Effect-site Concentration Of Remifentanil Research Articles

Effect-site concentration of remifentanil for preventing propofol injection pain during induction of balanced anesthesia.

BackgroundDespite various strategies designed for preventing pain from propofol injection, it is still common and distressing to the patients. The purpose of the present study was to investigate the adequate effect-site concentration (Ce) of remifentanil to prevent pain due to propofol injection.MethodsA total of 160 adults scheduled for elective surgery were randomly assigned to one of four groups receiving normal saline (group S) or remifentanil at a Ce of 2 (group R2), 3 (group R3), or 4 ng/ml (group R4), administered via target-controlled infusion, followed by the injection of 2 mg/kg of propofol (delivered with 1% lipid propofol). The severity and incidence of injection pain were assessed on a four-point scale.ResultsThe incidence of propofol injection pain was significantly lower in group R2, R3, or R4 than in group S (30%, 5%, or 2.5% vs. 70%, respectively). Moreover, the intensity of the pain was lesser in group R2, R3, or R4 than in group S. However, the incidence or severity of injection was not different between groups R3 and R4.ConclusionsDuring the induction of balanced anesthesia using propofol injection, pretreatment with remifentanil at a target Ce of 3 ng/ml effectively reduced propofol injection pain in adults.

A Comparison of Different Remifentanil Effect-Site Concentrations to Allow for Early Extubation After Cardiac Surgery

Assess different remifentanil effect-site concentrations (Ce) for readiness for extubation time after cardiac surgery. Prospective, randomized, blinded, controlled study. Single university hospital. Seventy-three patients scheduled for cardiac surgery. After ethical approval, patients scheduled for cardiac surgery with target-controlled propofol infusion were randomly assigned to receive remifentanil effect-site concentrations (Ce) of 1, 2, or 3 ng/mL (n = 25, 25, and 23, respectively). The primary endpoint was readiness for extubation. Secondary outcomes were also recorded, including the cumulative doses and number of changes of propofol and remifentanil, hemodynamic variables, time to spontaneous eye opening and breathing, actual extubation, incidences of light anesthesia and myocardial ischemia, need for vasopressors and inotropes, and intensive care unit (ICU) and hospital stays. There was no difference in the time to readiness for extubation in any of the groups (0.1 ng/mL: 11.5 min (5-37); 0.2 ng/mL: 22 min (10-35); and 0.3 ng/mL: 21 min (10-49), p < 0.532); however, there was a significant difference among the 3 groups regarding the cumulative remifentanil doses (p < 0.001). Time to spontaneous eye opening and breathing, actual extubation, use of vasopressors and inotropes, incidences of light anesthesia and myocardial ischemia, and length of ICU and hospital stay were similar for all groups. Forty-six of the 73 patients were extubated on-table. Remifentanil Ce 1, 2, and 3 ng/mL produced comparative effects on time to extubation and hemodynamic responses to cardiac surgery. The 3 Ce resulted in immediate on-table extubation in 50% of patients.

Effects of varying remifentanil concentrations on Analgesia Nociception Index® under propofol: an observational study.

Analgesia Nociception Index monitor provides a measurement of the nociception and anti-nociception balance based on heart-rate variability. The aim was to assess the ability of Analgesia Nociception Index (ANI) to detect standard noxious stimulation during anesthesia at different opioid concentrations in comparison to hemodynamic and Bispectral Index parameters. Sixteen patients undergoing general anesthesia with propofol and remifentanil. Standardized tetanic electrical stimulation was applied without any other concurrent stimuli, while different effect site concentrations of remifentanil were increased step-by-step (0.5, 1.5, 3.0, 5 and 7ng/ml). For each tetanic stimulus, values of the different variables 60s before and 120s following the stimulus were analyzed. ANI values decreased significantly 120s after the stimulus when compared to the mean ANI 60s before the stimulus (P < 0.01). At lower remifentanil concentrations (0.5ng/ml), all variables except electromyogram from the Bispectral Index significantly changed after the stimulus but in the higher concentrations (5.0 and 7.0ng/ml) there was not a significant change. The other variables did not change significantly after the noxious stimulation. ANI was the only variable that positively correlated with the different remifentanil concentrations (R = 0.959, P = 0.01). Our study showed that there was a significant decrease in Analgesia Nociception Index after a tetanic stimulation while hemodynamic and BIS parameters did not change, suggesting that the Analgesia Nociception Index may perform better than traditional hemodynamic parameters at reflecting noxious stimulation. Analgesia Nociception Index significantly changed at lower, but not at higher, remifentanil concentrations.

