Effect-site Concentration Of Remifentanil Research Articles

Experimental Pain and Opioid Analgesia in Volunteers at High Risk for Obstructive Sleep Apnea

BackgroundObstructive sleep apnea (OSA) is characterized by recurrent nocturnal hypoxia and sleep disruption. Sleep fragmentation caused hyperalgesia in volunteers, while nocturnal hypoxemia enhanced morphine analgesic potency in children with OSA. This evidence directly relates to surgical OSA patients who are at risk for airway compromise due to postoperative use of opioids. Using accepted experimental pain models, we characterized pain processing and opioid analgesia in male volunteers recruited based on their risk for OSA.MethodsAfter approval from the Intitutional Review Board and informed consent, we assessed heat and cold pain thresholds and tolerances in volunteers after overnight polysomnography (PSG). Three pro-inflammatory and 3 hypoxia markers were determined in the serum. Pain tests were performed at baseline, placebo, and two effect site concentrations of remifentanil (1 and 2 µg/ml), an μ-opioid agonist. Linear mixed effects regression models were employed to evaluate the association of 3 PSG descriptors [wake after sleep onset, number of sleep stage shifts, and lowest oxyhemoglobin saturation (SaO2) during sleep] and all serum markers with pain thresholds and tolerances at baseline, as well as their changes under remifentanil.ResultsForty-three volunteers (12 normal and 31 with a PSG-based diagnosis of OSA) were included in the analysis. The lower nadir SaO2 and higher insulin growth factor binding protein-1 (IGFBP-1) were associated with higher analgesic sensitivity to remifentanil (SaO2, P = 0.0440; IGFBP-1, P = 0.0013). Other pro-inflammatory mediators like interleukin-1β and tumor necrosis factor-α (TNF-α) were associated with an enhanced sensitivity to the opioid analgesic effect (IL-1β, P = 0.0218; TNF-α, P = 0.0276).ConclusionsNocturnal hypoxemia in subjects at high risk for OSA was associated with an increased potency of opioid analgesia. A serum hypoxia marker (IGFBP-1) was associated with hypoalgesia and increased potency to opioid analgesia; other pro-inflammatory mediators also predicted an enhanced opioid potency.Trial Registration: ClinicalTrials.gov NCT00672737.

Comparison between monitored anesthesia care with remifentanil under ilioinguinal hypogastric nerve block and spinal anesthesia for herniorrhaphy

BackgroundThe use of monitored anesthesia care (MAC) as the technique of choice for a variety of invasive or noninvasive procedures is increasing. The purpose of this study to compare the outcomes of two different methods, spinal anesthesia and ilioinguinal-hypogastric nerve block (IHNB) with target concentrated infusion of remifentanil for inguinal herniorrhaphy.MethodsFifty patients were assigned to spinal anesthesia (Group S) or IHNB with MAC group (Group M). In Group M, IHNB was performed and the effect site concentration of remifentanil, starting from 2 ng/ml, was titrated according to the respiratory rate or discomfort, either by increasing or decreasing the dose by 0.3 ng/ml. The groups were compared to assess hemodynamic values, oxygen saturation, bispectral index (BIS), observer assessment alertness/sedation scale (OAA/S), visual analogue scale (VAS) for pain score and patients' and surgeon's satisfaction.ResultsBIS and OAA/S were not significantly different between the two groups. Hemodynamic variables were stable in Group M. Thirteen patients in the same group showed decreased respiratory rate without desaturation, and recovered immediately by encouraging taking deep breaths without the use of assist ventilation. Although VAS in the ward was not significantly different between the two groups, interestingly, patients' and surgeon's satisfaction scores (P = 0.0004, P = 0.004) were higher in Group M. The number of the patients who suffered from urinary retention was higher in Group S (P = 0.0021).ConclusionsIHNB under MAC with remifentanil is a useful method for inguinal herniorrhaphy reflecting hemodynamic stability, fewer side effects and higher satisfaction. This approach can be applied for outpatient surgeries and patients who are unfit for spinal anesthesia or general anesthesia.

