Remifentanil update: clinical science and utility

Does remifentanil improve ECT seizure quality?

Studies have reported that co-adjuvant remifentanil can enhance electroconvulsive therapy (ECT) seizure quality, putatively by allowing a reduction in the dosage of the main anaesthetic agents, as the latter have anticonvulsant properties. However, whether remifentanil also has direct effects on ECT seizure quality, and by implication, treatment efficacy, is unknown. This is the first study examining the effect of adjuvant remifentanil on ECT seizure quality when the dose of conventional anaesthesia remained unchanged. A total of 96 ECT sessions (from 36 patients) were retrospectively analysed. Subjects received ECT with and without remifentanil (1 µg/kg), while the dose of thiopentone (3-5 mg/kg) or propofol (1-2 mg/kg) was unchanged. Seizure quality indices (time to slow wave activity or TSLOW, amplitude, regularity, stereotypy, post-ictal suppression) and duration were assessed through a structured rating scale by a single trained blinded rater. Linear mixed-effects models with random subject effects analysed the effect of remifentanil on seizure parameters, controlling for other variables that can affect seizure quality or duration. Remifentanil was given in 47.9 % of the ECT sessions. Co-adjuvant remifentanil had no effects on any of the seizure quality parameters analysed [TSLOW (E = -0.21, p > 0.1), amplitude (E = 0.08, p > 0.5), regularity (E = -0.05, p > 0.5), stereotypy (E = -0.02, p > 0.5), suppression (E = -0.3, p > 0.05)] or on seizure duration (E = -0.25, p > 0.1). While adjuvant remifentanil may be a useful strategy for reducing anaesthetic dosage in ECT, present evidence suggests that remifentanil does not have intrinsic properties that enhance ECT seizures.

Remifentanil in Combination With Propofol Is Suitable for Use in the Dental Outpatient Setting

Although several adjuncts to the general anesthetic propofol have been proposed, there is insufficient research identifying the ideal agent, and in what dosage, to combine with propofol in dental outpatient anesthesia. Here we examined the combination of remifentanil or nitrous oxide and propofol in patients with severe dental avoidance undergoing dental treatment in the outpatient setting. Eighty patients were randomized to 4 groups and administered propofol/saline solution (PS; n = 20), propofol/remifentanil 0.25 μg/kg/min (PRe-0.25; n = 20), propofol/remifentanil 0.125 μg/kg/min (PRe-0.125; n = 20), or propofol/66% nitrous oxide (PN; n = 20). During anesthesia, the bispectral index value was kept between 40 and 60. Body movements and hemodynamic changes during anesthesia, emergence, and recovery as well as anesthetic cost were compared between the combinations. Body movements were observed in all patients administered PS but in no patients administered PRe-0.25, PRe-0.125, or PN. Postoperative nausea was observed in 5 patients (25%) administered PRe-0.25 and in 1 patient (5%) administered PN. Although both PRe-0.125 and PN were useful clinically, PRe-0.125 was the least expensive combination.

Procedural sedation and analgesia for respiratory-gated MR-HIFU in the liver: a feasibility study

BACKGROUND

Previous studies demonstrated both pre-clinically and clinically the feasibility of magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) ablations in the liver. To overcome the associated problem of respiratory motion of the ablation area, general anesthesia (GA) and mechanical ventilation was used in conjunction with either respiratory-gated energy delivery or energy delivery during induced apnea. However, clinical procedures requiring GA are generally associated with increased mortality, morbidity, and complication rate compared to procedural sedation and analgesia (PSA). Furthermore, PSA is associated with faster recovery and an increased eligibility for non- and mini-invasive interventions.

METHODS

In this study, we investigate both in an animal model and on a small patient group the kinetics of the diaphragm during free-breathing, when a tailored remifentanil/propofol-based PSA protocol inducing partial respiratory depression is used. Subsequently, we demonstrate in an animal study the compatibility of the resulting respiratory pattern of the PSA protocol with a gated HIFU ablation in the liver by direct comparison with gated ablations conducted under GA. Wilcoxon signed-rank tests were performed for statistical analysis of non-perfused and necrosed tissue volumes. Duty cycles (ratio or percentage of the breathing cycle with the diaphragm in its resting position, such that acoustic energy delivery with MR-HIFU was allowed) were statistically compared for both GA and PSA using student's t tests.

