Variations of the analgesia nociception index during general anaesthesia for laparoscopic abdominal surgery

Evaluation of the Surgical Pleth Index (SPI) for the monitoring of the nociception-antinociception balance in dogs undergoing castration: A prospective clinical trial

The aim of this prospective clinical study was to evaluate the efficacy of the Surgical Pleth Index (SPI), a validated nociception monitor in human anaesthesia, in dogs. The technology uses a plethysmographic signal from a specific pulse oximetry probe to analyse pulse wave amplitudes and heartbeat intervals. Twenty-six healthy dogs anaesthetised for castration were included. SPI, invasive mean arterial pressure (MAP) and heart rate (HR) were continuously monitored. The occurrence or resolution of a haemodynamic reaction (HDR), defined as a > 20% increase in HR and/or MAP, was assessed at predefined times: cutaneous incision, testicles' exteriorization, cutaneous suture, and fentanyl administration. Following nociceptive events, the dogs presenting a HDR showed a significant 8% and 10% increase in SPI at 3 and 5 min respectively, whereas after fentanyl administration, a 13% and 16% significant decrease in SPI were noted. Receiver operating characteristic curves analysis indicated a moderate performance for the dynamic variations of SPI over 1 min to predict a HDR (AUC: 0.68, threshold value: +15%) or its resolution after fentanyl administration (AUC of 0.72, threshold value: -15%) within 3 min. The SPI varied according to perioperative nociceptive events and analgesic treatment; however, its performance to anticipate a HDR was limited with high specificity but low sensivity. Refinement of the algorithm to specifically accommodate for the canine species may be warranted. Further studies are required to evaluate the influence of other factors on the performance of this index.

Incorporation of "Artificial Intelligence" for Objective Pain Assessment: A Comprehensive Review

Pain is a significant health issue, and pain assessment is essential for proper diagnosis, follow-up, and effective management of pain. The conventional methods of pain assessment often suffer from subjectivity and variability. The main issue is to understand better how people experience pain. In recent years, artificial intelligence (AI) has been playing a growing role in improving clinical diagnosis and decision-making. The application of AI offers promising opportunities to improve the accuracy and efficiency of pain assessment. This review article provides an overview of the current state of AI in pain assessment and explores its potential for improving accuracy, efficiency, and personalized care. By examining the existing literature, research gaps, and future directions, this article aims to guide further advancements in the field of pain management. An online database search was conducted via multiple websites to identify the relevant articles. The inclusion criteria were English articles published between January 2014 and January 2024). Articles that were available as full text clinical trials, observational studies, review articles, systemic reviews, and meta-analyses were included in this review. The exclusion criteria were articles that were not in the English language, not available as free full text, those involving pediatric patients, case reports, and editorials. A total of (47) articles were included in this review. In conclusion, the application of AI in pain management could present promising solutions for pain assessment. AI can potentially increase the accuracy, precision, and efficiency of objective pain assessment.

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.

Analgesia nociception index is an indicator of laparoscopic trocar insertion-induced transient nociceptive stimuli

Objective

This study aimed to investigate whether analgesia nociception index (ANI) could be an indicator of perioperative pain during laparoscopic trocar insertion.

Methods

A total of 280 participants of anesthesia receiving laparoscopic surgery were enrolled. Anesthesia induction and maintenance were performed using the Marsh model for target propofol and the Minto model for remifentanil. Systolic blood pressure (SBP), heart rate (HR), and ANI were recorded at skin incision, the first-, second, the last-trocar insertion, and 5 min after the last trocar insertion.

Results

ANI was significantly different among the five groups in the last four time points (all P < 0.05). Pearson's correlation showed that ANI was negatively correlated with SBP (r = -0.114, P = 0.077) and HR (r = -0.247, P < 0.001). The area under the curve of ANI was positively correlated with those of SBP (r = 0.493, P < 0.001) and HR (r = -0.420, P < 0.001). Multivariate logistic regression showed that the ANI was an independent factor associated with intraoperative hemodynamic adverse events only at 5 min after the last trocar insertion.

Conclusions

Under general anesthesia, the change in ANI was consistent with changes in the balance between analgesia and nociceptive stimuli. The ANI can reflect the extent of transient pain but had a poor predictive performance for hemodynamic adverse events.

Predicting the optimal concentration of remifentanil for skull pin fixation with hemodynamic and analgesia nociception index monitoring

Inadequate antinociception during skull pin fixation may cause hemodynamic instability in intracranial surgery. The optimal concentration of remifentanil to provide adequate antinociception and stable hemodynamics during skull pin fixation under analgesia nociception index monitoring is unknown. This study is to assess the 90% effective concentration of remifentanil for skull pin fixation under hemodynamic and analgesia nociception index monitoring. Twenty-six patients were enrolled for intracranial surgery, anesthesia was induced and maintained under total intravenous anesthesia using target-controlled infusion for remifentanil and propofol under analgesia nociception index and bispectral index monitoring. Skull pin fixation was performed at different effect-site concentrations of remifentanil required for Dixon's up-and-down method with a step size of 0.5 ng/ml under bispectral index 40-60. Inadequate antinociception is defined when either ANI < 30 or > 20% in hemodynamic changes from baseline (e.g. heart rate > 100 beats/min, or blood pressure > 180/100 mmHg) and the effect-site concentration of remifentanil is considered as failure. It is considered success as ANI > 30 and < 20% hemodynamic changes from baseline simultaneously. Seven pairs of failure/success were used for probit analysis. The 90% effective concentration of remifentanil for skull pin fixation with adequate antinociception and hemodynamic stability was 4.7 ng/ml.

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.

Evaluation of the effectiveness of analgesia nociception index (ANI) predictability for surgical stimuli under personal analgesic sufficiency status (PASS) measured by pre-tetanus-induced ANI: a pilot study

The Analgesia Nociception Index (ANI) is a promising monitor to evaluate the balance of nociception and anti-nociception based on heart rate variability. This prospective, interventional, monocentric pilot study aimed to verify the effectiveness of the personal analgesic sufficiency status (PASS) measured by pre-tetanus-induced ANI variation for surgical stimuli. After Ethics approval and informed consent, participants were anesthetized with sevoflurane and increased effect-site concentrations of remifentanil step by step (2, 4, 6 ng ml-1). At each concentration, a standardized tetanic stimulus was applied (5 s, 60 mA, 50 Hz) with no other noxious stimuli presented. Through all the concentrations, defined the lowest concentration when ANI ≥ 50 as the PASS after tetanic stimuli. The surgical stimulus was conducted under at least 5-min of PASS. Thirty-two participants were analyzed. ANI, systolic blood pressure (SBP), and Heart rate (HR) except the Bispectral Index (BIS) were significantly changed at 2 ng ml-1 after tetanic stimuli, only ANI and SBP were significantly altered at 4 and 6 ng ml-1. ANI could predict inadequate analgesia status (an increase in SBP or HR of more than 20% from the baseline) at 2 and 4 ng ml-1 (P = 0.044, P = 0.049, respectively), but not at 6 ng ml-1. The PASS under pre-tetanus-induced ANI identification didn't meet the analgesic needs under surgical stimuli. Further investigations are required to provide a reliable prediction of individualized analgesia by objective nociception monitors.Trial registration NCT05063461.

