A Simulation Study of Propofol Effect-Site Concentration for Appropriate Sedation in Pediatric Patients Undergoing Brain MRI: Pharmacodynamic Analysis

PURPOSE: We aimed to establish the propofol effect-site concentration (Ce) for appropriate sedation by pharmacodynamic analysis and to determine the propofol Ce during occurrence of sedation-related side effects in pediatric patients undergoing brain magnetic resonance imaging (MRI). MATERIALS AND METHODS: In 50 pediatric patients scheduled for brain MRI, sedation was induced with 2.0 mg/kg propofol; additional propofol doses were 0.5–1 mg/kg. Propofol Ce was simulated by inputting the propofol administration profiles of patients into a pediatric compartmental model (Choi model). The relationship between propofol Ce and probabilities of sedation and recovery were analyzed using a sigmoidal Emax model. The simulated propofol Ce for sedation-related side effects was investigated. Population model parameters were estimated using the Nonlinear Mixed-Effects Modelling software. RESULTS: The mean values of propofol Ce₅₀ for sedation during the preparation, scanning, and recovery phases were 1.23, 0.43, and 0.39 µg/mL. The simulated propofol Ce values during oxygen desaturation (SpO₂<90%) (3 patients; 6%), hypotension (16 patients; 32%), and bradycardia (12 patients; 24%) were 3.01±0.04, 2.05±0.63, and 2.41±0.89 µg/mL, respectively. CONCLUSION: The required propofol Ce₅₀ for applying monitors during the preparation phase before the start of MRI was higher than the propofol Ce₅₀ required during the scanning phase. During low-intensity stimulation phases, such as scanning, propofol bolus dose should be strictly titrated not to exceed the propofol Ce that can lead to oxygen desaturation because of the relatively low propofol Ce (Ce₉₅, 1.43 µg/mL) required for sedation in most patients.

Predicted EC50 and EC95 of Remifentanil for Smooth Removal of a Laryngeal Mask Airway Under Propofol Anesthesia

PURPOSE: The purpose of this study was to determine the effect-site concentration (Ce) of remifentanil in 50% of patients (EC50) and 95% of patients (EC95) for smooth laryngeal mask airway (LMA) removal in adults under propofol and remifentanil anesthesia. MATERIALS AND METHODS: Twenty-five patients of ASA physical status I-II and ages 18-60 years who were to undergo minor gynecological or orthopedic surgery were assessed in this study. Anesthesia was induced and maintained with propofol and remifentanil target-controlled infusion (TCI). Remifentanil was maintained at a predetermined Ce during the emergence period. The modified Dixon's up-and-down method was used to determine the remifentanil concentration, starting from 1.0 ng/mL (step size of 0.2 ng/mL). Successful removal of the LMA was regarded as absence of coughing/gagging, clenched teeth, gross purposeful movements, breath holding, laryngospasm, or desaturation to SpO2<90%. RESULTS: The mean+/-SD Ce of remifentanil for smooth LMA removal after propofol anesthesia was 0.83+/-0.16 ng/mL. Using isotonic regression with a bootstrapping approach, the estimated EC50 and EC95 of remifentanil Ce were 0.91 ng/mL [95% confidence interval (CI), 0.77-1.07 ng/mL] and 1.35 ng/mL (95% CI, 1.16-1.38 ng/mL), respectively. CONCLUSION: Our results showed that remifentanil TCI at an established Ce is a reliable technique for achieving safe and smooth emergence without coughing, laryngospasm, or other airway reflexes.

