Ce Of Remifentanil Research Articles

Sex-related differences in effect-site concentration of remifentanil for preventing anesthetic emergence cough in elderly patients.

PurposeCough on anesthetic emergence should be prevented considering its dangerous complications. Target-controlled infusion (TCI) of remifentanil can reduce emergence cough effectively, and sex-related differences in effect-site concentration (Ce) of remifentanil have been evaluated in young patients. In this study, we determined the Ce of remifentanil for preventing emergence cough following extubation in male and female elderly patients and evaluated the sex-related difference.Patients and methodsTwenty-three male and 22 female elderly patients aged between 60 and 75 years were enrolled. Anesthesia was maintained with sevoflurane and remifentanil TCI. The Ce of remifentanil for preventing emergence cough was determined for each sex using isotonic regression method with a bootstrapping approach, following Dixon’s up-and-down method.ResultsThe Ce of remifentanil for preventing emergence cough in 50% (EC50) and 95% (EC95) of the population was significantly lower in females than in males. Isotonic regression revealed the EC50 (83% confidence interval [CI]) of remifentanil was 1.67 (1.55–1.83) ng/mL in females and 2.60 (2.29–2.91) ng/mL in males. The EC95 (95% CI) of remifentanil was 2.30 (2.02–2.62) ng/mL in females and 3.41 (3.27–3.58) ng/mL in males. Dixon’s up-and-down method indicated that the mean EC50 in females was lower than in males (1.56±0.26 ng/mL vs 2.56±0.37 ng/mL, P<0.001).ConclusionThe remifentanil requirement for preventing emergence cough was lower in female than in male elderly patients, indicative of sex-related differences in Ce of remifentanil. Sex should be considered when using remifentanil TCI for preventing emergence cough in elderly patients.

Comparison of the Effects of Dexmedetomidine on the Induction of Anaesthesia Using Marsh and Schnider Pharmacokinetic Models of Propofol Target-Controlled Infusion.

The study aimed to determine the effects of dexmedetomidine on the induction of anaesthesia using different models (Marsh and Schnider) of propofol target-controlled infusion (TCI). Sixty-four patients aged 18-60 years, American Society of Anaesthesiologists (ASA) class I-II who underwent elective surgery were randomised to a Marsh group (n = 32) or Schnider group (n = 32). All the patients received a 1 μg/kg loading dose of dexmedetomidine, followed by TCI anaesthesia with remifentanil at 2 ng/mL. After the effect-site concentration (Ce) of remifentanil reached 2 ng/mL, propofol TCI induction was started. Anaesthesia induction commenced in the Marsh group at a target plasma concentration (Cpt) of 2 μg/mL, whereas it started in the Schnider group at a target effect-site concentration (Cet) of 2 μg/mL. If induction was delayed after 3 min, the target concentration (Ct) was gradually increased to 0.5 μg/mL every 30 sec until successful induction. The Ct at successful induction, induction time, Ce at successful induction and haemodynamic parameters were recorded. The Ct for successful induction in the Schnider group was significantly lower than in the Marsh group (3.48 [0.90] versus 4.02 [0.67] μg/mL; P = 0.01). The induction time was also shorter in the Schnider group as compared with the Marsh group (134.96 [50.91] versus 161.59 [39.64]) sec; P = 0.02). There were no significant differences in haemodynamic parameters and Ce at successful induction. In the between-group comparison, dexmedetomidine reduced the Ct requirement for induction and shortened the induction time in the Schnider group. The inclusion of baseline groups without dexmedetomidine in a four-arm comparison of the two models would enhance the validity of the findings.

Optimal effective-site concentration of remifentanil for sedation during plate removal of maxilla.

