Surgical stress index reflects surgical stress in gynaecological laparoscopic day-case surgery

Progress in the validation of nociception monitoring in guiding intraoperative analgesic therapy

PURPOSE OF REVIEW

This article summarizes the current level of validation for several nociception monitors using a categorized validation process to facilitate the comparison of performance.

RECENT FINDINGS

Nociception monitors improve the detection of a shift in the nociception and antinociception balance during anesthesia, guiding perioperative analgesic therapy. A clear overview and comparison of the validation process for these monitors is missing.

RESULTS

Within a 2-year time-frame, we identified validation studies for four monitors [analgesia nociception index (ANI), nociception level monitor (NOL), surgical pleth index (SPI), and pupillometry]. We categorized these studies in one out of six mandatory validation steps: developmental studies, clinical validation studies, pharmacological validation studies, clinical utility studies, outcome improvement studies and economical evaluation studies. The current level of validation for most monitors is mainly focused on the first three categories, whereas ANI, NOL, and SPI advanced most in the availability of clinical utility studies and provide confirmation of a clinical outcome improvement. Analysis of economical value for public health effects is not yet publicly available for the studied monitors.

SUMMARY

This review proposes a stepwise structure for validation of new monitoring technology, which facilitates comparison between the level of validation of different devices and identifies the need for future research questions.

Surgical pleth index monitoring in perioperative pain management: usefulness and limitations

Surgical pleth index (SPI) monitoring is a representative, objective nociception-monitoring device that measures nociception using photoplethysmographic signals. It is easy to apply to patients and the numerical calculation formula is intuitively easy to understand; therefore, its clinical interpretation is simple. Several studies have demonstrated its efficacy and utility. Compared with hemodynamic parameters, the SPI can detect the degree of nociception during surgery under general anesthesia with greater accuracy, and therefore can provide better guidance for the administration of various opioids, including remifentanil, fentanyl, and sufentanil. Indeed, SPI-guided analgesia is associated with lower intraoperative opioid consumption, faster patient recovery, and comparable or lower levels of postoperative pain and rates of adverse events compared with conventional analgesia. In addition, SPI monitoring allows for the degree of postoperative pain and analgesic requirements to be predicted through the SPI values immediately before patient arousal. However, because patient age, effective circulating volume, position, concomitant medication and anesthetic regimen and level of consciousness may be confounding factors in SPI monitoring, clinicians must be careful when interpreting SPI values. In addition, as SPI values can differ depending on anesthetic and analgesic regimens and the underlying disease, an awareness of the effects of these variables with an understanding of the advantages and disadvantages of SPI monitoring compared to other nociception monitoring devices is essential. Therefore, this review aimed to help clinicians perform optimal SPI-guided analgesia and to assist with the establishment of future research designs through clarifying current usefulness and limitations of SPI monitoring in perioperative pain management.

[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.

Adequacy of Anaesthesia for Nociception Detection during Vitreoretinal Surgery

Vitreoretinal surgery (VRS) is one of the most widely performed precise procedures in ophthalmic surgery; the majority of cases are carried out under regional anaesthesia (RA) only. However, in specific situations (such as when the patient fails to cooperate with the operator for various reasons), general anaesthesia (GA), alone or in combination with GA (combined general-regional anaesthesia, CGR), is the only safe way to perform VRS. While monitoring the efficacy of an intraoperative rescue opioid analgesia (IROA) during surgery (assessing the adequacy of anaesthesia (AoA)) may be challenging, the surgical pleth index (SPI) is a useful tool for detecting the reaction to noxious stimuli and allows for the rational titration of opioid analgesics (AO) during surgery. The current study investigated the influence of the SPI-based titration of fentanyl (FNT) in combination with various pre-emptive analgesia (PA) techniques on intraoperative pain perception during various stages of VRS performed under AoA. A total of 176 patients undergoing VRS under GA were enrolled in the study. They were randomly assigned to one of the five following study arms: Group GA (control group)-patients who received general anaesthesia alone; Group PBB-GA with preprocedural peribulbar block (with 0.5% bupivacaine and 2% lidocaine); Group T-GA with preventive, topical 2% proparacaine; Group M-GA with a preprocedural intravenous infusion of 1.0 g of metamizole; and Group P-GA with a preprocedural intravenous infusion of 1.0 g of paracetamol. The whole procedure was divided in four stages: Stage 1 and 2-preoperative assessment, PA administration, and the induction of GA; Stage 3-intraoperative observation; Stage 4-postoperative observation. the SPI values were monitored during all stages. The occurrence of nociception (expressed as ∆SPI >15) during various manipulations in the surgical field was observed, as were cumulative doses of rescue analgesia, depending on the PA administered. During the course of VRS, rescue FNT doses varied depending on the stage of surgery and the group investigated. The majority of patients, regardless of their group allocation, needed complementary analgesia during trocar insertion, with Group GA patients requiring the highest doses. Likewise, the highest cumulative doses of IROA were noted during endophotocoagulation in Group GA. Preventive PBB and topical anaesthesia were proven to be most efficient in blunting the response to speculum installation, while topical anaesthesia and paracetamol infusion were shown to be more efficient analgesics during endophotocoagulation than other types used PA. In the performed study, none of the PA techniques used were superior to GA with FNT dosing under the SPI with respect to providing efficient analgesia throughout the whole surgery; there was a necessity to administer a rescue OA dose in both the control and investigated groups.

Photoplethysmogram Analysis and Applications: An Integrative Review

Beyond its use in a clinical environment, photoplethysmogram (PPG) is increasingly used for measuring the physiological state of an individual in daily life. This review aims to examine existing research on photoplethysmogram concerning its generation mechanisms, measurement principles, clinical applications, noise definition, pre-processing techniques, feature detection techniques, and post-processing techniques for photoplethysmogram processing, especially from an engineering point of view. We performed an extensive search with the PubMed, Google Scholar, Institute of Electrical and Electronics Engineers (IEEE), ScienceDirect, and Web of Science databases. Exclusion conditions did not include the year of publication, but articles not published in English were excluded. Based on 118 articles, we identified four main topics of enabling PPG: (A) PPG waveform, (B) PPG features and clinical applications including basic features based on the original PPG waveform, combined features of PPG, and derivative features of PPG, (C) PPG noise including motion artifact baseline wandering and hypoperfusion, and (D) PPG signal processing including PPG preprocessing, PPG peak detection, and signal quality index. The application field of photoplethysmogram has been extending from the clinical to the mobile environment. Although there is no standardized pre-processing pipeline for PPG signal processing, as PPG data are acquired and accumulated in various ways, the recently proposed machine learning-based method is expected to offer a promising solution.

Adverse Events during Vitreoretinal Surgery under Adequacy of Anesthesia Guidance—Risk Factor Analysis

Vitreoretinal surgeries require the administration of general anesthesia (GA) in selected groups of patients. The administration of intraoperative rescue narcotic analgesia (IRNA) during GA poses the risk of postoperative nausea and vomiting (PONV). The surgical pleth index (SPI), a crucial component of the adequacy of anesthesia (AoA) guidance of GA, optimizes the intraoperative titration of IRNA. The current analysis evaluated the risk factors for the occurrence of PONV and the oculo-cardiac reflex (OCR) in patients undergoing pars plana vitrectomy (PPV) under AoA guidance. In total, 175 patients undergoing PPV were randomly allocated to receive either GA with SPI-guided IRNA administration using fentanyl alone or in addition to different preoperative analgesia techniques. Any incidence of PONV or OCR was recorded. Obesity, overweight, smoking status, motion sickness, postoperative intolerable pain perception, female gender, fluid challenge and arterial hypertension did not correlate with an increased incidence of PONV or OCR under AoA guidance. Diabetes mellitus, regardless of insulin dependence, was found to correlate with the increased incidence of PONV. The AoA regimen including SPI guidance of IRNA presumably created similar conditions for individual subjects, so no risk factors of the occurrence of PONV or OCR were found, except for diabetes mellitus. We recommend using AoA guidance for GA administration to reduce OCR and PONV rates.

