Monitoring analgesia

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.

Genetic background and sex influence somatosensory sensitivity and oxycodone analgesia in the Hybrid Rat Diversity Panel

Opioid use disorder (OUD) is an ongoing public health concern in the United States, and relatively little work has addressed how genetic background contributes to OUD. Understanding the genetic contributions to oxycodone-induced analgesia could provide insight into the early stages of OUD development. Here, we present findings from a behavioral phenotyping protocol using several inbred strains from the Hybrid Rat Diversity Panel. Our behavioral protocol included a modified "up-down" von Frey procedure to measure inherent strain differences in the sensitivity to a mechanical stimulus on the hindpaw. We also performed the tail immersion assay, which measures the latency to display tail withdrawal in response to a hot water bath. Initial withdrawal thresholds were taken in drug-naïve animals to record baseline thermal sensitivity across the strains. Oxycodone-induced analgesia was measured after administration of oxycodone over the course of 2 h. Both mechanical and thermal sensitivity are shaped by genetic factors and display moderate heritability (h2 = 0.23-0.40). All strains displayed oxycodone-induced analgesia that peaked at 15-30 min and returned to baseline by 2 h. There were significant differences between the strains in the magnitude and duration of their analgesic response to oxycodone, although the heritability estimates were quite modest (h2 = 0.10-0.15). These data demonstrate that genetic background confers differences in mechanical sensitivity, thermal sensitivity, and oxycodone-induced analgesia.

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.

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.

Validation of three nociception indices to predict immediate postoperative pain before emergence from general anaesthesia: a prospective double-blind, observational study

BACKGROUND

Nociception monitoring devices are designed to estimate nociception during general anaesthesia. We evaluated the predictive accuracy of heart rate and three nociception indices to predict postoperative pain before emergence from general anaesthesia.

METHODS

In patients undergoing trauma or orthopaedic surgery, HR, Surgical Pleth Index® (SPI), Pupillary Pain Index® (PPI), and Nociception Level® (NOL) were simultaneously recorded for 5 min after the end of surgery but before return of consciousness. After admission to the recovery room, pain scores were assessed regularly for 2 h. HR, SPI, PPI, and NOL were analysed for their predictive accuracy of postoperative pain and opioid consumption with assessment of area under the receiver operating characteristic (AUC) curves, Spearman rank-correlation coefficient, and regression modelling.

RESULTS

Data for 60 subjects were analysed. The AUC (95% confidence interval [95% CI]) of the predictive accuracy for moderate-to-severe postoperative pain differed between nociception indices (HR=0.46 [0.29-0.64], P=0.671; SPI=0.46 [0.31-0.61], P=0.621; PPI=0.52 [0.36-0.68], P=0.770; NOL=0.66 [0.51-0.81], P=0.038). In a multivariable logistic regression model, a higher predictive accuracy was found for a multivariable predictor combining NOL values with ASA physical status and information about use of regional anaesthesia (AUC=0.83 [0.72-0.94], P<0.001).

CONCLUSIONS

Heart rate, Surgical Pleth Index, Pupillary Pain Index, and Nociception Level measured before emergence from general anaesthesia do not yet have sufficient diagnostic accuracy for prediction of postoperative pain.

CLINICAL TRIAL REGISTRATION

NCT05063227.

Wound infiltration or transversus abdominis plane block after laparoscopic radical prostatectomy: a randomized clinical trial

BACKGROUND

Regional anesthesia techniques are commonly used for postoperative pain management during laparoscopic surgery. Our aim was to compare the analgesic efficacy of pre-incisional subcutaneous wound infiltration (WI) with that of the transversus abdominis plane (TAP) block as part of a multimodal analgesic approach in laparoscopic radical prostatectomy.

METHODS

In this prospective, double-blinded, randomized controlled clinical trial, 60 patients were assigned to either TAP or WI group. The main outcome was acute postoperative pain control assessed using the mean numeric rating scale (NRS) at the 24 hours postoperatively. The secondary outcomes were opioid requirements, procedure-related complications, overall complications, and length of stay.

RESULTS

In this study, 60 patients were randomized: 30 to TAP group and 28 to WI (two were excluded due to conversion to open surgery). We found no significant difference in the median (1Q, 3Q) NRS scores during the 24 h postoperatively neither at rest (TAP, 0 (0, 1) vs. WI, 0 (0, 1), P = 0.812), nor during movement (TAP, 1 (0, 2) vs. WI, 1 (0, 2), P = 0.708). There were no statistical differences in the postoperative intravenous morphine requirements in the TAP vs. WI groups during the same period (1.7 ± 3.1 vs. 1.8 ± 4.1 mg; P = 0.910). Only one patient in the TAP group presented with postoperative nausea and vomiting.

CONCLUSIONS

Both pre-incisional subcutaneous WI and TAP blockade were associated with very low pain scores as part of a non-opioid multimodal analgesic regimen in laparoscopic radical prostatectomy. This study did not demonstrate the benefits of WI over TAP.

Evaluation of Nociception during Pediatric Surgery: A Topical Review

The association between intraoperative nociception and increased patient's morbidity is well established. However, hemodynamic parameters, such as heart rate and blood pressure, may result in an inadequate monitor of nociception during surgery. Over the last two decades, different devices have been marketed to "reliably" detect intraoperative nociception. Since the direct measure of nociception is impractical during surgery, these monitors measures nociception surrogates such as sympathetic and parasympathetic nervous systems responses (heart rate variability, pupillometry, skin conductance), electroencephalographic changes, and muscular reflex arc. Each monitor carries its own advantages and disadvantages. The manuscript aims to give an overview of the most up-to-date information available in the literature on current nociceptor monitors available in clinical practice, with particular focus on their applications in pediatrics.