BackgroundRemoval of the plate following Le Fort I osteotomy and BSSO (bilateral sagittal split osteotomy) is a common procedure. However, patients who undergo plate removal experience intense pain and discomfort. This study investigated the half-maximal effective concentration (Ce50) of remifentanil in the prevention of plate removal pain under sedation using dexmedetomidine.MethodsThe study evaluated 18 patients, between 18 and 35 years of age, scheduled for elective surgery. Remifentanil infusion was initiated after sedation using dexmedetomidine, and started at a dose of 1.5 ng/mL on the first patient via target-controlled infusion (TCI). Patients received a loading dose of 1.0 µg/kg dexmedetomidine over 10 min, followed by a maintenance dose of 0.7 µg/kg/h. When the surgeon removed the plate, the patient Modified Observer's Assessment of Alertness/Sedation (MOAA/S) score was observed.ResultsThe Ce of remifentanil ranged from 0.9 to 2.1 ng/mL for the patients evaluated. The estimated effect-site concentrations of remifentanil associated with a 50% and 95% probability of reaching MOAA/S score of 3 were 1.28 and 2.51 ng/mL, respectively.ConclusionsPlate removal of maxilla can be successfully performed without any pain or adverse effects by using the optimal remifentanil effect-site concentration (Ce50, 1.28 ng/mL; Ce95, 2.51 ng/mL) combined with sedation using dexmedetomidine.

The EC90 of remifentanil for blunting cardiovascular responses to head fixation for neurosurgery under total intravenous anesthesia with propofol and remifentanil based on bispectral index monitoring: estimation with the biased coin up-and-down sequential method

BackgroundHead fixation can induce hemodynamic instability. Remifentanil is commonly used with propofol for total intravenous anesthesia (TIVA) during neurosurgery. This study investigated the 90% effective concentration (EC90) of remifentanil for blunting of cardiovascular responses to head fixation during neurosurgery via bispectral index (BIS) monitoring.MethodsFifty patients undergoing neurosurgery requiring head fixation were enrolled. This study was performed using the biased coin up-and-down design sequential method (BCD). After tracheal intubation, the effect-site target concentration (Ce) of remifentanil was adjusted to achieve hemodynamic stability and reset to the level preoperatively assigned to each patient, according to the BCD method, approximately 10 min before head fixation. Baseline hemodynamic values were recorded before head fixation. An ineffective response was defined as a case with a > 20% increase in hemodynamic values from baseline. Otherwise, the response was determined to be effective. The EC90 of remifentanil was calculated as a modified isotonic estimator.ResultsForty-three patients completed this study. The EC90 of remifentanil for blunting cardiovascular responses to head fixation was estimated to be 6.48 ng/mL (95% CI, 5.94–6.83 ng/mL).ConclusionsAdjustment of the Ce of remifentanil to approximately 6.5 ng/mL before head fixation could prevent noxious cardiovascular responses in 90% of neurosurgical ASA I-II patients aged 20 to 65 years old during propofol target-controlled infusion titrated to maintain BIS between 40 and 50.Trial registrationClinicalTrials.gov Identifier NCT01489137, retrospectively registered 5 December 2011.

Motor Evoked Potentials and Bispectral Index-Guided Anaesthesia in Image-Guided Mini-Invasive Neurosurgery of Supratentorial Tumors Nearby the Cortico-Spinal Tract.

To describe and evaluate the anaesthesiological regimen used in neurophysiologically monitored image-guided mini-invasive neurosurgery. Twenty-four patients underwent elective surgery under general anaesthesia that was administered through Target Controlled Infusion (TCI) for effect-site concentration (Ce) of Propofol and Remifentanil, targeting the Bispectral Index (BIS) in the 40-60 intervals. The stimulating intensity of transcranial motor evoked potentials (tMEP), BIS, Propofol and Remifentanil Ce were collected at MEPs threshold (T) definition (respectively BIS@T, CeProp@T and CeRemi@T). Intraoperative seizure, explicit recall for intraoperative awareness and clinical motor status were assessed. CeProp@T and CeRemi@T ranged respectively between 1.5-2.2 μg/ml (Median 1.6 μg/ml) and 3.5-18 ng/ml (Median 8 ng/ml) that were effective in keeping the BIS@T between 40 and 60 in all surgeries. tMEP thresholds ranged between 45 and 120 mA. There was no correlation between CeProp@T, CeRemi@T and tMEP, as well as between BIS@T and respectively tMEP, CeProp@T, CeRemi@T. None of patients had induced electrical seizure or explicit recalls. Motor scores were equal to preoperative values in 22/24 patients. BIS-guided general anaesthesia within a 40-60 interval, with low Ce of Propofol (≤2 μ/ml) and high analgesic regime allow reliable tMEP measurements, avoiding postoperative neurological impairment and major adverse outcomes, such as seizure and awareness.