[New Approaches in Perioperative Algesimetry]

The measurement of anaesthetic depth and muscle relaxation have been routine procedures during general anaesthesia for years. Quantification of intraoperative nociception, on the other hand, is still largely impossible. Various methods have been tested and commercialised for more than 10 years. However, a real breakthrough has not yet been achieved and the routine application of all methods available so far is not without problems. This article explains methodological similarities, but also points to specific aspects of various commercial solutions for perioperative algesimetry.

Pain Assessment Using the Analgesia Nociception Index (ANI) in Patients Undergoing General Anesthesia: A Systematic Review and Meta-Analysis

The analgesia nociception index (ANI) has emerged as a potential measurement for objective pain assessment during general anesthesia. This systematic review and meta-analysis aimed to evaluate the accuracy and effectiveness of ANI in assessing intra- and post-operative pain in patients undergoing general anesthesia. We conducted a comprehensive search of Ovid-MEDLINE, Ovid-EMBASE, Cochrane Central Register of Controlled Trials, Google Scholar, public clinical trial databases (ClinicalTrials and Clinical Research Information Service), and OpenSIGLE to identify relevant studies published prior to May 2023 and included studies that evaluated the accuracy and effectiveness of ANI for intra- or post-operative pain assessment during general anesthesia. Among the 962 studies identified, 30 met the eligibility criteria and were included in the systematic review, and 17 were included in the meta-analysis. For predicting intra-operative pain, pooled sensitivity, specificity, diagnostic odds ratio (DOR), and area under curve of ANI were 0.81 (95% confidence interval [CI] = 0.79-0.83; I2 = 68.2%), 0.93 (95% CI = 0.92-0.93; I2 = 99.8%), 2.32 (95% CI = 1.33-3.30; I2 = 61.7%), and 0.77 (95% CI = 0.76-0.78; I2 = 87.4%), respectively. ANI values and changes in intra-operative hemodynamic variables showed statistically significant correlations. For predicting post-operative pain, pooled sensitivity, specificity, and DOR of ANI were 0.90 (95% CI = 0.87-0.93; I2 = 58.7%), 0.51 (95% CI = 0.49-0.52; I2 = 99.9%), and 3.38 (95% CI = 2.87-3.88; I2 = 81.2%), respectively. ANI monitoring in patients undergoing surgery under general anesthesia is a valuable measurement for predicting intra- and post-operative pain. It reduces the use of intra-operative opioids and aids in pain management throughout the perioperative period.

The validity and applications of the analgesia nociception index: a narrative review

Pain refers to the subjective, unpleasant experience that is related to illness or injury. In contrast to pain, nociception refers to the physiological neural processing of noxious stimuli, such as intra-operative surgical stimuli. One novel device, the Analgesia Nociception Index (ANI), aims to objectively measure intra-operative nociception by analyzing the heart rate variability in patients undergoing surgery. Through this method of nociceptive monitoring, the ANI device aims to provide an objective, continuous evaluation of patient comfort levels and allow anesthesiologists to better manage surgical stress and patient analgesia, perhaps with even better efficacy than current practices used to assess nociception. Additionally, ANI may have clinical application in settings outside of the operating room, such as in the intensive care unit. In this narrative review, we compiled and summarized the findings of many studies that have investigated ANI's validity and applications in different clinical settings. Currently, the literature appears mostly supportive of ANI's ability to detect nociception in both surgical and non-surgical settings. However, the ability for ANI to provide clinical benefits, such as decreased intra-operative opioid use, post-operative opioid use, and post-operative pain compared to standard practices appear controversial. Because of the wide variety of methodology, clinical settings, patient populations, and limitations in these studies, more investigation of ANI is needed before any firm conclusions can be drawn on its clinical benefits.

Effect of analgesia nociception index monitor-based nociception control on perioperative stress responses during laparoscopic surgery in Trendelenburg position: a randomized controlled trial

Introduction

The analgesia nociception index (ANI) monitor is a nociception monitoring device based on heart rate variability. We aimed to determine the effect of ANI monitor-based intraoperative nociception control on the perioperative stress response during laparoscopic surgery in the Trendelenburg position.

Methods

Altogether, 72 female patients who underwent total laparoscopic hysterectomy were randomized to either the control or ANI group. Intraoperative nociception was controlled by remifentanil administration in a conventional manner (based on blood pressure and heart rate) in the control group and by ANI monitoring in the ANI group. Perioperative stress responses were estimated by measuring the levels of serum catecholamines and catabolic stress hormones at three timepoints: after loss of consciousness, at the end of surgery, and 1 h after the end of surgery.

Results

The serum cortisol level at the end of surgery was significantly higher in the ANI group than in the control group (p < 0.001), although more remifentanil was administered in the ANI group than in the control group (p < 0.001). Changes in the other estimators' levels were comparable between groups during the perioperative period. The hemodynamic profiles during surgery were also significantly different between the two groups. Phenylephrine use to treat hypotension was more common in the ANI group than in the control group (p = 0.005). However, postoperative clinical outcomes such as pain and nausea/vomiting did not differ between groups.

Conclusion

ANI monitor-based nociception control in laparoscopic surgery in the Trendelenburg position did not improve perioperative stress responses, intraoperative opioid consumption, or postoperative clinical outcomes.Clinical trial registration: ClinicalTrials.gov (NCT04343638).

