Optimal Effect-site Concentration Research Articles

The Effect of Ramosetron on Remifentanil in Preventing Emergence Cough from Sevoflurane Anesthesia in Female Patients.

Remifentanil reduces cough during extubation. Ramosetron, a 5-HT3 receptor antagonist, is a potent antiemetic. Regarding the antitussive property of 5-HT receptor agonists, ramosetron can mediate the cough reflex by increasing the remifentanil requirement. This study evaluated the effect of ramosetron on the optimal effect-site concentration (Ce) of remifentanil for preventing emergence cough from sevoflurane anesthesia in female patients. Forty-seven randomly selected female patients undergoing laparoscopic cholecystectomy received either ramosetron 0.3 mg (n = 23) or the same volume of normal saline (n = 24) intravenously at the end of surgery. The remifentanil Ce using target-controlled infusion in 50% of patients (EC50) and 95% of patients (EC95) were assessed using Dixon's up-and-down or isotonic regression method with a bootstrapping approach. Using Dixon's up-and-down method, the EC50 of remifentanil in the control group (1.33 ± 0.38 ng/mL) was comparable to that of ramosetron group (1.50 ± 0.69 ng/mL) (P = 0.615). Using isotonic regression analysis, the EC50 (83% confidence interval) did not differ between the two groups (1.17 [0.86-1.43] ng/mL and 1.13 [0.68-1.56] ng/mL in control and ramosetron groups). However, the EC95 (95% confidence interval) was significantly lower in the control group than in the ramosetron group (1.90 [1.45-1.96] ng/mL and 2.92 [2.35-2.97] ng/mL). Remifentanil Ce for preventing emergence cough was higher in the ramosetron group than in the control group. It may indicate the lowering effect of ramosetron on the antitussive activity of remifentanil.

Effects of smoking on the optimal effect-site concentration of remifentanil required for preventing cough during anesthetic emergence in male patients undergoing laparoscopic or robotic cholecystectomy.

Target-controlled infusion of remifentanil is known to reduce cough effectively during emergence from general anesthesia. The effect of smoking on emergence cough remains controversial. Therefore, we aimed to investigate the effect-site concentration (Ce) of remifentanil in the male patients undergoing laparoscopic or robotic cholecystectomy for suppressing emergence cough in smokers and non-smokers.Twenty smokers and 24 non-smokers (sex, male; age range, 20–65 years) were enrolled in this study. Anesthesia was maintained using sevoflurane and remifentanil. The Ce of remifentanil in 50% (EC50) and 95% (EC95) of the patients required for suppressing emergence cough were determined for each group (smokers and non-smokers) using Dixon up-and-down method and isotonic regression method with a bootstrapping approach.Dixon up-and-down method revealed that the EC50 value was significantly higher in smokers (3.51 ± 0.60 ng/mL) than in non-smokers (2.71 ± 0.30 ng/mL) (P < 0.001). In smokers and non-smokers, isotonic regression revealed EC50 to be 4.40 (83% CI, 4.17–4.58) ng/mL and 2.58 (83% CI, 2.31–2.87) ng/mL, respectively, and EC95 to be 4.76 (95% CI, 4.73–4.78) ng/mL and 3.15 (95% CI, 3.04–3.18) ng/mL, respectively.The Ces of remifentanil required to prevent cough during emergence were significantly higher in smokers than in non-smokers. Therefore, clinicians should pay attention to the smoking history of a patient to prevent cough during emergence.

Optimal effect-site concentration of remifentanil to prevent hemodynamic changes during nasotracheal intubation using a video laryngoscope.