Changes of the nociceptive flexion reflex threshold in patients undergoing cardiac surgery-a prospective clinical pilot study

Opioid dosage for general anaesthesia and sedation relies on surrogate parameters such as heartrate and blood pressure. This implies the risk of both under- and overdosing. A promising tool to provide target-oriented opioid dosing is measuring the nociceptive flexion reflex threshold (NFRT). The aim of this study was to investigate the individual trajectories and to determine this methods' clinical practicability in the perioperative setting of cardiac surgery. NFRT was measured preoperatively (twice as baseline), immediately after surgery and later in the general ward (primary outcomes). No intraoperative measurements were performed since neuromuscular blockade hinders NFRT assessment. Administered analgesics and pain scores were also recorded (secondary outcomes). Data were collected from August 2019 to March 2020. 264 patients scheduled for cardiac surgery were screened for eligibility. 55 patients were included, 30 rendered datasets for analysis. Thresholds after conclusion of surgery [T_ICU: median (IQR), 31.1 mA (21.5-50.0 mA)] were significantly higher than preoperatively [T_pre: 9.2 mA (5.4-13.4 mA); P < 0.001]. In 11 patients (36.7%), no immediate postoperative reflex response was elicited. Later, all reflexes returned, but thresholds remained significantly higher than preoperatively [T_post: 11.9 mA (9.2-16.6 mA); P = 0.043]. NFRT values after surgery were higher compared to baseline measurements. Subsequently they decreased but did not reach their baseline levels. There was no corresponding dose-dependency, suggesting multimodal effects on the nociceptive system. Unless measurements are not prevented by technical issues NFRT-assessment appears to be a future tool to target analgesics in patients not able to self-report pain. Trial registration Study registration: DRKS00021617. https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00021617 (registered retrospectively).

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.

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.

Comparison of the Newborn Infant Parasympathetic Evaluation (NIPE™) index to changes in heart rate to detect intraoperative nociceptive stimuli in healthy and critically ill children below 2 years: An observational study

BACKGROUND

The validity of current tools for intraoperative objective assessment of nociception/antinociception balance during anesthesia in young and very young surgery children is unknown.

AIM

Primary aim of the study was to test the hypothesis that the Newborn Infant Parasympathetic Evaluation (NIPE) index performs better in indicating nociception in anesthetized children below 2 years than changes in heart rate. Secondary aims were to evaluate associations between intraoperative changes in NIPE index values and postoperative pain and emergence delirium.

METHODS

Fifty-one children aged <2 years who underwent surgery were included in this prospective observational study. Patients were assigned to either group 1 (healthy children, n = 31) or group 2 (critically ill, ventilated premature infants and neonates, n = 20). The NIPE index and heart rate in response to three defined nociceptive stimuli were continuously recorded. Two different scales, Kindliche Unbehagens- und Schmerzskala (KUS) and Pediatric Anesthesia Emergence Delirium (PAED) as well as a Pain Questionnaire were used to assess postoperative pain levels and emergence delirium.

RESULTS

In total, 110 nociceptive events were evaluated. The analysis revealed a statistically significant association between a decrease in the NIPE index and all nociceptive stimuli, with a sensitivity of 92% and a specificity of 96%. The mean percentage decrease ranged from approx. 15%-30% and was highly statistically significant in both groups and for each of the nociceptive events except for venous puncture (p = .004). In contrast, no consistent change in heart rate was demonstrated. The KUS and PAED scale scores were significantly associated with the duration of anesthesia (p = .04), but not with intraoperative NIPE depression.

CONCLUSION

The NIPE index was reliable for assessing intraoperative nociception in children aged <2 years and was more reproducible for detecting specific nociceptive stimuli during general anesthesia than heart rate. An effect on postoperative outcome is still elusive.

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

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

[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.

Incidence of post-anesthetic respiratory complications in pediatrics. Observational, single-center study in Medellin, Colombia

Introduction: Post-anesthetic complications, particularly respiratory complications, continue to be a source of concern due to their high frequency, particularly in pediatrics. Objective: To describe the incidence of respiratory complications in the post-anesthesia care unit of an intermediate complexity center during a six-month period, and to explore the variables associated with major respiratory complications. Materials and Methods: Retrospective cohort study based on clinical record reviews. The records of the post-anesthesia care unit of an intermediate complexity pediatric institution located in Medellin, Colombia, were reviewed. This center uses a nursing-based care model that includes patient extubation in the post-anesthesia care unit. Results: The records of 1181 patients were analyzed. The cumulative incidences of major complications were bronchospasm 1.44%, laryngospasm 0.68% and respiratory depression 0.59%. There were no cases of cardiac arrest or acute pulmonary edema. A history of respiratory infection less than 15 days before the procedure, rhinitis and female sex were associated with major respiratory complications. Conclusions: A low frequency of respiratory complications was found during care provided by nursing staff trained in anesthesia recovery and pediatric airway in the post-anesthesia care unit.

Clinical Use of The Parasympathetic Tone Activity Index As a Measurement of Postoperative Analgaesia in Dogs Undergoing Ovariohysterectomy

Introduction

While the current tools to assess canine postoperative pain using physiological and behavioural parameters are reliable, an objective method such as the parasympathetic tone activity (PTA) index could improve postoperative care. The aim of the study was to determine the utility of the PTA index in assessing postoperative analgaesia.