Adequacy of Anesthesia and Pupillometry for Endoscopic Sinus Surgery

Inadequate intraoperative analgesia causes the deterioration of the condition of the surgical field (CSF) as a result of hemodynamic instability. Analgesia monitors are used to guide remifentanil) infusion to optimize intraoperative analgesia. The main aim of the current randomized controlled trial was to investigate the potential advantages of intraoperative analgesia monitoring using surgical Pleth index (SPI)- or pupillometry (PRD)-guided remifentanil administration for managing the volume of total intraoperative blood loss (TEIBL), CSF, and length of operation (LOP) in comparison with the standard practice in patients undergoing endoscopic sinus surgery (ESS). The 89 patients in our study were grouped as follows: 30 patients were assigned to the general analgesia (GA) group, 31 patients were assigned to the SPI group, and 28 patients were assigned to the PRD group. The speed of remifentanil infusion was accelerated by 50% when SPI, PRD, or BSS were increased by >15 points, >5%, or >2, respectively, in adjacent groups until their normalization. The SPI group showed significantly lower TEIBL in comparison to the GA group (165.2 ± 100.2 vs. 283.3 ± 193.5 mL; p < 0.05) and a higher mean arterial pressure (MAP; 73.9 ± 8 vs. 69.2 ± 6.8 mmHg; p < 0.05). In the PRD group, a shorter LOP compared with the GA group was observed (63.1 ± 26.7 min vs. 82.6 ± 33.1 min; p < 0.05). It was noted that the PRD group had a lower total remifentanil consumption than the SPI group (1.3 ± 1.4 vs. 1.8 ± 0.9 mg; p < 0.05). In ASA I-III patients undergoing ESS, intraoperative monitoring based on state entropy and SPI values can optimize the CSF and reduce TEIBL, whereas monitoring based on state entropy and PRD measurements can optimize the cost effectiveness of anesthetic drugs and the use of the operation room.

Strong Early Phase Parasympathetic Inhibition Followed by Sympathetic Withdrawal During Propofol Induction: Temporal Response Assessed by Wavelet-Based Spectral Analysis and Photoplethysmography

Background: Induction of anesthesia with propofol is associated with a disturbance in hemodynamics, in part due to its effects on parasympathetic and sympathetic tone. The impact of propofol on autonomic function is unclear. In this study, we investigated in detail the changes in the cardiac autonomic nervous system (ANS) and peripheral sympathetic outflow that occur during the induction of anesthesia.

Methods: Electrocardiography and pulse photoplethysmography (PPG) signals were recorded and analyzed from 30 s before to 120 s after propofol induction. The spectrogram was derived by continuous wavelet transform with the power of instantaneous high-frequency (HFi) and low-frequency (LFi) bands extracted at 1-s intervals. The wavelet-based parameters were then divided into the following segments: (1) baseline (30 s before administration of propofol), (2) early phase (first minute after administration of propofol), and (3) late phase (second minute after administration of propofol) and compared with the same time intervals of the Fourier-based spectrum [high-frequency (HF) and low-frequency (LF) bands]. Time-dependent effects were explored using fractional polynomials and repeated-measures analysis of variance.

Results: Administration of propofol resulted in reductions in HFi and LFi and increases in the LFi/HFi ratio and PPG amplitude, which had a significant non-linear relationship. Significant between-group differences were found in the HFi, LFi, and LFi/HFi ratio and Fourier-based HF and LF after dividing the segments into baseline and early/late phases. On post hoc analysis, changes in HFi, LFi, and the LFi/HFi ratio were significant starting from the early phase. The corresponding effect size (partial eta squared) was > 0.3, achieving power over 90%; however, significant decreases in HF and LF were observed only in the late phase. The PPG amplitude was increased significantly in both the early and late phases.

Conclusion: Propofol induction results in significant immediate changes in ANS activity that include temporally relative elevation of cardiac sympathovagal balance and reduced sympathetic activity.

Clinical Trial Registration: The study was approved by the Institutional Review Board of Taipei Veterans General Hospital (No. 2017-07-009CC) and is registered at ClinicalTrials.gov (https://clinicaltrials.gov/ct2/show/NCT03613961).

[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.

Comparison of adequacy of anaesthesia monitoring with standard clinical practice monitoring during routine general anaesthesia: An international, multicentre, single-blinded randomised controlled trial

BACKGROUND

Previous studies have suggested that monitoring the levels of both hypnosis and antinociception could reduce periods of inadequate anaesthesia. However, the evidence regarding associated benefits of this monitoring is still limited.

OBJECTIVE

The primary objective of this study was to confirm that guidance of anaesthesia by depth of hypnosis and antinociception monitoring decreases the number of inadequate anaesthesia events in comparison with standard clinical practice.

DESIGN

A multicentre, single-blinded, randomised controlled trial.

SETTING

The study was conducted in four European University hospitals in four different countries between December 2013 and November 2016.

PATIENTS

The study population consisted of a total of 494 adult patients undergoing elective surgery requiring tracheal intubation.

INTERVENTIONS

The patients were allocated to one of two groups. The first group was treated using Entropy for depth of hypnosis and surgical pleth index to determine depth of antinociception (adequacy of anaesthesia group; AoA group). The second group was monitored using standard monitoring alone (control group). Anaesthesia was conducted with target-controlled infusions of propofol and remifentanil.

MAIN OUTCOME MEASURES

The primary outcome of the study was the number of total unwanted events for example signs of inadequately light or unintentionally deep anaesthesia.

RESULTS

Evidence of inadequate anaesthesia had an incidence of around 0.7 events per patient in both groups with no difference between groups (P = 0.519). In the AoA group, the overall consumption of propofol was significantly reduced (6.9 vs. 7.5 mg kg h, P = 0.008) in comparison with the control group. The consumption of remifentanil was equal in both groups. The times to emergence [8.0 vs. 9.6 min (P = 0.005)] and full recovery in the postanaesthesia care unit (P = 0.043) were significantly shorter in the AoA group. No differences were seen in postoperative pain scores or in the use of analgesics.

CONCLUSION

In the current study, the guidance of total intravenous anaesthesia by Entropy and surgical pleth index in comparison with standard monitoring alone was not able to validate reduction of unwanted anaesthesia events. However, there was a reduction in the use of propofol, and shorter times for emergence and time spent in the postanaesthesia care unit.

TRIAL REGISTRATION

at ClinicalTrials.gov NCT01928875.

Preventive Analgesia, Hemodynamic Stability, and Pain in Vitreoretinal Surgery

Background and Objectives: Although vitreoretinal surgery (VRS) is most commonly performed under regional anaesthesia (RA), in patients who might be unable to cooperate during prolonged procedures, general anaesthesia (GA) with intraprocedural use of opioid analgesics (OA) might be worth considering. It seems that the surgical pleth index (SPI) can be used to optimise the intraprocedural titration of OA, which improves haemodynamic stability. Preventive analgesia (PA) is combined with GA to minimise intraprocedural OA administration. Materials and Methods: We evaluated the benefit of PA combined with GA using SPI-guided fentanyl (FNT) administration on the incidences of PIPP (postprocedural intolerable pain perception) and haemodynamic instability in patients undergoing VRS (p < 0.05). We randomly assigned 176 patients undergoing VRS to receive GA with SPI-guided FNT administration alone (GA group) or with preventive topical 2% proparacaine (topical anaesthesia (TA) group), a preprocedural peribulbar block (PBB) using 0.5% bupivacaine with 2% lidocaine (PBB group), or a preprocedural intravenous infusion of 1.0 g of metamizole (M group) or 1.0 g of paracetamol (P group). Results: Preventive PBB reduced the intraprocedural FNT requirement without influencing periprocedural outcomes (p < 0.05). Intraprocedural SPI-guided FNT administration during GA resulted in PIPP in 13.5% of patients undergoing VRS and blunted the periprocedural effects of preventive intravenous and regional analgesia with respect to PIPP and haemodynamic instability. Conclusions: SPI-guided FNT administration during GA eliminated the benefits of preventive analgesia in the PBB, TA, M, and P groups following VRS.

