Autonomic Parameters Correlated to Acute Postoperative Pain in the Postanesthesia Care Unit: A Systematic Review.

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 P 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.

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

Prospective observational study of the non-invasive assessment of immediate postoperative pain using the analgesia/nociception index (ANI)

Prediction of immediate postoperative pain using the analgesia/nociception index: a prospective observational study

Predicting and evaluating pain after surgery…Newer methods to the rescue?

Patients assess their own pain with a numerical rating scale (NRS). In the postanaesthesia care unit (PACU), NRS helps to determine and monitor analgesic administration, but is useless in patients who are unable to communicate. In non-PACU patients, acute pain increases pupillary diameter and pupillary light reflex amplitude (PLRA), the difference between pupillary diameter before and after light stimulation. To study the association between postoperative pain (NRS) and pupillary diameter or PLRA in PACU patients after routine anaesthetic care. Cross-sectional cohort study. Bichat-Claude Bernard Hospital, Paris. One hundred and forty-five patients undergoing planned surgery under general anaesthesia. NRS, pupillary diameter and PLRA were measured on arrival in the PACU. When NRS was more than 4, intravenous morphine titration was started and a second measurement performed. Association between NRS and pupillary diameter or PLRA was assessed with Pearson correlation coefficient (r) as was association between changes in these variables after morphine titration. Mean NRS was 4.7, and was more than 4 in 79 patients (55%). No statistically significant association was observed between NRS and pupillary diameter (r = 0.10, P = 0.54) or PLRA (r = 0.03, P = 0.72). Twenty-seven patients (19%) received morphine titration with significant decreases in NRS, pupillary diameter and PLRA afterwards. No association was observed between NRS changes and pupillary diameter or PLRA changes. Acute postoperative pain is not associated with pupillary diameter or PLRA. Further research is required to develop tools to assess pain in the PACU.

Acetaminophen plus a nonsteroidal anti-inflammatory drug decreases acute postoperative pain more than either drug alone

We aim to explore the capacity of perioperative pupillary variables to predict acute pain in the post-anesthesia care unit (PACU). Patients scheduled to undergo thoracic or abdominal surgery under general anesthesia between April 2021 and June 2021 were enrolled. We measured the pupil diameter, pupillary light reflex (PLR), and pupillary reflex dilatation 5min before anesthesia induction (T1), 5min after intubation (T2), at the end of anesthesia (T3), immediately before extubation (T4), and 5min after extubation (T5). We assessed the early postoperative pain intensity in the PACU using Numeric Rating Scales (NRS) at recovery, 5min after recovery, and 10min after recovery. Logistic regression models were used to evaluate the association between perioperative pupillary variables and postoperative pain intensity. Fifty-one patients were enrolled, 50 of whom were included in the final analysis. A total of 13 patients (26%) needed remedial analgesia in the PACU. Pupil parameters at T1, T2, T3, and T5 were not associated with NRS in the PACU. Multiple logistic regression models and receiver operating characteristic (ROC) curves indicated that only latency of PLR at T4 can predict postoperative acute pain. The ROC analysis showed that the cutoff value for latency of PLR at T4 was 0.29s to discriminate between no pain and pain, and the area under the curve was 0.778 (95% CI 0.634-0.922, p=0.002) with sensitivity 50.0% and specificity 91.7%. The latency of PLR immediately before extubation may be a useful predictor for postoperative acute pain in the PACU.

