Exploration of a Multi-Parameter Technology for Pain Assessment in Postoperative Patients After Cardiac Surgery in the Intensive Care Unit: The Nociception Level Index (NOL)TM

Nociception level index variations in ICU: curarized vs non-curarized patients - a pilot study

PURPOSE

Pain is a major physiological stressor that can worsen critical medical conditions in many ways. Currently, there is no reliable monitoring tool which is available for pain monitoring in the deeply sedated ± curarized critically ill patients. This study aims to assess the effectiveness of the multiparameter nociception index (NOL®) in the critical care setting. We compared NOL with traditionally used neurovegetative signs and examined its correlation with sedation depth measured by bispectral index (BIS®) electroencephalographic (EEG) monitoring.

METHODS

This retrospective monocentric cohort study was conducted in a general intensive care unit, including patients who required moderate-to-deep levels of sedation with or without continuous neuromuscular blockade. The performance of NOL was evaluated both in the entire studied population, as well as in two subgroups: curarized and non-curarized patients.

RESULTS

NOL demonstrated greater accuracy than all other indicators in pain detection in the overall population. In the non-curare subgroup, all indices correctly recognized painful stimulation, while in the patients subjected to neuromuscular blocking agent's infusion, only NOL properly identified nociception. In the former group, EEG's relation to nociception was on the border of statistical significance, whereas in the latter BIS showed no correlation with NOL.

CONCLUSION

NOL emerges as a promising device for pain assessment in the critical care setting and exhibits its best performance precisely in the clinical context where reliable pain assessment methods are most lacking. Furthermore, our research confirms the distinction between sedation and analgesia, highlighting the necessity for distinct monitoring instruments to accurately assess them.

Pain monitoring in intensive care: How does the nociception level index affect treatment and prognosis? A randomized, controlled, double-blind trial

BACKGROUND

Effective pain management is vital in critical care settings, particularly post-surgery. Clinicians should maintain objective and efficient standards to assess pain in a patient-centered manner, in order to effectively manage this complex issue. A newer technology, the nociception level (NOL) index, shows promise in achieving this task through its multi-parameter evaluation.

METHODS

This study was a prospective, controlled, randomized trial involving two groups of patients (n=30 each) in a diverse intensive care unit. Participants were over 18 years old with American Society of Anesthesiology scores ranging from I to III and were scheduled for critical care follow-up after general anesthesia. All subjects followed a standard analgesia protocol that included rescue analgesia. Drug administration was guided by a numeric rating scale and the critical care pain observation tool in the Control Group, while it was guided by nociception level index monitoring in the NOL Group.

RESULTS

Pain scores between the two groups did not significantly differ. However, within the NOL Group, pain scores and noci-ception values displayed a strong positive correlation. Notably, total analgesic consumption was significantly lower in the NOL Group (p=0.036).

CONCLUSION

Monitoring pain using the nociception level index is an effective method for detecting pain compared to standard pain scores utilized in critical care. Its guidance facilitates personalized analgesic titration. Additionally, the potential of nociception level index guidance to reduce the duration of intensive care and hospital stays may be linked to its effects on delirium, a connection that awaits further exploration in future studies.

Noninvasive monitoring technologies to identify discomfort and distressing symptoms in persons with limited communication at the end of life: a scoping review

BACKGROUND

Discomfort and distressing symptoms are common at the end of life, while people in this stage are often no longer able to express themselves. Technologies may aid clinicians in detecting and treating these symptoms to improve end-of-life care. This review provides an overview of noninvasive monitoring technologies that may be applied to persons with limited communication at the end of life to identify discomfort.

METHODS

A systematic search was performed in nine databases, and experts were consulted. Manuscripts were included if they were written in English, Dutch, German, French, Japanese or Chinese, if the monitoring technology measured discomfort or distressing symptoms, was noninvasive, could be continuously administered for 4 hours and was potentially applicable for bed-ridden people. The screening was performed by two researchers independently. Information about the technology, its clinimetrics (validity, reliability, sensitivity, specificity, responsiveness), acceptability, and feasibility were extracted.