Effect-site concentration of sufentanil blunting responses to tracheal intubation with video laryngoscope during propofol TCI / 实用医学杂志

Objective To deter mine the effect-site concentration of sufentanil blunting responses to tracheal intubation with video laryngoscope during propofol target controlled infusion (TCI). Methods Twenty-three patients undergoing selective surgery under general anesthesia were enrolled in this study. Induction of anesthesia was initiated by TCI sufentanil at the target effect-site concentration 3 min later , TCI of propofol began at the target plasma concentration of 3 μg/mL. Cisatracurium 0.15 mg/kg was ad ministrated for video laryngoscope tracheal intubation after loss of consciousness. The target concentration of sufentanil for consecutive patients was deter mined using the modified Dixon′s up-and-down method by the intubation response of the previous patient , in an increment or decrement of 0.05 ng/mL. The initial concentration was set at 0.4 ng/mL. Results The EC50 of Sufentanil was 0.32 ng/mL with 95%confidence interval of 0.29~0.35 ng/mL; the EC95 was 0.38 ng/mL with 95%confidence interval 0.35-0.55 ng/mL during video laryngoscope tracheal intubation. Conclusion The EC50 and EC95of sufentanil blunting responses to tracheal intubation with video laryngoscope are 0.32 ng/mL and 0.38 ng/mL during propofol TCI.

Sex Differences in Remifentanil Requirements for Preventing Cough during Anesthetic Emergence

PURPOSE: Target-controlled infusion (TCI) of remifentanil can suppress coughing during emergence from general anesthesia; nevertheless, previous studies under different clinical conditions recommend significantly different effective effect-site concentrations (effective Ce) of remifentanil for 50% of patients (EC50). The differences among these studies include type of surgery and patient sex. In recent years, study of sex differences in regards to anesthetic pharmacology has drawn greater interest. Accordingly, we attempted to determine the effective Ce of remifentanil for preventing cough for each sex under the same clinical conditions. MATERIALS AND METHODS: Twenty female and 25 male ASA physical status I-II grade patients between the ages of 20 and 46 years who were undergoing thyroidectomy were enrolled in this study. The effective Ce of remifentanil for preventing cough was determined for each sex using the isotonic regression method with a bootstrapping approach, following Dixon's up-and-down method. RESULTS: Isotonic regression with a bootstrapping approach revealed that the estimated EC50 of remifentanil for preventing coughing during emergence was significantly lower in females {1.30 ng/mL [83% confidence interval (CI), 1.20-1.47 ng/mL]} than in males [2.57 ng/mL (83% CI, 2.45-2.70 ng/mL)]. Mean EC50 in females was also significantly lower than in males (1.23+/-0.21 ng/mL vs. 2.43+/-0.21 ng/mL, p<0.001). Mean arterial pressure, heart rate, and respiratory rate over time were not significantly different between the sexes. CONCLUSION: When using remifentanil TCI for cough prevention during anesthetic emergence, patient sex should be a considered for appropriate dosing.

The optimal effect-site concentration of remifentanil to attenuate the pain caused by propofol / 대한마취과학회지

BACKGROUND: The injection pain of propofol is a frequent and well-known adverse effect. This study was designed to determine the optimal effect-site concentration of remifentanil for minimizing injection pain during induction with propofol. METHODS: A total intravenous anesthetic technique was used for patients undergoing general anesthesia and remifentanil was pretreated to reach a certain target concentration before propofol injection. Using Dixon's up-and-down method, the degree of pain described by the patient was used to adjust the target concentration of remifentanil for the next patient. Ten success-failure curves (crossovers) were sought to find the effect-site concentration (EC) of remifentanil for minimizing injection pain of propofol. RESULTS: The EC of remifentanil in 50% and 95% of adult female population (EC50 and EC95) for minimizing injection pain of propofol were 3.09 ng/ml (95% confidence limits [CI] 2.92-3.30 ng/ml) and 3.78 ng/ml (95% CI 3.45-3.95 ng/ml), respectively. Clinically significant hemodynamic compromise or respiratory complications were not found during remifentanil infusion. CONCLUSIONS: Maintaining 3.78 ng/ml EC of remifentanil during induction with propofol attenuate propofol injection pain without serious adverse events in female patients undergoing general anesthesia and this method may provide the patient's comfort without preparing other drugs for pain relief.