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

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

Evaluation of the Averaged Parasympathetic Tone Activity and Its Dynamic Variation to Assess Intraoperative Nociception in Relation to Hemodynamic Changes in Dogs

This study aimed to determine the performance of the averaged parasympathetic tone activity (PTAm) and its dynamic variation (ΔPTA) to assess intraoperative nociception in relation to heart rate (HR) and direct mean arterial pressure (MAP) in dogs undergoing laparoscopic ovariectomy. This prospective, observational, clinical study included 32 bitches. The PTAm, HR, MAP, and bispectral index (BIS) were assessed before (pre-stimulus), as well as 1 min and 2 min after, four surgical stimuli: insufflation, introduction of trocars, and removal of the left and right ovaries. A two-way ANOVA was performed to compare PTAm, HR, MAP, and BIS data across surgical stimuli. A ≥20% drop in PTAm or a ≥20% increase in HR and/or MAP regarding the pre-stimulus values was considered a PTAm-drop and/or a hemodynamic response, respectively. The performance of PTAm pre-stimulus, PTAm 1 min, and ΔPTA in predicting the hemodynamic response was assessed by calculation of the area under the receiver operating characteristic (ROC) curve. At insufflation, PTAm decreased after 1 (p = 0.010) and 2 (p = 0.045)min, and ΔPTA was different (p = 0.005) between dogs that presented hemodynamic response and dogs that did not. At PTAm-drop, MAP increased after 1 min (p = 0.001) and 2 min (p = 0.001) with respect to pre-stimulus value, whereas HR and BIS did not change. ROC curves showed a threshold value of PTAm pre-stimulus ≤51 to detect hemodynamic response (sensitivity 69%, specificity 52%). The PTAm and ΔPTA only assessed intraoperative nociception during insufflation. The PTAm pre-stimulus association to the hemodynamic response in anaesthetized dogs showed poor sensitivity and no specificity.

Ability of the Analgesia Nociception Index variations to identify a response to a volume expansion of 250 mL of crystalloids in the operating room (REVANI): a prospective observational study

BACKGROUND

Analgesia Nociception Index (ANI) is a device based on analysis of the R-R interval and respiratory sinus arrhythmia to assess the balance between sympathetic and parasympathetic activity. The autonomic system is directly affected by load changes. Therefore, monitoring sympathetic tone and its change could theoretically allow tracking of load changes during volume expansion. The aim of the present study was to determine whether changes in ANI are able to track the increase in stroke volume caused by volume expansion (SV).

METHODS

This prospective observational study included mechanically ventilated patients undergoing neurosurgery and benefiting from SV monitoring. Exclusion criteria were cardiac dysfunction, arrhythmias, beta-blockade therapy, and dysautonomia. SV was optimized by fluid administration of 250 ml of crystalloid fluid. A positive fluid increase was defined as a SV increase of 10% or more from baseline. Changes in SV and medium ANI (ANIm) were recorded before and 4 to 5 min after volume expansion.

RESULTS

Sixty-nine patients had 104 fluid challenges (36 positive and 68 negative). Volume expansion resulted in a greater ANI increase in responders than in nonresponders. The change in ANIm > 5 predicted fluid responsiveness with a sensitivity of 68.4% (95% CI: 67.4% to 69.5%) and a specificity of 51.2% (95% CI: 50.1% to 52.3%). The area under the receiver operating characteristic curve was 0.546 (95% CI: 0.544 to 0.549) and appeared to be affected by remifentanil dose and baseline ANI.

CONCLUSION

Changes in ANIm induced by fluid challenge is not able to predict fluid responsiveness in mechanically ventilated patients undergoing neurosurgery.

TRIAL REGISTRATION

Clinical trial registration: NCT04223414.

Evaluation of nociception in unconscious critically ill patients using a multimodal approach

This prospective observational study included 80 adults (>18 years) patients admitted to the intensive care unit who were unconscious (Glasgow Coma Scale [GCS] score <9 with a motor response <5) and receiving mechanical ventilation. A tetanic stimulation was used to assess nociception; automated pupillometry (Algiscan, ID-MED, France) was used to compute the pupillary pain index score (PPI), with a PPI > 4 considered as nociception. Concomitantly, the number of skin conductance fluctuations (NSCF) per second, measured using a Skin Conductance Algesimeter (SCA, MEDSTORM Innovation AS, Norway; > 0.27 fluctuations/sec indicating nociception), and the instantaneous Analgesia Nociception Index (iANI, MDoloris Medical Systems, France; <50 indicating nociception) were collected. Tetanic stimulation resulted in a median pupillary dilation of 16 [6-25]% and a PPI of 5 [2-7]. According to the PPI assessment, 44 patients (55%) had nociception, whereas 23 (29%) and 18 (23%) showed nociception according to the algesimeter and iANI assessment, respectively. No significant changes in measured physiologic variables were observed after the tetanic stimulation. There were no correlations between PPI, post-stimulation iANI, and SCA-derived variables. There were no differences in PPI, iANI, and SCA variables in patients with low and normal baseline EEG power at baseline. PERSPECTIVES: Detection of nociception varies across different devices in unconscious critically ill patients. Further studies are required to understand which method to implement for analgesic administration in this patient population.

Analgesia nociception index and high frequency variability index: promising indicators of relative parasympathetic tone

At present, there is no objective and absolute measure of nociception, although various monitoring techniques have been developed. One such technique is the Analgesia Nociception Index (ANI), which is calculated from heart rate variability that reflects the relative parasympathetic tone. ANI is expressed on a non-unit scale of 0-100 (100 indicates maximal relative parasympathetic tone). Several studies indicated that ANI-guided anesthesia may help reduce intraoperative opioid use. The usefulness of ANI in the intensive care unit (ICU) and during surgery has also been reported. However, some limitations of ANI have also been reported; for example, ANI is affected by emotions and some drugs. In 2022, a high frequency variability index (HFVI), which was renamed from ANI and uses the same algorithm as ANI, was commercialized; therefore, ANI/HFVI are currently in the spotlight. Unlike ANI, HFVI can be displayed along with other biometric information on the Root® monitor. ANI/HFVI monitoring may affect the prognosis of not only patients in the perioperative period but those in ICU, those who receive home medical care, or outpatients. In this article, we present an updated review on ANI that has been published in the last decade, introduce HFVI, and discuss the outlooks of ANI/HFVI.

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.

Peri-operative multimodal monitoring: a real need or a luxury?

The present case of a patient with several co-morbidities undergoing complex vitrectomy under peribulbar block and sedation with Target Controlled Infusion (TCI of propofol and dexmedetomidine with EEG and Analgesia Nociception Index (ANI) monitoring illustrates the benefits of multimodal monitoring to differentiate the effect of hypnotic and antinociceptive drugs.It is highlighted the delta-alpha electroencephalographic pattern showing adequate sedation, the beta arousal pattern in the EEG concommitant to decrease in the ANI translating insufficient anti-nociception.

Evaluation of the Analgesia Nociception Index and videopupillometry to predict post-tonsillectomy morphine requirements in children: a single-centre, prospective interventional study

Background

Tonsil surgery causes significant and challenging postoperative pain. The Analgesia Nociception Index (ANI) and videopupillometry are two techniques of interest to monitor nociception in adults and may predict postoperative morphine requirements. We hypothesised that these techniques could predict the need for morphine after tonsillectomy in children. The main objective was to assess the prognostic significance of ANI and videopupillometry, measured at the end of surgery, on morphine consumption determined by a Face, Legs, Activity, Cry, Consolability (FLACC) scale score >3 in the Post Anesthesia Care Unit (PACU).