RESULTS

In both animal and human experiments, the breathing frequency was decreased below 9/min, while maintaining stable vital functions. Furthermore an end-exhalation resting phase was induced by this PSA protocol during which the diaphragm is virtually immobile. Median non-perfused volumes, non-viable volumes based on NADH staining, and duty cycles were larger under PSA than under GA or equal.

CONCLUSIONS

We conclude that MR-HIFU ablations of the liver under PSA are feasible and potentially increase the non-invasive nature of this type of intervention.

Impaired hippocampal synaptic plasticity and NR2A/2B expression ratio in remifentanil withdrawal rats

Remifentanil is a kind of synthetic opioid which has gained wide clinical acceptance by anesthesiologists. In this study, we attempted to test whether withdrawal effects on learning mechanisms can be triggered by repeated low-dose remifentanil treatment. Male Sprague-Dawley (SD) rats were subjected to remifentanil (50μg/kgs.c.) twice per day at 12h intervals for 15 days. When the animals of remifentanil group were withdrawn from remifentanil at 10h after the last injection, changes in open field test, Morris water maze test (MWM) and synaptic efficacy were examined in each group. We demonstrated that repeated exposure to 50μg/kg remifentanil produced enhanced locomotor activity indicating that a remifentanil addiction animal model in rats was established. MWM results showed that exposure to remifentanil had no influence on the spatial cognition. After withdrawal of remifentanil rats showed impaired spatial cognition. In electrophysiology test, remifentanil group rats showed a trend for a rightward shift of input/output relationship and significant deficits in maintenance of STP and LTP. Immunohistochemistry results demonstrated increased NR2A/NR2B ratio that should be included depression of LTP. In the whole-cell patch-clamp recording, after elimination from remifentanil incubation, mEPSC frequency was down regulated in hippocampal CA1 neurons, indicating that basal synaptic transmission were affected by remifentanil withdrawal. Taken together, the current findings demonstrate that the remifentanil withdrawn rats exhibit obvious impairment of hippocampus-dependent memory and synaptic plasticity. Increased hippocampal NR2A/NR2B expression ratio and the changes of basal synaptic transmission may participate in the impairment of LTP.

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

BACKGROUND

Endotracheal 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.

METHODS

Thirty 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.

RESULTS

The 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.

CONCLUSIONS

The 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.

Comparison of the Effects of Magnesium Sulfate and Remifentanil on Hemodynamic Responses During Tracheal Extubation After Laparotomy: A Randomized Double-blinded Trial

BACKGROUND

Because blood pressure and heart rate (HR) elevations during tracheal extubation are common, different medications have been studied to prevent such complications.

OBJECTIVES

To compare magnesium sulfate, remifentanil, and placebo regarding mean arterial pressure (MAP) and HR changes during/after tracheal extubation, in patients who underwent laparotomy.

MATERIALS AND METHODS

In this randomized double-blinded trial, 120 patients undergoing laparotomy were evenly divided into three groups, including remifentanil (1 mcg/kg), magnesium sulfate (50 mg/kg), or normal saline, as placebo. Hemodynamic responses (MAP and HR) were documented at different times (before operation, during medication administration, immediately before extubation, immediately after extubation, and also 3, 5, and 10 minutes after extubation). The double burst time (DBT) was determined using neuromuscular monitoring, as time interval, between administration of reverse medication and DBT of 100%.

RESULTS

The HR was significantly lower, immediately after extubation and 3, 5, and 10 minutes after extubation, in both magnesium and remifentanil groups, compared to normal saline (P < 0.001). The MAP was also lower in magnesium and remifentanil groups, immediately after extubation and 3 minutes after extubation, in comparison to the normal saline group (P < 0.001). Mean (± SD) DBT 100% was significantly higher in magnesium group (30.2 ± 15.3) vs. remifenatnil (13.6 ± 6.8) and normal saline (13.5 ± 8.2) groups (P < 0.001).

