Análisis de la profundidad anestésica mediante métodos electroencefalográficos

Different monitors have been tried to evaluate depth of anesthesia, and the most extended are the cerebral monitors of electroencephalography (EEG). Objectives: To establish the EEG pattern and hemodynamic variations of the desflurane. To observe the EEG parameters, during induction, maintenance, and recovery. To establish the changes in the anesthetic concentration, administered to maintain a bispectral index (BIS) between 40-50, when morphine is added to peridural solutions. Matherial and methods: Twenty-four patients of gynecological surgery were monitorized with the EEG. Desflurane was administered at 0.5, 1 and 1.5 MAC. Hemodynamic variables and the EEG parameters, spectral edge frequency (SEF90) and delta ratio were collected. The second part of the study on 50 patients of abdominal surgery, hemodynamic values and EEG parameters were collected at: basal situation; before and after orotracheal intubation; after surgical incision; at 60 minutes; at 90 minutes; when anesthetic was withdrawn and BIS reached 60; when movement appeared; and at extubation time. Finally, on 40 patients of colloproctological surgery a thoracic peridural catheter was placed. Patients were randomized to receive morphine 0.1% (2 ml). Sevoflurane concentration was titrated to maintain a BIS between 40-50. Results: Blood pressure fell at 1.5 MAC, but heart rate did not. A significant decrease in the SEF90 appeared at 1.5 MAC, indicating a deeper plane of anesthesia. BIS values decreased from 95,6 to 34.7 and SEF90 fell from 20.5 to 11.9 Hz after anesthesia induction. During recovery mean BIS increased from 59.2 to 92,3 and SEF90 from 15.1 to 22.2 Hz, heart rate increased but blood pressure did not. The EEG values recorded when movement appeared were 77 for BIS (range 58-96) and 18Hz for SEF90 (range13.18). The only findings were that the morphine group had a lower pain score level than the bupivacaine group ( no pain on movement, 79% vs 31.5%, p<0.01). Conclusions: We can conclude that EEG processing provides a good measure of depth of anesthesia. EEG parameters are useful for distinguishing between the states of consciousness and unconsciouness during the three phases of anesthesia. Adding morphine to the epidural solution did not reduce sevoflurane requirements but did provide high quality postoperative analgesia."