Abstract PR344

Background & Objectives: Bispectral index (BIS) is considered very useful to guide anaesthesia care in elderly patients, but it is controversial for the evaluation of the adequacy of analgesia. This study compared the BIS changes in response to loss of consciousness (LOC) and loss of somatic response (LOS) to nociceptive stimuli between elderly and young patients receiving intravenous target-controlled infusion (TCI) of propofol and remifentanil. Materials & Methods: This study was performed on 52 elderly patients (aged 65~78 yr) and 52 young patients (aged 25~58 yr), ASA physical status I or II. Anaesthesia was induced with propofol administered by TCI. A standardized noxious electrical stimulus (transcutaneous electrical nerve stimulation, TENS) was applied (50 Hz, 80 mA, 0.25 ms pulses for 4 s) to the ulnar nerve at increasing remifentanil effective-site concentration (Ce) until patients lost somatic response to TENS. Changes in awake, prestimulus, poststimulus BIS, heart rate (HR), mean arterial pressure (MAP), pulse oxygen saturation (SpO2), predicted plasma concentration (Cp), predicted effective-site concentration (Ce) of propofol and remifentanil at both LOC and LOS clinical points were investigated. Results: BISLOC in elderly group 65.4±9.7 was higher than that in young patient group (65.4±9.7 vs 57.6±12.3) (t=21.58, P<0.0001) after TCI propofol, and the propofol Ce at LOC was 1.6±0.3 μg/ml in elderly patients, which was significantly lower than that in young patients (2.3±0.5 μg/ml) (t=7.474, P<0.0001). As nociceptive stimulation induced BIS to increase, the mean of BIS maximum values after TENS was significantly higher than that before TENS in both age groups (t=8.902 and t=8.019, P<0.0001). With increasing Ce of remifentanil until patients lost somatic response to TENS, BISLOS was the same as the BISLOC in elderly patients (65.6±10.7 vs 65.4±9.7), and there were no marked differences between elderly and young patient groups in BISawake, BISLOS and Ce of remifentanil required for LOS. Conclusion: In elderly patients, BIS can be used as indicator for hypnotic-analgesic balance, and be helpful to guide the optimal administration of propofol and remifentanil individually. Disclosure of Interest: None declared

Effect of sex differences in remifentanil requirements for the insertion of a laryngeal mask airway during propofol anesthesia: A prospective randomized trial.

Background:Remifentanil can improve insertion of a laryngeal mask airway (LMA) during induction with propofol. Recently, it has been suggested that there is a sex difference in opioid requirements for this procedure. The purposes of this study were to determine the effective effect-site concentration (Ce) of remifentanil for the facilitation of LMA insertion in male and female patients during propofol anesthesia without neuromuscular blockade and to evaluate whether there are sex differences in the Ce of remifentanil required for successful LMA insertion.Methods:Forty-eight patients (24 male, 24 female) with American Society of Anesthesiologists physical status 1 or 2, aged 20 to 60 years, scheduled for minor orthopedic surgery under general anesthesia were enrolled. Anesthesia was induced by target-controlled infusion (TCI) of propofol and remifentanil. The target Ce of propofol was 5 μg/mL initially and was reduced to 3.5 μg/mL after loss of consciousness. The Ce of remifentanil given to each patient was determined by the response of the previously tested patient using 0.5 ng/mL as a step size. The 1st patient was tested at a Ce of 3.0 ng/mL of remifentanil. Successful LMA insertion was defined as smooth insertion without patient movement or significant resistance to mouth opening.Results:The effective Ce of remifentanil required for successful LMA insertion on 50% of occasions (effective effect-site concentration for 50% [EC50]) as estimated by Dixon method was significantly lower in women (2.18 ± 0.35 ng/mL) than in men (2.82 ± 0.53 ng/mL) (P = 0.02). Using the isotonic regression method, the effective Ce of remifentanil required for successful LMA insertion on 95% of occasions (EC95) (95% confidence interval [CI]) was significantly lower in women (3.38 [3.0–3.48] ng/mL) than in men (3.94 [3.80–3.98] ng/mL).Conclusion:The Ce of remifentanil required to facilitate successful LMA insertion is higher during propofol induction by TCI in men than in women. When using remifentanil for LMA insertion, patient sex should be taken into account for appropriate dosing.

