Author: Flora Liu, MD
IARS 2026 Annual Meeting coverage
Anesthesiologists routinely produce and reverse unconsciousness, yet the brain mechanisms responsible for losing and regaining consciousness remain incompletely understood. At the 2026 IARS and SOCCA Annual Meeting, investigators discussed how anesthetics alter brain networks, how consciousness may fluctuate despite stable drug concentrations, and how these findings could improve monitoring and recovery prediction.
Andrew McKinstry-Wu, MD, PhD, examined how researchers can distinguish the neurological effects of anesthetic drugs from the brain activity specifically associated with consciousness. Because changing anesthetic concentrations strongly influence EEG patterns, identifying a reliable marker of consciousness can be difficult.
Researchers used xenon anesthesia because its concentration in the brain could be measured noninvasively with serial CT imaging. After establishing a stable anesthetic concentration, they recorded EEG activity and behavioral responses while participants moved spontaneously between responsive and unresponsive states.
Traditional EEG measurements, including frontal peak alpha activity and dynamic criticality, did not significantly distinguish responsiveness from unresponsiveness. Statistical criticality, however, decreased during unresponsiveness and increased when consciousness returned. This suggests that statistical criticality may offer a promising EEG-based measure of consciousness that is less affected by changes in anesthetic concentration.
Catherine Duclos, PhD, discussed the use of propofol responses to evaluate patients with coma and other disorders of consciousness. She presented the Adaptive Reconfiguration Index, an EEG-based measurement that evaluates changes in brain-network hubs and directed functional connectivity.
Brain-injured patients who maintained the ability to reorganize their neural networks after receiving propofol appeared more likely to recover consciousness. Propofol did not affect every patient in the same way. Some demonstrated paradoxical increases in neurological patterns associated with consciousness rather than the expected suppression.
These findings support the criticality hypothesis, which proposes that a conscious brain functions near a transition point between excessive order and excessive disorder. Anesthesia generally moves the brain into a less responsive, subcritical state. In certain injured brains, however, GABAergic medications such as propofol may temporarily improve network organization because of abnormalities within the thalamic and basal ganglia circuits.
Responses may depend on several factors, including:
- The patient’s underlying brain-network condition
- The location and severity of the injury
- Differences in neural circuitry
- Genetic factors
- The integrity of the thalamocortical system
Paola Calderon, MD, PhD, explored whether motor behavior could provide a more accurate indication of arousal and consciousness during emergence from anesthesia. Reflexive movement alone may not indicate meaningful awareness because it can occur without substantial activation of higher motor-planning regions.
Reflexive movements produced little activation in the anterior lateral motor cortex. In contrast, voluntary and goal-directed behaviors generated significantly greater activity, particularly in superficial cortical layers involved in communication, planning, and coordinated movement.
Dr. Calderon introduced the concept of “arousal units,” coordinated patterns that combine motor behavior, autonomic responses, cortical activity, and EEG changes during recovery from anesthesia. These integrated measurements may ultimately provide a more reliable method of determining whether a patient is progressing from simple reflexive activity toward purposeful consciousness.
Key Takeaways
Consciousness cannot always be determined by anesthetic dose, isolated EEG patterns, or movement alone. Patients may transition between responsive and unresponsive states even when brain anesthetic concentrations remain stable.
Statistical criticality may become a useful EEG marker for detecting consciousness independently of drug concentration. The Adaptive Reconfiguration Index may help identify brain-injured patients who retain the neurological capacity to recover consciousness.
Purposeful, goal-directed movement appears to provide more meaningful information than reflexive movement during emergence. Combining EEG findings with motor behavior, autonomic activity, and network measurements may lead to better tools for assessing consciousness in the operating room, PACU, and ICU.
Thank you to IARS for allowing us to summarize this important coverage from the 2026 Annual Meeting.