Validation of the Nociception Level (NOLTM) Index for the detection of pain in critically ill adults: An Observational Study Protocol (Preprint)

Abstract

The patient’s self-report is the reference standard measure of pain. However, in the intensive care unit (ICU), many patients are unable to self-report due to their critical care condition, mechanical ventilation, and sedation. In such situations, behavioral scales are alternative standard measures of pain but are not applicable to ICU patients unresponsive to stimulation (e.g., heavily sedated or chemically paralyzed). Therefore, alternative pain assessment methods are urgently needed for this vulnerable patient population. In this study, the Nociception Level (NOL) index is a multi-parameter technology that will be tested for pain assessment in critically ill adults. The NOL was initially developed for the monitoring of nociception and related pain in anesthetized patients, and its use in the ICU is new.

To validate the NOL for the assessment of nociception and related pain in critically ill adults.

The NOL device generates an index value from 0 to 100 from multiple parameters (e.g., heart rate, skin temperature) captured simultaneously through a small finger probe. In this study, the ability of the NOL to detect pain using standard criteria (i.e., self-report and behavioral scores), and to discriminate between nociceptive and non-nociceptive procedures will be examined. The NOL will be tested before, during and after two types of standard care procedures: a) non-nociceptive (e.g., cuff inflation to measure blood pressure, soft touch), and b) nociceptive (e.g., tube or drain removal, endotracheal/tracheal suctioning). The NOL will be monitored in three ICU patient groups: a) Group A: participants able to self-report their pain (the reference standard criterion using the 0-10 Faces Pain Thermometer) and express behaviors; b) Group B: participants unable to self-report but express behaviors (the alternative standard criterion using the Critical-Care Pain Observation Tool or CPOT); and c) Group C: participants unable to self-report and to express behaviors. Sociodemographic and clinical information (e.g., administration of analgesic and sedative agents) will also be documented. Receiver Operating Characteristic curve analysis of the NOL will be performed using pain standard measures as reference criteria. Mixed linear models for repeated measures will be used to compare time points, procedures, and their interaction in each group.

Recruitment and data collection began at the primary site in July 2022, at the secondary site in March 2023 and is planned to be on-going until the fall of 2025

Expanding upon our pilot work, the primary strength of this study protocol is based on rigorous validation strategies with the use of pain standard measures (i.e., self-report and behavioral scales). Recruitment challenges and mitigation strategies are also discussed. If found to be valid, the NOL could be used as an alternative physiologic measure of pain in critically ill adults in whom no other pain assessment methods are available.

ClinicalTrials.gov ID NCT05339737; https://clinicaltrials.gov/study/NCT05339737