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).

Predictive Factors for Hypotension Associated With Supine-to-Prone Positional Change in Patients Undergoing Spine Surgery

Positional change during general anesthesia can cause hypotension. The objective of this retrospective study was to determine predictive factors for hypotension associated with supine-to-prone positional change in spinal surgery patients. Data on demographics, current medications, comorbidity, intraoperative mean arterial pressure (MAP), heart rate, pulse pressure variation, tidal volume, peak inspiratory pressure, and propofol and remifentanil effect-site concentrations were collected from 179 patients undergoing elective spine surgery. Hypotension associated with supine-to-prone positional change was defined as >20% reduction in MAP during positional change. Hypotension associated with supine-to-prone positional change was observed in 16 (8.9%) patients. The median (interquartile range) effect-site concentration of remifentanil (5.3 [4.0 to 8.5] vs. 4.0 [3.1 to 4.0] ng/mL, P<0.001), MAP (95.0 [86.0 to 103.5] vs. 80.0 [70.0 to 94.0] mm Hg, P=0.014), peak inspiratory pressure (16.5 [15.0 to 18.5] vs. 15.0 [14.0 to 17.0] hPa, P=0.040) in the supine position, and pulse pressure variation in the prone position (12.0 [9.0 to 16.4] vs. 9.0 [7.0 to 12.0]%, P=0.019) were significantly higher in the hypotension group. In multivariate logistic regression analysis, the effect-site concentration of remifentanil (odd ratio [95% confidence interval], 2.12 [1.51-2.96], P<0.001), preoperative use of beta-blocker (7.64 [1.21-48.36], P=0.031), and MAP in the supine position (1.04 [1.00-1.07], P=0.033) were independent predictive factors for hypotension associated with supine-to-prone positional change. Increased effect-site concentration of remifentanil, preoperative use of beta-blocker, and high MAP in the supine position were predictive factors for hypotension associated with supine-to-prone positional change in spinal surgery patients.

Pharmacodynamic modelling of the effect of remifentanil using the Pupillary Pain Index.

Using a targeted controlled infusion of remifentanil during total intravenous anesthesia, we investigated the effect-site concentrations of remifentanil that correlate with different values of the Pupillary Pain Index and which concentrations were necessary for achieving a Pupillary Pain Index ≤ 4 and its usefulness in titrating opioids. The Pupillary Pain Index was measured in 54 patients prior to surgery under different remifentanil effect-site concentrations and subsequently modeled. One hundred and twenty-eight measurements were taken at different remifentanil concentrations while titrating propofol for a similar depth of hypnosis using a BIS monitor. Our modeled Hill equation revealed a remifentanil of 2.96ng/mL for a PPI of 4, and the probability model a Ce of 3.22ng/mL for the probability of 50% of patients achieving a PPI score ≤ 4. For the probability of 80% of patients achievinga PPI score ≤ 4 the Ce of remifentanil was 4.39ng/mL. We conclude that concentrations of remifentanil that have been shown to suppress movement in response to noxious stimulation correspond to a Pupillary Pain Index ≤ 4.

Non-steady State Modeling of the Ventilatory Depressant Effect of Remifentanil in Awake Patients Experiencing Moderate-to-severe Obstructive Sleep Apnea.