Effect-Site Concentration of Remifentanil for Minimizing Cardiovascular Changes by Inhalation of Desflurane

PurposeThis study aims to investigate the most appropriate effect-site concentration of remifentanil to minimize cardiovascular changes during inhalation of high concentration desflurane.Materials and MethodsSixty-nine American Society of Anesthesiologists physical status class I patients aged 20-65 years were randomly allocated into one of three groups. Anesthesia was induced with etomidate and rocuronium. Remifentanil was infused at effect-site concentrations of 2, 4 and 6 ng/mL in groups R2, R4 and R6, respectively. After target concentrations of remifentanil were reached, desflurane was inhaled to maintain the end-tidal concentration of 1.7 minimum alveolar concentrations for 5 minutes (over-pressure paradigm). The systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR) and end-tidal concentration of desflurane were measured for 5 minutes.ResultsThe end-tidal concentration of desflurane increased similarly in all groups. The SBP, DBP, MAP and HR within group R4 were not significantly different as compared with baseline values. However, measured parameters within group R2 increased significantly 1-3 minutes after desflurane inhalation. The MAP within group R6 decreased significantly at 1, 2, 4, and 5 minutes (p<0.05). There were significant differences in SBP, DBP, MAP and HR among the three groups 1-3 minutes after inhalation (p<0.05). The incidence of side effects such as hyper- or hypo-tension, and tachy- or brady-cardia in group R4 was 4.8% compared with 21.8% in group R2 and 15.0% in group R6.ConclusionThe most appropriate effect-site concentration of remifentanil for blunting hemodynamic responses by inhalation of high concentration desflurane is 4 ng/mL.

The effect of a continuous infusion of low-dose esmolol on the requirement for remifentanil during laparoscopic gynecologic surgery

Study ObjectiveTo investigate whether a continuous infusion of low-dose esmolol results in an opioid-sparing effect during surgery. DesignRandomized, double-blinded, placebo-controlled clinical comparison study. SettingOperating room of a university hospital. Patients56 ASA physical status 1 and 2 patients, aged 20 to 60 years, undergoing laparoscopic gynecologic surgery of less than two hours’ duration. InterventionsThe esmolol group (n = 28) received a 0.5 mg/kg loading dose of esmolol followed by an infusion of esmolol 30 μg/kg/min; the saline group (n = 28) received equivalent volumes of normal saline. MeasurementsThe effect-site concentration of remifentanil (ng/mL) to maintain adequate anesthetic depth before infusion of the study drug (before-concentration) was measured. During infusion of study drug, the effect-site concentration of remifentanil was adjusted every 5 minutes to maintain systolic blood pressure within 15% of baseline and a Bispectral Index value between 50–60. The average of these adjusted concentrations (after-concentration) was measured and compared to the before-concentration. The quality of postoperative recovery was assessed. Main ResultsIn the esmolol group, the after-concentration of remifentanil was decreased by 33.3% compared with the before-concentration. The total dose of remifentanil infused was also lower in the esmolol group (0.09 ± 0.1 vs 0.14 ± 0.03 μg/kg/min; P = 0.031). The esmolol group had lower scores on a pain numerical rating scale and required less fentanyl in the Postanesthesia Care Unit. ConclusionsIntraoperative esmolol infusion decreases both the requirement for remifentanil and postoperative administration of rescue analgesics.