Effect-site concentration of remifentanil for blunting hemodynamic responses to tracheal intubation using light wand during target controlled infusion-total intravenous anesthesia / 대한마취과학회지

BACKGROUND: Transillumination using a light wand is an alternative type of laryngoscope used for tracheal intubation. There is little information available on the effect-site concentration of remifentanil required to control hemodynamic changes induced by tracheal intubation using the transillumination method during total IV anesthesia. We therefore conducted this study to determine the effect-site concentration of remifentanil blunting hemodynamic responses after tracheal intubation in patients receiving propofol anesthesia. METHODS: We enrolled 26 healthy adult patients (ASA physical status I-II), aged 16-67 scheduled for surgery within 2 hours. All patients received a target-controlled infusion of 4 microg/ml propofol. The effect-site target-concentration of remifentanil of 5.0 ng/ml was chosen for the first patient. We used the Dixon's up-and-down sequential allocation method for determining the next remifentanil concentration. The time required for tracheal intubation was measured as the level of intubation stimulation. RESULTS: The average intubation time was 13.9 +/- 9.1 seconds. From the Dixon's method, the EC50 of remifentanil blunting the hemodynamic response to tracheal intubation was 2.94 ng/ml. CONCLUSIONS: This study shows that effect-site concentrations of remifentanil of 2.94 ng/ml is effective in blunting sympathetic responses to tracheal intubation in 50% of patients with normal airway anatomy when combined with a target controlled infusion of propofol (4 microg/ml).

Optimal effect-site concentration of remifentanil for preventing development of hypertension during tracheal intubation with inhaled desflurane induction / 대한마취과학회지

BACKGROUND: The aim of the present study was to determine the effect-site concentration of remifentanil needed to prevent haemodynamic instability during tracheal intubation with inhaled desflurane induction. METHODS: One hundred American Society of Anesthesiologists I and II female patients were randomized to receive an effect-site concentration of remifentanil of 0, 1, 2, 3, or 4 ng/ml. Induction of anaesthesia was started with intravenous injection of propofol 2 mg/kg. Ninety seconds after the completion of propofol injection, rocuronium (0.8 mg/kg) and remifentanil were administered simultaneously with 3% desflurane inhalation. Tracheal intubation was attempted 150 sec after the commencement of remifentanil administration. RESULTS: A probit model of remifentanil concentration was predictive of successful intubation without development of hypertension (P for goodness-of-fit = 0.419). The effect-site concentration of remifentanil needed to achieve successful intubation without development of hypertension in 95% of the patients was 3.3 ng/ml (95% confidence interval, 2.6-4.8 ng/ml). CONCLUSIONS: The effect-site concentration of remifentanil of 3.3 ng/ml is effective in blunting the haemodynamic response in 95% of the patients when 2.0 mg/kg of propofol induction was followed by 3% desflurane inhalation.

Comparative study of effective-site target controlled infusion with standard bolus induction of propofol for laryngeal mask airway insertion

Background: The laryngeal mask airway (LMA) is widely used in emergency medicine and surgical anesthesia. Several studies demonstrated induction of anesthesia with different plasma target-controlled infusion (TCI) of propofol for LMA insertion. However, there has been no study to compare the standard bolus propofol induction with the effective site TCI for LMA insertion. Objective: Compare the efficacy of induction of anesthesia with propofol for LMA insertion between the effective-site TCI, using 6 μg/mL, and the standard bolus propofol dose of 2.5 mg/kg in elective surgical patients. Methods: A randomized, prospective, single-blinded, clinical study was used for this study. Seventy-eight unpremedicated patients, American Society of Anesthesiologists (ASA) physical status I and II undergoing elective surgical procedure were randomly allocated between two groups. Group 1 received the standard bolus propofol dose of 2.5 mg/kg. Group 2 received effective site TCI (Schnider model) dose of 6 μg/mL for LMA insertion. The hemodynamics and anesthetic depth (Bispectral index score) were monitored and recorded during and immediately after LMA insertion. The number of insertion attempted, insertion quality score, induction time, and propofol doses used were recorded and compared between groups. Results: The success rate of first insertion attempt was equal in both groups (92.3%). There was no significant hemodynamic response difference between the groups during pre-induction, induction, insertion, and post insertion period. The BIS score was significantly lower during post insertion period in group 1 (51.4+11.0) than group 2 (58.4+3.2) (p=0.013). The propofol doses in group 2 were significantly lower than in group 1 (110.6+14.8 vs. 153.5+21.5) (p <0.001). Patients in group 2 required significantly more induction time than group 1 (146.9+42.3 vs. 103.4+33.6 (p <0.001). Conclusion: Propofol induction with TCI provided equal success rate as compared with standard bolus propofol induction for LMA insertion and insertion quality score. TCI significantly lowered the propofol consumption when compared with the standard 2.5 mg/kg propofol dose.