Evidence suggests that obstructive sleep apnea promotes postoperative pulmonary complications by enhancing vulnerability to opioid-induced ventilatory depression. We hypothesized that patients with moderate-to-severe obstructive sleep apnea are more sensitive to remifentanil-induced ventilatory depression than controls. After institutional approval and written informed consent, patients received a brief remifentanil infusion during continuous monitoring of ventilation. We compared minute ventilation in 30 patients with moderate-to-severe obstructive sleep apnea diagnosed by polysomnography and 20 controls with no to mild obstructive sleep apnea per polysomnography. Effect site concentrations were estimated by a published pharmacologic model. We modeled minute ventilation as a function of effect site concentration and the estimated carbon dioxide. Obstructive sleep apnea status, body mass index, sex, age, use of continuous positive airway pressure, apnea/hypopnea events per hour of sleep, and minimum nocturnal oxygen saturation measured by pulse oximetry in polysomnography were tested as covariates for remifentanil effect site concentration at half-maximal depression of minute ventilation (Ce50) and included in the model if a threshold of 6.63 (P < 0.01) in the reduction of objective function was reached and improved model fit. Our model described the observed minute ventilation with reasonable accuracy (22% median absolute error). We estimated a remifentanil Ce50 of 2.20 ng · ml (95% CI, 2.09 to 2.33). The estimated value for Ce50 was 2.1 ng · ml (95% CI, 1.9 to 2.3) in patients without obstructive sleep apnea and 2.3 ng · ml (95% CI, 2.2 to 2.5) in patients with obstructive sleep apnea, a statistically nonsignificant difference (P = 0.081). None of the tested covariates demonstrated a significant effect on Ce50. Likelihood profiling with the model including obstructive sleep apnea suggested that the effect of obstructive sleep apnea on remifentanil Ce50 was less than 5%. Obstructive sleep apnea status, apnea/hypopnea events per hour of sleep, or minimum nocturnal oxygen saturation measured by pulse oximetry did not influence the sensitivity to remifentanil-induced ventilatory depression in awake patients receiving a remifentanil infusion of 0.2 μg · kg of ideal body weight per minute.

The effect of isocapnic hyperventilation on early recovery after remifentanil/sevoflurane anesthesia in O2/air: A randomized trial

Isocapnic hyperventilation (ICHV) may hasten emergence from general anesthesia but remains inadequately studied. We prospectively determined emergence time after sevoflurane anesthesia of variable duration with and without ICHV. In 25 ASA I-II patients, general anesthesia was maintained with one age-adjusted MAC sevoflurane in O2 /air and target-controlled remifentanil delivery. At the start of skin closure, the remifentanil effect-site concentration was reduced to 1.5ng/mL, any residual neuromuscular block reversed, and once the remifentanil effect-site concentration had decreased to 1.5ng/mL, remifentanil and sevoflurane administration was stopped, and the fresh gas flow increased above minute ventilation. Patients randomly received either normoventilation (n=13) or ICHV (doubling minute ventilation while titrating CO2 into the inspiratory limb to maintain isocapnia [n=12]). Three early recovery end points were determined: time to proper response to verbal command; time to extubation; and time to stating one's name. Demographics were the same in both groups. Recovery end points were reached faster in the ICHV group compared to the normoventilation group: time to proper response to verbal command was 7.6±2.2 vs 9.9±2.9min (P=0.03); time to extubation was 7.6±2.6 vs 11.0±2.4min (P=0.002); and time to stating one's name was 8.9±2.8 vs 12.5±2.6min (P=0.003). Within each group, duration of anesthesia only marginally affected the times to reach these recovery end points. Isocapnic hyperventilation only had a small effect on emergence times after anesthesia, suggesting that isocapnic hyperventilation may have limited clinical benefits with modern potent inhaled anesthetics.

High-dose intraoperative remifentanil infusion increases early postoperative analgesic consumption: a prospective, randomized, double-blind controlled study.