BackgroundNasotracheal intubation is the most commonly used method to secure the field of view when performing surgery on the oral cavity or neck. Like orotracheal intubation, nasotracheal intubation uses a laryngoscope. Hemodynamic change occurs due to the stimulation of the sympathetic nervous system. Recently, video laryngoscope with a camera attached to the end of the direct laryngoscope blade has been used to minimize this change. In this study, we investigated the optimal effect-site concentration (Ce) of remifentanil for minimizing hemodynamic responses during nasotracheal intubation with a video laryngoscope.MethodsTwenty-one patients, aged between 19 and 60 years old, scheduled for elective surgery were included in this study. Anesthesia was induced by slowly injecting propofol. At the same time, remifentanil infusion was initiated at 3.0 ng/ml via target-controlled infusion (TCI). When remifentanil attained the preset Ce, nasotracheal intubation was performed using a video laryngoscope. The patient's blood pressure and heart rate were checked pre-induction, right before and after intubation, and 1 min after intubation. Hemodynamic stability was defined as an increase in systolic blood pressure and heart rate by 20% before and after nasotracheal intubation. The response of each patient determined the Ce of remifentanil for the next patient at an interval of 0.3 ng/ml.ResultsThe Ce of remifentanil administered ranged from 2.4 to 3.6 ng/ml for the patients evaluated. The estimated optimal effective effect-site concentrations of remifentanil were 3.22 and 4.25 ng/ml, that were associated with a 50% and 95% probability of maintaining hemodynamic stability, respectively.ConclusionNasotracheal intubation using a video laryngoscope can be successfully performed in a hemodynamically stable state by using the optimal remifentanil effect-site concentration (Ce50, 3.22 ng/ml; Ce95, 4.25 ng/ml).

The optimal effect-site concentration of propofol for endotracheal suctioning in intensive care unit patients

Objective: To evaluate the optimal effect-site concentration (Ce) of propofol during endotracheal suction (ETS) in the postoperative Intensive Care Unit (ICU) sedated patients. Design and Setting: The study design was a prospective randomized clinical study in a 13-bed ICU in a medical center. Patients: Thirteen mechanically ventilated patients were included in this study. Methods: All included postoperative patients received sedation by target-controlled infusion (TCI) of propofol under bispectral index (BIS) monitoring and 2–4 μg/kg/h fentanyl infusion for analgesia to keep numerical rating scale ≤4. While ETS was need, the sedation interventions were performed. We used the up-and-down method with a step size of propofol Ce 0.2 μg/ml for the next intervention. The sedation interventions of 1, 2, and 3 were baseline propofol Ce, baseline propofol Ce +0.2 mg/ml, and baseline propofol Ce +0.4 μg/ml, respectively. The predetermined propofol Ce was maintained for 5 min before ETS. Arterial systolic blood pressures (SBPs), arterial diastolic blood pressure (DBP), heart rates (HRs), and BIS before and after ETS were recorded. No moderate or severe coughing with limb movement was the primary outcome, and the surge of SBP, DBP, and HR ≤20% of baseline was the secondary outcome. Results: There were 39, 72, and 45 ETS were performed in the intervention 1, 2, and 3, respectively. In the primary outcome, the successful rates of ETS were 100%, 37.5%, and 15.4% in the intervention 3, 2, and 1, respectively (P < 0.001). In the secondary outcomes, the successful rates were 100% in all interventions. However, the surge of SBP (P = 0.009), DBP (P = 0.025), and HR (P = 0.009) were significant higher in the intervention 1 and 2 than the intervention 3. Right after the ETS, significant increase in BIS level was observed in the intervention 1 (13.9± 7.9) and 2 (14.4± 7.5) except for intervention 3 (−2.8± 14.5) (P = 0.003). Conclusions: An increase of propofol Ce 0.4 mg/ml for 5 min before ETS provided adequate sedation result in markedly attenuated ETS-induced coughing, limb movement, and hyperdynamic status during ETS while the use of TCI propofol sedation in postoperative ICU patients.

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.

Effective method of continuous rocuronium administration based on effect-site concentrations using a pharmacokinetic/pharmacodynamic model during propofol-remifentanil anesthesia.

Rocuronium bromide (Rb) is a rapid onset, intermediate-acting neuromuscular blocking agent that is suitable for continuous administration. The appropriate rate of rocuronium administration is, however, difficult to determine due to large interindividual differences in sensitivity to rocuronium. The aim of this study was to clarify whether the simulated rocuronium concentration at the time of recovery to %T1 > 0 % after the initial administration of rocuronium is a good indicator of optimal effect-site concentrations during continuous rocuronium administration. Twenty-one patients were anesthetized with propofol. After induction, Rb 0.6 mg/kg was administered intravenously, and nerve stimulation using the single stimulation mode was conducted every 15 s. When %T1 recovered to >0 % after the initial administration of Rb, the effect-site concentration of rocuronium, calculated by pharmacokinetic simulation with Wierda's set of parameters, was recorded and defined as the recovery concentration (Rb r.c.). The administration rate of rocuronium was adjusted to maintain the Rb r.c. during surgery. Rb administration was discontinued just before the end of surgery, and the recovery time until %T1 > 25 % was recorded. Plasma Rb concentrations were measured at 1 and 3 h after the initiation of continuous Rb administration. The mean Rb r.c. was 1.56 ± 0.35 μg/ml, with minimum and maximum values of 1.09 and 2.08 μg/ml, respectively. The %T1 did not increase above 10 % in any of the patients during continuous administration of Rb, and the recovery period to %T1 > 25 % ranged from 9 to 29 min. The effect-site concentrations of Rb calculated with Wierda's parameters significantly correlated with plasma concentrations (P < 0.01) at both 1 and 3 h after the initial administration of Rb. The results suggest that our method may be one of the most reliable protocols for the continuous administration of Rb described to date for maintaining suitable muscle relaxation during surgery without excessively prolonged effects.

