Abstract
Nitrous oxide is a common gaseous anesthetic used in a wide range of medical procedures due to its desirable combination of anesthetic and analgesic properties. Deep brain stimulation surgery, a well-established treatment for movement disorders like Parkinson's disease, often requires precise microelectrode recordings of the awake brain's electrical signals for optimal results. However, the influence of anesthetics on these brain signals remains a critical consideration. This study investigated how nitrous oxide general anesthesia supplemented by ketamine affects the electrophysiology of the subthalamic nucleus compared to awake and low-dose ketamine sedation during deep brain stimulation procedures targeting the subthalamic nucleus of Parkinson's disease patients. Spectral analysis of subthalamic nucleus electrophysiological characteristics and statistical analysis of its electrophysiological dimensions were performed on retrospective data from three medical centers. Our findings revealed that nitrous-ketamine general anesthesia allows electrophysiological subthalamic nucleus identification, despite a slight decrease in overall activity level. Nevertheless, nitrous-ketamine showed significantly lower beta frequency power inside the nucleus compared to the ketamine and awake groups. At the group level, and in many trajectories, delineation of subthalamic nucleus subdomains can be achieved by detection of changes in the delta frequency oscillations. Notably, no differences in electrophysiological nucleus dimensions were found between the three groups. These findings suggest that it is possible to recognize the entrance and exit of the subthalamic nucleus with high confidence under nitrous oxide-ketamine anesthesia. However, the motor subregion of the nucleus is more difficult to delineate under nitrous anesthesia than ketamine sedation or awake, which may affect outcome.