Material and Methods

Thirty healthy bitches of different breeds were randomly allocated into three groups for analgaesic treatment: the paracetamol group (G_PARAC, n = 10) received 15 mg/kg b.w., the carprofen group (G_CARP, n = 10) 4 mg/kg b.w., and the meloxicam group (G_MELOX, n = 10) 0.2 mg/kg b.w. for 48 h after surgery. G_PARAC was medicated orally every 8 h, while G_CARP and G_MELOX were medicated intravenously every 24 h. The PTA index was used to measure the analgaesia–nociception balance 1 h before surgery (baseline), and at 1, 2, 4, 6, 8, 12, 16, 20, 24, 36, and 48 h after, at which times evaluation on the University of Melbourne Pain Scale (UMPS) was made.

Results

The baseline PTA index was 65 ± 8 for G_PARAC, 65 ± 7 for G_CARP, and 62 ± 5 for G_MELOX. Postoperatively, it was 65 ± 9 for G_PARAC, 63 ± 8 for G_CARP, and 65 ± 8 for G_MELOX. No statistically significant difference existed between baseline values or between values directly after treatments (P = 0.99 and P = 0.97, respectively). The PTA index showed a sensitivity of 40%, specificity of 98.46% and a negative predictive value of 99.07%.

Conclusion

Our findings suggest that the PTA index measures comfort and postoperative analgaesia objectively, since it showed a clinical relationship with the UMPS.

Comparison of remifentanil consumption in pupillometry-guided versus conventional administration in children: a randomized controlled trial

BACKGROUND

Remifentanil is a commonly used opioid analgesic during anesthesia in children. Objective measurement of pain is required for adequate dosing of remifentanil. We investigated whether pupillometry-guided remifentanil administration can reduce intraoperative consumption of remifentanil in children.

METHODS

We performed a single-blinded, prospective, randomized controlled trial from December 2018 through June 2019. Children who were 3-12 years of age and classified as having an American Society of Anesthesiologists physical status I-II and undergoing elective surgery under general anesthesia were included. Fifty-six fulfilled the inclusion criteria, and fifty-four completed the study. Participants were randomly assigned to either a pupillometry or conventional group. Patients in both groups received target-controlled infusion of remifentanil. In the pupillometry group, the adjustment of the remifentanil effect site concentration was determined by the pupillary diameter, whereas in the conventional group, the adjustment was based on the anesthesiologist's experience. Primary outcome was intraoperative remifentanil consumption, divided by patient weight and infusion time (ng kg^-1 min^-1).

RESULTS

Remifentanil consumption was reduced by 25% in the pupillometry group compared to the conventional group (116.7±56.0 ng kg^-1 min^-1 vs. 155.8±64.9 ng kg^-1 min^-1, respectively; P=0.02). There were no differences in intra- and postoperative blood pressure and heart rate. The incidences of postoperative desaturation or nausea/vomiting were not significantly different.

CONCLUSIONS

Pupillometry-guided remifentanil administration in children undergoing general anesthesia can reduce the intraoperative remifentanil consumption.

Comparison of bispectral index-guided and fixed-gas concentration techniques in desflurane and remifentanil anesthesia: A randomized controlled trial

Anesthesia with desflurane and remifentanil can be maintained with either fixed or titrated desflurane concentration. We hypothesized that the fixed-gas concentration (FG) method would reduce the number of anesthetic titrations without hypnotic and hemodynamic instability compared to the bispectral index (BIS)-guided (BG) method. Forty-eight patients were randomly allocated to the FG or BG groups. In the FG group, desflurane vaporizer setting was fixed at 1 age-corrected minimum alveolar concentration (MAC). In the BG group, desflurane was titrated to target a BIS level at 50. Remifentanil was titrated to maintain a systolic arterial pressure (SAP) of 120 mmHg in both groups. Our primary endpoint was the hypnotic stability measured by the wobble of BIS in performance analysis, and the secondary endpoints included the wobble of SAP, mean BIS value during surgery, and the number of anesthetic titrations. The BIS in the FG group showed significantly less wobble (3.9 ± 1.1% vs 5.5 ± 1.5%, P <0.001) but lower value (33 ± 6 vs 46 ± 7, P <0.001) than BG group. The wobble of SAP showed no difference between groups [median (inter-quartile range), 5.0 (4.1-7.5)% vs 5.2 (4.2-8.3)%, P = 0.557]. The numbers of anesthetic titrations in the FG group were significantly lower than the BG group (0 ± 0 vs 8 ± 5, P<0.001 for desflurane, 13 ± 13 vs 22 ± 17, P = 0.047 for remifentanil). Less wobble in BIS and reduced anesthetic titration without hemodynamic instability during the FG technique may be practical in balanced anesthesia using desflurane and remifentanil anesthesia. Clinical trial: This study was registered at ClinicalTrials.gov (NCT02283866).

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.

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

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

Prediction of Hemodynamic Reactivity by Electroencephalographically Derived Pain Threshold Index in Children Undergoing General Anesthesia: A Prospective Observational Study

Purpose

The pain threshold index (PTI) is a novel measure of nociception based on integrated electroencephalogram parameters during general anesthesia. The wavelet index (WLI) reflects the depth of sedation. This study aims to evaluate the ability of the PTI and WLI to predict hemodynamic reactivity after tracheal intubation and skin incision in pediatric patients.

Patients and methods

Pediatric patients (n=134) undergoing elective general surgery or urinary surgery were analyzed. Measurements at predefined time-points during tracheal intubation and skin incision included the PTI, WLI, heart rate (HR), and mean blood pressure (MBP). Receiver-operating characteristic (ROC) curves were computed to evaluate the predictive performance of the PTI and WLI in measuring hemodynamic reactivity (an increase of more than 20% in either MBP or HR) during general anesthesia.