Methods

A single-centre, prospective, interventional study evaluating children between 2 and 7 yr old undergoing tonsil surgery was performed. ANI and videopupillometry with tetanic stimulation were measured under general anaesthesia 4 min after the end of the surgical procedure. Each child was evaluated every 10 min by a nurse using the FLACC scale in the PACU and blinded to the measurements performed in the operating theatre.

Results

Eighty-nine children were analysed and 39 (44%) received morphine in the PACU. Neither ANI values nor videopupillometry values were predictive of postoperative morphine consumption (areas under the receiver operating characteristic curve 0.54, 95% confidence interval [CI; 0.42-0.65], and P=0.57; and 0.52, 95% CI [0.41-0.63], and P=0.69, respectively). Neither ANI values nor videopupillometry values were correlated to the maximum FLACC scale score in the PACU with ρ=0.04 (P=0.71) and ρ=0.06 (P=0.57), respectively.

Conclusions

Neither ANI nor videopupillometry performed at the end of surgery can predict morphine consumption in the PACU in children undergoing tonsillectomy.

Comparison of Deep Learning Algorithms in Predicting Expert Assessments of Pain Scores during Surgical Operations Using Analgesia Nociception Index

There are many surgical operations performed daily in operation rooms worldwide. Adequate anesthesia is needed during an operation. Besides hypnosis, adequate analgesia is critical to prevent autonomic reactions. Clinical experience and vital signs are usually used to adjust the dosage of analgesics. Analgesia nociception index (ANI), which ranges from 0 to 100, is derived from heart rate variability (HRV) via electrocardiogram (ECG) signals, for pain evaluation in a non-invasive manner. It represents parasympathetic activity. In this study, we compared the performance of multilayer perceptron (MLP) and long short-term memory (LSTM) algorithms in predicting expert assessment of pain score (EAPS) based on patient's HRV during surgery. The objective of this study was to analyze how deep learning models differed from the medical doctors' predictions of EAPS. As the input and output features of the deep learning models, the opposites of ANI and EAPS were used. This study included 80 patients who underwent operations at National Taiwan University Hospital. Using MLP and LSTM, a holdout method was first applied to 60 training patients, 10 validation patients, and 10 testing patients. As compared to the LSTM model, which had a testing mean absolute error (MAE) of 2.633 ± 0.542, the MLP model had a testing MAE of 2.490 ± 0.522, with a more appropriate shape of its prediction curves. The model based on MLP was selected as the best. Using MLP, a seven-fold cross validation method was then applied. The first fold had the lowest testing MAE of 2.460 ± 0.634, while the overall MAE for the seven-fold cross validation method was 2.848 ± 0.308. In conclusion, HRV analysis using MLP algorithm had a good correlation with EAPS; therefore, it can play role as a continuous monitor to predict intraoperative pain levels, to assist physicians in adjusting analgesic agent dosage. Further studies may consider obtaining more input features, such as photoplethysmography (PPG) and other kinds of continuous variable, to improve the prediction performance.

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.

Effect of GOAL-Directed ANalgesia using ANI (Analgesia/Nociception Index) during general anesthesia on immediate postoperative pain and intraoperative hemodynamics in adult patients (GOALDAN study): a study protocol for randomized, controlled, multicenter trial

Background

Severe postoperative pain remains a major problem that is seen in 20 to 40% of patients. The Analgesia/Nociception Index (ANI) is a 0–100 index reflecting the relative parasympathetic activity allowing for intraoperative analgesia monitoring. We have previously shown that an ANI value < 50 immediately before extubation may predict the occurrence of immediate postoperative pain with good performance. We hypothesized that GOAL-Directed ANalgesia may provide reduced immediate postoperative pain and optimized intraoperative remifentanil administration (GOLDAN study).

Methods

The GOALDAN study is an international, multicenter, simple-blind, parallel, prospective, randomized, controlled, two-armed trial. Patients are randomly assigned in a 1:1 ratio in the control group or in the experimental group. Patients will be randomly allocated to either the intervention group (ANI) or the control group (standard care only). In the ANI group, the administration of remifentanil will be goal-directed targeting a 50–80 ANI range, with a prophylactic injection of morphine immediately after extubation if the case of ANI < 50. Our primary objective was to determine whether the prophylactic administration of morphine at the end of the procedure in patients at risk of immediate postoperative pain (ANI < 50 immediately before extubation) could reduce the incidence of the latter by 50% in the post-anesthetic care unit. Our secondary objective was to determine whether the intraoperative use of goal-directed analgesia with an ANI target of 50 to 80 could improve intraoperative hemodynamics and postoperative outcome.

Discussion

Because of the paucity of well-conducted trials, the authors believe that a randomized-controlled trial will improve the evidence for using analgesia monitoring during general anesthesia and strengthen current recommendations for intraoperative analgesia management.

Trial registration

ClinicalTrials.gov NCT03618082. Registered on 7 August 2018

Multimodal Analgesia with Extended-Release Dinalbuphine Sebacate for Perioperative Pain Management in Upper Extremity Trauma Surgery: A Retrospective Comparative Study

Introduction

Patients undergoing upper extremity fracture surgery (UEFS) commonly suffer from unbearable acute pain. Opioids remain the mainstay of moderate to severe pain alleviation, although there is a growing concern regarding the increasing trend in misuse and abuse. This study aimed to observe the safety and efficacy of dinalbuphine sebacate (DS), a novel extended-release analgesic, along with multimodal analgesia (MMA) for post-UEFS pain control.

Methods

We retrospectively reviewed the records of patients undergoing UEFS between August 2020 and January 2021. Eligible patients were included and divided into two groups, depending on the analgesic regimen. In the DS group, 150 mg DS was administered intramuscularly at least 12 h pre-operatively, while in the conventional analgesia (CA) group, 40 mg parecoxib was given within 3 h before surgery. Intraoperative fentanyl administration was guided by the Analgesia Nociception Index System in both groups. For breakthrough pain, fentanyl was used as rescue medicine in the postanaesthesia care unit while tramadol and parecoxib were administered in the ward.

Results

Forty-nine patients were allocated to the DS group and 60 patients were allocated to the CA group. In comparison with the CA group, the proportion of patients requiring opioids for breakthrough pain post-operatively was significantly lower in the DS group (fentanyl: 31% vs. 68%, p < 0.001; tramadol: 27% vs. 70%, p < 0.001). The DS group also consumed lower amounts of post-operative rescue opioids. Furthermore, both mean worst and least pain scores were significantly lower in the DS group from post-operative day (POD) 1 to POD 5. There was no significant difference in intraoperative consumption of fentanyl or incidence of adverse events.