Effect-site concentration of remifentanil for smooth inhalational induction with desflurane.

ObjectiveTo determine the effect-site concentration (Ce) of remifentanil target-controlled infusion required for a smooth inhalational induction without airway irritation using desflurane in a stepwise incremental manner for 50% of patients (EC50) and 95% of patients (EC95).MethodsPatients with an American Society of Anesthesiologists physical status I and II, aged 19–60 years undergoing elective surgery were enrolled in this study. When target Ce of remifentanil was reached, desflurane was inhaled at 4 vol% initially and then it was increased to 8 and 12 vol% at intervals of 30 s. Smooth induction was regarded as an absence of airway irritation signs and excitatory movements. The EC50 and EC95 values for remifentanil were determined using a modified Dixon’s up-and-down method as well as an isotonic regression method with a bootstrapping approach.ResultsThe EC50 and EC95 of remifentanil for smooth induction during inhalation of desflurane were 3.40 ng/ml (95% confidence interval [CI] 2.42, 4.38 ng/ml) and 4.31 ng/ml (95% CI 2.15, 5.98 ng/ml), respectively.ConclusionPrior administration of remifentanil could provide smooth inhalational induction with desflurane in a stepwise increment.

Optimal effect-site concentration of remifentanil for preventing cough during removal of the double-lumen endotracheal tube from sevoflurane-remifentanil anesthesia: A prospective clinical trial.

Opioids are used as a treatment for coughing. Recent studies have reported an antitussive effect of remifentanil during recovery from general anesthesia by suppressed coughing. The coughing reflex may differ throughout the respiratory tract from the larynx to the bronchi. But the proper dose of remifentanil to prevent cough during double-lumen tube (DLT) extubation is unknown.Twenty-five ASA physical status 1 and 2 patients, 20 to 65 years of age who were undergoing video-assisted thoracoscopic lung surgery requiring 1-lung ventilation were enrolled. The effective effect-site concentration (Ce) of remifentanil for 50% and 95% of patients (EC50 and EC95) for preventing cough was determined using the isotonic regression method with a bootstrapping approach, following the Dixon up-and-down method. Recovery profiles and hemodynamic values after anesthesia were compared between patients with cough and patients without cough.EC50 and EC95 of remifentanil was 1.670 ng/mL [95% confidence interval (95% CI) 1.393–1.806] and 2.275 ng/mL (95% CI 1.950–2.263), respectively. There were no differences in recovery profiles and hemodynamic values after anesthesia between patients with/without cough. No patients suffered respiratory complications during the emergence period.Remifentanil can be a safe and reliable method of cough prevention during emergence from sevoflurane anesthesia after thoracic surgery requiring DLT. EC50 and EC95 of remifentanil that suppresses coughing is 1.670 and 2.275 ng/mL, respectively.

Changes in the Bispectral Index in Response to Loss of Consciousness and No Somatic Movement to Nociceptive Stimuli in Elderly Patients.