Results

Of the 134 patients evaluated, positive reactivity of HR and MBP was observed in 95 (70.9%) and 61 (45.5%) patients induced by intubation, respectively, and 19 (14.2%) and 24 (17.9%) patients induced by skin incision, respectively. Using either HR or MBP reactivity induced by intubation as a dichotomous variable, the areas under the curves (AUCs) [95% CI] of PTI and WLI were 0.81[0.73–0.87] and 0.58[0.49–0.67] with the best cutoff values of 62 and 49. The AUCs [95% CI] of PTI and WLI were 0.82[0.75–0.88] and 0.61[0.52–0.69] after skin incision. The best cutoff values of PTI and WLI were 60 and 46, respectively.

Conclusion

The PTI can predict hemodynamic reactivity with the best cutoff values of 62 and 60 after tracheal intubation and skin incision in pediatric patients during general anesthesia. The WLI failed in predicting hemodynamic changes.

Effects of midazolam on cardiovascular responses and isoflurane requirement during elective ovariohysterectomy in dogs

Background

A prospective, randomized, placebo-controlled, blinded clinical study was conducted to determine whether a single dose of midazolam affects the cardiovascular response to surgical manipulation of the ovaries during elective ovariohysterectomy. Thirty-nine client-owned dogs undergoing elective ovariohysterectomy were recruited. After scoring cage demeanour, dogs were premedicated with acepromazine (0.03 mg kg^-1) and pethidine (3 mg kg^-1) intramuscularly into the quadriceps muscle and 20 min later sedation was scored. Anaesthesia was induced with propofol intravenously (IV) to effect. The study treatment (group M: midazolam (0.25 mg kg^-1); or group P: placebo (Hartmann’s solution) (0.125 ml kg^-1)) was administered IV before the intra-operative manipulation of the first ovary. Anaesthesia was maintained with isoflurane in oxygen. Morphine (0.3 mg kg^-1 IV) was administered prior to the start of surgery. The vaporizer setting was adjusted according to the depth of anaesthesia. If an end-tidal isoflurane concentration (FE’Iso) above 1.6% was required additional analgesia was provided with fentanyl (2 μg kg^-1). Dogs received meloxicam (0.2 mg kg^-1 IV) at the end of procedure. Heart rate, mean arterial blood pressure, respiratory rate and end-tidal partial pressure of carbon dioxide as well as FE’Iso were recorded and analysed.

Results

A statistical significant difference between groups was detected in FE’Iso, with group M requiring a significantly lower FE’Iso than group P (14.3%) after administration of midazolam. No differences between groups was shown for percentage change in heart rate and mean arterial blood pressure, or end-tidal carbon dioxide and requirement for mechanical ventilation, or rescue analgesia. There was no statistically significant difference in the incidence of complications in group M and P. Group M received significantly more succinylated gelatin solution pre-administration of midazolam than group P, but no differences in fluid administration post-administration of the study treatment (midazolam/placebo) were detected. No statistical significant difference was demonstrated for the use of anticholinergic agents, dobutamine or noradrenaline.

Conclusion

No significant effect on cardiovascular parameters could be observed with administration of midazolam, but a modest (14.3%) isoflurane-sparing effect was detected.

Automatic anesthesia depth staging using entropy measures and relative power of electroencephalogram frequency bands

Many of the surgeries performed under general anesthesia are aided by electroencephalogram (EEG) monitoring. With increased focus on detecting the anesthesia states of patients in the course of surgery, more attention has been paid to analyzing the power spectra and entropy measures of EEG signal during anesthesia. In this paper, by using the relative power of EEG frequency bands and the EEG entropy measures, a new method for detecting the depth of anesthesia states has been presented based on the least squares support vector machine (LS-SVM) classifiers. EEG signals were recorded from 20 patients before, during and after general anesthesia in the operating room at a sampling rate of 200 Hz. Then, 12 features were extracted from each EEG segment, 10 s in length, which are used for anesthesia state monitoring. No significant difference was observed (p > 0.05) between these features and the bispectral index (BIS), which is the commonly used measure of anesthetic effect. The used LS-SVM classifier based method is able to identify the anesthesia states with an accuracy of 80% with reference to the BIS index. Since the underlying equation of the utilized LS-SVM is linear, the computational time of the algorithm is not significant and therefore it can be used for online application in operation rooms.

Pain assessment by pupil dilation reflex in response to noxious stimulation in anaesthetized adults

BACKGROUND

In response to noxious stimulation, pupillary dilation reflex (PDR) occurs even in anaesthetized patients. The aim of the study was to evaluate the ability of pupillometry with an automated increasing stimulus intensity to monitor intraoperative opioid administration.

METHODS

Thirty-four patients undergoing elective surgery were enrolled. Induction by propofol anaesthesia was increased progressively until the sedation depth criteria (SeD) were attained. Subsequently, a first dynamic pupil measurement was performed by applying standardized nociceptive stimulation (SNS). A second PDR evaluation was performed when remifentanil reached a target effect-site concentration. Automated infrared pupillometry was used to determine PDR during nociceptive stimulations generating a unique pupillary pain index (PPI). Vital signs were measured.

RESULTS

After opioid administration, anaesthetized patients required a higher stimulation intensity (57.43 mA vs 32.29 mA, P < .0005). Pupil variation in response to the nociceptive stimulations was significantly reduced after opioid administration (8 mm vs 28 mm, P < .0005). The PPI score decreased after analgesic treatment (8 vs 2, P < .0005), corresponding to a 30% decrease. The elicitation of PDR by nociceptive stimulation was performed without changes in vital signs before (HR 76 vs 74/min, P = .09; SBP 123 vs 113 mm Hg, P = .001) and after opioid administration (HR 63 vs 62/min, P = .4; SBP 98.66 vs 93.77 mm Hg, P = .032).