Conclusion

This result suggests that extended-release DS is a suitable analgesic incorporated in MMA and a promising solution to the misuse and abuse of opioids.

Parasympathetic Tone Changes in Anesthetized Horses after Surgical Stimulation, and Morphine, Ketamine, and Dobutamine Administration

Simple Summary

A parasympathetic tone activity (PTA) monitor has been developed similar to the analgesia nociception index (ANI) used in human medicine to evaluate the changes in the autonomic nervous system based on heart rate variability. The autonomic nervous system acts unconsciously and regulates body functions (autonomic response). Examples of autonomic response are decreases of heart rate or/and blood pressure due to an increase of parasympathetic tone activity. It is important to know how stimuli and medication may affect the autonomic nervous system since they can modify heart rate and blood pressure. This study attempts to find how a surgical nociceptive stimulus, along with the administration of medication frequently used in horses, can affect mean parasympathetic tone activity (PTAm) (one of the values of the PTA monitor), heart rate and blood pressure in clinically anesthetized horses. Values of the PTAm, heart rate, and blood pressure were registered before and after surgical incision and after the administration of morphine, ketamine, and dobutamine at defined time points. No changes were found after the incision or the administration of morphine and dobutamine. It seems that only ketamine affects the autonomic nervous system by decreasing PTAm.

Abstract

Autonomic nervous system (ANS) activity can modify cardiovascular parameters in response to nociceptive stimuli or drugs in anesthetized animals. The aim of this study was to determine if a surgical nociceptive stimulus and morphine, ketamine, and dobutamine administration would modify ANS activity observed as a change in the mean parasympathetic tone activity (PTAm) in anesthetized horses. In 20 anesthetized horses, heart rate (HR), mean arterial pressure (MAP), and PTAm were monitored before and 1, 3, and 5 min after surgical incision, and before and 10 min after the administration of morphine (0.2 mg/kg IV). If nystagmus or spontaneous ventilation was observed, ketamine (0.5 mg/kg IV) was given, and the three variables were registered before and 3 and 5 min afterward. If MAP reached ≤62 mmHg, a dobutamine infusion was administered, and the three variables were recorded before and 5 min after starting/increasing the infusion (0.25 μg/kg/min IV every 5 min). The three variables were registered before and 1, 3, and 5 min after a PTAm decrease of ≥20%, HR increase of ≥10%, or MAP increase of ≥20%. The PTAm decreased 3 min after the administration of ketamine and 1 min after a PTA event. The surgical incision, dobutamine, and morphine did not modify PTAm. The absence of changes in ANS activity after the nociceptive stimulus and lack of correlation between PTAm and HR or MAP suggest that PTAm is a poor indicator of sympathetic activation under the study conditions. Ketamine seems to affect ANS activity by decreasing PTAm.

Comparison between Analgesia Nociception Index (ANI) and self-reported measures for diagnosing pain in conscious individuals: a systematic review and meta-analysis

The Analgesia Nociception Index (ANI), an objective measure of pain based on heart rate variability (HRV), has its usefulness in awake patients still unclear. This systematic review and meta-analysis aimed to assess ANI's accuracy compared to self-reported pain measures in conscious individuals undergoing medical procedures or painful stimuli. PubMed, Ovid, Web of Science, Scopus, Embase, and grey literature were searched until March 2021. Of the 832 identified citations, 16 studies complied with the eligibility criteria. A meta-analysis including nine studies demonstrated a weak negative correlation between ANI and NRS for pain assessment in individuals in the post-anesthetic recovery room (r = − 0.0984, 95% CI = − 0.397 to 0.220, I² = 95.82%), or in those submitted to electrical stimulus (r = − 0.089; 95% CI = − 0.390 to 0.228, I² = 0%). The evidence to use ANI in conscious individuals is weak compared to self-report measures of pain, yet ANI explains a part of self-report. Therefore, some individuals may be benefited from the use of ANI during procedures or in the immediate postoperative period.

Different perspectives for monitoring nociception during general anesthesia

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

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

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

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

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

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

Effect of Fentanyl Infusion on Heart Rate Variability and Anaesthetic Requirements in Isoflurane-Anaesthetized Horses

Controversy continues to surround the use of opioids in equine anaesthesia, with variable effects reported. This blinded clinical study aimed to investigate the influence of a low-dose fentanyl continuous rate infusion (CRI) on isoflurane requirements, parasympathetic tone activity (PTA), and anaesthetic parameters in horses during general anaesthesia. All of the twenty-two horses included in the research underwent a standard anaesthetic protocol. Eleven horses in the fentanyl group (Group F) received a loading dose of fentanyl at 6 µg/kg, followed by a CRI of 0.1 µg/kg/min during anaesthesia. A further 11 horses in the control group (Group C) received equivalent volumes of normal saline. Anaesthetic parameters and PTA index were recorded during anaesthesia. The achieved mean fentanyl plasma concentration was 6.2 ± 0.83 ng/mL. No statistically significant differences between groups were found in isoflurane requirements, MAP values, and mean dobutamine requirements. However, horses in Group F required a significantly lower dose of additional ketamine to maintain a sufficient depth of anaesthesia. Significantly higher PTA values were found in the fentanyl group. Further research is warranted to determine the limitations of PTA monitoring, and the influence of various anaesthetics on its values.

[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.

Performance of the Parasympathetic Tone Activity (PTA) index to predict changes in mean arterial pressure in anaesthetized horses with different health conditions

The parasympathetic tone activity (PTA) index is based on heart rate variability and has been developed recently in animals to assess their relative parasympathetic tone. This study aimed to evaluate PTA index in anaesthetized horses with different health conditions and the performance of PTA variations (∆PTA) to predict changes in mean arterial pressure (MAP). Thirty-nine client-horses were anaesthetized for elective or colic surgery and divided into "Elective" and "Colic" groups. During anaesthesia, dobutamine was administered as treatment of hypotension (MAP <60 mmHg). In both groups, no significant variation of PTA and MAP were detected immediately before and after cutaneous incision. The PTA index increased 5 min before each hypotension, whereas it decreased 1 min after dobutamine administration. Horses of the Colic group had lower PTA values than those of the Elective group, whereas MAP did not differ between groups. To predict a 10% decrease in MAP, ΔPTA performance was associated with: AUC ROC [95% CI] =0.80 [0.73 to 0.85] (p < 0.0001), with a sensitivity of 62.5% and a specificity of 94.6% for a threshold value of 25%. The PTA index in anaesthetized horses appears to be influenced by the health condition. The shift toward lower PTA values in colic horses may reflect a sympathetic predominance. An increase in PTA of >25% in 1 min showed an acceptable performance to predict MAP decrease of >10% within 5 min. Even though these results require further evaluation, this index may thus help to predict potential autonomic dysfunctions in sick animals.