Novel Analgesic Index for Postoperative Pain Assessment Based on a Photoplethysmographic Spectrogram and Convolutional Neural Network: Observational Study

Background

Although commercially available analgesic indices based on biosignal processing have been used to quantify nociception during general anesthesia, their performance is low in conscious patients. Therefore, there is a need to develop a new analgesic index with improved performance to quantify postoperative pain in conscious patients.

Objective

This study aimed to develop a new analgesic index using photoplethysmogram (PPG) spectrograms and a convolutional neural network (CNN) to objectively assess pain in conscious patients.

Methods

PPGs were obtained from a group of surgical patients for 6 minutes both in the absence (preoperatively) and in the presence (postoperatively) of pain. Then, the PPG data of the latter 5 minutes were used for analysis. Based on the PPGs and a CNN, we developed a spectrogram–CNN index for pain assessment. The area under the curve (AUC) of the receiver-operating characteristic curve was measured to evaluate the performance of the 2 indices.

Results

PPGs from 100 patients were used to develop the spectrogram–CNN index. When there was pain, the mean (95% CI) spectrogram–CNN index value increased significantly—baseline: 28.5 (24.2-30.7) versus recovery area: 65.7 (60.5-68.3); P<.01. The AUC and balanced accuracy were 0.76 and 71.4%, respectively. The spectrogram–CNN index cutoff value for detecting pain was 48, with a sensitivity of 68.3% and specificity of 73.8%.

Conclusions

Although there were limitations to the study design, we confirmed that the spectrogram–CNN index can efficiently detect postoperative pain in conscious patients. Further studies are required to assess the spectrogram–CNN index’s feasibility and prevent overfitting to various populations, including patients under general anesthesia.

Trial Registration

Clinical Research Information Service KCT0002080; https://cris.nih.go.kr/cris/search/search_result_st01.jsp?seq=6638

Effects of the ultra-short-acting beta-blocker Esmolol infusion on cardiovascular parameters and quality of postoperative recovery in patients scheduled for elective plastic surgery

Background/Aim: Esmolol is an ultra-short-acting, easily titratable b-adrenergic receptor antagonist used for urgent treatment of hypertension and tachycardia in non-surgical and surgical settings. Aim of this clinical study was to investigate its cardiovascular effects and quality of the emergence from anaesthesia in patients scheduled for elective plastic surgery under general balanced anaesthesia. Methods: A total of 30 ASA I/II patients were randomised in two groups of similar demographic characteristics and baseline values of cardiovascular parameters. Esmolol group received esmolol dissolved in glucose 5 % as an intravenous infusion, 0.3 mg/kg/min during the first 5 min and at a rate of 0.1 mg/kg/ min thereafter. Control patients received the solvent only, at the same rate and volume. General balanced anaesthesia was induced with thiopentone sodium and fentanyl and maintained with nitrous oxide and oxygen. Neuromuscular relaxation was assured with pancuronium bromide and was antagonised at the end of operation with atropine and neostigmine. Systolic and diastolic blood pressure and heart rate were registered at all critical phases: (1) immediately prior to the induction (baseline value), (2) induction to anaesthesia, (3) tracheal intubation, (4) first skin incision, (5) surgical manipulation with organs, (6) suture of the surgical wound and (7) tracheal extubation. Drug consumption and quality of postoperative recovery were monitored. Results: In most of the critical phases of anaesthesia and operation, patients from the Esmolol group had significantly lower values of cardiovascular parameters than the patients from the Control group. Esmolol-treated patients needed less fentanyl, droperidol and pancuronium and had faster and smoother emergence from anaesthesia than the control patients. Conclusion: Esmolol improved haemodynamics and post-anaesthesia recovery in patients undergoing elective plastic surgery under general balanced anaesthesia.

EEG-derived pain threshold index for prediction of postoperative pain in patients undergoing laparoscopic urological surgery: a comparison with surgical pleth index

Recently a novel pain recognition indicator derived from electroencephalogram(EEG) signals, pain threshold index(PTI) has been developed. The aim of this study was to determine whether PTI can be used for prediction of postoperative acute pain while surgical pleth index(SPI) applied as control. Eighty patients undergoing laparoscopic urological surgery under general anesthesia were enrolled. Data of SPI, PTI and a sedative index-wavelet index(WLI) were recorded within last 10 min at the end of surgery. The postoperative pain scores (NRS, numerical rating scale) were obtained. The Bland-Altman analysis was used for evaluation of consistency between PTI and SPI, whereas receiver-operating characteristic (ROC) curves was used for the mean values of PTI, SPI, and WLI to distinguish between mild (NRS 0-3) and moderate-severe (NRS 4-10) pain, and calculate their "best-fit" cut-off values. Data from 76 patients were included for final analysis. There was a good agreement between SPI and PTI values at the end of surgery. The ROC analysis showed a cut-off PTI value of 53 to discriminate between mild and moderate-to-severe pain, while SPI is 44 for this discrimination. Further analysis indicated that PTI had a best predictive accuracy reflected by highest area under curve (AUC)(0.772, 95% CI: 0.661-0.860)with sensitivity(62.50%) and specificity(90.91%) and a best positive predictive value(83.3%,95% CI: 68.4-98.2%). PTI obtained at the end of surgery, which have better predictive accuracy for postoperative pain than SPI, could differentiate the patients with moderate-to-severe pain from those with mild pain after they awaken from anesthesia.Clinical trial registration Chinese Clinical Trials Registry: ChiCTR1900024789.

Effect of dexmedetomidine on intraoperative Surgical Pleth Index in patients undergoing video-assisted thoracoscopic lung lobectomy

Background

The Surgical Pleth Index (SPI) is a monitoring method that reflects painful stimuli during general anesthesia, and dexmedetomidine is an analgesic adjuvant with an opioid-sparing effect. But up to now, it is still unclear whether dexmedetomidine has any influence on SPI. To investigate whether dexmedetomidine has an effect on SPI during video-assisted thoracoscopic surgery.

Methods

We enrolled 94 patients who underwent video-assisted thoracoscopic lung lobectomy. Patients were randomly assigned to a dexmedetomidine group (dexmedetomidine: 0.8 μg/kg administered for 10 min before anesthesia) or normal saline group (equal volume of normal saline). SPI and vital signs were recorded. The number rating scale (NRS) pain score was also evaluated.

Results

SPI values were significantly lower in the dexmedetomidine group than in the normal saline group at intubation and at discharge from the postanesthesia care unit. Compared with the normal saline group, mean arterial pressure and heart rate were both significantly lower in the dexmedetomidine group at intubation. Heart rate was lower at skin incision in the dexmedetomidine group. The NRS score in the normal saline group was noticeably higher vs. the dexmedetomidine group at discharge from the postanesthesia care unit.