CONCLUSIONS

During propofol anaesthesia, pupillometry with the possibility of low-intensity standardized noxious stimulation via PPI protocol can be used for PDR assessment in response to remifentanil administration.

Pupillary dilation reflex and pupillary pain index evaluation during general anaesthesia: a pilot study

Background

Pupillary response by pupillary dilatation reflex (PDR) is a robust reflex, even measurable during general anaesthesia. However, the ability of infrared pupillometry to detect PDR differences obtained by intraoperative opioid administration in anaesthesized patients remains largely unknown. We analyzed the performance of automated infrared pupillometry in detecting differences in pupillary dilatation reflex response by a inbuilt standardized nociceptive stimulation program in patients under general anesthesia with a standardized propofol/fentanyl scheme.

Methods

In this single center, interventional cohort study 38 patients (24-74 years) were enrolled. Patients were anesthetized with propofol until loss of consciousness. Two dynamic pupil measurements were performed in each patient (before opioid administration and after opioid steady state). Automated infrared pupillometry was used to determine PDR during nociceptive stimulations (10-60 mA) applied by a inbuilt pupillary pain index protocol (PPI) to the skin area innervated by the median nerve. Increasing stimulations by protocol are device specific and automatically performed until pupil dilation of > 13%. Pupil characteristics, blood pressure, heart rate values were collected.

Results

After opioid administration, patients needed a higher stimulation intensity (45.26 mA vs 30.79 mA, p = 0.00001). PPI score showed a reduction after analgesic treatment (5.21 vs 7.68, p = 0.000001), resulting in a 32.16% score reduction.

Conclusions

PDR via automated increased tetanic stimulation may reflect opioid effect under general anaesthesia. Further research is required to detect possible confounding factors such as medication interaction and optimization of individualized opioid dosage.

Pain assessment in the critically ill mechanically ventilated adult patients: Comparison between skin conductance algesimeter index and physiologic indicators

Background and Objectives:

Critically ill patients are unable to communicate effectively, so it is difficult to assess their pain and analgesic requirement. Skin conductance algesimeter (SCA) index is a device that primarily measures changes in skin conductance real time to assess pain.

Methods:

We planned this quantitative prospective observational study to assess pain in the critically ill mechanically ventilated patients in comparison to physiologic indicators such as blood pressure and heart rate. A repeated measures design was chosen, and a sample size of 180 was taken from 60 patients with sepsis, acute exacerbations of chronic obstructive pulmonary disease, community-acquired pneumonia, and postsurgical patients in the Intensive Care Unit (ICU). The two painful procedures chosen were tracheal suction and patient positioning. The data were collected at rest, at tracheal suctioning, 20 min later at positioning of the patient, and final reading 20 min later. Three testing periods, each including 4 assessments for a total of 12 pain assessments with sixty patients, were completed during each patient's ICU course. A total of six assessments were done with the patient at rest and three each with pain stimulus of tracheal suctioning and patient positioning.

Results:

There was a significant increase in both hemodynamic variables during painful procedures except for the heart rate during positioning. The correlation between the SCA index and Ramsay scale was negative and significant.

Conclusions:

This instrument might prove useful to measure pain in uncommunicative critically ill patients and to evaluate the effectiveness of analgesic treatment and adapt it.

Comparison of the effect of different infusion rates of sufentanil on surgical stress index during cranial pinning in children under general anaesthesia: a randomized controlled study

Background

Surgical stress index (SSI) is an established indicator for intraoperative nociception. Opioids are used to block stimulus of cranial pinning in neurosurgery. We investigated the effect of different infusion rates of sufentanil on SSI during cranial pinning in children under general anaesthesia.

Methods

Forty-nine children (2–12 years of age) underwent neurosurgery with pinning. The children were randomized into three groups based on the rate of sufentanil infusion: 0.2, 0.5, and 0.8 μg·kg⁻¹·hr.⁻¹. Continuous sufentanil infusion began following neuromuscular blockade administration, at a rate determined by each patient’s assigned treatment group. Following preparation for surgery, cranial pinning was performed. Systolic, diastolic, and mean blood pressures, along with heart rate and photoplethysmographic data, were continuously recorded from 1 min prior to cranial pinning through 5 min after cranial pinning, in 1-min intervals. SSI was calculated following the completion of surgery. Differences in measured outcomes over time among the three groups were evaluated using a generalized estimation equation. Differences in pinning outcomes in the same group were evaluated with Freidman test.

Results

We found no statistical differences in long-term SSI that were associated with different infusion rates of sufentanil during cranial pinning. Blood pressures in all groups increased for 2 min after cranial pinning, and then decreased; we found no statistical difference in long-term blood pressure values among the groups. Heart rate increased after pinning in the group that received a low-dose infusion of sufentanil.

Conclusions

Since SSI was intended to measure the blunting effects of sufentanil towards the noxious stimulus of cranial pinning, our results suggest that SSI might not be sufficiently sensitive to monitor the nociceptive response in children.

Trial registration

(KCT0000978, Jan-07, 2014).

Differences in heart rate variability may be related to the appearance of postoperative pain in patients undergoing breast cancer surgery

Background

Some reports have highlighted the relationship between heart rate variability (HRV) and the degree of postoperative pain experienced. This study retrospectively examined whether differences in heart rate variability may be related to the appearance of postoperative pain in patients undergoing breast cancer surgery.

