Nociception Evaluated by the NOL® Index in Sedated Patients in the Intensive Care Unit

Due to their underlying pathology and the necessary complicated procedures to which they are exposed, patients in the intensive care unit experience varying degrees of pain at some point in their evolution. Evidence has established short-term and long-term negative consequences of unresolved pain or excessive analgesic sedation. However, pain assessment or adequate nociceptive monitoring remains a significant challenge, especially in non-communicative patients under deep sedation, who urgently need to expand and improve current tools.

Pain assessment in critically ill patients is challenging; limitations in their ability to communicate (neurocognitive deficit, use of endotracheal tube) or altered consciousness (deep sedation) make them unable to self-report their pain with standard pain scales. The Behavioral Pain Scale (BPS) and the Critical-Care Pain Observation Tool (CPOT) are the pain assessment tools with the best performance and reliability for patients in these conditions.

Different technologies are used to monitor nociceptive responses caused by surgical stress in patients under general anesthesia that together with the clinical evaluation, manage to keep patients in the best analgesic conditions, improving the post-surgical prognosis. In particular, the NOL® nociceptive index (Medasense, Ramat Gan, Israel) is a multiparametric detection of nociception/pain, delivering a dimensionless score (0 -100) calculated through an algorithm (patented) and based on the registry of four biometric sensors (photoplethysmography, galvanic skin response, temperature, and accelerometer). NOL index value between 10-25 is the most appropriate for maintaining analgesia during general anesthesia.

The ease and low invasiveness of this system (all sensors are implemented in a finger clip, similar to an oxygen saturation monitor) may allow its potential use in the context of intensive care unit patients. Some studies have recently been published that highlight the possible usefulness of the NOL® index in critically ill patients. However, in these studies, the assessment of nociception was limited to acute nociceptive procedures only.