Relationship between Bispectral index,Narcotrend index and the predicted effect-site concentration at different clinical end-point during target-controlled infusion of propofol / 临床麻醉学杂志

Objective To explore the relationship between Bispectral index （BIS） values,Narcotrend index （NTI） values and the predicted effect-site concentration （EC）during target-controlled infusion of propofol. Methods In 30 patients during target-controlled infusion of propofol,the propofol infusion was set at an initial EC of 0.5 mg/L and increased by 0.5 mg/L steps every 5 min until 5 min after the modified observer＇s assessment of alertness/sedation scale（OAA/S） values reached zero. The predicted EC of propofol,the values of NTI,NTS and BIS were recorded,and the sedation level were examined by the modified OAA/S every 20 s. The predicted EC of propofol and the values of BIS and NTI at LVC and LOC in 5%,50% and 95% of patients were calculated. Results There were good linear correlations between BIS,NTI and the predicted EC of propofol （r2=0.787,0.792）.The predicted EC of propofol at LVC in 5%,50% and 95% of patients were 1.2,1.8 and 2.5 mg/L,respectively. The values of BIS and NTI at LVC in 5%,50% and 95% of patients were 78.2,68.2 and 58.2; 73.9,64.9 and 55.8,respectively.The predicted EC of propofol at LOC in 5%,50% and 95% of patients were 1.6,2.6 and 3.5 mg/L,The values of BIS and NTI at LOC in 5%,50% and 95% of patients were 74.6,58.2 and 41.5,66.2,55.8 and 45.3,respectively. Conclusion During target-controlled infusion of propofol,LVC and LOC occurred within a definite range of predicted effect-site concentrations.There were the good linear correlations between BIS,NTI and the predicted EC of propofol.NTI may be more useful than BIS in predicting LVC and LOC because of the smaller range of values for the two clinical end-points.

Correlations of preoperative hormonal changes with propofol and remifentanil requirements in pituitary adenoma patients

BACKGROUND: Anesthetic requirements are affected by the preoperative levels of some hormones. This study investigated to identify the hormonal status such as plasma level and maximal secretary capacity correlating with propofol and remifentanil requirements in pituitary adenoma patients who show various hormonal secretory states perioperatively. METHODS: From 51 adult female pituitary adenoma patients, preoperative basal values and maximal stimulated levels of various hormones related to the axis of hypothalamus-pituitary-target organs on combined pituitary function test were recorded. Total intravenous anesthesia using target controlled infusion with propofol and remifentanil was administered. The effect-site concentration (Ce) of propofol reaching anesthetic induction and the consumed dosages of propofol and remifentanil during operation were measured. Anesthetic maintenance was controlled within 30% of preanesthetic hemodynamic variables by remifentanil and within ranges of BIS 45 +/- 10 by propofol. Spearman correlations between hormonal status and anesthetic requirements such as propofol Ce for induction, total consumed doses of propofol and remifentanil were performed with a statistical significance at P of 0.05. RESULTS: The preoperative basal level of ACTH was correlated positively with propofol induction Ce and maintenance dose, and the maximal secretory capacity of prolactin also correlated positively with propofol induction Ce. Remifentanil consumption dose was not related with any hormones measured regardless of either preoperative basal levels or maximal secretory levels. CONCLUSIONS: Propofol requirements may be related with preoperative plasma level of ACTH or maximal secretory capacity of prolactin.

