Assessment of Amnesic Effect and the Depth of Hypnosis During Therapeutic Inhalation of Xenon-Oxygen Mixture

The current literature lacks data on the incidence of intraoperative awakening during xenon anesthesia. This could be due to amnesia preventing memories of the intraoperative awakening. The objective: to determine the concentration of xenon in the xenon-oxygen mixture, which causes amnesia for events during inhalation in 100% of patients, and to make correlations with the depth of hypnosis as per Kugler scale. Subjects and Methods: 34 patients with chronic neurogenic pain who received 111 20-minute inhalations with concentration of xenon up to 50% were included in the study. Amnesia evaluation, EEG monitoring, and pain assessment on a visual analog scale (VAS) were performed. Results. Amnesic effect developed in 100% of patients at xenon concentration of 45%. On inhalation of xenon at concentrations of up to 50%, EEG changes did not exceed D1 grade on Kugler scale. The decrease in bispectral index (BIS) did not reach the level of deep sedation (Me 96.2%) at xenon concentration of 50%. The decrease in pain on VAS was approximately 60%. Conclusions. Xenon inhalations cause transient congradic amnesia at concentrations of 45% or more. The accuracy of the BIS monitoring readings may be reduced when using xenon in a monovariant. Inhalations of xenon-oxygen mixture in concentrations up to 50% showed good analgesic properties in the framework of combined therapy of chronic pain syndrome.