RESULTS

Of the 3,414 identified manuscripts, 229 met the eligibility criteria. A variety of monitoring technologies were identified, including actigraphy, brain activity monitoring, electrocardiography, electrodermal activity monitoring, surface electromyography, incontinence sensors, multimodal systems, and noncontact monitoring systems. The main indicators of discomfort monitored by these technologies were sleep, level of consciousness, risk of pressure ulcers, urinary incontinence, agitation, and pain. For the end-of-life phase, brain activity monitors could be helpful and acceptable to monitor the level of consciousness during palliative sedation. However, no manuscripts have reported on the clinimetrics, feasibility, and acceptability of the other technologies for the end-of-life phase.

CONCLUSIONS

Noninvasive monitoring technologies are available to measure common symptoms at the end of life. Future research should evaluate the quality of evidence provided by existing studies and investigate the feasibility, acceptability, and usefulness of these technologies in the end-of-life setting. Guidelines for studies on healthcare technologies should be better implemented and further developed.

Skin conductance algesimeter is unreliable during sudden perioperative temperature increases

OBJECTIVES

Pain assessment in anesthetized and non-communicative patients remains a challenge. Clinical signs such as tachycardia, hypertension, sweat and tears, have a low specificity for pain and should therefore ideally be replaced by more specific monitoring techniques. Skin conductance variability has been demonstrated to establish a patients' sensitivity to pain, but may be influenced by temperature changes that leads to profuse sweating. The aim of this pilot study was to test skin conductance changes during sudden temperature changes due to hyperthermic intraperitoneal chemotherapy (HIPEC) perfusation.

METHODS

We investigated skin conductance algesimeter (SCA) in ten consecutive patients undergoing cytoreductive surgery and HIPEC. Results from the SCA was compared to other standard physiological variables at seven time points during the surgical procedure, in particular during the period with hyperthermic intraabdominal perfusion leading to an increase in the patients core temperature.

RESULTS

Nine out of ten patients had an increase in the SCA measurements during the HIPEC phase correlating the increase in temperature.

CONCLUSION

SCA is unreliable to detect increased pain sensation during sudden perioperative temperature changes in adult patients.

Continuous visualization and validation of pain in critically ill patients using artificial intelligence: a retrospective observational study

Machine learning tools have demonstrated viability in visualizing pain accurately using vital sign data; however, it remains uncertain whether incorporating individual patient baselines could enhance accuracy. This study aimed to investigate improving the accuracy by incorporating deviations from baseline patient vital signs and the concurrence of the predicted artificial intelligence values with the probability of critical care pain observation tool (CPOT) ≥ 3 after fentanyl administration. The study included adult patients in intensive care who underwent multiple pain-related assessments. We employed a random forest model, utilizing arterial pressure, heart rate, respiratory rate, gender, age, and Richmond Agitation-Sedation Scale score as explanatory variables. Pain was measured as the probability of CPOT scores of ≥ 3, and subsequently adjusted based on each patient's baseline. The study included 10,299 patients with 117,190 CPOT assessments. Of these, 3.3% had CPOT scores of ≥ 3. The random forest model demonstrated strong accuracy with an area under the receiver operating characteristic curve of 0.903. Patients treated with fentanyl were grouped based on CPOT score improvement. Those with ≥ 1-h of improvement after fentanyl administration had a significantly lower pain index (P = 0.020). Therefore, incorporating deviations from baseline patient vital signs improved the accuracy of pain visualization using machine learning techniques.

Analgesic Efficacy of Erector Spinae Plane Block in Pediatric Abdominal Surgery: Guidance with Conventional Method and NOL: Case Series

Background

Erector spinae plane (ESP) block is a regional anesthesia technique that blocks both somatic and visceral nerve fibers. Despite its high analgesic potential, its mechanism of action is not yet fully understood. The ultrasound-guided ESP block, which can be easily performed, makes important contributions to the control of intraoperative pain in pediatric patients undergoing abdominal surgery. The follow-up of pain in the intraoperative period is usually done by evaluating the changes in hemodynamic parameters. Due to physiological differences in pediatric patients, it is more difficult to do this with only hemodynamic changes than in adult patients. Aim: The NOL® (Nociception Level) monitor calculates the nociception/pain score by evaluating many parameters through a proprietary algorithm. Our primary aim was to demonstrate the effectiveness of ESP block with an advanced pain monitor in this patient group; our secondary aim was to investigate the necessity of pain monitors in the pediatric patient group.