Effect-site concentration of remifentanil for blunting hemodynamic response to double lumen endobronchial intubation during target controlled infusion-total intravenous anesthesia using propofol with remifentanil / 대한마취과학회지

BACKGROUND: This study was undertaken to determine the effect-site concentration of remifentanil for blunting hemodynamic responses to double lumen endobronchial intubation during target controlled infusion (TCI)-total intravenous anesthesia (TIVA) using 4.0 microg/ml of propofol with remifentanil. METHODS: Sixty patients (American society of anesthesiologists physical status classification 1 or 2) were randomly allocated according to the target effect-site concentration of remifentanil (R3.0: remifentanil 3.0 ng/ml; R3.5: remifentanil 3.5 ng/ml; R4.0: remifentanil 4.0 ng/ml). The effect-site concentration of propofol at loss of consciousness was recorded. Mean arterial pressure (MAP), heart rate (HR) and bispectral index (BIS) were recorded at just before remifentanil administration (baseline), at the time of target effect site concentration of remifentanil and propofol, at just before intubation and 1, 2, 3 min after intubation. RESULTS: MAP was significantly increased compared with baseline at 1, 2 min after intubation in R3.0, but was significantly decreased in R4.0. MAP of R3.5 was not different from the baseline after intubation. HR was significantly decreased compared with baseline at the time of target effect site concentration of propofol and immediate before intubation in R3.5 and R4.0. After intubation, HR was significantly increased compared with baseline at only 1 min after intubation and returned to the baseline in R3.0. However, HR was continuously decreased in R4.0. CONCLUSIONS: These findings suggest that effective target effect-site concentration of remifentanil for blunting hemodynamic responses to double lumen endotracheal intubation was 3.5 ng/ml during TCI-TIVA using 4.0 microgram/ml of propofol with remifentanil.

What is the optimal effect-site concentration of remifentanil for minimizing the cardiovascular changes to endotracheal intubation during induction with propofol in elderly patients? / 대한마취과학회지

BACKGROUND: The addition of remifentanil during propofol TCI (target controlled infusion) attenuates the hemodynamic changes induced by endotracheal intubation. This study examined the optimal effect-site concentration of remifentanil to minimize the cardiovascular changes to endotracheal intubation in elderly patients. METHODS: Fifty ASA 1 or 2 elderly patients scheduled for elective surgery under general anesthesia were assigned randomly to one of two groups according to the effect-site concentration of remifentanil. Each group was administered 4 microgram/ml of propofol TCI with 1 ng/ml (group R1) or 3 ng/ml (group R3) of remifentanil. The heart rate (HR), systolic (SAP), mean (MAP) and diastolic arterial pressure (DAP) were measured at pre-induction, before and after endotracheal intubation. RESULTS: After intubation, the HR, SAP, MAP and DAP increased significantly in the two groups compared with the pre-intubation values. However, the HR, SAP, MAP and DAP for group R3 were lower than group R1 for 5 min after intubation. CONCLUSIONS: In elderly patients administered 4 microg/ml of propofol TCI, we suggest that the optimal effect-site concentration of remifentanil to minimize the cardiovascular changes to endotracheal intubation is 3 ng/ml rather than 1 ng/ml.

What is the Optimal Effect-site Concentration of Remifentanil for Minimizing the Cardiovascular Changes to Endotracheal Intubation during Induction with Propofol? / 대한마취과학회지

BACKGROUND: In this study, the optimal effect-site concentration of remifentanil for blunting hemodynamic responses to endotracheal intubation during total intravenous anesthesia using propofol were evaluated. METHODS: 137 ASA class I and II patients, aged 18-60 years, were randomly allocated to one of six groups according to the effect-site concentration of remifentanil. Remifentanil was then infused at a target effect-site concentration of 0, 1, 2, 3, 4 or 6 ng/ml in groups R0, R1, R2, R3, R4 and R6, respectively. Anesthesia was induced with propofol infusion at a target effect-site concentration of 4microgram/ml endotracheal intubation was performed 5 minutes after remifentanil administration. Blood pressure (BP), heart rate (HR) and cardiac index (CI) were recorded at the baseline and then every 30 seconds until 3 minutes after intubation. RESULTS: BP and HR in groups R0, R1 and R2 increased significantly after intubation when compared with the baseline values. The CI in group R0 also increased significantly after intubation when compared with the baseline values. Incidences of hypertension and hypotension were 50% and 5% in R0, 32% and 14% in R1, 18% and 32% in R2, 10% and 48% in R3, 8% and 54% in R4, and 0% and 81% in R6. There were also 2 cases in which the mean blood pressure was less than 50 mmHg in group R6. CONCLUSIONS: We suggest that the optimal target effect-site concentrations of remifentanil for blunting hemodynamic responses to endotracheal intubation are 3 or 4 ng/ml during total intravenous anesthesia using propofol at an effect-site concentration of 4microgram/ml.