The newborn infant parasympathetic evaluation in pediatric and neonatology: a literature review

PURPOSE

The Newborn Infant Parasympathetic Evaluation (NIPE) is a heart rate variability-based technology for assessing pain and comfort in neonates and infants under 2-years-old. This review aims to investigate the clinical utility of the NIPE.

METHODS

Two investigators screened Pubmed/Medline and Google Scholar for relevant studies, independently. One investigator extracted data, which were reviewed by a second investigator.

RESULTS

The NIPE was used during/after painful stimuli (6 studies), in the context of general anaesthesia (2 studies), and for comfort assessment (6 studies). A) Evaluation of procedural pain/distress: 2 studies reported that the mean-NIPE could be used for reliable monitoring of prolonged pain, and one study reported the association between instant-NIPE and pain after a stimulus but the instant-NIPE represents the NIPE average over 3 min. Two studies found no correlation between the NIPE and comfort behavior/pain scales, but they mainly differed in patients' gestational age and evaluation methodology. B) There are only 2 studies for the evaluation of nociception during surgery under general anaesthesia with contradictory results. C) Studies assessing neonates' comfort reported increased NIPE scores during skin-to-skin contact and during facilitated tucking associated with a human voice. No effect on NIPE scores of facilitated tucking during echocardiography was reported in preterm infants. One study reported significantly different NIPE scores with 2 surfactant therapy protocols. Overall, study populations were small and heterogeneous.

CONCLUSION

The results regarding NIPE's performances differ between studies. Given the limited number of studies and the heterogeneous outcomes, more studies are required to confirm the NIPE usefulness in the different clinical settings.

Comparative study of analgesia nociception index (ANI) vs. standard pharmacokinetic pattern for guiding intraoperative fentanyl administration among mastectomy patients

Background

The Analgesia Nociception Index (ANI) has been suggested as a non-invasive guide for analgesia. Our objective was to compare the efficacy of ANI vs. standard pharmacokinetic pattern for guiding intraoperative fentanyl administration.

Methods

This was a prospective, randomized, controlled study of adult female patients undergoing elective mastectomy under general anesthesia. The patients were randomized to the ANI-guided group receiving a loading dose of 75 μg of fentanyl followed by 25 μg when the ANI score was under 50. The Control group received the same loading dose followed by 25 μg every 30 min with additional doses when there were signs of inadequate analgesia (viz., tachycardia or hypertension).

Results

Sixty patients—30 in each group—were recruited. Although the actual mean ANI score was higher in the ANI-guided than in the Control group (mean difference 2.2; 95% CI: 0.3 to 4.0, P = 0.022), there was no difference in the primary outcome—i.e., intraoperative fentanyl consumption (mean difference − 4.2 μg; 95% CI: − 24.7 to 16.4, P = 0.686 and − 0.14 μg·kg^− 1·h^− 1; 95% CI: − 0.31 to 0.03, P = 0.105). No difference between groups was shown for either intraoperative blood pressure and heart rate, or for postoperative outcomes (i.e., pain scores, morphine consumption, or sedation scores) in the postanesthesia care unit.

Conclusions

Intraoperative fentanyl administration guided by ANI was equivalent to that guided by a modified pharmacologic pattern. In a surgical model of mastectomy, the ANI-guided intraoperative administration of fentanyl had no impact on clinical outcomes.

Trial registration

The study was registered with ClinicalTrials.gov (NCT03716453) on 21/10/2018.

Pain and Stress Detection Using Wearable Sensors and Devices-A Review

Pain is a subjective feeling; it is a sensation that every human being must have experienced all their life. Yet, its mechanism and the way to immune to it is still a question to be answered. This review presents the mechanism and correlation of pain and stress, their assessment and detection approach with medical devices and wearable sensors. Various physiological signals (i.e., heart activity, brain activity, muscle activity, electrodermal activity, respiratory, blood volume pulse, skin temperature) and behavioral signals are organized for wearables sensors detection. By reviewing the wearable sensors used in the healthcare domain, we hope to find a way for wearable healthcare-monitoring system to be applied on pain and stress detection. Since pain leads to multiple consequences or symptoms such as muscle tension and depression that are stress related, there is a chance to find a new approach for chronic pain detection using daily life sensors or devices. Then by integrating modern computing techniques, there is a chance to handle pain and stress management issue.

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.

Multidisciplinary management and outcome in pancreatic cancer patients treated with high-intensity focused ultrasound

Introduction: High-intensity focused ultrasound (HIFU) for pancreatic cancer is a growing therapeutic field which has been proven to reduce cancer pain and provide a local tumor control additionally to standard palliative care. However, less is known about the multidisciplinary and especially anesthesiological management of HIFU treatment although an interdisciplinary approach is crucial for treatment success.Material and methods: Anesthesiological and radiological records of 71 HIFU-treated pancreatic cancer patients were analyzed with regard to the following items: intervention time, sonication time, total energy, anesthesia time, peri-interventional medication, body temperature maximum and minimum, pain scores before and 1 day, 6 weeks and 3 months after intervention, peri-interventional complications. Effects on pain scores were estimated with a mixed panel data model. Bivariate associations between interventional variables were examined with the Spearman's correlation.Results: HIFU treatment was performed without major adverse events. Peri-procedural hyperthermia >37.5 °C occurred in 2 patients, hypothermia <35 °C in 8 cases. Interventional variables did not correlate significantly with pain scores, opioid dose, nor body temperature. 85.5% of patients experienced significant early pain relief within the first week after intervention. Post-interventional pain relief is associated with morphine equivalent opioid dose (p = 0.025) and treatment time (p = 0.040).Conclusion: While HIFU can be considered safe and effective treatment option, procedure-associated pain and temperature management represent challenges for the interdisciplinary HIFU intervention team. Especially short-term pain relief depends on the combined effort of the radiologist and anesthesiologist.