The purpose of this study was to determine whether intraoperative infusion of remifentanil induces acute tolerance to opioids, and compare the postoperative pain and opioid consumption by the effect site concentrations of remifentanil. One hundred and ninety-eight patients undergoing gastrectomy were randomly assigned to maintain target effect site concentrations of remifentanil at 0 (Group 1, n = 39), 2 (Group 2, n = 40), 4 (Group 3, n = 39), 8 (Group 4, n = 40), or 12ng/ml (Group 5, n = 40) during operation. Postoperative pain intensities and fentanyl requirement were recorded at postoperative 2, 6, 24, and 48h. Fentanyl requirement for postoperative 2h was significantly greater in Group 5 compared to Group 1 (376 ± 116 vs. 283 ± 129µg, P = 0.03). However, there were no differences in fentanyl requirements among the groups after postoperative 2h. Also, total fentanyl consumption for 48h was similar in all groups (Group 1; 3106 ± 629, Group 2; 2970 ± 705, Group 3; 3017 ± 555, Group 4; 3151 ± 606, and Group 5; 2984 ± 443 µg, P = 0.717). Pain scores at rest and during deep breathing were comparable in all groups at the time of each examination. Intraoperative infusion of remifentanil with 12ng/ml of effect site concentration in patients undergoing gastrectomy increases early postoperative fentanyl requirement. Acute opioid tolerance would be developed by higher concentration of remifentanil than dosage of common anesthetic practice.

A comparison of propofol-to-BIS post-operative intensive care sedation by means of target controlled infusion, Bayesian-based and predictive control methods: an observational, open-label pilot study

PurposeWe evaluated the feasibility and robustness of three methods for propofol-to-bispectral index (BIS) post-operative intensive care sedation, a manually-adapted target controlled infusion protocol (HUMAN), a computer-controlled predictive control strategy (EPSAC) and a computer-controlled Bayesian rule-based optimized control strategy (BAYES).MethodsThirty-six patients undergoing short lasting sedation following cardiac surgery were included to receive propofol to maintain a BIS between 40 and 60. Robustness of control for all groups was analysed using prediction error and spectrographic analysis.ResultsAlthough similar time courses of measured BIS were obtained in all groups, a higher median propofol effect-site concentration (CePROP) was required in the HUMAN group compared to the BAYES and EPSAC groups. The time course analysis of the remifentanil effect-site concentration (CeREMI) revealed a significant increase in CeREMI in the EPSAC group compared to BAYES and HUMAN during the case. Although similar bias and divergence in control was found in all groups, larger control inaccuracy was observed in HUMAN versus EPSAC and BAYES. Spectrographic analysis of the system behavior shows that BAYES covers the largest spectrum of frequencies, followed by EPSAC and HUMAN.ConclusionsBoth computer-based control systems are feasible to be used during ICU sedation with overall tighter control than HUMAN and even with lower required CePROP. EPSAC control required higher CeREMI than BAYES or HUMAN to maintain stable control.Clinical trial number: NCT00735631.

Comparison of sevoflurane and desflurane on effect-site concentration of remifentanil for preventing anesthetic emergence cough in elderly female patients undergoing laparoscopic cholecystectomy

PurposeAmong inhalational anesthetics, desflurane is widely believed to provoke upper airway irritation including coughing and laryngospasm. Remifentanil has been generally used to prevent cough due to its unique pharmacodynamics. However, there was no study that compared optimal remifentanil effect-site concentration (Ce) to prevent emergence cough according to the type of inhalational agent in elderly female patients. Thus, we investigated the Ce of remifentanil for preventing cough during emergence from sevoflurane and desflurane anesthesia in elderly female patients.MethodsForty-three female patients between 60 and 75 years of age undergoing laparoscopic cholecystectomy were randomly allocated to sevoflurane group (n=22) or desflurane group (n=21). The optimal remifentanil Ce using target-controlled infusion for 50% of patients (EC50) and 95% of patients (EC95) was assessed by Dixon’s up-and-down method or isotonic regression method with a bootstrapping approach.ResultsBy Dixon’s up-and-down method, the EC50 of remifentanil in sevoflurane group (2.08±0.47 ng/mL) was comparable with that in desflurane group (2.25±0.40 ng/mL) (P=0.385). The EC50 (83% CIs) and EC95 (95% CIs) by isotonic regression also did not show significant difference between two groups [2.06 (1.45–2.23) and 2.46 (2.35–2.48) ng/mL in sevoflurane group and 2.14 (1.45–2.56) and 2.88 (2.47–2.98) ng/mL in desflurane group, respectively].ConclusionThere was no difference in the remifentanil Ce to prevent emergence cough between sevoflurane and desflurane anesthesia. Therefore, the clinicians may not need to adjust the remifentanil Ce to prevent emergence cough according to inhalational agents in elderly female patients.