Conclusions

Dexmedetomidine decreased intraoperative SPI and NRS scores. Our results showed that dexmedetomidine attenuated noxious stimuli.

Trial registration

Chinese Clinical Trial Registry (ChiCTR): ChiCTR-OOC-16009450, Registered 16 October, 2016.

Influence of infiltration anaesthesia on perioperative outcomes following lumbar discectomy under surgical pleth index-guided general anaesthesia: A preliminary report from a randomised controlled prospective trial

PURPOSE

Severe postoperative pain (SPP) may occur after lumbar discectomy. To prevent SPP and reduce rescue opioid consumption, infiltration anaesthesia (IA) has been combined with general anaesthesia (GA). This study verified how GA combined with IA facilitated intra- and postoperative demand for opioids and affected the incidence of SPP in patients subjected to open lumbar discectomy.

MATERIALS/METHODS

Ninety-nine patients undergoing lumbar discectomy under GA with Surgical Pleth Index (SPI)-guided fentanyl (FNT) administration were randomly assigned to receive IA combined with either 0.2% bupivacaine (BPV) or 0.2% ropivacaine (RPV) with FNT 50 μg and compared with controls (BF, RF, and C groups, respectively).

RESULTS

Ninety-four patients were included in the final analysis. Adjusted according to SPI, total intraoperative FNT dosages did not differ between the study groups (p = 0.23). The proportion of patients who reported SPP was the highest in group C (41.9%) than in the RF (12.9%) and BF groups (31.3%) (p < 0.05). Mild pain was experienced by 67.7%, 53.1% and 32.3% of patients from the RF, BF and C groups, respectively (p < 0.01). Morphine requirement was the highest in the control group (7.1 ± 5.9 mg), followed by the RF (2.7 ± 5.3 mg) and BF groups (4 ± 4.9 mg) (p < 0.05).

CONCLUSIONS

IA using RPV/FNT mixture significantly reduced SPP and postoperative demand for morphine in patients subjected to lumbar discectomy under GA.

Heart rate variability and surgical pleth index under anesthesia in poor and normal sleepers

Poor sleep quality is associated with autonomic dysfunctions and altered pain perception and tolerance. To investigate whether autonomic dysregulations related to insomnia would still exist under general anesthesia, we adopt heart rate variability (HRV) analysis to evaluate ANS activity and surgical pleth index (SPI) to compare nociceptive/anti-nociceptive balance. We enrolled 61 adult females scheduled for gynecological surgeries under general anesthesia. All the subjects were ASA Class I to III without using medicines affecting HRV. We used the Insomnia Severity Index to evaluate sleep qualities. ECG data were recorded and signals which denote four different surgical stages were extracted (baseline, incision, mid-surgery, and end of surgery). We analyzed the HRV changes across the whole surgical period and differences among good and poor sleepers. We also compared the SPI differences among groups. For baseline HRV analysis, we found significant differences in the RMSSD (p = 0.043), pNN50 (p = 0.029), VLF power (p = 0.035), LF power (p = 0.004), and HF power (p = 0.037) between the good and poor sleeper groups. However, all intergroup differences disappeared after anesthesia induction. Temporal HRV changes significantly among different perioperative stages (RMSSD, p < 0.001; pNN50, p = 0.004; LF, p < 0.001; and HF, p < 0.001). Patients with different sleep qualities did not exhibit different SPI levels in all four periods. Poor sleepers exhibited attenuated parasympathetic activities at the baseline but no differences after the induction. Nociceptive/anti-nociceptive balance seems not be altered by poor sleep condition under general anesthesia.

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.

The quantification and monitoring of intraoperative nociception levels in thoracic surgery: a review

Nociception is the unconscious perception of a stimulus applied by trauma or surgery and expressed through a response of the autonomous nervous system. Local anaesthetics (LAs), opioids and other modulating agents such as ketamine are usually utilised to blunt nociception as a component during general anaesthesia (GA) and surgery. The effectiveness of these measures, however, are still difficult to quantify and monitoring of anti-nociception has been confined to assess variation of heart rate (HR) or blood pressure (BP). Recently, various monitoring concepts have been introduced to quantify nociception more systematically and on the other hand guide anti-nociceptive interventions more appropriately. This review describes the various technologies, their performance in clinical studies and provides a critical appraisal with particular application to thoracic anaesthesia and surgery and their relevance in the context of chronic pain after surgery.

Postoperative Pain Assessment Model Based on Pulse Contour Characteristics Analysis

This study aims to develop a new postoperative pain assessment model based on pulse contour analysis and to evaluate its effectiveness in postoperative pain assessment. We derived candidate features from photoplethysmography (PPG) and developed an assessment model based on multiple logistic regressions with a combination of features. This study also includes investigations into the optimal unit of analysis and number of features. For model development, PPGs obtained from 78 surgical patients with a six-min duration in pre- and post-operation conditions, including a training set of 56 pairs and a test set of 22 pairs, were used. We tested models with 5, 10, 20, 30, 40, 50, 60, 70, and 80 beats as an analysis unit, and with 1 to 8 of features for optimization, then determined 20 beats and three features to be the simplest optimal unit of analysis and number of features, respectively. The selected features were RMSSD-ACV_onset/ACA_bl, AV-A_sys/A_total, and SD-RS, where RMSSD-ACV_onset/ACA_bl is the root mean square of the successive difference of the ratio of pulse onset amplitude to the pulse onset-to-peak amplitude, AV-A_sys/A_total is the average value of a normalized systolic area of a pulse with a total pulse area, and SD-RS is the standard deviation of a rising slope of a pulse. The accuracy (AC) and the area under the curve (AUC) of the proposed model were 0.793 and 0.872 in the development set (N = 56), respectively, which were superior to those of SPI (AC: 0.643, AUC: 0.716) and ANI (AC: 0.633 AUC: 0.671). In the test set (N = 22), the AC and AUC of the proposed model were 0.712 and 0.808, respectively, which were superior to those of SPI (AC: 0.640, AUC: 0.709) and ANI (AC: 0.640, AUC: 0.680).

Usefulness of surgical pleth index-guided analgesia during general anesthesia: a systematic review and meta-analysis of randomized controlled trials

Objective

Previous studies comparing surgical pleth index (SPI)-guided and conventional analgesia have shown differing results. Therefore, we compared the intraoperative opioid requirement, extubation time, postoperative pain scores, and perioperative adverse events between these two modalities.

Methods

A comprehensive literature search was conducted to identify randomized controlled trials comparing the intraoperative opioid requirement and other outcomes between the two modalities. The mean difference (MD) or the pooled risk ratio and corresponding 95% confidence interval (CI) were used for analysis. A heterogeneity (I²) assessment was performed.

Results

Six randomized controlled trials comparing 463 patients were included. Intraoperative opioid consumption was significantly lower in the SPI-guided than conventional analgesia group (standardized MD, −0.41; 95% CI, −0.70 to −0.11; I² = 53%). No significant intergroup difference was observed in the pain score on the first postoperative day or the incidence of perioperative adverse events. The extubation time was considerably shorter in the SPI-guided than conventional analgesia group (MD, −1.91; 95% CI, −3.33 to −0.49; I² = 67%).

Conclusions

Compared with conventional analgesia, SPI-guided analgesia can reduce intraoperative opioid consumption and facilitate extubation. Moreover, no intergroup difference was observed in the degree of postoperative pain or incidence of perioperative adverse events.