Changes in the photoplethysmogram with tracheal intubation and remifentanil concentration

Autonomic sympathetic activation, for instance following noxious stimuli, decreases the size and flattens the shape of the photoplethysmographic peripheral pulse waveform. We report a simple measure of the waveform shape, the ratio of mean-to-peak wave amplitude, for measuring nociception level during general anaesthesia. Fifty participants, anaesthetised with propofol and remifentanil, were randomly allocated to one of three different remifentanil effect-site concentrations (1, 3 and 5 ng.ml(-1) ). Tracheal intubation increased the mean (SD) plethysmographic ratio from 0.38 (0.06) to 0.48 (0.04), p = 2.6 × 10(-16) . The mean (SD) ratios following intubation at remifentanil effect-site concentrations of 1 ng.ml(-1) , 3 ng.ml(-1) and 5 ng.ml(-1) , were 0.49 (0.03), 0.48 (0.03) and 0.45 (0.04), respectively. Remifentanil therefore suppressed changes in the mean-to-peak ratio caused by tracheal intubation (p = 0.006). The ratio of the mean-to-peak plethysmographic amplitude may represent a simple measure of the balance of autonomic sympathetic and parasympathetic activity under general anaesthesia, and its performance following intubation was significantly different from peak amplitude (p = 0.046).

Target-Controlled Infusion of Remifentanil for Laryngeal Mask Airway Insertion during Sevoflurane Induction in Adults

This randomized, double-blind study investigated the suitable target effect-site concentration of remifentanil for laryngeal mask airway (LMA) insertion during inhalation induction with sevoflurane. Patients aged 18 - 60 years were randomly assigned to one of three groups receiving infusions of normal saline (control group), or infusions with target effect-site remifentanil concentrations of either 1 ng/ml (R1 group) or 2 ng/ml (R2 group), 1 min after the induction of anaesthesia with sevoflurane. LMA insertion was attempted 2 min after induction. Insertion conditions were graded using a six-variable, three-point scale (excellent, intermediate or poor). A total of 102 patients were included. The proportion of patients ranked as excellent for the LMA insertion was significantly higher in groups R1 and R2 compared with the control group. The incidence of apnoea was significantly more frequent in the R2 group than in the control or R1 groups. Compared with 1 ng/ml remifentanil or normal saline, target-controlled infusion of 2 ng/ml remifentanil significantly improved the LMA insertion conditions during sevoflurane inhalational induction, although apnoeic episodes were more frequently observed.

Ideal body weight-based remifentanil infusion is potentially insufficient for anesthetic induction in mildly obese patients

We evaluated whether the effect of remifentanil treatment differs between normal weight (NW) patients with real body weight-based remifentanil and mildly obese (Ob) patients with ideal body weight based-remifentanil during short-term anesthetic induction. We enrolled 20 patients aged between 20 and 64 years in each group (NW group: 18.5 kg/m(2) ≤ BMI < 25 kg/m(2); Ob group: BMI ≥ 25 kg/m(2)). Tracheal intubation (TI) was performed after administration of 0.5 μg/kg/min remifentanil for 5 min, including 2 min of antecedent administration, with propofol and rocuronium. Hemodynamic parameters (SBP, DBP, and HR) were measured. Percent changes in hemodynamics resulting from anesthetic induction and TI were calculated, and effect-site concentration (ESC) in each patient was calculated by performing pharmacokinetic simulation. All hemodynamic values in the Ob group after TI were significantly higher than those in the NW group. Percent increases in SBP and HR in the Ob group were significantly higher than the corresponding values in the NW group. ESC of remifentanil at the time of TI in the NW group was higher than that in the Ob group. Remifentanil treatment with anesthetic induction based on the Japanese package insert might have insufficient effects in obese patients.

Comparison of the Optimal Effect-Site Concentrations of Remifentanil for Preventing Cough during Emergence from Desflurane or Sevoflurane Anaesthesia

