[To the effective concentration of xenon]

The present literature discusses what effective concentration of xenon may be used to induce adequate anesthesia. To examine the analgesic properties of the substance, 38 patients undergone laparoscopic operations for calculous cholecystitis under informational saturation EEG (INEEG) monitoring were included into this study. All the patients were divided into 3 groups in accordance to the mode of anesthesia maintenance and INEEG monitoring. In Groups 1 and 2, the concentration of xenon was maintained at 70%; INEEG monitoring was made in the of-line mode. In Group 3, the concentration of xenon was gradually decreased from 70% to the minimum value at which the level of INEEG was 40-50%, which corresponds to the adequate depth of anesthesia. The use of 70% xenon concentration and the standard doses offentanyl (3.1 +/- 1.6 microg/kg/h) resulted in excessively deep anesthesia (38 +/- 4% INEEG). Reduction of the dose of fentanyl on an average to 1.5 +/- 0.8 microg/kg/h permitted more adequate anesthesia; however, an excessively deep anesthesia is encountered in 40% of cases, as evidenced by INEEG. The active use of INEEG monitoring in Group 3 makes it possible to perform an adequate anesthesia (46 +/- 4% INEEG) and to determine the xenon concentration necessary for this, which is equivalent to 42 +/- 11% with the dose of fentanyl of 0.9 +/- 0.8 microg/kg/h.