A beat-by-beat cardiovascular index, CARDEAN, to titrate opioid administration in the setting of orthopaedic surgery: a prospective randomized trial

To determine whether a beat-by-beat cardiovascular index (CARDEAN: cardiovascular depth of analgesia, Alpha-2 Ltd, Lyon, France) reduces the incidence of tachycardia in ASA I-III patients undergoing orthopaedic surgery. A total of 76 patients were prospectively randomized into (1) a control group or (2) the CARDEAN group, in which the nurse anaesthetist was blinded to CARDEAN application. In addition to conventional signs, an external observer instructed the nurse anaesthetist to administer sufentanil 0.1 µg kg^-1 when the CARDEAN crossed a threshold (≥ 60). The primary outcome was the incidence of tachycardia (> 120% of reference heart rate, HR). Non-invasive blood pressure (BP), electrocardiogram (ECG), O₂ saturation-photoplethysmography and the bispectral index (40 < BIS < 60) were monitored. HR and an estimation of beat-by-beat BP changes acquired from photoplethysmography and ECG were combined in an algorithm that detected hypertension followed by tachycardia (index scaled 0-100). Sufentanil 0.1 µg kg^-1 was administered when tachycardia, hypertension or movement ("conventional signs") was observed. Data for 66 patients (27 with known hypertension) were analysed. In the CARDEAN group, (a) the dose of sufentanil was higher (control: 0.46 µg kg^-1 100 min^-1, CARDEAN: 0.57 µg kg^-1 100 min^-1, p = 0.016), (b) the incidence rates of tachycardia and untoward events were lower (respectively: - 44%; control: 2.52 events 100 min^-1 [1.98-3.22]; CARDEAN: 1.42 [1.03-1.96], p = 0.005, hazard ratio: 0.56; movement, muscular contraction, or coughing: control: 0.74 events 100 min^-1 [0.47-1.16]; CARDEAN: 0.31 [0.15-0.62], p = 0.038), and (c) extubation occurred more often in the operating room (control: 76.5%, CARDEAN: 97%, p = 0.016). CARDEAN-titrated opioid administration was associated with a higher dose of sufentanil, a reduction in tachycardia and earlier emergence in ASA I-III patients undergoing major orthopaedic surgery.

Advances in infrared thermography: Surgical aspects, vascular changes, and pain monitoring in veterinary medicine

One of the main functions of infrared thermography (IRT) consists in detecting temperature changes in organisms caused by variations in surface blood circulation. IRT is a useful tool that has been used mainly as a diagnostic method for various stress-causing pathologies, though recent suggestions indicate that it can be used to assess the block quality of certain body regions. In the field of anaesthesiology, IRT has been applied to brachial and epidural blocks, while in algology, changes in surface blood circulation associated with sympathetic activity have been investigated. Thermography has also been employed to complement pain level scales based on the facial expressions of patients in critical condition, or after surgery. In addition, it has been used as a tool in research designed to evaluate different surgical procedures in human medicine, as in the case of surgical burrs for placing dental implants, where IRT helps assess the degree of heating associated with bone devascularisation, reduction in vascular perfusion as a consequence of stroke, and changes in the autonomous nervous system, or the degree of vascular changes in flaps applied to burn patients. In veterinary medicine, thermography has brought several benefits for animals in terms of evaluating lesions, diseases, and surgical procedures. The aim of this review is to evaluate how IRT can be used as a tool in surgical procedures, cases of vascular change, and pain monitoring in veterinary medicine with an emphasis on small animals.

High-Frequency Heart Rate Variability Index: A Prospective, Observational Trial Assessing Utility as a Marker for the Balance Between Analgesia and Nociception Under General Anesthesia

BACKGROUND

Maintaining a balance between nociception and analgesia perioperatively reduces morbidity and improves outcomes. Current intraoperative analgesic strategies are based on subjective and nonspecific parameters. The high-frequency heart rate (HR) variability index is purported to assess the balance between nociception and analgesia in patients under general anesthesia. This prospective observational study investigated whether intraoperative changes in the high-frequency HR variability index correlate with clinically relevant nociceptive stimulation and the addition of analgesics.

METHODS

Instantaneous and mean high-frequency HR variability indexes were measured continuously in 79 adult subjects undergoing general anesthesia for laparoscopic cholecystectomy. The indexes were compared just before and 2 minutes after direct laryngoscopy, orogastric tube placement, first skin incision, and abdominal insufflation and just before and 6 minutes after the administration of IV hydromorphone.

RESULTS

Data from 65 subjects were included in the final analysis. The instantaneous index decreased after skin incision ([SEM], 58.7 [2.0] vs 47.5 [2.0]; P < .001) and abdominal insufflation (54.0 [2.0] vs 46.3 [2.0]; P = .002). There was no change in the instantaneous index after laryngoscopy (47.2 [2.2] vs 40.3 [2.3]; P = .026) and orogastric tube placement (49.8 [2.3] vs 45.4 [2.0]; P = .109). The instantaneous index increased after hydromorphone administration (58.2 [1.9] vs 64.8 [1.8]; P = .003).

CONCLUSIONS

In adult subjects under general anesthesia for laparoscopic cholecystectomy, changes in the high-frequency HR variability index reflect alterations in the balance between nociception and analgesia. This index might be used intraoperatively to titrate analgesia for individual patients. Further testing is necessary to determine whether the intraoperative use of the index affects patient outcomes.

Machine learning based method for the evaluation of the Analgesia Nociception Index in the assessment of general anesthesia

Measuring the level of analgesia to adapt the opioids infusion during anesthesia to the real needs of the patient is still a challenge. This is a consequence of the absence of a specific measure capable of quantifying the nociception level of the patients. Unlike existing proposals, this paper aims to evaluate the suitability of the Analgesia Nociception Index (ANI) as a guidance variable to replicate the decisions made by the experts when a modification of the opioid infusion rate is required. To this end, different machine learning classifiers were trained with several sets of clinical features. Data for training were captured from 17 patients undergoing cholecystectomy surgery. Satisfactory results were obtained when including information about minimum values of ANI for predicting a change of dose. Specifically, a higher efficiency of the Support Vector Machine (SVM) classifier was observed compared with the situation in which the ANI index was not included: accuracy: 86.21% (83.62%-87.93%), precision: 86.11% (83.78%-88.57%), recall: 91.18% (88.24%-91.18%), specificity: 79.17% (75%-83.33%), AUC: 0.89 (0.87-0.90) and kappa index: 0.71 (0.66-0.75). The results of this research evidenced that including information about the minimum values of ANI together with the hemodynamic information outperformed the decisions made regarding only non-specific traditional signs such as heart rate and blood pressure. In addition, the analysis of the results showed that including the ANI monitor in the decision making process may anticipate a dose change to prevent hemodynamic events. Finally, the SVM was able to perform accurate predictions when making different decisions commonly observed in the clinical practice.

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.

Can postoperative pain be predicted? New parameter: analgesia nociception index

Background/aim

The Analgesia Nociception Index (ANI) is a new method of identifying nociception-analgesia balance. In this study, we investigate the correlation between the ANI and numeric rating scale (NRS) values immediately before and after extubation. The NRS values were recorded in the postanesthesia care unit, in a group of patients who underwent laparoscopic cholecystectomy, with the aim of evaluating the potential use of ANI values in the prediction of postoperative pain levels.