Adequate Combination of Target Effect-site Concentration of Propofol and Remifentanil for Tracheal Intubation / 대한마취과학회지

BACKGROUND: We wanted to determine an adequate combination of target effect-site concentrations of remifentanil and propofol during anesthetic induction with target controlled infusion (TCI).We also determined whether increasing remifentanil concentrations might reduce propofol consumption at loss of consciousness (LOC). METHODS: Sixty ASA 1 or 2 patients were randomly allocated according to the target effect-site concentration of remifentanil and propofol (R7P3: remifentanil 7 ng/ml + propofol 3microgram/ml, R5P4: remifentanil 5 ng/ml + propofol 4microgram/ml, R3P5: remifentanil 3 ng/ml + propofol 5microgram/ml). After the target effect-site concentration of remifentanil had been reached, the TCI of propofol was started. The effect-site concentration of propofol at LOC was recorded. When the target effect-site concentration of propofol was reached, 0.6 mg/kg of rocuronium was administered. Tracheal intubation was performed after 2 minutes. The noninvasive blood pressure, heart rate (HR), bispectral index (BIS), and infused dose of remifentanil and propofol were recorded. RESULTS: R3P5 groupd showed a significant increase in mean blood pressure after intubation (104 +/- 31.9 mmHg, P < 0.05) compared to R7P3 and R5P4. BIS at the time when propofol reached its target effect-site concentration was significantly higher in the R7P3 group (71.6 +/- 9.9, P < 0.05 compared to R5P4 and R3P5). There was a significant relationship between the effect-site concentration of remifentanil and propofol at LOC (Y = 2.032 - 0.351X, R(2) = 0.551, P < 0.0001). CONCLUSIONS: The R5P4 target effect-site concentrations are adequate dosing combinations during TCI induction based on hemodynamic responses and BIS values.

The effect of music on the effect-site concentration of propofol for loss of consciousness / 대한마취과학회지

BACKGROUND: Music reduces anxiety and the need for sedatives in preoperative patients. Currently, propofol is usually infused using target controlled infusion device. With the use of such a device, we investigated the effects of music on the effect-site concentration of propofol for loss of consciousness. METHODS: Sixty-five ASA 1 or 2 patients aged 35 to 55 years who were scheduled for general anesthesia were randomly allocated to either the control, music or headphone group. The control group patients were exposed to the ambient operating room atmosphere (n = 17), the music group patients listened to music (n = 25), and headphone group wore a headphone alone without listening to music (n = 23). Propofol was infused with a predetermined effect-site concentration and we determined loss of consciousness in patients by a verbal response and eyelash reflex for 3 minutes. Each concentration of propofol was predetermined by the up-and-down method with 0.4microgram/ml as the step size. RESULTS: Loss of consciousness was observed at a concentration of 4.20 +/- 0.25microgram/ml in the control group, 3.60 +/- 0.34microgram/ml in the music group, and 3.73 +/- 0.47microgram/ml in the headphone group. The effect-site concentration for loss of consciousness was significantly lower in the music group as compared to the control group (P < 0.05). The effect-site concentration in the headphone group, however, showed no statistical difference as compared to the control group (P = 0.117). CONCLUSIONS: Listening to music reduced overall propofol effect-site concentration for loss of consciousness that was required by patients.