Pain intensity is usually self-rated by patients with a numeric rating scale (NRS) but this scale cannot be used for noncommunicating patients. In anesthetized patients, experimental noxious stimulus increases pupillary diameter (PD) and pupillary light reflex amplitude (PLRA), the difference between PD before and after light stimulation. Labor pain is an intense acute nonexperimental stimulus, effectively relieved by epidural analgesia. In this prospective observational study, we therefore describe the effects of labor pain and pain relief with epidural analgesia on PD and PLRA, determine their association with pain intensity and determine the ability of a single measurement of PD or PLRA to assess pain. In the first stage, pain (11-point NRS), PD, and PLRA were measured in 4 conditions in 26 laboring women: before and after epidural analgesia and in the presence and absence of a uterine contraction. Pupillometry values among the 4 conditions were compared, and the strength of the association between absolute values of pain and PD or PLRA and between pain and changes in PD or PLRA brought about by uterine contraction was assessed with r(2). In the second stage, 1 measurement was performed in 104 laboring women. The strength of the association between pain and PD or PLRA was assessed with r(2). The ability of PD or PLRA to discriminate pain (NRS > 4) was also assessed. In the first stage, a statistically significant increase in pain, PD, and PLRA was observed during a contraction, and this change was abolished after epidural analgesia. The r(2) for the association between pain and changes in PD (r(2) = 0.25 [95% confidence interval, 0.07-0.46] or PLRA (r(2) = 0.34 [0.14-0.56]) brought about by a uterine contraction was higher than the r(2) for the association between pain and absolute values of PD (r(2) = 0.14 [0.04-0.28]) or PLRA (r(2) = 0.22 [0.10-0.37]) suggesting a stronger association for changes than for absolute values. In the second stage, r(2) was 0.23 [0.10-0.38] for PD and 0.26 [0.11-0.40] for PLRA and the area under the receiver operating characteristics curve was 0.82 [0.73-0.91] and 0.80 [0.71-0.89], respectively. Changes in PD and PLRA brought about by a uterine contraction may be used as a tool to assess analgesia in noncommunicating patients.

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. 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. 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. 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.

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

ONE potential adverse outcome from surgery is chronic pain. Analysis of predictive and pathologic factors is important to develop rational strategies to prevent this problem. Additionally, the natural history of patients with and without persistent pain after surgery provides an opportunity to improve the understanding of the physiology and psychology of chronic pain. Ideally, studies of chronic postoperative pain should include (1) sufficient preoperative data (assessment of pain, physiologic and psychologic risk factors for chronic pain); (2) detailed descriptions of the operative approaches used (location and length of incisions, handling of nerves and muscles); (3) the intensity and character of acute postoperative pain and its management; and (4) follow-up at intervals to 1 yr or more. In addition, there would be information about postoperative interventions that may influence pain, such as radiation therapy or chemotherapy. At long-term follow-up visits, patient function, physical signs, and symptoms would be evaluated using a standardized algorithm, including quantitative and descriptive pain assessments. We found no studies that contain all of these data. For this review, we specifically sought population data that reflect the incidence of chronic postoperative pain or predictors (medical, physiologic, and psychologic) of chronic pain. We selected five groups of surgeries (limb amputations, breast surgery, gallbladder surgery, lung surgery, and inguinal hernia surgery). These surgeries were selected because the incidence of pain is known to be high, thus improving the probability of detecting predictive factors. They also represent a range of major surgical procedures.

This paper reports a study to assess the usability and use of different pain assessment tools and to compare patients' and nurses' pain assessments in the recovery room after prostatectomy. Pain assessment is the first step towards providing adequate pain relief but poses problems because of the subjective nature of the pain experience and the lack of quantifiable measurements. Pain tools have been tested in several clinical settings, but not in the recovery room. Data were collected in the recovery room from 45 consecutive patients who had undergone prostatectomy by asking them to evaluate their pain intensity using visual analogue scale, numeric rating scale and verbal expressions. One of two research nurses measured patients' pain at regular intervals and at the same time as the patients. Physiological parameters were also evaluated. Data were analysed as frequencies and percentages. Sum variables were formed and results were analysed using Spearman's rank correlation, Pearson's correlation and with multiple regression analysis. Patients varied in their ability to assess the intensity of their pain using different tools, but assessments were correlated with each other and with nurses' estimations. Nurses and patients obtained similar assessments, but nurses both underestimated and overestimated patients' pain. Patients' verbal assessments varied widely. Patients' and nurses' pain assessments showed no association with patients' pulse or mean arterial blood pressure. According to our results, it is not totally clear whether pain tools are usable in the recovery room. This issue calls for further research.