Postoperative Pain Assessment Indices Based on Photoplethysmography Waveform Analysis

The purpose of this study was to derive parameters that might reflect postoperative pain from photoplethysmography (PPG) and verify the derived parameters in postoperative pain assessment. We obtained preoperative and postoperative PPG and 100-mm visual analog scale (VAS) from 65 surgical patients and extracted a total of 51 PPG morphology-based parameters and their normalized parameters from these PPGs obtained. Pain discrimination performances of these derived parameters were assessed by statistical analyses, including Wilcoxon signed rank test with Bonferroni correction, classification accuracy based on logistic regression, and 4-fold cross validation. After comparing these parameters derived from PPG in pre- and post-operative conditions, statistically significant difference was found in 36 of the 51 parameters. Using logistic classification, dynamic between-pulse parameters such as normalized systolic amplitude variation and normalized diastolic amplitude variation showed better pain classification performance than the static within-pulse parameters. VAS score was 0 in every pre-operation condition, but >60 VAS was observed in the post-operative condition. Systolic peak amplitude variation normalized by PPG AC amplitude showed the best performance in classifying post-operative pain, with accuracy, sensitivity, specificity, and positive predictivity values of 79.5, 74.0, 86.0, and 84.5%, respectively. These results are superior to those of the surgical pleth index (SPI, GE Healthcare, Chicago, IL, United States) at 65.9, 65.9, 66.5, and 66.5%, respectively.

Measurement of area difference ratio of Photoplethysmographic pulse wave in patients with pre-eclampsia

Background

Preeclampsia (PE) is associated with an increase in maternal arterial stiffness, which may be reflected by photoplethysmography (PPG) of the pulse wave. The aim of this study was to investigate area difference ratio (ADR), a novel parameter derived from PPG, in women with and without preeclampsia.

Methods

Patients with and without preeclampsia in the third trimester were enrolled. All patients had photoplethysmography of the pulse wave assessed. ADR was compared between the two groups.

Results

Seventy-two patients in the third trimester of gestation, of which 36 had preeclampsia and 36 did not, were enrolled. The ADR was lower in the preeclampsia group vs. the non-preeclampsia group (0.725 [IQR 0.681–0.779] vs. 0.752 [IQR 0.717–0.910], P < 0.01).

Conclusions

Measuring the ADR through analyzing PPG of the pulse wave may be a useful diagnostic tool in patients with preeclampsia.

Two different methods to assess sympathetic tone during general anesthesia lead to different findings

Noxious stimulation influences the autonomic nervous system activity. Sympathetic tone monitoring is currently used to assess the adequacy of the balance between nociception and anti-nociception during general anesthesia. The Surgical Plethysmographic Index (SPI) and the EBMi software (Custos©) are commercial devices that use different algorithms to measure it. We aimed at determining whether those devices provide similar information during routine surgical procedures under general anesthesia. Data acquired during a previously published study in patients undergoing surgery under general anesthesia were retrospectively analyzed and passed through the EBMi software. The occurrence of EBMi alarms of increased sympathetic tone was compared to the occurrence of SPI values ≥ 60, a commonly recommended intraoperative SPI threshold. Trends in classical parameters of sympathetic tone during the 5 min preceding a SPI ≥ 60, namely blood pressure, heart rate, and plethysmographic pulse amplitude were assessed. SPI ≥ 60 episodes (n = 307) were more frequent than EBMi alerts (n = 240). Approximately 70% of EBMi alerts occurred during periods where the SPI was below 60. Among all episodes of SPI ≥ 60, absence of any EBMi alerts was much more frequent than the inverse. A majority, but not all SPI ≥ 60 episodes were consistently preceded by an increase in heart rate and/or a decrease in pulse amplitude. Blood pressure did not significantly change before SPI ≥ 60. Longer SPI ≥ 60 episodes were associated with lower anti-nociception anesthetic regimen. Different methods of sympathetic tone assessment during general anesthesia provide conflicting information. Prospective studies should be undertaken to clarify the clinical indications of both techniques.

The Effect of Tracheal Intubation-Induced Autonomic Response on Photoplethysmography

Introduction. Intraoperative stress responses and postoperative pain can be monitored using photoplethysmography (PPG). PPG signal has two components, AC and DC. Effects of noxious stimuli-induced stress responses have not been studied on the DC component of PPG. The aim of this study was to investigate the effect of a known noxious stimulus (endotracheal intubation) on both the AC and DC components of PPG. Methods. 15 surgical patients having general anesthesia were enrolled into this clinical study. PPG was recorded electronically from a pulse oximeter. Maximum changes in the AC and DC components of the PPG and pulse rate were determined in response to endotracheal intubation from high frequency (62.5 Hz) PPG recordings. Results. Endotracheal intubation-induced autonomic stress response resulted in a significant decrease in the AC component of the PPG and an increase in pulse rate in every subject (p < 0.05 for all). The decrease in the AC component of the PPG was 50 ± 12% (p < 0.05) and the increase in pulse rate was 26 ± 10 bpm (p < 0.05). The response of the DC component was variable (p = NS). Conclusion. Endotracheal intubation-induced stress response resulted in a significant and consistent change in the AC, but not the DC component of the PPG. This trial is registered with ClinicalTrials.gov Identifier NCT03032939.

The effect of nicardipine on the surgical pleth index during thyroidectomy under general anesthesia: A prospective double-blind randomized controlled trial

BACKGROUND

The effectiveness of surgical pleth index (SPI) for managing nociception-antinociception balance during general anesthesia with vasodilators, including nicardipine has not been demonstrated. We aimed to compare the time course during surgery in SPI values in patients receiving nicardipine or remifentanil infusion during thyroidectomy.

METHODS

Forty patients undergoing thyroidectomy were randomly assigned to receive nicardipine (group N; n = 19) or remifentanil (group R; n = 21) along with induction (propofol, fentanyl, and rocuronium) and maintenance (50% desflurane/nitrous oxide in oxygen) anesthesia (goal bispectral index [BIS] ∼50). The infusion of nicardipine or remifentanil was started before the 1st incision and adjusted to keep mean blood pressure (MBP) within ±20% of the preoperative value. SPI, BIS, end-tidal desflurane concentration (EtDes), MBP, and heart rate were recorded at 2.5 minute intervals from the 1st incision to the end of surgery. Extubation and recovery times, pain score/rescue ketorolac consumption, and adverse events in postanesthesia care unit (PACU) were recorded.

RESULTS

The trend of SPI during surgery was comparable between the 2 groups (P = 0.804), although the heart rates in group N were significantly higher than those in group R (P = 0.040). The patient characteristics, trends of BIS, EtDes, and MBP during surgery, extubation and recovery times, and incidence of nausea/vomiting were comparable between the groups. Group N had significantly lower pain scores and rescue ketorolac consumption at PACU.

CONCLUSION

SPI was comparable between patients receiving nicardipine or remifentanil infusion during thyroidectomy under general anesthesia, which suggests that the administration of nicardipine may confound the interpretation of SPI values during general anesthesia.

CLINICAL TRIAL REGISTRATION

This trial was registered in the UMIN clinical trials registry (unique trial number: UMIN000019058; registration number: R000022028; principal investigator's name: Young Ju Won; date of registration: September 17, 2015).

Basic Features and Clinical Applicability of 'Preliminary Universal Surgical Invasiveness Score' (pUSIS): A Multi-Centre Pilot Study

OBJECTIVE

There is still a lack of a universally applicable and comprehensive scoring system for documenting the invasiveness of surgical procedures. The proposed preliminary 'Universal Surgical Invasiveness Score' (pUSIS) is intended to fill this gap.

METHODS

We used the recently developed pUSIS to obtain values from 8 types of surgery and 80 individual interventions. The results were analysed using descriptive statistical methods. The degree of difficulty on a scale from 0 (very easy) to 10 (extremely difficult) and time expenditures for assessing pUSIS were documented.

