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.

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

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

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.

INTRODUCTION: The aim of this study was to explore the use of a multi-parameter technology, the Nociception Level (NOL) index (Medasense Biometrics Ltd, Ramat Gan, Israel), for pain assessment in postoperative awake patients after cardiac surgery during non-nociceptive and nociceptive procedures in the intensive care unit (ICU). MATERIALS AND METHODS: A prospective cohort repeated-measures design was used. Patients were included if they were in the ICU after undergoing cardiac surgery and if they could self-report their pain. A non-invasive probe was placed on the patient's finger for the continuous monitoring of the NOL index. Patients' self-reports of pain and anxiety (0-10 Numeric Rating Scale or NRS), and behavioral scores with the Critical-Care Pain Observation Tool (CPOT) were obtained before and during a non-nociceptive procedure (ie, non-invasive blood pressure [NIBP] using cuff inflation), and before, during and after a nociceptive procedure (ie, chest tube removal [CTR]) for a total of five time points. Non-parametric tests were used to compare scores at different time points, and receiver operating characteristic curve analysis was performed. RESULTS: Fifty-four patients were included in the analysis. The NOL index, pain and anxiety scores were significantly higher during CTR compared to rest and NIBP (p < 0.001). During CTR, the NOL was associated with self-reported pain intensity and unpleasantness but not with anxiety and CPOT scores. The NOL showed a modest performance in detecting pain (NRS ≥1 and ≥5) in this sample with sensitivity and specificity ranging from 61% to 85%. CONCLUSION: The NOL index was able to discriminate between a non-nociceptive and a nociceptive procedure and was associated with self-reported pain. Further validation testing of the NOL is necessary in a heterogeneous sample of ICU patients.

Exploration of the Nociception Level (NOL™) Index for Pain Assessment during Endotracheal Suctioning in Mechanically Ventilated Patients in the Intensive Care Unit: An Observational and Feasibility Study.

BACKGROUND: Many patients in the intensive care unit (ICU) suffer from pain and are non-communicative. Therefore, alternative pain measures are necessary. Although behavioral pain measures are available, physiological measures are lacking. The Nociception Level index (NOL™) provides a value from combination of multiple physiological parameters to measure pain and its use in the ICU is new. AIM: To explore the use of a multiple physiological parameter measure for pain assessment, the NOL™ index, in mechanically ventilated patients able to self-report pain in the ICU. METHODS: A prospective cohort study was performed. Data were collected before, during, and 15 minutes after a non-nociceptive procedure (noninvasive blood pressure using cuff inflation) and a nociceptive procedure (endotracheal suctioning). NOL index, 0 to 10 pain intensity, and Critical-Care Pain Observation Tool (CPOT) scores were also obtained. Data were analyzed using Friedman and Mann-Whitney tests. Feasibility of study procedures was described. RESULTS: Out of 28 patients who consented, 17 remained eligible and data were analyzed for 15. Technical issues prevented obtaining a NOL signal in 2 patients. NOL values were higher during endotracheal suctioning (median = 41.6) compared with before (median = 11.2) and after the procedure (median = 11.8) and compared with cuff inflation (median = 15.1; Friedman test, p < .001). NOL values were associated with pain intensity and CPOT scores (Mann-Whitney tests, p < .05). CONCLUSIONS: The study procedures with the NOL were found feasible; NOL values could discriminate between nociceptive and non-nociceptive procedures, and values were associated with reference pain measures. Further NOL testing is required in other ICU patient groups and procedures.

A Psychometric Analysis Update of Behavioral Pain Assessment Tools for Noncommunicative, Critically Ill Adults.

This is an updated, comprehensive review of the psychometric properties of behavioral pain assessment tools for use with noncommunicative, critically ill adults. Articles were searched in 5 health databases. A total of 106 articles were analyzed, including 54 recently published papers. Nine behavioral pain assessment tools developed for noncommunicative critically ill adults and 4 tools developed for other non-communicative populations were included. The scale development process, reliability, validity, feasibility, and clinical utility were analyzed using a 0 to 20 scoring system, and quality of evidence was also evaluated. The Behavioral Pain Scale, the Behavioral Pain Scale-Nonintubated, and the Critical-Care Pain Observation Tool remain the tools with the strongest psychometric properties, with validation testing having been conducted in multiple countries and various languages. Other tools may be good alternatives, but additional research on them is necessary.