The "Analgesia Nociception Index" (ANI; MetroDoloris Medical Systems, Lille, France) is a proposed noninvasive guide to analgesia derived from an electrocardiogram trace. ANI is scaled from 0 to 100; with previous studies suggesting that values ≥50 can indicate adequate analgesia. This clinical trial was designed to investigate the effect of intraoperative ANI-guided fentanyl administration on postoperative pain, under anesthetic conditions optimized for ANI functioning. Fifty patients aged 18 to 75 years undergoing lumbar discectomy or laminectomy were studied. Participants were randomly allocated to receive intraoperative fentanyl guided either by the anesthesiologist's standard clinical practice (control group) or by maintaining ANI ≥50 with boluses of fentanyl at 5-minute intervals (ANI group). A standardized anesthetic regimen (sevoflurane, rocuronium, and nonopioid analgesia) was utilized for both groups. The primary outcome was Numerical Rating Scale pain scores recorded from 0 to 90 minutes of recovery room stay. Secondary outcomes included those in the recovery room period (total fentanyl administration, nausea, vomiting, shivering, airway obstruction, respiratory depression, sedation, emergence time, and time spent in the recovery room) and in the intraoperative period (total fentanyl administration, intraoperative-predicted fentanyl effect-site concentrations over time [CeFent], the correlation between ANI and predicted CeFent and the incidence of movement). Statistical analysis was performed with 2-tailed Student t tests, χ tests, ordinal logistic generalized estimating equation models, and linear mixed-effects models. Bonferroni corrections for multiple comparisons were made for primary and secondary outcomes. Over the recovery room period (0-90 minutes) Numerical Rating Scale pain scores were on average 1.3 units lower in ANI group compared to the control group (95% confidence interval [CI], -0.4 to 2.4; P= .01). Patients in the ANI group additionally had 64% lower recovery room total fentanyl administration (95% CI, -12% to 85%; P= .44, unadjusted P= .026), 82% lower nausea scores (95% CI, -19% to 96%; P= .43, unadjusted P= .03), and a reduced incidence of shivering (ANI 4%, control 27%, P= .80, unadjusted P= .047) compared to the control group. Intraoperatively, ANI group patients had on average 27% higher predicted CeFent levels during the highly nociceptive periods of intubation and first incision (5-30 minutes) compared with control group patients (95% CI, 3%-57%; P= .51, unadjusted P= .03). For a 1-unit decrease in ANI scores, predicted CeFent on average increased by an estimated 1.98% in the ANI group (95% CI, 1.7%-2.26%; P< .0001) and 1.08% in the control group (95% CI, 0.76%-1.39%; P< .0001). This correlation was significantly different between groups (0.9%, 95% CI, 0.5%-1.3%; P< .0001). Recovery room vomiting, airway obstruction, respiratory depression, sedation, emergence time, time spent in the recovery room as well as total intraoperative fentanyl administration, hypnotic parameters, and incidence of intraoperative movement were not different between groups. Patients receiving intraoperative ANI-guided fentanyl administration during sevoflurane anesthesia for lumbar discectomy and laminectomy demonstrated decreased pain in the recovery room, likely as a result of more objective intraoperative fentanyl administration.

BackgroundSevere postoperative pain remains a major problem that is seen in 20 to 40% of patients. The Analgesia/Nociception Index (ANI) is a 0–100 index reflecting the relative parasympathetic activity allowing for intraoperative analgesia monitoring. We have previously shown that an ANI value < 50 immediately before extubation may predict the occurrence of immediate postoperative pain with good performance. We hypothesized that GOAL-Directed ANalgesia may provide reduced immediate postoperative pain and optimized intraoperative remifentanil administration (GOLDAN study).MethodsThe GOALDAN study is an international, multicenter, simple-blind, parallel, prospective, randomized, controlled, two-armed trial. Patients are randomly assigned in a 1:1 ratio in the control group or in the experimental group. Patients will be randomly allocated to either the intervention group (ANI) or the control group (standard care only). In the ANI group, the administration of remifentanil will be goal-directed targeting a 50–80 ANI range, with a prophylactic injection of morphine immediately after extubation if the case of ANI < 50. Our primary objective was to determine whether the prophylactic administration of morphine at the end of the procedure in patients at risk of immediate postoperative pain (ANI < 50 immediately before extubation) could reduce the incidence of the latter by 50% in the post-anesthetic care unit. Our secondary objective was to determine whether the intraoperative use of goal-directed analgesia with an ANI target of 50 to 80 could improve intraoperative hemodynamics and postoperative outcome.DiscussionBecause of the paucity of well-conducted trials, the authors believe that a randomized-controlled trial will improve the evidence for using analgesia monitoring during general anesthesia and strengthen current recommendations for intraoperative analgesia management.Trial registrationClinicalTrials.gov NCT03618082. Registered on 7 August 2018