Use of Intra-Operative EEG Monitoring for Nociception Balance Quantification-A Narrative Review
Crina-Elena Leahu1,2, Sonia Luka3, Cristina Petrisor2,4
1Department of Surgery, Discipline of Surgery, Iuliu Hatieganu University of Medicine and Pharmacy, 8 Victor Babes Street, 400012 Cluj-Napoca, Romania.
Journal of Clinical Medicine
|March 14, 2026
Summary
Electroencephalogram (EEG)-derived indices qCON and qNOX offer valuable insights into hypnosis and nociception during anesthesia. While validated for monitoring anesthetic brain states, technical limitations like processing delays require careful integration into multimodal strategies.
Area of Science:
- Anesthesiology and Neuroscience
- Intraoperative Monitoring
Background:
- Traditional clinical and hemodynamic signs inadequately reflect cortical and nociceptive processing during general anesthesia.
- Electroencephalogram (EEG)-derived indices like qCON (hypnosis) and qNOX (nociception probability) have been developed to assess anesthetic depth and nociception.
- The clinical utility, technical limitations, and impact on drug titration of these EEG indices require further definition.
Purpose of the Study:
- To review and synthesize evidence on the validation, clinical application, and technical characteristics of EEG-derived indices for monitoring hypnosis and nociception.
- To evaluate the role of qCON and qNOX in guiding anesthetic and opioid administration.
- To identify the technical limitations and pharmacodynamic implications of using these EEG indices.
Main Methods:
- A structured narrative review of studies investigating IoC/qCON and qNOX in anesthetic depth or nociception monitoring.
- Studies were categorized into validation, clinical guidance, and technical characteristics domains.
- Inclusion criteria focused on studies assessing EEG-derived indices against clinical or EEG standards, their use in drug titration, and their technical performance.
Main Results:
- Sixteen studies were included, showing strong correlations between IoC/qCON and clinical sedation scales/EEG indices.
- qCON-guided hypnosis control had limited impact on anesthetic consumption.
- qNOX/IoC2 guidance showed more consistent effects on opioid dosing and intraoperative stability.
- qCON exhibited processing delays of tens of seconds, manageable with pharmacodynamic modeling.
Conclusions:
- qCON and qNOX are complementary EEG indices for assessing hypnosis and nociceptive responsiveness.
- Evidence supports their validity for indicating anesthetic brain state, but technical limitations exist.
- Optimal use involves multimodal monitoring strategies integrating EEG with traditional parameters.