RESULTS

Individual pUSIS values ranged from 8 in a laparoscopic cholecystectomy case to 36 in a total hip replacement case. The lowest median pUSIS value of 11.5 was found for laparoscopic cholecystectomy and the highest value of 24.5 was found for open thoracic surgery. The correlation between pUSIS values and the duration of surgery resulted in a tight linear regression (R2=0.6419). The lowest mean (±SD) difficulty level to obtain pUSIS values was 1.6±0.6 for sleeve gastrectomy and the highest one was 2.9±0.6 for knee replacement. The duration to finalise the calculations was 4.1±1.1 min for video-assisted thoracoscopy (VATS) and 9.4±1.3 min for sleeve gastrectomy.

CONCLUSION

We concluded that pUSIS has the potential to be a useful, simply obtainable and universal assessment tool for quantification of the magnitude and invasiveness of individual surgical operations and can serve as a means to quantify surgical interventions for outcome research and evaluate surgical performance.

Anaesthetic interventions for prevention of awareness during surgery

BACKGROUND

General anaesthesia is usually associated with unconsciousness. 'Awareness' is when patients have postoperative recall of events or experiences during surgery. 'Wakefulness' is when patients become conscious during surgery, but have no postoperative recollection of the period of consciousness.

OBJECTIVES

To evaluate the efficacy of two types of anaesthetic interventions in reducing clinically significant awareness:- anaesthetic drug regimens; and- intraoperative anaesthetic depth monitors.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, ISSUE 4 2016); PubMed from 1950 to April 2016; MEDLINE from 1950 to April 2016; and Embase from 1980 to April 2016. We contacted experts to identify additional studies. We performed a handsearch of the citations in the review. We did not search trial registries.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) of either anaesthetic regimens or anaesthetic depth monitors. We excluded volunteer studies, studies of patients prior to skin incision, intensive care unit studies, and studies that only randomized different word presentations for memory tests (not anaesthetic interventions).Anaesthetic drug regimens included studies of induction or maintenance, or both. Anaesthetic depth monitors included the Bispectral Index monitor, M-Entropy, Narcotrend monitor, cerebral function monitor, cerebral state monitor, patient state index, and lower oesophageal contractility monitor. The use of anaesthetic depth monitors allows the titration of anaesthetic drugs to maintain unconsciousness.

DATA COLLECTION AND ANALYSIS

At least two authors independently scanned abstracts, extracted data from the studies, and evaluated studies for risk of bias. We made attempts to contact all authors for additional clarification. We performed meta-analysis statistics in packages of the R language.

MAIN RESULTS

We included 160 studies with 54,109 enrolled participants; 53,713 participants started the studies and 50,034 completed the studies or data analysis (or both). We could not use 115 RCTs in meta-analytic comparisons because they had zero awareness events. We did not merge 27 of the remaining 45 studies because they had excessive clinical and methodological heterogeneity. We pooled the remaining 18 eligible RCTs in meta-analysis. There are 10 studies awaiting classification which we will process when we update the review.The meta-analyses included 18 trials with 36,034 participants. In the analysis of anaesthetic depth monitoring (either Bispectral Index or M-entropy) versus standard clinical and electronic monitoring, there were nine trials with 34,744 participants. The overall event rate was 0.5%. The effect favoured neither anaesthetic depth monitoring nor standard clinical and electronic monitoring, with little precision in the odds ratio (OR) estimate (OR 0.98, 95% confidence interval (CI) 0.59 to 1.62).In a five-study subset of Bispectral Index monitoring versus standard clinical and electronic monitoring, with 34,181 participants, 503 participants gave awareness reports to a blinded, expert panel who adjudicated or judged the outcome for each patient after reviewing the questionnaires: no awareness, possible awareness, or definite awareness. Experts judged 351 patient awareness reports to have no awareness, 87 to have possible awareness, and 65 to have definite awareness. The effect size favoured neither Bispectral Index monitoring nor standard clinical and electronic monitoring, with little precision in the OR estimate for the combination of definite and possible awareness (OR 0.96, 95% CI 0.35 to 2.65). The effect size favoured Bispectral Index monitoring for definite awareness, but with little precision in the OR estimate (OR 0.60, 95% CI 0.13 to 2.75).We performed three smaller meta-analyses of anaesthetic drugs. There were nine studies with 1290 participants. Wakefulness was reduced by ketamine and etomidate compared to thiopental. Wakefulness was more frequent than awareness. Benzodiazepines reduces awareness compared to thiopental, ketamine, and placebo., Also, higher doses of inhaled anaesthetics versus lower doses reduced the risk of awareness.We graded the quality of the evidence as low or very low in the 'Summary of findings' tables for the five comparisons.Most of the secondary outcomes in this review were not reported in the included RCTs.

AUTHORS' CONCLUSIONS

Anaesthetic depth monitors may have similar effects to standard clinical and electrical monitoring on the risk of awareness during surgery. In older studies comparing anaesthetics in a smaller portion of the patient sample, wakefulness occurred more frequently than awareness. Use of etomidate and ketamine lowered the risk of wakefulness compared to thiopental. Benzodiazepines compared to thiopental and ketamine, or higher doses of inhaled anaesthetics versus lower doses, reduced the risk of awareness.

Comparison of simultaneous and sequential administration of fentanyl-propofol for surgical abortion: a randomized single-blinded controlled trial

Propofol lipid emulsion (PLE) is a nanosized sedative, and it is used with a combination of salted antalgic prodrug, fentanyl citrate (FC). To illustrate the synergistic effect of mixing, we compared the sedation/analgesia resulting from simultaneous and sequential administration in surgically induced abortion (No. ChiCTR-IPC-15006153). Simultaneous group showed lower bispectral index, blood pressure, and heart rate, when cannula was inserted into the uterus. It also showed less frequency of hypertension, sinus tachycardia, movement, pain at the injection site, and additional FC. Therefore, premixing of PLE and FC enhanced the sedation and analgesia; stabilized the hemodynamics; lessened the incidence of movement and injection pain; and reduced the requirement of drugs.

Comparison of relative oxycodone consumption in surgical pleth index-guided analgesia versus conventional analgesia during sevoflurane anesthesia: A randomized controlled trial

BACKGROUND

The surgical pleth index (SPI) is proposed for titration of analgesic drugs during general anesthesia. Several reports have investigated the effect of SPI on the consumption of opioids including remifentanil, fentanyl, and sufentanil during anesthesia, but there are no reports about oxycodone. We aimed to investigate intravenous oxycodone consumption between SPI-guided analgesia and conventional analgesia practices during sevoflurane anesthesia in patients undergoing thyroidectomy.

METHODS

Forty-five patients undergoing elective thyroidectomy were randomly assigned to an SPI group (SPI-guided analgesia group, n = 23) or a control group (conventional analgesia group, n = 22). Anesthesia was maintained with sevoflurane to achieve bispectral index values between 40 and 60. In the SPI group, oxycodone 1 mg was administered intravenously at SPI values over 50; in the control group, oxycodone 1 mg was administered intravenously at the occurrence of tachycardia or hypertension event. Intraoperative oxycodone consumption and extubation time were recorded. The number of hemodynamic and somatic movement events was recorded, as were postoperative pain and recovery scores.

RESULTS

Patients' characteristics were comparable between the groups. Intraoperative oxycodone consumption in the SPI group was significantly lower than the control group (3.5 ± 2.4 vs 5.1 ± 2.4 mg; P = 0.012). Extubation time was significantly shorter in the SPI group (10.6 ± 3.5 vs 13.4 ± 4.6 min; P = 0.026). Hemodynamic and somatic movement events during anesthesia were comparable between the groups, as were numeric rating scales for pain and modified Aldrete scores at postanesthesia care unit.

