The Index of Anesthetic Depth in Enflurane Anesthesia

Cho, Myung Won; Kim, Chong Sung; Kwak, Il Yong

Abstract

It is essential for the safe conduction of anesthsia to monitor the depth of anesthesia during aperation. However no one method has been confirmed to be objective and accurate as yet. Hecently lower esophageal contractility (LEC) has emerged as a means of mesuring anesthetic depth. To evaluate the usefulness as an index of anesthetic depth, the author compared the cardio- vascular signs (blood pressure, heart rate), EMG, EEG, plasma epinephrine and norepinephrine concentrations and LEC, until now known to be relevent to the anesthetic depth, at varing conditions of of no anesthesia, under anesthesia and after stimulation. The subjects were 30 ASA class 1 surgical patients, aged from 20 to 49, who had no specific past midical history and no recent medications. Patients were given thiopental sodium 4 mg/kg and vecuronium 0.1 mg/kg for induction and intubation and respiration controlled with 100% oxygen, then baseline measurements were taken (control) and compard the values of under enflurane anesthesia with 1 minimum alveolar concentration (MAC), 1.7%, (anesthesia) and after surgical stimulation (stimulation) with each other. The results were as follows ; 1) EEG, response rate and frequency of spontaneous LEC, amplitude of provoked LEC, LEC index of under enflurane anesthesia and after stimulation revealed significant differences compared with control but no significant differences between under anesthesia and after stimulation values. 2) Systolic, diastolic, mean blood pressure revelaled significant differences among control, under anesthesia and after stimulation values. 3) Heart rate, EMG, plasma epinephrine and norepinephrine concentrations, amplitude of spontaneous LEC revealed no significant differences among control, under anesthesia and after stimulation values. According to the above results, compared to the control value, EEG, and LEC reflected anesthetic depth under 1 MAC enflurane anesthesia but were meaningless in the evaluation of surgical stimulation. Blood pressure change which revealed significant differences among three values could be judged to be useful as an index of anesthetic depth most commonly applicable in practice.