To compare the effect-site concentrations of remifentanil target-controlled infusion (TCI) that produced 50% and 95% of the maximal effect (EC50 and EC95, respectively) for preventing cough during emergence from desflurane or sevoflurane anaesthesia, in patients undergoing elective thyroidectomy. Adults undergoing elective thyroidectomy were randomized to receive anaesthesia with desflurane or sevoflurane. The EC50 and EC95 values for remifentanil TCI were determined using Dixon's up-and-down method and probit analysis with sigmoid curve. In total, 48 patients aged 20-64 years were enrolled in the study. The EC50±SD of remifentanil TCI, determined by Dixon's up-and-down method, were 1.54±0.70 and 1.11±0.24 ng/ml for desflurane and sevoflurane, respectively. The EC95 of remifentanil TCI, analysed by probit analysis, were 2.88 ng/ml and 2.29 ng/ml for desflurane and sevoflurane, respectively. The effect-site concentration of remifentanil TCI for preventing cough during emergence from desflurane anaesthesia was not significantly higher than that observed for sevoflurane. During emergence from anaesthesia, variations in effect-site concentrations of remifentanil for preventing cough are of limited importance as they do not generate significant differences in results.

Effect of a fluid challenge on the Surgical Pleth Index during stable propofol–remifentanil anaesthesia

The Surgical Pleth Index (SPI), derived from pulse amplitude and heartbeat interval, is proposed to monitor anti-nociception during anaesthesia. Its response to noxious stimulation can be affected by the intravascular volume status. This study investigated the effect of a fluid challenge (FC) on SPI during steady-state conditions. After Institutional Review Board approval, 33 consenting patients undergoing neurosurgery received a 4 ml/kg starch FC over less than 5 min under stable surgical stimulation conditions and stable propofol (Ce(PPF) ) and remifentanil (Ce(REMI) ) effect-site concentrations as estimated by target-controlled infusion systems. Intravascular volume status was assessed using the Delta Down (DD). We looked at the SPI response to FC according to DD, Ce(PPF) , and Ce(REMI) . Following FC, SPI did not change in 16, increased in 12, and decreased in 3 patients. Ce(REMI) poorly affected the SPI response to FC. In normovolaemic patients, the probability of an SPI change after FC was low under common Ce(PPF) (0.9 to 3.9 μg/ml). A decrease in SPI was more probable with worsening hypovolaemia and lowering Ce(PPF) , while an increase in SPI was more probable with increasing Ce(PPF) . SPI changes were only attributable to modifications in pulse wave amplitude and not in heart rate. During stable anaesthesia and surgery, SPI may change in response to FC. The effect of FC on SPI is influenced by volaemia and Ce(PPF) through pulse wave amplitude modifications. These situations may confound the interpretation of SPI as a surrogate measure of the nociception-anti-nociception balance.

Smooth emergence in men undergoing nasal surgery: the effect site concentration of remifentanil for preventing cough after sevoflurane‐balanced anaesthesia

Suppression of cough during emergence after nasal surgery is practical to avoid bleeding from the surgical site. Previously recommended effect-site concentration of remifentanil for preventing cough during emergence is restricted to female patients undergoing thyroid surgery, so we evaluated effective effect-site concentration of remifentanil for preventing cough during emergence for men undergoing nasal surgery. Twenty-four American Society of Anesthesiologists (ASA) physical status I or II, between the ages of 18 and 60 years old, non-smoker male patients undergoing nasal surgery were enrolled in this study. The effective effect-site concentration for 50% of patients (EC(50) ) and and that for 95% of patients (EC(95) ) of remifentanil for preventing cough were determined by Dixon's up-and-down method and by isotonic regression method with a bootstrapping approach. Haemodynamic variables were compared in patients with cough and without cough during emergence. The EC(50) of remifentanil for preventing cough during emergence by Dixon's method was 2.17 ng/ml [standard deviation (SD) 0.38]. The estimated EC(50) and EC(95) of remifentanil using isotonic regression model with a bootstrapping approach were 2.35 ng/ml [95% confidence interval (CI) 1.89-2.66] and 2.94 ng/ml (95% CI 2.83-2.97), respectively. Mean arterial pressure and heart rate were significantly higher in patients with cough during emergence. Three out of 13 patients that received more than 2.5 ng/ml of remifentanil experienced a brief episode of bradypnea. The EC(95) of remifentanil for preventing cough in men after nasal surgery is 2.94 ng/ml. Remifentanil target-controlled infusion with established effect-site concentration could suppress cough in men during emergence from sevoflurane anaesthesia after nasal surgery, though reversible respiratory depression might arise at high effect-site concentration of remifentanil.