Background:Bispectral index (BIS) is considered very useful to guide anesthesia care in elderly patients, but its use is controversial for the evaluation of the adequacy of analgesia. This study compared the BIS changes in response to loss of consciousness (LOC) and loss of somatic response (LOS) to nociceptive stimuli between elderly and young patients receiving intravenous target-controlled infusion (TCI) of propofol and remifentanil.Methods:This study was performed on 52 elderly patients (aged 65–78 years) and 52 young patients (aged 25–58 years), American Society of Anesthesiologists physical status I or II. Anesthesia was induced with propofol administered by TCI. A standardized noxious electrical stimulus (transcutaneous electrical nerve stimulation, [TENS]) was applied (50 Hz, 80 mA, 0.25 ms pulses for 4 s) to the ulnar nerve at increasing remifentanil predicted effective-site concentration (Ce) until patients lost somatic response to TENS. Changes in awake, prestimulus, poststimulus BIS, heart rate, mean arterial pressure, pulse oxygen saturation, predicted plasma concentration, Ce of propofol, and remifentanil at both LOC and LOS clinical points were investigated.Results:BISLOC in elderly group was higher than that in young patient group (65.4 ± 9.7 vs. 57.6 ± 12.3) (t = 21.58, P < 0.0001) after TCI propofol, and the propofol Ce at LOC was 1.6 ± 0.3 μg/ml in elderly patients, which was significantly lower than that in young patients (2.3 ± 0.5 μg/ml) (t = 7.474, P < 0.0001). As nociceptive stimulation induced BIS to increase, the mean of BIS maximum values after TENS was significantly higher than that before TENS in both age groups (t = 8.902 and t = 8.019, P < 0.0001). With increasing Ce of remifentanil until patients lost somatic response to TENS, BISLOS was the same as the BISLOC in elderly patients (65.6 ± 10.7 vs. 65.4 ± 9.7), and there were no marked differences between elderly and young patient groups in BISawake, BISLOS, and Ce of remifentanil required for LOS.Conclusion:In elderly patients, BIS can be used as an indicator for hypnotic-analgesic balance and be helpful to guide the optimal administration of propofol and remifentanil individually.Trial Registration:CTRI Reg. No: ChiCTR-OOC-14005629; http://www.chictr.org.cn/showproj.aspx?proj=9875.

Effect-site concentrations of remifentanil causing bradycardia in hypnotic and non-hypnotic patients

Although the induction of anaesthesia with remifentanil often causes bradycardia, the relationship between the effect-site concentration (Ce) of remifentanil and instantaneous heart rate (HR) has remained unclear. The present study examined the relationship between instantaneous HR and remifentanil Ce at the induction of anaesthesia with and without propofol hypnosis, to facilitate safe management of anaesthesia induction with remifentanil. Instantaneous HR was calculated every 5s using an electrocardiographic real-time analysis system (MemCalc/Makin2; GMS, Tokyo, Japan). At the beginning of anaesthesia induction, continuous infusion of remifentanil (1μgmin-1kg-1) preceded hypnosis with propofol in 13 patients [non-hypnosis group; mean age, 67.8 (17.5) years], while propofol bolus (30-50mg) was injected together with continuous remifentanil medication in 18 patients [hypnosis group; mean age, 62.9 (16.5)years]. Remifentanil Ce was estimated every 5s using the three-compartment model proposed by Minto et al. and the relationship between estimated remifentanil Ce and instantaneous HR was examined. In the hypnosis group, HR was significantly lower than basal HR when remifentanil Ce was increased to 3.5ngml-1 (p<0.05), whereas no significant HR reduction was found in the non-hypnosis group until remifentanil Ce reached >5ngml-1 (p<0.05). The induction of anaesthesia using remifentanil with propofol hypnotics significantly reduces HR even in a low remifentanil Ce insufficient to suppress the cardiovascular response at tracheal intubation. Preparations to treat bradycardia are recommended for the safe management of anaesthesia induction when remifentanil is combined with hypnotics.

Effect-site concentration of remifentanil for attenuating QTc interval prolongation following intubation in hypertensive female patients.

