Propofol has a very rapid onset of action and a short half life; it is associated with a fast recovery time from the sedation. Several studies have shown that propofol was superior to ben- zodiazepines and narcotics with regard to rapid induction of sedation and fast recovery.22-25 A recent study showed a higher satisfaction with BIS monitoring of propofol induced sedation during ESD procedures.14 However, propofol has a narrow ther- apeutic range and older patients have an increased sensitivity to its effects. In addition, it has no analgesic effects and narcotics are required during painful procedures. The combined use of narcotics or benzodiazepines can add to the risk of respiratory depression caused by unplanned deep sedation and general anesthesia. Although propofol induced sedation was safe with appropriate monitoring systems, the nurse or endoscopist ad- ministrated propofol induced sedation is not yet generally rec- ommended in various countries. The combination of midazolam and meperidine for sedation without assistance of anesthetics or intensive-care specialists is safe and useful. Therefore, we investigated whether midazolam and meperidine induced sedation using BIS monitoring affect the satisfaction of patients and endoscopist in lengthy and com- plicated ESD procedure. Contrary to our expectations, the over- all satisfaction of the patients and endoscopist, the complication rate, and the patients’ recall of pain during the ESD procedure, did not differ in the comparisons between BIS and non-BIS groups. In addition, subgroup analysis of ESD procedure taking more than 60 minutes did not showed statistical difference of satisfaction of patients and endoscopist. This findings suggest that BIS monitoring system for midazolam and meperidine in- duced sedation during ESD procedure do not give the additional efficacy of increasing satisfaction and decreasing complication rate. This was consistent with other studies which demonstrated that BIS monitoring did not improve any measure of patients outcome during endoscopic sedation.12,13 The midazolam and meperidine being used for sedation require 2 to 6 minutes for peak effect. Consequently, an under-sedated patient with a BIS level of 88 will remain under-sedated. Therefore, the value of BIS as an “early warning” sign of patient under sedation is not fully appreciated with midazolam and meperidine induced seda- tion. We excluded 2 patients in BIS group and 4 patients in non- BIS group because of paradoxical reaction. Generally, the in- cidence rate of paradoxical reaction was reported less than 1 percent during midazolam induced sedation.26 However, other study reported that a lengthy and painful procedure such as ERCP was more frequently experienced paradoxical reaction because of increased anxiety before performing procedure.25 The high incidence of paradoxical reaction in this study may be as- sociated with anxiety of patients due to invasive ESD procedure. Several reports showed temporally significant correlation BIS levels and MOAA/S scores.6,11,27,28 However, there was weak cor- relation between BIS levels and MOAA/S scores in this study. Kang KJ, et al: Efficacy of BIS during ESD 163 This finding might be induced from the feature of lengthy and invasive ESD procedure of our study compared to previous reports which included in the simple diagnostic and short dura- tion of endoscopic procedures. In this study, the mean dose of midazolam in non-BIS group was lower than in the BIS group. This finding might be ex- plained by the following. First, there was a significant overlap of the BIS scores between the deep and moderate levels of seda- tion. Second, the BIS scores were generally more specific than sensitive for the levels of deep sedation, i.e., more sedative drugs might be administrated to patients with BIS monitoring even with adequate sedation.11 Although midazolam and meperidine induced sedation using BIS monitoring did not showed efficacy, this was the first study to evaluate the usefulness of BIS monitoring with midazolam and meperidine induced sedation during ESD procedures. In conclusion, the results of this study show that midazolam and meperidine induced sedation using BIS monitoring do not provide to increase satisfaction of patients and endoscopist, to decrease complication rate, and to reduce dose of midazolam and meperidine during ESD procedures. Thus, we suggest that BIS monitoring does not have additional role in the the mid- azolam and meperidine induced sedation during ESD procedure. ACKNOWLEDGEMENTS Conflict of interest statement: All of doctors have no conflicts of interest or financial ties to disclose. They agreed to sign the Copyright Transfer Statement. This manuscript was written en- tirely by the authors, with no external assistance. No grant sup- port was received for this study. REFERENCES 1. Imagawa A, Okada H, Kawahara Y, et al. Endoscopic submucosal dissection for early gastric cancer: results and degrees of technical difficulty as well as success. Endoscopy 2006;38:987-990. 2. Ono H, Kondo H, Gotoda T, et al. Endoscopic mucosal resection for treatment of early gastric cancer. Gut 2001;48:225-229. 3. Ohkuwa M, Hosokawa K, Boku N, Ohtu A, Tajiri H, Yoshida S. New endoscopic treatment for intramucosal gastric tumors using an insulated-tip diathermic knife. Endoscopy 2001;33:221-226. 4. 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