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

BackgroundThe 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.MethodsA 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.ResultsThe 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.ConclusionsMaintaining 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.

The median effective effect-site concentration of remifentanil for minimizing the cardiovascular changes to endotracheal intubation during desflurane anesthesia in pediatric patients

BackgroundDesflurane has the most rapid onset and offset of action among the volatile anesthetic agents used for general anesthesia, but it can cause airway reactivity, tachycardia, and hypertension during induction, especially in pediatric patients. This study was designed to determine a median effective effect-site concentration (EC50) of remifentanil to prevent the cardiovascular changes due to tracheal intubation during the 1 minimum alveolar concentration (MAC) desflurane inhalation, which was required to prevent movement in response to a noxious stimulus in 50% of subjects, in pediatric patients.MethodsTwenty-four pediatric patients between the ages 5-15 years were enrolled in this study. We injected thiopental intravenously, at the same time remifentanil was infused by Target Controlled Infusion (TCI) device. When the target effect-site concentration (Ce) of remifentanil reached a preset level, desflurane was administrated through the facial mask. Then, we assessed the signs of desflurane related airway reactivity and cardiovascular changes for 2 min. The up-and-down criteria was a 20% change in systolic blood pressure (SBP) and a heart rate (HR) between just prior to intubation and 1 min after intubation. The EC50 of remifentanil was calculated from 8 independent pairs using Dixon's up-and-down method.ResultsWe studied 24 pediatric patients in range of 1-5 ng/ml of the Ce of remifentanil. No patient showed airway reactivity during the study. The EC50 of remifentanil to suppress the hemodynamic changes after tracheal intubation during desflurane anesthesia was calculated as 3.4 ± 0.9 ng/ml.ConclusionsIn pediatric anesthesia, the EC50 of remifentanil to minimize the cardiovascular changes due to tracheal intubation during 1 MAC desflurane anesthesia was 3.4 ± 0.9 ng/ml.

The effect of gender on EC50of remifentanil to prevent pain during injection of microemulsion propofol

BackgroundPropofol injection pain is an unpleasant experience to patients and its prevalence can be influenced by age and gender. We determined the half maximal effective concentration (EC50) of remifentanil for preventing the microemulsion propofol injection pain in the male and female adult groups.MethodsAfter institutional review board approval, a total of 60 patients were assigned into 2 groups depending on their gender: group M (male, 20-65 yr) and group F (female, 20-65 yr). Anesthesia was induced with propofol and remifentanil, by a target-controlled infusion. Target effect-site concentration (Ce) of propofol and remifentanil for the first patient started at 4.0 ug/ml and 4.0 ng/ml. Ce of remifentanil for each subsequent patient was determined by the response of the previous patient by the Dixon's up-and-down method (DUDM) with an interval of 0.2 ng/ml. After equilibration of plasma and effect site remifentanil concentration, propofol was administered, and the pain responses were observed.ResultsThe remifentanil EC50 was 3.8 ± 0.2 and 2.7 ± 0.2 ng/ml in groups M and F, respectively, by DUDM. From Probit regression model, the remifentanil EC50 was 3.7 (3.0-4.3) and 2.7 (1.8-2.9) ng/ml in groups M and F, respectively.ConclusionsThe remifentanil EC50 for preventing the moderate to severe injection pain of propofol was higher in males than in females.