Effects of age on effect-site concentration of remifentanil for suppressing anesthetic emergence cough in male patients undergoing laparoscopic cholecystectomy.

BackgroundRemifentanil infusion during emergence lowers cough. Effect-site concentration (Ce) of remifentanil using target-controlled infusion (TCI) has been evaluated in previous studies. Recent studies revealed the existence of sex-related differences in remifentanil Ce in young and elderly patients. Thus, there was the need to re-evaluate the effect of age in single sex. We investigated the remifentanil Ce for suppressing emergence cough in young and elderly male patients and evaluated the age-related differences.Patients and methodsIn total, 25 young (ages between 20 and 50 years) and 24 elderly (ages between 65 and 75 years) male patients undergoing laparoscopic cholecystectomy were enrolled. Anesthesia was implemented with remifentanil using TCI and sevoflurane. The remifentanil Ce for suppressing emergence cough was estimated for each group using Dixon’s up-and-down method and isotonic regression method with a bootstrapping approach.ResultsThe remifentanil Ce for suppressing emergence cough in 50% (EC50) and 95% (EC95) of the patients was comparable between the young and elderly patients. Isotonic regression demonstrated that the EC50 (83% confidence interval [CI]) of remifentanil was 2.56 (2.39−2.75) ng/mL in the young patients and 2.15 (1.92−2.5) ng/mL in the elderly patients. The EC95 (95% CI) of remifentanil was 3.33 (2.94−3.46) ng/mL in the young patients and 3.41 (3.18−3.48) ng/mL in the elderly patients. Dixon’s up-and-down method also demonstrated that the EC50 was comparable between the two groups (2.69±0.32 ng/mL vs 2.39±0.38 ng/mL, P=0.132).ConclusionThe remifentanil Ce for suppressing emergence cough following extubation during general anesthesia was comparable between young and elderly male patients. It indicates that age-related differences in remifentanil requirement for suppressing emergence cough did not exist in male sex.

Standardised noxious stimulation-guided individual adjustment of remifentanil target-controlled infusion to prevent haemodynamic responses to laryngoscopy and surgical incision: A randomised controlled trial.

The surgical plethysmographic index (SPI) is one of the available indexes of the nociception-antinociception (NAN) balance. Individually adjusting the NAN balance to prevent somatic responses to noxious stimulation remains a challenge. To assess whether guiding remifentanil administration according to the SPI response to a calibrated noxious stimulus (NANCAL) can blunt the haemodynamic response to tracheal intubation and surgical incision. Randomised multicentre study. Two Belgian university hospitals from January 2014 to April 2015. After ethic review board approval and informed consent, 48 American Society of Anesthesiologists I or II adult patients scheduled for surgery under general anaesthesia were enrolled. Patients were randomly assigned to a SPI group, where remifentanil effect-site concentration was adjusted according to NANCAL, or a control group, where it was fixed at 4 ng ml. Propofol concentration was always adjusted to maintain the bispectral index close to 40. NANCAL consisted of a 100 Hz, 60 mA electrical tetanic stimulation during 30 s at the wrist before tracheal intubation and before surgical incision. The primary endpoint was the efficacy of the NANCAL-guided remifentanil administration to prevent the haemodynamic response to tracheal intubation and surgical incision. The secondary aim was to compare the ability of SPI, analgesia nociception index, pupil diameter and mean arterial pressure response to NANCAL to predict the haemodynamic response to tracheal intubation and surgical incision. Our SPI response to NANCAL-based correcting scheme for remifentanil administration was not superior to a fixed remifentanil concentration at blunting the haemodynamic response to tracheal intubation or surgical incision. Among all tested NAN balance indices, only mean arterial pressure had significant predictive ability with regard to the haemodynamic response to surgical incision. Further research is needed to define the best NANCAL stimulus and the best remifentanil correcting scheme to help individualised tailoring of antinociception for each specific subpopulation of surgical patients. Clinicaltrials.gov NCT: 02884310; https://clinicaltrials.gov/ct2/show/NCT02884310.

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.

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.