Haemodynamic changes after sympathetic stimuli like tracheal intubation are more pronounced in hypertensive patients than in normotensive patients. Heart rate (HR)-corrected QT (QTc) interval changes related to intubation may also be more prominent in hypertensive patients. We hypothesised that there would be a difference in the effect-site concentration (Ce) of remifentanil to attenuate QTc interval prolongation in normotensive and hypertensive patients following intubation. Twenty-two normotensive and 22 hypertensive female patients (≥ 50year) were enrolled and anaesthesised with remifentanil and propofol using a target-controlled infusion. All hypertensive patients received oral antihypertensive medications for > 6months and took the medications in the morning of the surgery. The effective concentration of remifentanil Ce in 50% (EC50 ) and 95% of the population (EC95 ) required to maintain QTc interval prolongation < 15ms following intubation was calculated using the isotonic regression and a bootstrapping approach following the Dixon's up-and-down method. Median duration of hypertension was 6years. Isotonic regression revealed that the EC50 (83% confidence interval) of remifentanil Ce for reducing QTc interval prolongation following intubation was 3.8 (3.5-4.1) ng/ml in normotensive and 6.1 (5.8-6.2) ng/ml in hypertensive female patients. The EC95 (95% confidence interval) of remifentanil Ce was 4.4 (4.3-4.5) ng/ml in normotensive and 6.5 (6.4-6.5) ng/ml in hypertensive female patients. The Ce of remifentanil required to attenuate QTc interval prolongation following intubation was significantly higher in hypertensive patients than it was in normotensive patients. Thus, more caution should be taken related to QTc interval prolongation when intubating hypertensive patients.

Prediction of movement to surgical stimulation by the pupillary dilatation reflex amplitude evoked by a standardized noxious test.

Individual assessment of the amplitude of a physiologic reflex evoked by a standardized noxious test (SNT) before surgical stimulation has been suggested to predict movement upon the forthcoming surgical stimulation. This study aimed to compare the ability of pupillary dilatation reflex amplitude (PDRA) evoked by an SNT and estimated remifentanil effect-site concentration (Ce) to predict movement upon surgical stimulation. Eighty female patients were anesthetized for vacuum aspiration with propofol (Ce 4 μg/ml) and remifentanil. Remifentanil Ce was randomized to 0, 1, 3, or 5 ng/ml. SNT was a 60-mA, 5-s, 100-Hz tetanus applied on median nerve before cervix dilatation. PDRA was calculated as the difference in pupillary diameter after and before SNT. Movement upon cervix dilatation was recorded by an independent observer. Ability of PDRA and estimated remifentanil Ce to discriminate movers from non-movers during cervix dilatation was measured as the area under the receiver operating characteristics curve. Twenty-one of the 76 patients analyzed moved during cervix dilatation. Mean PDRA (±1 SD) evoked by SNT was 2.0 ± 1.2 mm in movers and 0.6 ± 0.7 in non-movers (P < 0.0001). Remifentanil Ce was 0.2 ± 0.4 ng/ml in movers and 3.0 ± 1.7 in non-movers (P < 0.0001). Area under the receiver operating characteristics curve for PDRA was 0.90 (95% CI, 0.83 to 0.96) and for remifentanil Ce 0.94 (0.89 to 0.98), without any significant difference between the two areas. PDRA evoked by an SNT is as accurate as the estimated remifentanil Ce to predict movement upon cervix dilatation. PDRA could be valuable when estimated opioid Ce is not available or reliable.

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

PurposeThe 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 MethodsTwenty-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%.ResultsThe 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.ConclusionOur 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.

Optimal effect-site concentration of remifentanil for minimizing cardiovascular changes caused by fiberoptic nasotracheal intubation.

BackgroundEndotracheal intubation induces clinically adverse cardiovascular changes. Various pharmacological strategies for controlling these responses have been suggested with opioids being widely administered. In this study, the optimal effect-site concentration (Ce) of remifentanil for minimizing hemodynamic responses to fiberoptic nasotracheal intubation was evaluated.MethodsThirty patients, aged 18-63 years, scheduled for elective surgery were included. Anesthesia was induced with a propofol and remifentanil infusion via target-controlled infusion (TCI). Remifentanil infusion was initiated at 3.0 ng/mL, and the response of each patient determined the Ce of remifentanil for the next patient by the Dixon up-and-down method at an interval of 0.5 ng/mL. Rocuronium was administered after propofol and remifentanil reached their preset Ce; 90 seconds later fiberoptic nasotracheal intubation was initiated. Non-invasive blood pressure and heart rate (HR) were measured at pre-induction, the time Ce was reached, immediately before and after intubation, and at 1 and 3 minutes after intubation. The up-and-down criteria comprised a 20% change in mean blood pressure and HR between just prior to intubation and 1 minute after intubation.ResultsThe median effective effect-site concentration (EC50) of remifentanil was 3.11 ± 0.38 ng/mL by the Dixon's up-and-down method. From the probit analysis, the EC50 of remifentanil was 3.43 ng/mL (95% confidence interval, 2.90-4.06 ng/mL). In PAVA, the EC50 and EC95 of remifentanil were 3.57 ng/mL (95% CI, 2.95-3.89) and 4.35 ng/mL (95% CI, 3.93-4.45). No remifentanil-related complications were observed.ConclusionsThe EC50 of remifentanil for minimizing the cardiovascular changes and side effects associated with fiberoptic nasotracheal intubation was 3.11-3.43 ng/mL during propofol TCI anesthesia with a Ce of 4 ug/mL.