The EC50of remifentanil to minimize the cardiovascular changes during head holder pinning in neurosurgery

BackgroundDuring neuroanesthesia, head holder pinning commonly results in sympathetic stimulation manifested by hemodynamic changes, such as increased heart rate and arterial blood pressure. Remifentanil has been used successfully to control acute autonomic responses during neurosurgical procedures. The objective of this study was to determine effect-site concentration of remifentanil for suppressing the hemodynamic response to head holder pinning with the probability of 50% (EC50).MethodsForty-one ASA physical status I or II patients, between the ages of 20-70, who were scheduled for neurosurgery were recruited into this study. After arrival in the operating room, standard monitoring was applied throughout the study, which included a bispectral index monitor. Both propofol and remifentanil were administered by Target-control infusion device. The Dixon "up-and-down" sequential allocation method was used to determine the EC50 of remifentanil.ResultsThe EC50 of remifentanil was 2.19 ± 0.76 ng/ml by the turning point estimate (TPE). In probit analysis, EC50 was 2.42 ng/ml (95% CI : -0.62-4.66) and EC95 was 5.70 ng/ml (95% CI : 4.02-67.53). The EC50 estimator comes from isotonic regression is 2.90 ng/ml (95% CI : 1.78-3.65). The EC95 estimator comes from isotonic regression is 4.28 ng/ml (95% CI : 3.85-4.41).ConclusionsThis study showed that EC50 of remifentanil was 2.19 ± 0.76 ng/ml by TPE. EC50 was 2.42 ng/ml (95% CI -0.62-4.66) in probit analysis, as back up analysis. The EC50 estimator comes from isotonic regression is 2.90 ng/ml (95% CI : 1.78-3.65).

Reduction of Microemulsion Propofol-Induced Injection Pain via Target-Controlled Remifentanil Infusion

The intravenous injection of microemulsion propofol to induce anaesthesia causes more intense and frequent pain than lipid emulsion propofol. This study investigated whether different target effect-site concentrations of remifentanil could prevent pain due to microemulsion propofol injection. In total, 96 patients were randomly assigned to one of three groups receiving target effect-site concentrations of remifentanil 0 (control group), 4 or 6 ng/ml, followed by injection with microemulsion propofol. Remifentanil pretreatment significantly reduced the incidence and severity of injection pain compared with the control group. Although no difference in pain reduction between the two remifentanil-treated groups was observed, those receiving a target effect-site concentration of 6 ng/ml exhibited an increased rate of complications, compared with those receiving 4 ng/ml. In conclusion, prior administration of remifentanil at a target effect-site concentration of 4 ng/ml is a useful strategy to decrease the injection pain of microemulsion propofol.

Effect-Site Concentration of Remifentanil for Nasotracheal versus Orotracheal Intubation during Target-Controlled Infusion of Propofol

The concentration of remifentanil required for acceptable nasotracheal intubation in adults after target-controlled infusion (TCI) of propofol without neuromuscular blockade was compared with that required for orotracheal intubation. Twenty-five patients undergoing oral and maxillofacial surgery received nasotracheal intubation and 25 undergoing ear, nose and throat surgery received orotracheal intubation. Anaesthesia was induced with propofol TCI at a target effect-site concentration of 5.0 μg/ml. The 50% and 95% effective concentrations (EC(50) and EC(95), respectively) for remifentanil, calculated using isotonic regression, were 5.40 and 6.85 ng/ml, respectively, in the orotracheal group and 5.75 and 7.43 ng/ml in the nasotracheal group. The EC(50) (± SD) values for remifentanil, calculated using a modified Dixon's up-and-down method, were 6.08 ± 0.75 and 5.58 ± 0.75 ng/ml for nasotracheal and orotracheal intubation, respectively. Effect-site remifentanil concentrations did not differ significantly between the two groups of patients. Coadministration of propofol and remifentanil can provide acceptable conditions for nasotracheal intubation without neuromuscular blockade.