Intraoperative naloxone reduces remifentanil-induced postoperative hyperalgesia but not pain: a randomized controlled trial

BackgroundIntraoperative use of a high-dose remifentanil may induce postoperative hyperalgesia. Low-dose naloxone can selectively reverse some adverse effects of opioids without compromising analgesia. We thus hypothesized that the intraoperative use of a high-dose remifentanil combined with a low-dose naloxone infusion reduces postoperative hyperalgesia compared with the use of remifentanil alone. MethodsPatients undergoing elective thyroid surgery were randomly assigned into one of three groups, depending on the intraoperative effect-site concentration of remifentanil, with or without a continuous infusion of naloxone: 4 ng ml−1 remifentanil with 0.05 μg kg−1 h−1 naloxone in the high-remifentanil with naloxone group, and 4 or 1 ng ml−1 remifentanil with a placebo in the high- or low-remifentanil groups, respectively. We measured the pain thresholds (primary outcome) to mechanical stimuli using von Frey filaments and incidence of hyperalgesia on the peri-incisional area 24 h after surgery. We also measured pain intensity, analgesic consumptions and adverse events up to 48 h after surgery. ResultsThe pain threshold presented as von Frey numbers [median (interquartile range)] was significantly lower in the high-remifentanil group (n=31) than in the high-remifentanil with naloxone (n=30) and the low-remifentanil (n=30) groups [3.63 (3.22–3.84) vs 3.84 (3.76–4.00) vs 3.80 (3.69–4.08), P=0.011]. The incidence of hyperalgesia was also higher in the high-remifentanil group than in the other groups [21/31 vs 10/30 vs 9/30, P=0.005]. Postoperative pain intensity, analgesic consumptions and adverse events were similar between groups. ConclusionsThe intraoperative use of low-dose naloxone combined with high-dose remifentanil reduced postoperative hyperalgesia but not pain. Clinical trial registrationNCT02856087.

Effect of ear point embedding on plasma and effect site concentrations of propofol-remifentanil in elderly patients after target-controlled induction

To observe the clinical effect of ear point embedding on plasma and effect site concentrations of propofol-remifentanil in elderly patients who underwent abdominal external hernia surgery at the time of consciousness and pain disappearing by target-controlled infusion (TCI) and bispectral index (BIS). Fifty patients who underwent elective abdominal hernia surgery were randomly assigned into an observation group and a control group, 25 cases in each one. In the observation group, 30 minutes before anesthesia induction, Fugugou (Extra), Gan (CO12), Pizhixia (AT4), and Shenmen (TF4) were embedded by auricular needles until the end of surgery, 10 times of counter press each point. In the control group, the same amount of auricular tape was applied until the end of surgery at the same points without stimulation 30 minutes before anesthesia induction. Patients in the two groups were given total intravenous anesthesia, and BIS was monitored by BIS anesthesia depth monitor. Propofol was infused by TCI at a beginning concentration of 1.5μg/L and increased by 0.3μg/L every 30s until the patients lost their consciousness. After that, remifentanil was infused by TCI at a beginning concentration of 2.0μg/L and increased by 0.3μg/L every 30s until the patients had no body reaction to pain stimulation (orbital reflex). Indices were recorded, including mean arterial pressure (MAP), heart rate (HR) and the BIS values, at the time of T0 (entering into the operation room), T1 (losing consciousness) and T2 (pain relief), the plasma and effect site concentrations of propofol at T1, the plasma and effect site concentrations of remifentanil at T2. After surgery we recorded the total amounts of propofol and remifentanil, surgery time and anesthesia time. At T1 and T2, MAP and HR of the observation group were higher than those of the control group (P<0.05, P<0.01). At T1, the plasma and effect site concentrations of propofol in the observation group were significantly lower than those in the control group (P<0.05, P<0.01). At T2, the plasma and effect site concentrations of remifentanil in the observation group were significantly lower than those in the control group (P<0.05, P<0.01). There was no significant difference in BIS values at T1 and T2 between the two groups (bothP>0.05). There was no significant difference in operation time and anesthesia time between the two groups (bothP>0.05). The total amount of remifentanil in the observation group was significantly lower than that in the control group (P<0.01). There was no significant difference in the total amount of propofol between the two groups (P>0.05). Ear points embedding combined with propofol-remifentanil TCI could reduce the plasma and effect site concentrations of propofol and remifentanil and the total amount of remifentanil in elderly patients with extra-abdominal hernia surgery, and had the effect of assisting sedation and analgesia.

