Introduction: Dexmedetomidine (Dex) is being explored as a superior anesthetic for achieving conscious sedation in awake craniotomies, a preferable method for resection of glioma and epileptic foci near eloquent regions. Multiple studies have shown Dex provides optimal sedation for longer periods, while reducing narcotic use and retaining the ability to perform neurocognitive testing. There have been limited studies and mixed results on the effect of Dex on electrocorticography (ECoG) activity. The objective of this study is to determine neural oscillations associated with consciousness and return-of-pre-anesthetic-performance (ROPAP).
Methods: We conducted microelectrode array intracortical recordings in the somatosensory (S1) and frontal ventral premotor (PMv) areas of non-human primates (NHPs). Dex infusion was administered through a vascular port, following a behavioral task. NHP task performance was analyzed during loss-of-consciousness (LOC), return-of-consciousness (ROC), and ROPAP.
Results: During wakefulness, beta oscillations dominated in S1 and PMv, while the onset of LOC was identified by a brief increase of alpha power oscillations more obvious in S1 than PMv. Throughout anesthesia, slow-delta oscillations appeared, while ROC was associated with a return of alpha oscillation dominance and decrease of slow-delta waves. As the animal recovered, alpha waves appeared to increase its frequency toward the beta range. Single neuron spike analysis showed PMv spike firing rate increased upon LOC while S1 neurons decreased; a response that continued through recovery.
Conclusions: These findings suggest that Dex-induced LOC and ROC are both associated with an increase of alpha oscillations in S1 and PM. The slow-delta oscillations are dominant while the animals are unconscious. Spike firing response appears to be region specific, but clearly associated with consciousness changes. Understanding Dex-induced regional spiking activity could perhaps inform neurosurgeons on areas of increased epileptiform susceptibility. Effects on task-related performance could help guide appropriate use of intraoperative anesthetic titration and neurological assessment.
Patient Care: This research will improve patient care by informing neurosurgeons and researchers on potential uses of dexmedetomidine anesthesia for awake craniotomy resections of tumor and epileptic foci. By exploring dexmedetomidine effects on neural dynamics surgeons will have more information on how to use electrophysiologic data for optimal surgical outcomes.
Learning Objectives: 1. Describe the neurophysiological effects of dexmedetomidine anesthesia.
2. Analyze the isolated effects of dexmedetomidine on the neural dynamics of task-performance.