When Duzitol Does Not Do It All

When Duzitol Does Not Do It All

The optimal effect-site concentration of remifentanil for lightwand tracheal intubation during propofol induction without muscle relaxation

Study Objective To determine the most suitable effect-site concentration of remifentanil during lightwand intubation when administered with a target-controlled infusion (TCI) of propofol at 4.0 μg/mL without neuromuscular blockade. Design Prospective study using a modified Dixon's up-and-down method. Setting Operating room of an academic hospital. Patients 28 ASA physical status 1 and 2 patients, aged 18-65 years, scheduled for minor elective surgery. Interventions Anesthesia was induced by TCI propofol effect-site concentration to 4.0 μg/mL, and the dose of remifentanil given to each patient was determined by the response of the previously tested patient using 0.2 ng/mL as a step size. The first patient was tested at a target effect-site concentration of 4.0 ng/mL of remifentanil. If intubation was successful, the remifentanil dose was decreased by 0.2 ng/mL; if it failed, the remifentanil dose was increased by 0.2 ng/mL. Successful intubation was defined as excellent or good intubating conditions. Measurements and Main Results The remifentanil effect-site concentration was measured. The optimal effect-site concentration of remifentanil for lightwand tracheal intubation during propofol induction using 2% propofol target effect-site concentration to 4 μg/mL was 2.16 ± 0.19 ng/mL. From probit analysis, the effect-site concentration of remifentanil required for successful lightwand intubation in 50% (EC50) and 95% (EC95) of adults was 2.11 ng/mL (95% CI 1.16-2.37 ng/mL) and 2.44 ng/mL (95% CI 2.20-3.79 ng/mL), respectively. Conclusion A remifentanil effect-site concentration of 2.16 ± 0.19 ng/mL given before a propofol effect-site concentration of 4 μg/mL allowed lightwand intubation without muscle relaxant.

Comparison of the Effect-Site Concentrations of Remifentanil for Streamlined Liner of the Pharynx Airway (SLIPA™) versus Laryngeal Mask Airway Softseal™ insertion during Target-Controlled Infusion of Propofol

This study was designed to determine the optimal dose of remifentanil required for the successful insertion of Streamlined Liner of the Pharynx Airway (SLIPA) and to compare it to that required for laryngeal mask airway (LMA) insertion in patients receiving a propofol infusion at a standard effect-site concentration. Fifty-eight patients scheduled to undergo general anaesthesia were randomly assigned to either the SLIPA (n = 29) or LMA (n = 29) group. All patients were premedicated with midazolam 0.05 mg x kg(-1) and glycopyrrolate 0.004 mg x kg(-1) intramuscularly. After the administration of lignocaine 1 mg x kg(-1) intravenously, a propofol infusion was started at an effect-site concentration of 3.5 microg x ml(-1) with a remifentanil infusion without a neuromuscular blocking agent. The remifentanil dose was determined by the modified up-and-down method starting in each group at 4 ng x ml(-1). Six minutes after induction, the airway device was inserted. Airway device insertion was classified as 'success' or 'failure' based on patient response. From the isotonic regression analysis and bootstrap distribution, the EC50 of remifentanil for SLIPA and LMA were 0.93 ng x ml(-1) (95% confidence interval [CI] 0.81 to 1.50 ng x ml(-1) and 1.36 ng x ml(-1) (95% CI 1.19 to 2.06 ng x ml(-1)) respectively, and the EC95 for SLIPA and LMA insertions were 1.90 ng x ml(-1) (95% CI 1.39 to 1.95) and 2.43 ng x ml(-1) (95% CI 1.80 to 2.46 ng x ml(-1)) respectively. Using the 83% CIs from the bootstrap distribution, EC50 for SLIPA was significantly less than that of LMA (0.83 to 1.23 vs 1.26 to 2.00, respectively) (P < 0.05). These findings suggest that the insertion of SLIPA needs about a 32% lower depth of anaesthesia than LMA insertion.

The effect site concentration of remifentanil for preventing cough during emergence from sevoflurane and desflurane anaesthesia

The effect site concentration of remifentanil for preventing cough during emergence from sevoflurane and desflurane anaesthesia