Findings

We retrospectively analyzed 20 postoperative patients who had no pain immediately upon admission to the post-anesthesia care unit (PACU), divided into two groups: group A (n = 16) had no pain on admission to PACU, remaining pain free upon discharge (12 h after surgery); group B (n = 4) comprised patients with no pain on admission to PACU but who experienced increasing pain requiring intervention in PACU 1 h after surgery. HRV was measured immediately on admission to PACU and 2 h after surgery; this included variables of low-frequency power (LF), high-frequency power (HF), and LF/HF. There were significant differences in HF and LF/HF in group A compared with those in group B on admission to PACU (immediately after arrival): HF, group A, 35.4 ± 18.1; group B, 64.2 ± 9.5*; LF/HF group A, 2.7 ± 2.4; group B, 0.6 ± 0.2*, *p < 0.05). There was no significant difference in the Numerical rating scale (NRS) between the two groups immediately after admission to PACU. At 1 h after the surgery, NRS in Group B increased, and there were significant differences in NRS values between the two groups 1 h after surgery prior to the use of analgesic agents (NRS, group A, 1.0 ± 0.9; group B, 4.0 ± 1.4*, *p < 0.01). Patients in group A required no analgesic agents for at least 12 h after surgery.

Conclusions

Lower HF and higher LF/HF values immediately after arrival in PACU were observed in patients remaining pain free for 12 h after surgery compared to patients who experienced increasing postoperative pain 1 h after surgery. The data suggest that differences in HRV may be related to the appearance of postoperative pain.

Patient-Specific Classification of ICU Sedation Levels From Heart Rate Variability

OBJECTIVE

To develop a personalizable algorithm to discriminate between sedation levels in ICU patients based on heart rate variability.

DESIGN

Multicenter, pilot study.

SETTING

Several ICUs at Massachusetts General Hospital, Boston, MA.

PATIENTS

We gathered 21,912 hours of routine electrocardiogram recordings from a heterogenous group of 70 adult ICU patients. All patients included in the study were mechanically ventilated and were receiving sedatives.

MEASUREMENTS AND MAIN RESULTS

As "ground truth" for developing our method, we used Richmond Agitation Sedation Scale scores grouped into four levels denoted "comatose" (-5), "deeply sedated" (-4 to -3), "lightly sedated" (-2 to 0), and "agitated" (+1 to +4). We trained a support vector machine learning algorithm to calculate the probability of each sedation level from heart rate variability measures derived from the electrocardiogram. To estimate algorithm performance, we calculated leave-one-subject out cross-validated accuracy. The patient-independent version of the proposed system discriminated between the four sedation levels with an overall accuracy of 59%. Upon personalizing the system supplementing the training data with patient-specific calibration data, consisting of an individual's labeled heart rate variability epochs from the preceding 24 hours, accuracy improved to 67%. The personalized system discriminated between light- and deep-sedation states with an average accuracy of 75%.

CONCLUSIONS

With further refinement, the methodology reported herein could lead to a fully automated system for depth of sedation monitoring. By enabling monitoring to be continuous, such technology may help clinical staff to monitor sedation levels more effectively and to reduce complications related to over- and under sedation.

Comparison of Bispectral Index Monitoring With the Critical-Care Pain Observation Tool in the Pain Assessment of Intubated Adult Patients After Cardiac Surgery

Background

Detecting pain is crucial in sedated and mechanically ventilated patients, as they are unable to communicate verbally.

Objectives

This study aimed to compare Bispectral index (BIS) monitoring with the Critical-care pain observation tool (CPOT) and vital signs for pain assessment during painful procedures in intubated adult patients after cardiac surgery.

Materials and Methods

Seventy consecutive patients who underwent cardiac surgery (coronary artery bypass graft or valvular surgery) were enrolled in the study. Pain evaluations were performed early after the operation in the intubated and sedated patients by using BIS and CPOT, and also checking the vital signs. The pain assessments were done at three different times: 1) baseline (immediately before any painful procedure, including tracheal suctioning or changing the patient’s position), 2) during any painful procedure, and 3) five minutes after the procedure (recovery time).

Results

The mean values for CPOT, BIS, and mean arterial pressure (MAP) scores were significantly different at different times; they were increased during suctioning or changing position, and decreased five minutes after these procedures (CPOT: 3.98 ± 1.65 versus 1.31 ± 1.07, respectively (P ≤ 0.0001); BIS: 84.94 ± 10.52 versus 63.48 ± 12.17, respectively (P ≤ 0.0001); MAP: 92.88 ± 15.37 versus 89.77 ± 14.72, respectively (P = 0.003)). Change in heart rate (HR) was not significant over time (95.68 ± 16.78 versus 93.61 ± 16.56, respectively; P = 0.34). CPOT scores were significantly positively correlated with BIS at baseline, during painful stimulation, and at recovery time, but were not correlated with HR or MAP, except at baseline. BIS scores were significantly correlated with MAP but not with HR.

Conclusions

It appears that BIS monitoring can be used for pain assessment along with the CPOT tool in intubated patients, and it is much more sensitive than monitoring of hemodynamic changes. BIS monitoring can be used more efficiently in intubated patients under deep sedation in the ICU.

Heart rate variability and cardiac baroreflex inhibition-derived index predicts pain perception in burn patients

BACKGROUND

Dressing changes induce acute pain in burn patients. This pain is difficult to predict and may be therefore undertreated. Two different non-invasive electrophysiological indices from heart rate variability and baroreflex inhibition-derived indices, analgesia/nociception index (ANI) and cardiovascular depth of analgesia (CARDEAN), have been proposed to predict and better assess adequacy of anti-nociception. The aim of this study was to evaluate these techniques as early pain alert tools in conscious burnt patients during dressing changes' procedures.