Optimal effect-site concentration of remifentanil for inhibiting response to laryngeal mask airway removal during emergence.

PurposeThis randomized, controlled, double-blind study was designed to determine the optimal dose of remifentanil for preventing complications associated with the removal of a laryngeal mask airway (LMA) without delaying emergence.Materials and MethodsThis study randomly assigned 128 patients to remifentanil effect-site concentrations (Ce) of 0 ng/mL (group R0), 0.5 ng/mL (group R0.5), 1.0 ng/mL (group R1.0), and 1.5 ng/mL (group R1.5) during emergence. The emergence and recovery profiles were recorded. Adverse events such as coughing, airway obstruction, breath-holding, agitation, desaturation, nausea, and vomiting were also evaluated.ResultsThe number of patients with respiratory complications such as coughing and breath-holding was significantly lower in the R1.0 and R1.5 groups than in the R0 group (p<0.05). Emergence agitation also decreased in the R1.0 and R1.5 groups (p<0.0083). The time to LMA removal was significantly longer in the R1.5 group than in the other groups (p<0.05).ConclusionMaintaining a remifentanil Ce of 1.0 ng/mL during emergence may suppress adverse events such as coughing, breath-holding, and agitation following the removal of LMA without delayed awakening.

Neuromuscular effects of cisatracurium besylate in obese patients

To explore the neuromuscular effects of cisatracurium besylate in morbidly obese patients when dosed according to real body weight under total intravenous anesthesia with propofol. Thirty-six ASA I-II patients aged 18-65 years scheduled for elective procedures at our hospital during July 2012 to December 2012 were allocated into 2 groups according to body mass index (normal weight: body mass index: <24, overweight: body mass index >28). Anesthesia was induced with target-controlled infusion of propofol (Cp 3 µg/ml) and remifentanil (Ce 3-5 ng/ml). A bolus of cisatracurium 0.2 mg/kg was administered intravenously over 5-10 s as soon as a patient lost consciousness. Neuromuscular block was monitored with TOF-Watch SX (Oaganon, the Netherlands). Single stimulation (0.1 Hz) was applied to ulnar nerve at wrist. The maximal degree of neuromuscular block, onset time, clinical duration and recovery index were recorded. They were intubated and mechanically ventilated when neuromuscular block reached the maximal degree. The intubation condition was evaluated. The average onset time was (164 ± 25) s in obese group versus (201 ± 48) s in normal weight group. And there was significant difference between groups (t = 2.83, P < 0.05) . The clinical duration was (68.4 ± 9.6) min in obese group versus (62.0 ± 6.5) min in normal weight group. And there was significant difference between groups (t = 2.33, P < 0.05). The recovery index was (15.6 ± 4.7) min in obese group versus (10.8 ± 4.2) min in normal weight group. And there was significant difference between groups (t = 3.03, P < 0.05) . Also 75% recovery time was (83.9 ± 11.5) min in obese group versus (73.0 ± 9.2) min in normal weight group. And there was significant difference between groups (t = 2.94, P < 0.05). But no differences existed in intubation conditions. When dosed according to real body weight, onset time of cisatracurium is shorter while clinical duration and recovery index are prolonged in morbidly obese patients compared with normal weight counterparts.

Sex Differences in Remifentanil Requirements for Preventing Cough during Anesthetic Emergence

PurposeTarget-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 MethodsTwenty 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.ResultsIsotonic 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.ConclusionWhen using remifentanil TCI for cough prevention during anesthetic emergence, patient sex should be a considered for appropriate dosing.