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.

Intrathecal fentanyl decreases the optimal effect site concentration of propofol during spinal anaesthesia

The aim of this study was to assess the possible difference in the optimal effect site concentration of propofol for conscious sedation during spinal anaesthesia with or without intrathecal fentanyl in patients undergoing urologic surgery. The hypothesis was that intrathecal fentanyl would decrease the effect site concentration of propofol needed for conscious sedation. Among 43 patients, 23 patients received fentanyl 25 mcg and 20 patients received normal saline in addition to hyperbaric bupivacaine 10 mg during spinal anaesthesia. Propofol was infused at a dose determined by a modified Dixon's up-and-down method. The Cerebral State Index was recorded once target effect site concentration was reached to determine the effect of the successfulness of the conscious sedation. The half maximal effective concentration (EC50) of the effect-site concentration of propofol for sedation was 1.67 ± 0.28 mcg/ml in the control group and 0.87 ± 0.15 mcg/ml in the fentanyl group (P = 0.02). The propofol dose for conscious sedation during spinal anaesthesia was decreased by 48% when intrathecal fentanyl 25 mcg was added to local anaesthetics. The EC50 of the effect-site concentration of propofol for sedation decreased from 1.67 ± 0.28 mcg/ml to 0.87 ± 0.15 mcg/ml with the addition of 25 mcg fentanyl to a spinal anaesthetic in patients undergoing urologic surgery.

The optimal effect-site concentration of sufentanil for laryngeal mask insertion during induction with target-controlled propofol infusion at 4.0 μg/mL.

Objective:The objective of this study is to determine the optimal effect-site concentration (Ce) of sufentanil for satisfactory insertion of laryngeal mask airway (LMA) when administered with a target-controlled infusion (TCI) of propofol at 4.0 μg/mL.Materials and Methods:A total of 25 adult patients scheduled for minor elective surgery were enrolled in this study. All patients received induction with a combination of propofol and sufentanil TCI. The TCI of sufentanil was started at a target Ce of 0.1 ng/mL. After equilibrium with the plasma concentration, the TCI of propofol was initiated, targeting a preset Ce of 4.0 μg/mL. After the loss of consciousness, LMA was inserted and assessed by an experienced Anesthesiologist. The Ce of sufentanil for the next patient was guided by modified Dixon's up-and-down method using 0.05 ng/mL as a step size. The Ce of sufentanil required for successful LMA insertion in 50% of adults (EC50) was determined by calculating the midpoint concentration of all independent pairs of patients after at least seven crossover points.Results:The optimal Ce (EC50) of sufentanil for LMA insertion during propofol induction using target Ce of 4 μg/mL was 0.16 ng/mL (95% confidence interval [CI] = 0.12-0.20). There was a significant reduction in propofol induced pain score P = 0.0275 and insignificant hemodynamic changes.Conclusion:Ce of sufentanil required for successful LMA insertion in 50% of patients (EC50) using propofol target Ce of 4.0 μg/mL was 0.16 ng/mL (95% CI = 0.12-0.20) with a significant reduction in the propofol induced pain and hemodynamic stability.

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.