Methods

In this case series, we applied intraoperative NOL® monitoring in addition to standard monitoring (ECG, SpO2, heart rate, EtCO₂) in pediatric patients (16 cases) who were scheduled for abdominal surgery and underwent ESP block.

Results

Considering the hemodynamic data, NOL values, postoperative pain scores, side effects, and complications, it was concluded that ESP block can be used safely in this patient group. Although the hemodynamic data and the NOL® index were compatible with each other after a nociceptive stimulus, the NOL index was less affected by other variables and gave the clinician clearer information about pain.

The Validity of Vital Signs for Pain Assessment in critically Ill Adults: A Narrative Review

OBJECTIVES

Pain assessment in the intensive care unit (ICU) is challenging because many patients are unable to self-report or exhibit pain-related behaviors. In such situations, vital signs (VS) through continuous monitoring are alternative cues for pain assessment. This review aimed to describe the reliability and validity of VS for ICU pain assessment.

DESIGN

Narrative review of the literature.

DATA SOURCES

Medline, Embase, CINAHL, Cochrane.

REVIEW/ANALYSIS METHODS

A narrative review was conducted with a comprehensive search in four databases. Search terms included VS, pain assessment, and ICU.

RESULTS

Out of 1,359 results, 30 studies from 17 countries were included. Heart rate, blood pressure, and respiratory rate were most used for ICU pain assessment. Assessments were performed at rest before procedures, during nociceptive and non-nociceptive procedures, and after procedures. Increases in respiratory rate were clinically significant by more than 25% during nociceptive procedures (e.g., endotracheal suctioning, turning) compared with rest/pre-procedures in five studies. Correlations of VS with self-reported pain (reference standard measure) and behavioral pain scores (alternative measure) were absent or weak.

CONCLUSIONS

VS are not valid indicators for ICU pain assessment. Increases of respiratory rate may be a cue for the detection of pain. However, fluctuations in respiratory rate can be influenced by opioids or controlled ventilation mode. Our results dissuade the use of VS for pain assessment because of the lack of association with ICU pain reference standards. Other physiologic measures of pain in critically ill adults should be explored.

Opioid Dose, Pain, and Recovery following Abdominal Surgery: A Retrospective Cohort Study

Background: The optimal dosage for opioids given to patients after surgery for pain management remains controversial. We examined the association of higher post-surgical opioid use with pain relief and recovery. Methods: We retrospectively enrolled adult patients who underwent elective abdominal surgery at our hospital between August 2021 and April 2022. Patients were divided into the “high-intensity” or “low-intensity” groups based on their post-surgical opioid use. Generalized estimating equation models were used to assess the associations between pain scores at rest and during movement on days 1, 2, 3, and 5 after surgery as primary outcomes. The self-reported recovery and incidence of adverse events were analyzed as secondary outcomes. Results: Among the 1170 patients in the final analysis, 293 were in the high-intensity group. Patients in the high-intensity group received nearly double the amount of oral morphine equivalents per day compared to those in the low-intensity group (84.52 vs. 43.80), with a mean difference of 40.72 (95% confidence interval (CI0 38.96−42.48, p < 0.001) oral morphine equivalents per day. At all timepoints, the high-intensity group reported significantly higher pain scores at rest (difference in means 0.45; 95% CI, 0.32 to 0.58; p < 0.001) and during movement (difference in means 0.56; 95% CI, 0.41 to 0.71; p < 0.001) as well as significantly lower recovery scores (mean difference (MD) −8.65; 95% CI, −10.55 to −6.67; p < 0.001). A post hoc analysis found that patients with moderate to severe pain during movement were more likely to receive postoperative high-intensity opioid use. Furthermore, patients in the non-high-intensity group got out of bed sooner (MD 4.31 h; p = 0.001), required urine catheters for shorter periods of time (MD 12.26 h; p < 0.001), and were hospitalized for shorter periods (MD 1.17 days; p < 0.001). The high-intensity group was at a higher risk of chronic postsurgical pain (odds ratio 1.54; 95% CI, 1.14 to 2.08, p = 0.005). Conclusions: High-intensity opioid use after elective abdominal surgery may not be sufficient for improving pain management or the quality of recovery compared to non-high-intensity use. Our results strengthen the argument for a multimodal approach that does not rely so heavily on opioids.