Evaluation of Effect-site Concentration of Remifentanil for Blunting Hemodynamic Responses to Endotracheal Intubation during Total Intravenous Anesthesia using Propofol / 대한마취과학회지

BACKGROUND: The present study was undertaken to determine the effect-site concentration of remifentanil for blunting hemodynamic responses to tracheal intubation during total intravenous anesthesia (TIVA) using propofol. METHODS: In this prospective, randomized, double-blind study, a total of 126 patients, aged 18-60 (ASA I or II), having undergone elective surgery under TIVA using propofol were investigated. Anesthesia was induced using propofol (target effect-site concentration 4microgram/ml) and rocuronium (0.9 mg/kg). Remifentanil was infused at target effect-site concentrations of 0, 2, 4, 6 ng/ml: groups R1, R2, R3 and R4, respectively. The systolic arterial pressure (SAP), diastolic arterial pressure (DAP) and heart rate (HR) were measured pre-induction, and before and after tracheal intubation. RESULTS: After intubation, the SAP, DAP and HR increased significantly (P < 0.05) in all groups compared to the pre-intubation values. Compared with pre-induction values, the SAP and DAP in groups R1 and R2 increased significantly after intubation (P < 0.05), but those in group R3 remained constant until 1 min after intubation. The SAP and DAP in group 4 however, decreased significantly (P < 0.05) for 3 min after intubation. The HR increased significantly after intubation in groups R1, R2 and R3 compared to the values before intubation (P < 0.05), but that in group R4 being remained constant. CONCLUSIONS: We suggest that the optimal target effect-site concentrations of remifentanil for blunting hemodynamic responses to tracheal intubation were 4 or 6 ng/ml during TIVA using propofol.

Target Effect-site Controlled Infusion of Propofol by Schnider Model: Comparison of Gender and Age / 대한마취과학회지

BACKGROUND: We investigated effect-site median effective concentration (EC50) of propofol for loss of consciousness and effect-site concentration at each anesthetic stage and awakening time to compare the differences by gender or age of patients using Schnider model. METHODS: Total 91 patients were allocated into 4 groups: male patients aged 18-34 year (Group 1), male patients aged 35-55 years (Group 2), female patients aged 18-34 years (Group 3) and female patients aged 35-55 years (Group 4). The effect-site EC50 for loss of consciousness was calculated and the effect-site concentration of propofol at each anesthetic stage and the awakening time of each group were recorded. RESULTS: The effect-site EC50 of propofol for loss of consciousness was 4.53 +/- 0.30microgram/ml, 4.60 +/- 0.25microgram/ml, 4.13 +/- 0.39microgram/ ml and 4.47 +/- 0.65microgram/ml in group 1, 2, 3, and 4, respectively. The effect-site concentrations in male patients aged 18-34 years were significantly higher than those in female patients. The awakening time of female patients aged 35-55 years was shorter than that of male patients. CONCLUSIONS: There were no significant differences of effect-site EC50 for the loss of consciousness of propofol with target effect-site controlled infusion by Schnider model among the groups. However the effect-site concentrations and the awakening time of propofol by Schnider model showed differences in patients' gender and age.

Comparison of Laryngeal Tube Insertion Condition according to Effect-Site Concentration during Target-Controlled Infusion (TCI) of Propofol / 대한마취과학회지

BACKGROUND: The aim of the study was to compare the laryngeal tube (LT) insertion conditions at 3.0 and 3.5microgram/ml effect site concentrations (ECs) during anesthesia induction using the target-controlled infusion (TCI) of propofol. METHODS: The forty patients were randomly divided into two groups. The patients received TCI of propofol with a 6.0 microgram/ml target plasma concentration (Cpt) and then an LT was inserted without the aid of a muscle relaxant when the predicted EC reached 3.0microgram/ml (group 1) or 3.5microgram/ml (group 2). The conditions of LT insertion, i.e., mouth opening, gagging, coughing, head or limb movement, laryngospasm, and overall ease, and hemodynamic responses were evaluated 3 min after midazolam injection, at loss of consciousness and eyelash reflex, and immediately before, immediately after, 1 min after, and 3 min after LT insertion. We also compared times required to insert LTs, cuff volumes, and incidences of blood staining and of postoperative sore throat. RESULTS: The conditions of LT insertion, except laryngospasm and overall ease, were not significantly different in the two groups. The incidence of laryngospasm in group 1 (25%) was significantly higher than in group 2 (0%) and group 2 was better than group 1 in terms of overall ease of insertion (P<0.05). No significant differences were observed between the two groups in terms of hemodynamic responses. Minimum cuff volume to 60 cmH2O was 64.0 +/- 8.3 ml in Group 1 and 63.9 +/- 6.5 ml in Group 2, and time required for LT insertion was 21.0 +/- 11.0 sec in Group 1 and 24.7 +/- 16.6 sec in Group 2. Postoperative sore throat and blood stain incidences were not significantly different in the two groups. CONCLUSIONS: After induction with 6microgram/ml of Cpt using propofol TCI for LT insertion, LT insertion at 3.5microgram/ml of EC provided a lower incidence of laryngospasm and better overall ease than insertion at 3.0microgram/ml of EC.