METHODS

Twenty adult burnt patients undergoing scheduled wound treatment procedures were included in this prospective observational study. Pain intensity was assessed using a 0-10 numerical rating scale (NRS) and was compared with both ANI and CARDEAN, during the procedures. Non parametric rank sum test and linear discriminant analysis were used for evaluating potential differences of measured variables between periods with different pain intensities. Receiver-operating characteristic (ROC) curves were built to assess their performance to detect pain within following 15s.

RESULTS

The sensitivity and specificity of ANI to detect pain were 67% and 70% and those of CARDEAN were 77% and 80%, with area under the curve (AUC) values of 0.75 and 0.83, respectively. Their combination increased AUC to 0.87.

CONCLUSIONS

Both ANI and CARDEAN indices during wound treatment procedures seem to discriminate periods with and without pain within 15s, serving as a potential complementary tool for early optimized pain control.

Postoperative pain assessment in children: a pilot study of the usefulness of the analgesia nociception index

BACKGROUND

The ability to perform objective pain assessment is very important in paediatric patients. The goal of this study was to investigate the relationship between the analgesia nociception index (ANI), which is based on the heart rate variability, and objective measurements of pain intensity in young or cognitively impaired children, after surgical or imaging procedures (control group) under general anaesthesia.

METHODS

On arrival in the recovery room and subsequently at 5-10 min intervals, the level of pain was rated using the FLACC pain scale (0-10). The ANI values (0-100; 0 indicating the worst pain) were recorded simultaneously. The area under the receiver operating characteristic curve (AUC) and grey zone approach were used to evaluate the performance of the ANI to detect patients with FLACC >4. Instantaneous ANI values were compared with ANI values averaged over 256 s periods of time.

RESULTS

All children in the surgical group (n=32) developed moderate-to-severe pain (FLACC >4). Children in the control group (n=30) exhibited minimal pain. Instantaneous ANI values were lower in children of the surgical group than in the control group [52 (sd16) vs 69 (16), P<0.001]. The AUC for the 256 s ANI recording period [0.94 (95% confidence interval 0.85-0.99)] was significantly higher than for instantaneous ANI (P<0.05). When measured for a period of 256 s, an ANI cut-off value of 56 (grey zone [58-60]) was most predictive of a FLACC ≥4.

CONCLUSIONS

The ANI may provide an objective measurement of acute postoperative pain, which is correlated with that measured on a FLACC scale in young or cognitively impaired children.

Prediction of hemodynamic reactivity using dynamic variations of Analgesia/Nociception Index (∆ANI)

The Analgesia/Nociception Index (ANI), a 0-100 non-invasive index calculated from heart rate variability, reflects the analgesia/nociception balance during general anesthesia. We hypothesized that dynamic variations of ANI (∆ANI) would provide better performance than static values to predict hemodynamic reactivity during desflurane/remifentanil general anesthesia. One hundred and twenty-eight patients undergoing ear-nose-throat or lower limb orthopedic surgery were analyzed in this prospective observational study. The ANI, heart rate and systolic blood pressure were recorded before induction, at skin incision, during procedure and at emergence from general anesthesia. Changes in these variables were recorded after 1 min for ANI (ANI_1min) and 5 min for heart rate and systolic blood pressure. The dynamic variation of ANI at the different time points was defined as: ∆ANI = (ANI_1min - ANI)/([ANI + ANI_1min]/2). Receiver-operating characteristic (ROC) curves were built to evaluate the performance of ANI, ANI1 min and ∆ANI to predict hemodynamic reactivity (increase by more than 20 % in heart rate and/or systolic blood pressure within 5 min). For the prediction of hemodynamic reactivity, better performance was observed with ∆ANI (area under ROC curve (AUC ROC) = 0.90) in comparison to ANI (ROC AUC = 0.50) and ANI_1min (ROC AUC = 0.77). A ∆ANI threshold of -19 % predicts hemodynamic reactivity with 85 % [95 % CI 77-91] sensitivity and 85 % [95 % CI 81-89] specificity. Dynamic variations of ANI provide better performance than static values to predict hemodynamic reactivity during desflurane/remifentanil general anesthesia. These findings may be of interest for the individual adaptation of remifentanil doses guided by ∆ANI during general anesthesia, although this remains to be demonstrated.

Computational Depth of Anesthesia via Multiple Vital Signs Based on Artificial Neural Networks

This study evaluated the depth of anesthesia (DoA) index using artificial neural networks (ANN) which is performed as the modeling technique. Totally 63-patient data is addressed, for both modeling and testing of 17 and 46 patients, respectively. The empirical mode decomposition (EMD) is utilized to purify between the electroencephalography (EEG) signal and the noise. The filtered EEG signal is subsequently extracted to achieve a sample entropy index by every 5-second signal. Then, it is combined with other mean values of vital signs, that is, electromyography (EMG), heart rate (HR), pulse, systolic blood pressure (SBP), diastolic blood pressure (DBP), and signal quality index (SQI) to evaluate the DoA index as the input. The 5 doctor scores are averaged to obtain an output index. The mean absolute error (MAE) is utilized as the performance evaluation. 10-fold cross-validation is performed in order to generalize the model. The ANN model is compared with the bispectral index (BIS). The results show that the ANN is able to produce lower MAE than BIS. For the correlation coefficient, ANN also has higher value than BIS tested on the 46-patient testing data. Sensitivity analysis and cross-validation method are applied in advance. The results state that EMG has the most effecting parameter, significantly.

