Korean J Anesthesiol to commands (Table 2). Chest wall rigidity was defined as decreased chest wall compliance to external positive ventilatory pressure. During ventilation with a mask, chest wall rigidity was monitored for improper ventilation and the increase of peak inspiratory pressure above 20 mmHg [13]. After the effect-site concentration of remifentanil reached the target concentration, 0.3 mg/kg of etomidate (Etomidate-Lipuro, B. Braun Melsungen, Melsungen, Germany) was injected intravenously for over 1 min, then patients were observed visually for myoclonus. When myoclonus is present, its severity was graded by an anesthesiologist who was blinded to the effect site concentration of remifentanil. Intensity of myoclonic movement was graded as 0 (none), 1 (mild; movement at the finger or wrist only), 2 (moderate; involving the face and leg), or 3 (severe; generalized response or fast abduction of the limb) [8,11]. Two minutes after etomidate administration, rocuronium 0.8 mg/kg was administered to facilitate tracheal intubation. After ventilation with 6 vol% sevoflurane for 90 seconds, an endotracheal tube was intubated. The expected incidence of myoclonus in the control group (Group N) was 80% and 28 patients were required in each group to detect a 50% difference at a 95% significance level and a power of 0.8 based on previous studies [1,3]. Thirty three Table 3. Frequency and Severity of Myoclonus after Injection of Etomidate Numbers are Frequencies Group N Group R Group Q None Mild Moderate Severe 6 6 9 12 29 3 1 0 33 0 0 0 Group N: normal saline, Group R: pretreatment with 2 ng/ml of remifentanil, Group Q: pretreatment with 4 ng/ml of remifentanil. Ri, et al. patients were included in each group. Statistical analysis was performed by SPSS 12.0 (SPSS, Chicago, IL). Comparison of demographic data was performed by one way ANOVA and the chi-square test. The incidence and severity of myoclonus were analysed by Pearson's chi-square test and linear by linear association. The changes in BP and HR over time were analyzed by repeated measures ANOVA. Results were considered statistically significant when P < 0.05. Results The incidence of myoclonus of each group was significantly different according to the Pearson chi-square test (P < 0.01). The incidence of myoclonus in Groups N, R, and Q were 81%, 12%, and 0%, respectively (P < 0.01) (Table 3). The severity of myoclonus decreased with an increasing effect site concentration of remifentanil, which was revealed by the linear by linear association. Cough (13/33 patients), chest wall rigidity (15/33 patients), apnea (2/33 patients), and sedation (15/33 patients) occurred in Group Q. No side effects occurred Table 4. Number of Side Effects Cough (n) Chest wall rigidity (n) Apnea (n) Sedation (n) Group N (n = 33) 0 0 0 0 Group R (n = 33) 0 0 0 0 Group Q (n = 33) 13 15 2 2 Chest wall rigidity was evaluated by improper ventilation and an increase in peak inspiratory pressure over 20 mmHg during mask ventilation. Sedationindicates a 4 on the Ramsay sedation scale. Group N: normal saline, Group R: pretreatment with 2 ng/ml of remifentanil, Group Q: pretreatment with 4 ng/ml of remifentanil. Fig. 1. The change of BP (A) and HR (B) in Group R and Group Q were lesser than that in Group N, and BP was lower in Group R and Group Q than Group N. Group N: normal saline, Group R: pretreatment with 2 ng/ml of remifentanil, Group Q: pretreatment with 4 ng/ml of remifentanil. *P < 0.05 compared to the other group. www.ekja.org 129