The optimal effect-site concentration of sufentanil for laryngeal mask insertion during induction with target-controlled propofol infusion at 4.0 μg/mL

King Fahad Hospital/Dammam University, Dept of Anaesthesiology & Intensive Care, Alkhobar, Saudi Arabia

Effect‐site concentration of remifentanil to prevent cough after laryngomicrosurgery

The aim of this study was to discover the optimal effect-site concentration of remifentanil for cough prevention that does not delay awakening or cause respiratory depression during emergence from anesthesia with propofol and remifentanil in laryngomicrosurgery patients. Prospective, randomized, controlled trial. One hundred five patients were randomly assigned to maintain an effect-site concentration (Ce) of remifentanil at a predetermined value of 1 (R1), 1.5 (R1.5), and 2 (R2) ng/mL during emergence. The incidence and grade (0, no coughing; 1, single cough; 2, more than one episode of nonsustained coughing; 3, sustained and repetitive coughing with head lift) of cough, emergence time, blood pressure (MAP), heart rate (HR), spontaneous respiratory rate, oxygen saturation, and postoperative nausea and vomiting (PONV) were recorded during emergence and recovery. The total number of patients with coughing during emergence was lower in groups R1.5 and R2 than in group R1. The cough grade during tracheal extubation was lower in groups R1.5 and R2 than in group R1. In group R2, emergence time was longer and postanesthesia care unit score was lower than in groups R1 and R1.5. Also in group R2, transient hypoventilation and PONV were more frequent compared to group R1. There were no differences in MAP and HR among the three groups during emergence and recovery. Maintenance of remifentanil at Ce 1.5 and 2 ng/mL suppressed coughing without serious adverse events during emergence from anesthesia with propofol and remifentanil in patients undergoing laryngomicrosurgery.

The optimal effect site concentration of propofol for conscious sedation in elderly male patients undergoing urologic surgery under spinal anesthesia with or without intrathecal fentanyl

The optimal effect site concentration of propofol for conscious sedation in elderly male patients undergoing urologic surgery under spinal anesthesia with or without intrathecal fentanyl

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.

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

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. Prospective study using a modified Dixon's up-and-down method. Operating room of an academic hospital. 28 ASA physical status 1 and 2 patients, aged 18-65 years, scheduled for minor elective surgery. 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. 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. 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.

Remifentanil as single agent to facilitate awake fibreoptic intubation in the absence of premedication*

Remifentanil is increasingly being used as the primary agent to provide sedation during awake fibreoptic nasal intubation. In this observational study, we aimed to determine the optimal effect site concentration of remifentanil, using a target controlled infusion based on the Minto pharmacological model, to provide optimal safe intubation conditions without the use of other sedatives/premedication and/or spray-as-you-go local anaesthesia. Twenty patients with anticipated difficult airway participated in the study. Good intubating conditions were achieved in all patients with mean (SD) effect site concentration of 6.3 (3.87) ng.ml(-1) of remifentanil recorded at nasal endoscopy and 8.06 (3.52) ng.ml(-1) during tracheal intubation. No serious adverse event occurred during any of these procedures. These preliminary findings suggest that this is a feasible and safe technique for awake fibreoptic nasal intubation.

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

BackgroundThe 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.MethodsOne 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.ResultsA 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).ConclusionsThe 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.

The optimal effect site concentration of remifentanil for tracheal intubation without muscle relaxant during inhalation anesthetic induction using sevoflurane in adult.

Sevoflurane has been shown to be suitable for inhalation induction of anesthesia in adults. The addition of remifentanil during sevoflurane induction allows for rapid and smooth tracheal intubation without muscle relaxant. The high concentration of remifentanil can result in improved conditions for tracheal intubation but also caused a cardiovascular instability. We tried to estimate optimal effect site concentration of remifentanil for tracheal intubation without muscle relaxants during inhalation anesthetic induction with 8 vol% sevoflurane and 50% N2O. One hundred five ASA I and II patients were randomly allocated to receive an effect site concentration of remifentanil 2, 4, or 6 ng/ml. Trachea was intubated without muscle relaxant after 3 minutes of inhalation induction with 8 vol% sevoflurane and 50% N2O. The intubating conditions for tracheal intubation were assessed and blood pressure and heart rate were recorded at the baseline, before intubation, just after intubation, 1, and 3 minute after intubation. Tracheal intubation was successful in all patients. Clinically acceptable intubation conditions were 60%, 94%, and 100% in 2 ng/ml, 4 ng/ml, and 6 ng/ml group respectively. However, the number of patient who requested rescue medication for bradycardia in 6 ng/ml group was significantly higher than that in the other group (P < 0.05). We concluded that 4 ng/ml effect site concentration of remifentanil is adequate concentration for tracheal intubation without muscle relaxants during inhalation induction using sevoflurane.