Optimal effect-site concentration of remifentanil when combined with dexmedetomidine in patients undergoing cystoscopy

BackgroundCystoscopic procedure is a very common practice in the field of urology due to its ability to survey the bladder for a variety of indications. However, patients who undergo cystoscopy feel intense pain and discomfort. This study investigated the half maximal effective concentration (EC50) of remifentanil in preventing cystoscope insertion pain under sedation using dexmedetomidine.MethodsThe study was prospectively conducted on 18 male patients, aged 18 to 65. Remifentail infusion was initiated together with dexmedetomidine, and started at a dose of 2.4 ng/ml on the first patient. The effect-site concentration (Ce) of remifentanil for each subsequent patient was determined by the previous patient's response using Dixon's up-and-down method with an interval of 0.3 ng/ml. Patients received a loading dose of 1.0 µg/kg dexmedetomidine over 10 minutes, followed by a maintenance dose of 0.6 µg/kg/hr. After the patient's OAA/S score (Observer's Assessment of Alertness/Sedation scale) reached 3-4, and the Ce of remifentanil reached target concentration, the urologist was allowed to insert the cystoscope and the pain responses were observed.ResultsThe effect-site concentration of remifentanil required to prevent cystoscope insertion pain in 50% of patients under sedation using dexmedetomidine was 1.30 ± 0.12 ng/ml by Dixon's up-and-down method. The logistic regression curve of the probability of response showed that the EC50 and EC95 values (95% confidence limits) of remifentanil were 1.33 ng/ml (1.12-1.52 ng/ml) and 1.58 ng/ml (1.44-2.48 ng/ml), respectively.ConclusionsCystoscopic procedure can be carried out successfully without any pain or adverse effects by optimal remifentanil effect-site concentration (EC50, 1.33 ng/ml; EC95, 1.58 ng/ ml) combined with sedation using dexmedetomidine.

A Comparison of the Recovery Characteristics between Propofol-remifentil and Sevoflurane-remifentail Anesthesia for Total Thyroidectomy

ObjectivesThis study was investigated the recovery characteristics of propofol-remifentanil and sevoflurane-remifentanil anesthesia for total thyroidectomy MethodsEighty patients in ASA physical status 1 and 2 scheduled for total thyroidectomy were allocated randomly to either group P (n = 40) or group S (n = 40). Anesthesia was maintained with remifentanil effect site concentration (Ce) 1-3 ng/mL and propofol Ce 2-4 μ g/mL in the group P, and was maintained with remifentanil Ce 1-3 ng/mL and sevoflurane 1.5-2% in the group S. Blood pressure, heart rate, and bispectral (BIS) index were measured during perioperative period. The times from discontinuance of anesthetic agent to eye opening, to extubation, and to stating name were measured. Postoperative complications were evaluated. ObjectivesThis study was investigated the recovery characteristics of propofol-remifentanil and sevoflurane-remifentanil anesthesia for total thyroidectomy MethodsEighty patients in ASA physical status 1 and 2 scheduled for total thyroidectomy were allocated randomly to either group P (n = 40) or group S (n = 40). Anesthesia was maintained with remifentanil effect site concentration (Ce) 1-3 ng/mL and propofol Ce 2-4 μ g/mL in the group P, and was maintained with remifentanil Ce 1-3 ng/mL and sevoflurane 1.5-2% in the group S. Blood pressure, heart rate, and bispectral (BIS) index were measured during perioperative period. The times from discontinuance of anesthetic agent to eye opening, to extubation, and to stating name were measured. Postoperative complications were evaluated. ResultsThere were no significant differences between group P and S on the blood pressure, heart rate, and recovery time. BIS index of group P showed lower than that of group S during operation (P &amp;lt; 0.05). The incidences of side effects were similar in the two groups, though the incidence of nausea was higher in the group S (P &amp;lt; 0.05). ConclusionsPropofol-remifentanil anesthesia was more advantageous than sevoflurane-remifentanil anesthesia for thyroidectomy in view of side effect incidences.