 (0%) vs 2 (9.5%) p = 0.49). Overall, the algorithm based on the pupillometry pain index decreased the dose of sufentanyl infused during cardiac surgery.

Clinical trial number: NCT03864016.

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.

Reduced postoperative pain using Nociception Level-guided fentanyl dosing during sevoflurane anaesthesia: a randomised controlled trial

Background

The majority of postoperative patients report moderate to severe pain, possibly related to opioid underdosing or overdosing during surgery. Objective guidance of opioid dosing using the Nociception Level (NOL) index, a multiparameter artificial intelligence-driven index designed to monitor nociception during surgery, may lead to a more appropriate analgesic regimen, with effects beyond surgery. We tested whether NOL-guided opioid dosing during general anaesthesia results in less postoperative pain.

Methods

In this two-centre RCT, 50 patients undergoing abdominal surgery under fentanyl/sevoflurane anaesthesia were randomised to NOL-guided fentanyl dosing or standard care in which fentanyl dosing was based on haemodynamics. The primary endpoint of the study was postoperative pain assessed in the PACU.

Results

Median postoperative pain scores were 3.2 (inter-quartile range 1.3–4.3) and 4.8 (3.0–5.3) in NOL-guided and standard care groups, respectively (P=0.006). Postoperative morphine consumption (standard deviation) was 0.06 (0.07) mg kg⁻¹ (NOL-guided group) and 0.09 (0.09) mg kg⁻¹ (control group; P=0.204). During surgery, fentanyl dosing was not different between groups (NOL-guided group: 6.4 [4.2] μg kg⁻¹vs standard care: 6.0 [2.2] μg kg⁻¹, P=0.749), although the variation between patients was greater in the NOL-guided group (% coefficient of variation 66% in the NOL-guided group vs 37% in the standard care group).

Conclusions

Despite absence of differences in fentanyl and morphine consumption during and after surgery, a 1.6-point improvement in postoperative pain scores was observed in the NOL-guided group. We attribute this to NOL-driven rather than BP- and HR-driven fentanyl dosing during anaesthesia.

Clinical trial registration

www.trialregister.nl under identifier NL7845.

A prospective randomized controlled study of combined spinal-general anesthesia vs. general anesthesia for laparoscopic gynecological surgery: Opioid sparing properties

STUDY OBJECTIVE

We aimed to determine the magnitude of peri-operative opioid sparing effect when general anesthesia is combined with spinal analgesia for laparoscopic gynecological surgery.

DESIGN

A prospective randomized controlled study; a three-group trial with two comparisons (each intervention group to control).

SETTING

Operating room and postoperative recovery area.

PATIENTS

Patients aged between 18 and 65 years with American Society of Anesthesiologists physical status 1 or 2 who were scheduled for inpatient elective laparoscopic gynecological surgery with expected pneumoperitoneum duration of at least 20 min. Of 102 randomized patients, 99 completed the study.

INTERVENTIONS

Patients were randomized to general anesthesia alone (control group) or combined with very-low-dose (levobupivacaine 3.75 mg; sufentanil 2.5 μg) or low-dose (levobupivacaine 7.5 mg; sufentanil 2.5 μg) spinal analgesia.

MEASUREMENTS

Primary endpoints were perioperative opioid consumption and pain scores (11-point numeric rating scale) at 30 min, 1 h, 2 h, 4 h and 24 h post-surgery. Secondary endpoints were patient satisfaction with anesthetic care and participation in research, sevoflurane consumption and adverse effects.

MAIN RESULTS

Intra-operative sufentanil (median [95% CI]) consumption was 16.1 (10.5-22.6) μg/h in the control group versus 4.7 (3.2-9.2) μg/h in the very-low-dose and versus 2.9 (0.0-4.0) μg/h in the low-dose spinal analgesia groups (p < 0.001, for both comparisons). Median (95% CI) piritramide consumption at 24 h post-surgery was 7.5 (3-8) mg in the control group versus 5 (0-7.5) mg in the very-low dose spinal analgesia group (p = 0.182) and versus 2 (0-2.5) mg in the low-dose spinal analgesia group (p = 0.001). Postoperative pain scores were consistently <3 only in the low dose spinal analgesia group. Patient satisfaction with anesthetic care and participation in research was very high in all groups.

CONCLUSIONS

Low-dose spinal analgesia in combination with general anesthesia reduces peri-operative opioid consumption in laparoscopic gynecological surgery in immediate postoperative period.

Usefulness of ANI (analgesia nociception index) monitoring for outpatient saphenectomy surgery outcomes: an observational study

The Analgesia Nociception Index (ANI), derived from heart rate variability is a proposed guide to obtain an adequate control of the analgesic component during anaesthesia. This single blind observational study was designed to evaluate the relationship between intraoperative ANI values and length of stay in Day Surgery Units (DSU) in patients undergoing varicose vein intervention. 131 patients (ASA I-II) scheduled for elective varicose vein surgery were studied. A propofol closed-loop TCI was used to maintain a specific level of BIS. To control analgesia, a remifentanil TCI was used, modifying the target according to hemodynamic changes. Patients were included in the ANI > 50 sub-group or in the ANI < 50 sub-group depending on whether the ANI value was greater than 50 for at least 60% of the anaesthesia maintenance period (AMP) or not. The primary endpoint was the length of stay in DSU. Other variables studied were ANI values, duration of the AMP, remifentanil TCI target average, postoperative pain, rescue-analgesia needs and postoperative nausea and vomiting (PONV) were analysed. Statistical analysis of length of stay in DSU was performed with Mann-Whitney test. ANI > 50 sub-group showed a lower length of stay in the DSU [165 min (118-212) vs 186.5 min (119-254), p = 0.0425]. Discharge timing from DSU was statistically different among study sub-groups (p = 0.005). An adequate nociception level measured by ANI during varicose vein surgery might reduce the length of stay at DSU. Further studies are needed to assess the usefulness of ANI in other anaesthesia conditions.