CONCLUSIONS

SPI-guided analgesia reduces intravenous oxycodone consumption and extubation time compared with conventional analgesia based on clinical parameters during sevoflurane anesthesia in patients undergoing thyroidectomy.

Ambulatory pain evaluation based on heart rate variability analysis: Application to physical therapy

Pain assessment is critical for efficient pain management. Clinicians usually use self-report or behavioral pain scales. In practice, the choice of the most adaptive scale depends on several parameters like the clinical context, the patient consciousness or its age, but all evaluation scales are known to be more or less subjective and to present high inter and intra individual variability. Recently, several innovative medical devices have been developed in order to provide to the clinicians a physiological measure of pain. These technologies are mainly used for the continuous monitoring of patients in intensive care or during surgery. As an example, we have developed a heart rate variability analysis based technology for analgesia/nociception monitoring in patients undergoing surgery under general anesthesia. Even if this technology is now used in other clinical settings, the resulting device presents some mobility constraints. In this paper, we describe the adaptation of this technology to the ambulatory pain evaluation and its clinical validation in the particular context of physical therapy. In the frame of this validation, we showed the device usability and efficiency for pain evaluation during physical therapy sessions.

Automated analgesic drugs delivery guided by vagal tone evaluation: interest of the Analgesia Nociception Index (ANI)

Analgesic drugs delivery optimization constitutes one of the main objectives of modern anesthesia. Indeed, their over or under determination constitutes a risk for anesthetized patient in terms of hemodynamic reactivity or post-operative hyperalgesia. Nowadays, new physiological indexes allow anesthesiologists to evaluate the balance between the analgesia level and the noxious stimulus importance. ANI is an index related to the autonomic nervous system activity based on heart rate variability analysis. Its ability for the analgesia / nociception balance evaluation has been established bringing evidences about its helpfulness for analgesic drug delivery. In this article, we describe a device for automatic analgesic drugs administration based on the ANI evolution during surgical procedures under general anesthesia. We hypothesized that such a device could improve the quality and safety of anesthesia by reducing adverse cardiovascular events and delivered analgesic drugs doses.

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.

Comparison of Surgical Pleth Index-guided Analgesia with Conventional Analgesia Practices in Children: A Randomized Controlled Trial

BACKGROUND

To compare surgical pleth index (SPI)-guided analgesia with conventional analgesia by evaluating intraoperative analgesic requirements, postoperative pain, and emergence agitation in children.

METHODS

This study was designed as a parallel, two-arm, double-blind, randomized controlled trial. Forty-five children undergoing elective adenotonsillectomy were randomly allocated to SPI-guided group (SPI-guided analgesia group, n = 21) or control group (conventional analgesia group, n = 24). Anesthesia was maintained with sevoflurane 2 to 3 vol% in 50% nitrous oxide and oxygen to achieve state entropy between 40 and 60. Intraoperative fentanyl 0.5 μg/kg was administered for the first event persisting 3 min and subsequent events persisting 5 min. An event was defined as an SPI over 50 (SPI-guided group) or a blood pressure or heart rate 20% above the baseline (control group). The primary outcome was intraoperative fentanyl requirement. Secondary outcomes included intraoperative sevoflurane consumption, postoperative emergence agitation and pain score, and postoperative rescue analgesic requirements.

RESULTS

Intraoperative fentanyl requirement was lower in SPI-guided group than in control group (0.43 ± 0.53 vs. 1.73 ± 0.59 μg/kg; P < 0.001). Intraoperative sevoflurane consumption was similar. The proportion of patients with high emergence agitation scores (4 to 5) was greater in SPI-guided group (61.9 vs. 25.0%; P = 0.01). The postoperative pain score and rescue fentanyl consumption were higher in SPI-guided group (7 [4.5; 9] vs. 3 [2; 6.75]; P = 0.002; 0.50 ± 0.34 vs. 0.29 ± 0.30 μg/kg; P = 0.04).

CONCLUSIONS

As currently constructed, SPI does not appear to be valid in children. This may be due to both differences in blood vessel distensibility and baseline increased heart rates in children versus adults.

Assessing pain objectively: the use of physiological markers

Pain diagnosis and management would benefit from the development of objective markers of nociception and pain. Current research addressing this issue has focused on five main strategies, each with its own advantages and disadvantages. These encompass: (i) monitoring changes in the autonomic nervous system; (ii) biopotentials; (iii) neuroimaging; (iv) biological (bio-) markers; and (v) composite algorithms. Although each strategy has shown areas of promise, there are currently no validated objective markers of nociception or pain that can be recommended for clinical use. This article introduces the most important developments in the field and highlights shortcomings, with the aim of allowing the reader to make informed decisions about what trends to watch in the future.

Monitoring depth of anesthesia: from consciousness to nociception. A window on subcortical brain activity

Anesthesia results from several inhibitor processes, which interact to lead to loss of consciousness, amnesia, immobility, and analgesia. The anesthetic agents act on the whole brain, the cortical and subcortical areas according to their receptor targets. The conscious processes are rather integrated at the level of the cortical neuronal network, while the nonconscious processes such as the nociception or implicit memory require subcortical processing. A reliable and meaningful monitoring of depth of anesthesia should provide assessment of these different processes. Besides the EEG monitoring which gives mainly information on cortical anesthetic effects, it would be relevant to have also a subcortical feedback allowing an assessment of nociception. Several devices have been proposed in this last decade, to give us an idea of the analgesia/nociception balance. Up to now, most of them are based on the assessment of the autonomic response to noxious stimulation. Among the emerging clinical devices, we can mention those which assess vascular sympathetic response (skin conductance), cardiac and vascular sympathetic response (surgical pleth index), parasympathetic cardiac response (analgesia nociception index), and finally the pupillometry which is based on the assessment of the pupillary reflex dilatation induced by nociceptive stimulations. Basically, the skin conductance might be the most adapted to assess the stress in the awake or sedated neonate, while the performances of this method appear disappointing under anesthesia. The surgical pleth index is still poorly investigated in children. The analgesia nociception index showed promising results in adults, which have to be confirmed, especially in children and in infants, and lastly pupillometry, which can be considered as reliable and reactive in children as in adults, but which is still sometimes complicated in its use.

Influence of gravitational sympathetic stimulation on the Surgical Plethysmographic Index

Surgical Plethysmographic Index (SPI), calculated from pulse photo-plethysmographic amplitude oscillations, has been proposed as a tool to measure nociception anti-nociception balance during general anesthesia, but it is affected by several confounding factor that alter the autonomic nervous system (ANS) modulation. We hypothesized that SPI may be mainly affected by sympathetic stimulation independently from nociception. We studied the effects of two sympathetic stimuli on SPI, delivered through passive head-up tilt at 45 and 90 degrees angles, in nine awake healthy adults. The sympathetic modulation was assessed by means of heart rate variability (HRV) analysis. Mean (SD) SPI significantly increased from baseline to 45 degrees [from 38.6 (13.7) to 60.8 (7.6), p<0.001)] and to 90 degrees angle tilt [82.3 (5.4), p<0.001]. The electrocardiographic mean R-to-R interval significantly shortened during both passive tilts, whereas systolic arterial pressure did not change during the study protocol. HRV changed significantly during the study protocol towards a predominance of sympathetic modulation during passive tilt. Gravitational sympathetic stimulation at two increasing angles, in absence of any painful stimuli, affects SPI in awake healthy volunteers. SPI seems to reflect the sympathetic outflow directed to peripheral vessels.