[Monitoring of pain, nociception, and analgesia under general anesthesia: Relevance, current scientific status, and clinical practice]

BACKGROUND

To avoid negative effects of painful stimuli under general anesthesia, an adequate analgesia is needed. Since both overdosing and underdosing of analgesics may lead to negative consequences, an optimal dosing is crucial, requiring a continuous monitoring of the balance between the ongoing nociception and the level of analgesia.

METHODS

This review describes current methods for the monitoring of nociception and analgesia as well as their inherent differences.

RESULTS

Monitors of nociception register organic responses that are triggered through painful stimuli and therefore allow the detection of phases of excessive nociception during inadequate analgesia. In contrast, monitors of analgesia register nociception-specific organic responses that are triggered through test stimuli and allow a preemptive adaption of the level of analgesia, before a painful clinical stimulus is applied, but require the application of test stimuli. Preliminary proof-of-concept studies were able to demonstrate the potential of the here described methods; however, an effect on the clinical outcome of patients has not yet been shown for either of the two types of monitoring.

CONCLUSIONS

For the routine application of monitors of nociception and analgesia in daily clinical practice, large clinical studies are necessary, proving a positive outcome effect. Without reliable parameters for nociception and analgesia it was hitherto impossible to perform such studies. The progress made in recent years generates optimism that in the not too distant future the currently available methods to monitor nociception and analgesia might improve to a level of reliability to allow them to be used to investigate the clinical outcome relevance of nociception and analgesia.

Reliability of the surgical Pleth index for assessment of postoperative pain: a pilot study

BACKGROUND

Postoperative pain control is essential and may have a beneficial effect on postoperative outcome and morbidity. Analgesia quality is controlled using tools such as a Numerical Rating Scale (NRS). These tools require cooperation and often fail in the presence of reduced awareness. The Surgical Pleth index (SPI) has been introduced as a monitoring tool for intraoperative pain under general anaesthesia.

OBJECTIVE

We investigated the correlation between SPI and pain intensity, analgesic consumption and fitness for discharge in the postanaesthesia care unit.

DESIGN

An observational study.

SETTING

The central postanaesthesia care unit of our tertiary care hospital.

PATIENTS

Written informed consent was obtained from 100 patients scheduled for elective surgery under general anaesthesia. Patients below the age of 18 years and those with an abnormal cardiac rhythm were excluded from the study.

INTERVENTION

Patients were interviewed every 10 min for 2 h.

MAIN OUTCOME MEASURES

Pain intensity measured by NRS, discomfort and Aldrete and Post-Anaesthetic Discharge Scoring System (PADSS) scores were noted. SPI and total dose of opioids administered were recorded.

RESULTS

A total of 1300 pain measurements were recorded; 482 (37%) reflected no or mild pain (NRS 0 to 3), 532 (41%) moderate pain (NRS 4 to 6) and 286 (22%) severe pain (NRS 7 to 10). Both NRS (r = 0.62, P < 0.001) and SPI (r = 0.38, P < 0.001) correlated significantly with total opioid consumption. SPI showed a moderate correlation with NRS (r = 0.49, P < 0.001). Receiver operating characteristic analysis showed moderate sensitivity and specificity for discrimination between low and moderate pain (NRS ≤3) (sensitivity 67%, specificity 69% for SPI ≤45), and between moderate and severe pain (NRS >6) (sensitivity 72%, specificity 72% for SPI ≥57). SPI and NRS showed weak negative correlations with Aldrete and PADSS scores.

CONCLUSION

Sensitivity and specificity of SPI to discriminate between low, moderate and severe pain levels was moderate. Both NRS and SPI correlated significantly with total opioid consumption.

Postoperative pain after laparoscopic cholecystectomy is not reduced by intraoperative analgesia guided by analgesia nociception index (ANI®) monitoring: a randomized clinical trial

BACKGROUND

Laparoscopic cholecystectomy frequently results in significant immediate postoperative pain. A new pain monitor, analgesic nociception index (ANI®), based on heart rate variability, has recently been approved for intraoperative nociception monitoring. We designed a single-blind, parallel-group, randomized control trial to test the hypothesis that protocol-driven intraoperative analgesia guided by ANI during laparoscopic cholecystectomy would improve titration of intraoperative analgesics leading to decreased postoperative pain.

METHODS

One hundred and twenty consecutive adult participants presenting for elective laparoscopic cholecystectomy were recruited. Participants were randomly allocated by sealed envelope to receive intraoperative morphine either guided by ANI via a protocol (intervention group) or guided by the anaesthetist with ANI concealed (control group). All participants received paracetamol, parecoxib, fentanyl at induction, and local anaesthetic to port sites. The primary endpoint was the presence of moderate/severe pain (visual analogue scale ≥50 mm) at any of the four time points in the first postoperative hour. Secondary endpoints included postoperative rescue morphine.

RESULTS

Sixty participants were randomized to each group, and all but one drop-out from the intervention group were analysed. The usage of ANI guidance did not result in a decrease in the rate of moderate/severe pain (50.8% vs 45.0%: difference of -5.8%, 95% confidence interval, -23.7% to 12.1%, P=0.58), or the use of postoperative rescue analgesia.

CONCLUSIONS

This randomized control trial of intraoperative ANI-guided morphine administration in elective laparoscopic cholecystectomy failed to show any advantage over the current standard of care, and demonstrated a high level of postoperative pain, despite the use of multimodal analgesia.

CLINICAL TRIAL REGISTRATION

ANZCTR Reference ACTRN12612000953831 (URL: http://www.anzctr.org.au/trial_view.aspx?ID=362949).