Materials and methods

The ANI and NRS values, heartbeat rate (HR), systolic and diastolic arterial pressure (SAP/DAP), and oxygen saturation (SpO2) values of the patients were recorded into three groups based on the initial NRS values recorded in the postanesthesia care unit (group I: NRS ≤ 3, group II: NRS 4–6, group III: NRS ≥ 7). Patients whose ANI values were lower than 47, considered as the pain threshold, and the groups to which these patients belonged were also recorded.

Results

Statistically significant increases were noted in HR, SAP, and DAP after extubation, while there was no significant change in ANI values. A weak correlation was identified between the ANI and NRS values of all patient groups.

Conclusion

We failed to identify a correlation between ANI and NRS values before and after extubation. Previous studies suggested that the ANI provides more valuable information in anesthetized patients, whereas our findings show that it is ineffective in the prediction of potential postoperative pain.

Effects of varying remifentanil concentrations on Analgesia Nociception Index® under propofol: an observational study

Analgesia Nociception Index monitor provides a measurement of the nociception and anti-nociception balance based on heart-rate variability. The aim was to assess the ability of Analgesia Nociception Index (ANI) to detect standard noxious stimulation during anesthesia at different opioid concentrations in comparison to hemodynamic and Bispectral Index parameters. Sixteen patients undergoing general anesthesia with propofol and remifentanil. Standardized tetanic electrical stimulation was applied without any other concurrent stimuli, while different effect site concentrations of remifentanil were increased step-by-step (0.5, 1.5, 3.0, 5 and 7 ng/ml). For each tetanic stimulus, values of the different variables 60 s before and 120 s following the stimulus were analyzed. ANI values decreased significantly 120 s after the stimulus when compared to the mean ANI 60 s before the stimulus (P < 0.01). At lower remifentanil concentrations (0.5 ng/ml), all variables except electromyogram from the Bispectral Index significantly changed after the stimulus but in the higher concentrations (5.0 and 7.0 ng/ml) there was not a significant change. The other variables did not change significantly after the noxious stimulation. ANI was the only variable that positively correlated with the different remifentanil concentrations (R = 0.959, P = 0.01). Our study showed that there was a significant decrease in Analgesia Nociception Index after a tetanic stimulation while hemodynamic and BIS parameters did not change, suggesting that the Analgesia Nociception Index may perform better than traditional hemodynamic parameters at reflecting noxious stimulation. Analgesia Nociception Index significantly changed at lower, but not at higher, remifentanil concentrations.

Autonomic Cardiac Reactivity to Painful Procedures Under Hypnosis in Pediatric Emergencies: A Feasibility Study

Pain sensation is characterized by abrupt changes in central nervous system activity producing autonomic reactivity. While clinical hypnosis has demonstrated its benefits for children in pain management, it is not clear whether hypnosis modulated autonomic pain response in children in clinical conditions. Here, we studied autonomic responses under hypnosis to sutures in pediatric emergencies. For that, 42 children (mean age: 6.5 years, range 1.5 to 13) were divided into two groups consecutively (hypnosis and control groups), according to their choice. Time-frequency analysis was applied on RR intervals (heart rate interbeat intervals, or RRI) to estimate parasympathetic reactivity based on high frequency power (HF) and the Analgesia Nociception Index (ANI®) and on sympathetic reactivity (low frequency power [LF]) and LF/HF ratio). We observed that RRI and LF/HF ratio varied according to suture and hypnosis (p < 0.05): RRI was higher and LF/HF ratio was lower during sutures in the hypnosis group in comparison to the control group whereas HF and ANI® increased only during hypnosis. To conclude, hypnosis in pediatric emergencies reduces sympathetic cardiac pain reactivity and could be a marker of pain relief under hypnosis, while parasympathetic activity seems to be a better marker of hypnosis.

Intraoperative nociception-antinociception monitors: A review from the veterinary perspective

OBJECTIVE

To review monitors currently available for the assessment of nociception-antinociception in veterinary medicine.

DATABASES USED

PubMed, Web of Science and Google Scholar. The results were initially filtered manually based on the title and the abstract.

CONCLUSIONS

The provision of adequate antinociception is difficult to achieve in veterinary anaesthesia. Currently, heart rate and arterial blood pressure are used to monitor the response to a noxious stimulus during anaesthesia, with minimum alveolar concentration-sparing effect and stress-related hormones used for this purpose in research studies. However, since none of these variables truly assess intraoperative nociception, several alternative monitoring devices have been developed for use in humans. These nociceptive-antinociceptive monitoring systems derive information from variables, such as electroencephalography, parasympathetic nervous system (PNS) response, sympathetic nervous system response and electromyography. Several of these monitoring systems have been investigated in veterinary medicine, although few have been used to assess intraoperative nociception in animals. There is controversy regarding their effectiveness and clinical use in animals. A nociceptive-antinociceptive monitoring system based on the PNS response has been developed for use in cats, dogs and horses. It uses the parasympathetic tone activity index, which is believed to detect inadequate intraoperative nociception-antinociception balance in veterinary anaesthesia. Nonetheless, there are limited published studies to date, and cardiovascular variables remain the gold standard. Consequently, further studies in this area are warranted.

Nociception monitoring tools using autonomic tone changes for intraoperative analgesic guidance in pediatric patients

Nociception monitoring devices using changes in autonomic nervous system activity have been developed in numerous ways. Although there have been few studies conducted on children, compared to the relatively higher number of studies on adults, most of the nociception monitors in children, as in adults, appear to be more useful than the standard clinical practice that uses hemodynamic parameters in the evaluation and treatment of intraoperative nociception (pain) during general anesthesia. Particularly, when monitoring the surgical pleth index (SPI) in anesthetized children, the application of a new target range of SPI values (≤ 40) to the SPI monitoring criteria seems to be necessary for providing a more proper intraoperative analgesia. The analgesia nociception index (ANI) shows promising results in anesthetized adults, and recently, positive results along with cardiorespiratory coherence have been reported in pediatric patients. Newborn infant parasympathetic evaluation (NIPE) could be useful for providing adequate analgesia in newborns, infants, and children under 2 years of age in anesthetized or awake states. In cases of skin conductance and pupillometry, further studies are needed. Understanding the pros, cons, and limitations of these nociception monitoring tools will provide more effective and safe intraoperative analgesia to pediatric patients undergoing general anesthesia, and it may also help to plan and conduct promising research on the use of perioperative nociception monitoring in pediatric patients in the future.

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.