Comparison of the Surgical Pleth Index with autonomic nervous system modulation on cardiac activity during general anaesthesia: A randomised cross-over study

BACKGROUND

Surgical plethysmographic index (SPI) has been proposed as a tool to measure the nociception/antinociception balance during general anaesthesia. Untreated nociception may increase sympathetic tone, but the relationship between SPI and the autonomic nervous system (ANS) is poorly understood.

OBJECTIVE

We hypothesised that two different levels of SPI might be associated with differences in ANS modulation, measured by the frequency domain analysis of heart rate variability (HRV).

DESIGN

A randomised, cross-over group study, conducted between February and November 2009.

SETTING

University tertiary referral hospital in Milan, Italy.

PATIENTS

Forty-two adult patients undergoing scheduled laparoscopic abdominal surgery.

INTERVENTIONS

ECG, noninvasive arterial blood pressure and SPI were recorded during balanced general anaesthesia with inhaled sevoflurane and intravenous remifentanil. After pneumoperitoneum induction, the remifentanil infusion rate was set to obtain two different levels of SPI (>50, HI-SPI, and <50, LO-SPI) for each patient.

MAIN OUTCOME MEASURES

Arterial pressure, heart rate (HR), low-frequency and high-frequency spectral components, the low frequency/high frequency ratio (measure of sympathovagal balance) and whole power spectrum density of HRV were measured at the two different levels of SPI.

RESULTS

Thirty-nine patients were included in the final analysis. During LO-SPI, HR and systolic and mean blood pressures were significantly lower than HI-SPI. The median low frequency/high frequency ratio was reduced during LO-SPI [1.29 interquartile range (IQR) 0.66 to 2.05) vs. 2.36 (1.30 to 3.62), P = 0.008]. The sensitivity analysis revealed a significant correlation between SPI changes and changes of all ANS indices, arterial pressure and HR, with a slightly better correlation for low frequency/high frequency (Spearman ρ = 0.70, IQR 0.484 to 0.834, P < 0.001).

CONCLUSION

In the context of a balanced general anaesthesia in healthy patients undergoing laparoscopic abdominal surgery, ANS modulation seems to correlate with changes in SPI. Further studies are warranted to assess whether this may reflect a change in nociception/antinociception balance or a pharmacodynamic effect of remifentanil.

Assessment of postoperative pain intensity by using photoplethysmography

PURPOSE

Timely assessment of acute postoperative pain is very important for pain management. No objective and reliable method to assess postoperative pain intensity exists till now. The aim of the study was to investigate the feasibility of photoplethysmography (PPG) signals in postoperative pain assessment.

METHODS

Thirty patients scheduled for elective abdominal surgery under general anesthesia were examined. Finger PPG signals and visual analogue scale (VAS) score were acquired before and 5, 10, 20, and 30 min after sufentanil administration when the patients were awake and transferred to the post-anesthesia care unit (PACU). During each pain rating, the patient's blood pressure, heart rate, and pulse oxygen saturation were recorded. The amplitude of alternating current (AC) and direct current (DC) extracted from finger PPG signals were analyzed, and the ratio of AC and DC (AC/DC) was calculated. Receiver operating characteristic (ROC) curves were built to assess the performance of AC and AC/DC to detect patients with VAS >4 in the PACU.

RESULTS

After administration of sufentanil, VAS scores decreased significantly (p < 0.05), as did blood pressure and heart rate. Simultaneously, both values of AC and AC/DC increased significantly. The VAS score had significant correlations with AC (r = -0.477; p < 0.01), AC/DC (r = -0.738; p < 0.01) and heart rate (r = 0.280; p < 0.01). In contrast, no statistical correlations between VAS score and blood pressure were found. Further analysis found significant differences in both AC and AC/DC among different pain levels, but no obvious differences in blood pressures and heart rate. The area under the ROC curves were 0.754 for AC and 0.795 for AC/DC, respectively.

CONCLUSION

The finger PPG signal can be used in acute postoperative pain assessment. Both AC/DC and AC had significant correlations with the pain rating levels, while blood pressure and heart rate were unreliable in pain assessment.

Surgical pleth index-guided remifentanil administration reduces remifentanil and propofol consumption and shortens recovery times in outpatient anaesthesia

BACKGROUND

The surgical pleth index (SPI) is an index based on changes in plethysmographic characteristics that correlate with the balance between the sympathetic and parasympathetic nervous system. It has been proposed as a measure of the balance between nociception and anti-nociception. The goal of this study was to test whether it could be used to titrate remifentanil in day-case anaesthesia.

METHODS

A total of 170 outpatients were given total i.v. anaesthesia with propofol and remifentanil. The patients were randomized to have the remifentanil dose either adjusted according to the SPI (SPI group) or to clinical parameters (control group). The propofol dose was adjusted according to entropy in both groups. The consumption of anaesthetic drugs, recovery times, and complications were compared.

RESULTS

The mean [standard deviation (SD)] remifentanil and propofol infusion rates in the SPI and control groups were 0.06 (0.04) vs 0.08 (0.05) µg kg(-1) min(-1) and 6.0 (2.1) vs 7.5 (2.2) mg kg(-1) h(-1), respectively (both P<0.05). The mean (SD) times to eye opening were -0.08 (4.4) and 3.5 (4.3) min and to extubation were 1.2 (4.4) and 4.4 (4.5) min in the SPI and control groups, respectively (both P<0.05). There was no difference between the groups with regard to satisfaction with the anaesthetic or intensity of postoperative pain. No patient reported intraoperative awareness.

CONCLUSIONS

Adjusting the remifentanil dosage according to the SPI in outpatient anaesthesia reduced the consumption of both remifentanil and propofol and resulted in faster recovery.

Correlation of surgical pleth index with stress hormones during propofol-remifentanil anaesthesia

Eighty patients undergoing elective ear-nose-throat surgery were enrolled in the present study to investigate the relationship between surgical pleth index (SPI) and stress hormones (ACTH, cortisol, epinephrine, norepinephrine) during general anaesthesia which was induced and maintained with propofol and remifentanil using a target-controlled infusion. The study concluded that the SPI had moderate correlation to the stress hormones during general anaesthesia, but no correlation during consciousness. Furthermore, SPI values were able to predict ACTH values with high sensitivity and specificity.

Increased variation of the response index of nociception during noxious stimulation in patients during general anaesthesia

OBJECTIVE

Analgesia is an important part of general anaesthesia, but no direct indicators of nociceptive-anti-nociceptive balance have been validated in detail. The Response Index of Nociception (RN) is a multiparameter approach which combines photoplethysmographic waveform (PPG), State Entropy (SE), Response Entropy (RE), and heart rate variability (HRV). We aimed at evaluating RN during general anaesthesia; especially we wanted to compare pre- and post-index values of certain noxious stimuli to the average index values. Our assumption was that RN could be a useful indicator of nociceptive-anti-nociceptive balance during the surgery.

METHODS

Sixty women undergoing gynaecological or breast surgery participated in the study. All patients had elective surgery and anaesthesia was maintained with propofol-remifentanil target controlled infusion. Neuromuscular blocking agent rocuronium was used at the beginning of the surgery. Electrocardiography (ECG), photoplethysmography (PPG) and electroencelophalography (EEG) were registered and extracted off-line. An index, reflecting amplitude and frequency of occurrence of abrupt increases ("peaks") in the RN was evaluated during surgery in general and around occurrences of predefined noxious stimuli in particular.

RESULTS

Fifty-four patients were eligible for analysis. Patient movement was associated with increased index values, both before and after the event. Post-event values of the index for intubation and skin incision were higher than its intra-surgery baseline, while pre-event values remained unchanged.

CONCLUSION

Changes in RN can be used to detect noxious stimuli during surgery. RN also predicted movement in our patients under propofol-remifentanil anaesthesia.