The effect-site concentration of remifentanil for blunting hemodynamic responses: comparative study in single-lumen endotracheal and double-lumen endobronchial intubation

The effect-site concentration of remifentanil for blunting hemodynamic responses: comparative study in single-lumen endotracheal and double-lumen endobronchial intubation

The concentration of desflurane preventing spectral entropy change during surgical stimulation: A prospective randomized trial

Study objectiveTo determine the concentration of desflurane necessary to blunt changes in spectral entropy during surgical incision when two different target-controlled effect-site concentrations of remifentanil (1 and 3ng/ml) were infused. DesignProspective, randomized controlled study. SettingOperating room of a university hospital. InterventionsForty-two patients undergoing general anesthesia for elective surgery were enrolled and randomly allocated to the R1 (1ng/ml of remifentanil, n=21) or R3 (3ng/ml of remifentanil, n=21) group. After at least a 10-min administration of target-controlled remifentanil concentration and predetermined end-tidal desflurane following endotracheal intubation, changes in spectral entropy in response to surgical incision were evaluated. MeasurementsConcentration of desflurane necessary to blunt changes in spectral entropy during surgical incision for each group was determined using Dixon's up-and-down method. Hemodynamic variables including mean arterial pressure (MAP) and heart rate (HR) were measured. Main resultsConcentration of desflurane necessary to blunt changes in spectral entropy during surgical incision in 50% of patients (EC50) was 4.1% (95% CI: 3.5–4.7%) for the R1 group and 3.4% (95% CI: 3.0–3.8%) for the R3 group (P=0.033). Additionally, the calculated EC95 values using the logistic regression analysis for the R1 and R3 groups were 5.8% (95% CI: 5.0–10.8%) and 5.1% (95% CI: 4.3–10.6%), respectively. MAPs and HRs were significantly higher in the R1 than in the R3 group after surgical incision. ConclusionsDesflurane 4.1% with remifentanil 1ng/ml and desflurane 3.4% with remifentanil 3ng/ml significantly blunt the change in spectral entropy after surgical incision in 50% of patients.

Effect-site concentration of remifentanil for preventing cough during emergence in elderly patients undergoing nasal surgery: a comparison with adult patients.

PurposePrevention of cough during emergence after nasal surgery is important for avoiding surgical site bleeding. We investigated the remifentanil effect-site concentration in 50% (EC50) of the elderly patients undergoing nasal surgery for smooth emergence without cough and compared it with that of adult patients.MethodsTwenty-two elderly (aged 65–80 years) and 25 adult patients (aged 20–60 years) with an American Society of Anesthesiologists physical status I/II undergoing nasal surgery were enrolled. Anesthesia was maintained with sevoflurane and remifentanil. Remifentanil EC50 and EC95 for preventing cough were determined using the modified Dixon’s up-and-down method and isotonic regression with bootstrapping approach. Recovery profiles were also recorded.ResultsWith Dixon’s up-and-down method, the EC50 of remifentanil in elderly patients (2.40±0.25 ng/mL) was not significantly different from that of adults (2.33±0.30 ng/mL) (P=0.687). With isotonic regression, the EC95 of remifentanil in elderly patients (3.32 [95% confidence interval: 3.06–3.38] ng/mL) was not significantly different from that of adults (3.30 [95% confidence interval: 2.96–3.37] ng/mL). However, eye opening time (14.1±3.8 vs 12.0±2.9 seconds), extubation time (17.2±4.1 vs 14.0±3.0 seconds), and postanesthesia care unit duration (44.5±7.6 vs 38.7±3.4 minutes) in elderly patients were significantly longer than those in adults (P<0.05).ConclusionRemifentanil EC50 for preventing cough after nasal surgery with sevoflurane anesthesia did not differ between elderly and adult patients. However, delayed awakening and respiratory adverse events may warrant attention in elderly patients.