Correlations between the Modified Observer's Assessment of Alertness/Sedation Scale, Bispectral Index and Propofol Effect Site Concentrations in Sedated Elderly Patients under Regional Anesthesia / 대한마취과학회지

BACKGROUND: To maintain an adequate sedation level in elderly patients (over 65 years) under regional anesthesia, we evaluated the correlations between the modified observer's assessment of alertness/sedation (OAA/S) scale, bispectral index (BIS), propofol effect site concentrations. METHODS: In elderly patients (over 65 years) scheduled for transurethral resection of a bladder tumor or prostate, we measured BISs and started propofol infusion using the target controlled infusion (TCI) method to sedate patients after regional anesthesia. OAA/S composite scores, measured BISs propofol effect site concentrations and vital signs were determined. RESULTS: When the OAA/S composite score was 5, mean BIS was 97.2 +/- 1.1; when the OAA/S was 4, mean BIS was 84.3 +/- 4.6 and mean propofol effect site concentration was 0.8 +/- 0.3microgram/ml; when the OAA/S was 3, mean BIS was 78.4 +/- 4.3 and mean propofol effect site concentration was 1.2 +/- 0.3microgram/ml; and when the OAA/S was 2, mean BIS was 73.2 +/- 5.9 and mean propofol effect site concentration was 1.5 +/- 0.4microgram/ml. The OAA/S scale was found to be well correlated with BIS (Pearson's r = 0.973) and the propofol effect site concentration (Pearsons's r = -0.968). BIS was also well correlated with propofol effect site concentration (Pearson's r = -1.0). CONCLUSIONS: BIS was found to be a good tool for monitoring sedation level in elderly patients under regional anesthesia with propofol sedation.

Is it Safe to Use Target-Controlled Propofol Infusion with DiprifusorTM for Children of School Age? / 대한마취과학회지

BACKGROUND: A commercially available target-controlled propofol infusion system, the 'Diprifusor'TM is used for the induction and maintenance of anesthesia in adults, not in children because the pharmacokinetics of propofol in children. We wondered whether it is safe to use the 'Diprifusor'TM in children weighing over 30 kg in clinical practice? METHODS: Twenty unpremedicated children (8-15 yr, group 1) and sixty five unpremedicated adults (16-65 yr, group 2) scheduled for elective surgery were enrolled. After intravenous injection of fentanyl 1microgram/kg, a propofol infusion was started at a target concentration of 4microgram/ml using a 'Diprifusor'TM. We recorded the time to loss of eyelash reflex and effect site concentration at the time of loss of consciousness. Anesthesia was maintained with propofol-fentanyl-50% N2O-rocuronium. We also checked the effect site concentration at the time of eye opening to verbal command. RESULTS: The effect site concentrations at loss of eyelash reflex were 1.19 +/- 0.66microgram/ml (group 1) and 0.96 +/- 0.55microgram/ml (group 2), and these were not significantly different between the two groups. But the effect site concentrations at eye opening were 1.66 +/- 0.38microgram/ml (group 1) and 1.47 +/- 0.32microgram/ml (group 2) which were significantly different (P <0.05). CONCLUSIONS: 'Diprifusor'TM can be used safely in children weighing over 30 kg with a similar effect site concentration at loss of eyelash reflex as adults, but the effect site concentration at eye opening in children is slightly higher than that of adults.