Nociception level index variations in patients with complex regional pain syndrome: a pilot study

The nociception level index (NOL) is a multi-parameter index that incorporates changes in autonomic parameters to evaluate nociception, with more painful stimuli causing more pronounced index variations. How this nociception monitor relates to the pain experience is uncertain, and patients with chronic pain may respond differently to acute pain due to alterations in pain processing. The goal of this pilot study was to evaluate NOL index variations after a painful physiotherapy exercise in patients with upper limb complex regional pain syndrome. Baseline NOL indexes were recorded using a finger probe (PMD-200™ Monitor, Medasense, Israel) and patient reported baseline pain scores using an 11-point numeric rating scale (NRS). Patients then performed a painful physiotherapy exercise and NOL index and pain scores were again recorded. The same procedure and recordings were repeated after a stellate ganglion block. Data were analyzed using a paired Student T test and a P value < 0.05 was considered statistically significant. Twenty patients (12/20 female, 10/20 right-sided) were included in this study. Patients reported moderate baseline pain (4.0 ± 2.7) despite having a low baseline NOL index (7.66 ± 5.76 out of 100). NRS and NOL index scores increased significantly during exercise, both before and after the block. The NOL index increased significantly when patients reported increased pain, indicating that it could eventually be useful in the objective assessment of acute pain in the chronic pain patients. However, NOL index was not able to reflect pain levels at rest, before the painful stimulation, in this chronic pain population. Further studies are needed to better assess NOL index utility at rest and to confirm these findings in this specific chronic pain population.

Nociception Level Index-Directed Erector Spinae Plane Block in Open Heart Surgery: A Randomized Controlled Clinical Trial

Background and Objectives: The erector spinae plane block (ESPB) is a multimodal opioid-sparing component, providing chest-wall analgesia of variable extent, duration, and intensity. The objective was to examine the ESPB effect on perioperative opioid usage and postoperative rehabilitation when used within a Nociception Level (NOL) index-directed anesthetic protocol. Materials and Methods: This prospective, randomized, controlled, open-label study was performed in adult patients undergoing on-pump cardiac surgery in a single tertiary hospital. Eighty-three adult patients who met eligibility criteria were randomly allocated to group 1 (Control, n = 43) and group 2 (ESPB, n = 40) and received general anesthesia with NOL index-directed fentanyl dosing. Preoperatively, group 2 also received bilateral single-shot ultrasound-guided ESPB (1.5 mg/kg/side 0.5% ropivacaine mixed with dexamethasone 8 mg/20 mL). Postoperatively, both groups received intravenous paracetamol (1 g every 6 h). Morphine (0.03 mg/kg) was administered for numeric rating scale (NRS) scores ≥4. Results: The median (IQR, 25th−75th percentiles) intraoperative fentanyl and 48 h morphine dose in group 2-to-group 1 were 1.2 (1.1−1.5) vs. 4.5 (3.8−5.5) µg·kg−1·h−1 (p < 0.001) and 22.1 (0−40.4) vs. 60.6 (40−95.7) µg/kg (p < 0.001). The median (IQR) time to extubation in group 2-to-group 1 was 90 (60−105) vs. 360 (285−510) min (p < 0.001). Two hours after ICU admission, 87.5% of ESPB patients were extubated compared to 0% of controls (p < 0.001), and 87.5% were weaned off norepinephrine compared to 46.5% of controls (p < 0.001). The median NRS scores at 0, 6, 12, 24, and 48 h after extubation were significantly decreased in group 2. There was no difference in opioid-related adverse events and length of stay. Conclusions: NOL index-directed ESPB reduced intraoperative fentanyl by 73.3% and 48 h morphine by 63.5%. It also hastened the extubation and liberation from vasopressor support and improved postoperative analgesia.

Pain Assessment in Intensive Care Unit: A Forgotten Entity or a Quality Indicator?

How to cite this article: Havaldar AA. Pain Assessment in Intensive Care Unit: A Forgotten Entity or a Quality Indicator? Indian J Crit Care Med 2022;26(4):419–420.