Control pain. Avoid overdose. Eliminate doubt.

The NOL® Index

NOL (Nociception Level) is the index and technology developed by Medasense to objectively quantify a patient’s physiological pain response (nociception), enabling surgical teams to provide personalized pain treatment for anaesthetized, non-communicating patients.

NOL-guided analgesia reduces the risk of excessive use or underuse of opioids and associated complications.1

NOL index monitoring | PMD-200 surgical analgesia monitor

Control pain

Enhance intraoperative pain control to meet the patient’s analgesic needs and improve postoperative pain scores.

Avoid overdose

Patients vary in their pain threshold and opioid tolerance. Avoiding excessive use of opioids can improve patient safety and outcomes.

Eliminate doubt

NOL monitoring enables confident assessment of the adequacy of analgesia throughout the surgical procedure.

How We Complete the Missing Piece in Anaesthesia

NOL Index Monitoring - The Missing Piece in Anesthesia Monitoring

The Physiological Principles Behind NOL

NOL is based on a proprietary, patented artificial intelligence technology that quantifies the individual physiological response to pain in real-time, continuously and noninvasively.

Activation of the sympathetic nervous system, as a result of multiple stimuli and inputs, leads to a constellation of nociception-related physiological responses, with complex inter-associations and different response profiles. Recognizing the complex nature of this process, the Nociception Level (NOL) index was developed as a multiparameter composite of autonomic signals.


Shown to reduce reported pain scores in the PACU4

Reducing hypotension, improving haemodynamic stability and sparing opioids1

Potential cost savings within one year – and better use of healthcare resources5

Safe, noninvasive, continuous and simple to use


Video Highlights

How NOL helps personalize opioid administration, with Dr. Hugo Vereecke, Belgium

Lecture series: Prof. Stefan Schraag on NOL Monitoring in Thoracic Anaesthesia

Lecture series: Prof. Dan Longrois on NOL Monitoring and Titration of Anaesthetic Drugs


  1. Meijer, F., Martini, C., Broens, S., Boon, M., Niesters, M., Aarts, L., Olofsen, E., van Velzen, M., Dahan, A. (2019). Nociception-guided versus Standard Care during Remifentanil–Propofol Anesthesia: A Randomized Controlled Trial. Anesthesiology, 130(5), 745-755. doi:10.1097/ALN.0000000000002634
  2. Edry, R., Recea, V., Didust, Y. & Sessler, D. I. (2016). Intraoperative validation of the NOL Index, a non-invasive nociception monitor. Anesthesiology, 125, 193-203.
  3. Martini, C. H., Boon, M., Broens, S. J. L., Hekkelman, E. F., Oudhoff, L. A., Buddeke, A. W., Dahan, A. (2015). Ability of the Nociception Level (NOL), a multiparameter composite of autonomic signals, to detect noxious stimuli during propofol-remifentanil anesthesia. Anesthesiology, 123, 524-534.
  4. Meijer, F., Honing, M., Roor, T., Toet, S., Calis, P., Olofsen, E., Martini, C., van Velzen, M., Aarts, L., Niesters, M., Boon, M., Dahan, A. (2020). Reduced postoperative pain using Nociception Level-guided fentanyl dosing during sevoflurane anaesthesia: a randomised controlled trial. British Journal of Anaesthesia, 125(6), 1070-1078.
  5. Saunders R., Weissbrod R. (2020). Cost benefit of personalizing intraoperative pain management. Presented at ISPOR Virtual Conference, May 2020.