CONCLUSIONS

Both remifentanil and magnesium had favorable outcomes in preventing HR and MAP elevation after tracheal extubation. However, remifentanil was associated with more rapid regaining of consciousness and reversal of muscular relaxation.

Assessing the stability and safety of procedure during endoscopic submucosal dissection according to sedation methods: a randomized trial

BACKGROUND

Although endoscopic submucosal dissection (ESD) is routinely performed under sedation, the difference in ESD performance according to sedation method is not well known. This study attempted to prospectively assess and compare the satisfaction of the endoscopists and patient stability during ESD between two sedation methods.

METHODS

One hundred and fifty-four adult patients scheduled for ESD were sedated by either the IMIE (intermittent midazolam/propofol injection by endoscopist) or CPIA (continuous propofol infusion by anesthesiologist) method. The primary endpoint of this study was to compare the level of satisfaction of the endoscopists between the two groups. The secondary endpoints included level of satisfaction of the patients, patient's pain scores, events interfering with the procedure, incidence of unintended deep sedation, hemodynamic and respiratory events, and ESD outcomes and complications.

RESULTS

Level of satisfaction of the endoscopists was significantly higher in the CPIA Group compared to the IMIE group (IMIE vs. CPIA; high satisfaction score; 63.2% vs. 87.2%, P=0.001). The incidence of unintended deep sedation was significantly higher in the IMIE Group compared to the CPIA Group (IMIE vs. CPIA; 17.1% vs. 5.1%, P=0.018) as well as the number of patients showing spontaneous movement or those requiring physical restraint (IMIE vs. CPIA; spontaneous movement; 60.5% vs. 42.3%, P=0.024, physical restraint; 27.6% vs. 10.3%, P=0.006, respectively). In contrast, level of satisfaction of the patients were found to be significantly higher in the IMIE Group (IMIE vs. CPIA; high satisfaction score; 85.5% vs. 67.9%, P=0.027). Pain scores of the patients, hemodynamic and respiratory events, and ESD outcomes and complications were not different between the two groups.

CONCLUSION

Continuous propofol and remifentanil infusion by an anesthesiologist during ESD can increase the satisfaction levels of the endoscopists by providing a more stable state of sedation.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01806753.

Assessing pain objectively: the use of physiological markers

Pain diagnosis and management would benefit from the development of objective markers of nociception and pain. Current research addressing this issue has focused on five main strategies, each with its own advantages and disadvantages. These encompass: (i) monitoring changes in the autonomic nervous system; (ii) biopotentials; (iii) neuroimaging; (iv) biological (bio-) markers; and (v) composite algorithms. Although each strategy has shown areas of promise, there are currently no validated objective markers of nociception or pain that can be recommended for clinical use. This article introduces the most important developments in the field and highlights shortcomings, with the aim of allowing the reader to make informed decisions about what trends to watch in the future.

Hypotensive anesthesia versus normotensive anesthesia during major maxillofacial surgery: a review of the literature

Steady blood pressure within normal limits during surgery is one of the markers of the ideal and skillful anesthesia. Yet, reduced blood pressure is advantageous in some settings because it can contribute to a reduction in overall blood loss and improve the surgical field conditions. Controlled hypotension during anesthesia or hypotensive anesthesia is often used in major maxillofacial operations. Since hypotensive anesthesia carries the risk of hypoperfusion to important organs and tissues, mainly the brain, heart, and kidneys, it cannot be applied safely in all patients. In this paper we review the medical literature regarding hypotensive anesthesia during major maxillofacial surgery, the means to achieve it, and the risks and benefits of this technique, in comparison to normotensive anesthesia.

Context-sensitive half-time of fentanyl in dogs

Context-sensitive half-times (CSHTs) of fentanyl in dogs were determined using pharmacokinetic models reported by Murphy et al. and Sano et al., and compared with a human model. The CSHT was defined as the time required for a 50% decrease in drug concentration in the central compartment after the termination of infusion. Although CSHTs increased gradually as the infusion time increased, the CSHTs in dogs were shorter than those in humans. The CSHTs at steady-state were 31.3 and 69.2 min in dogs, and 306.5 min in humans. The CSHTs of fentanyl in dogs are apparently shorter than those in humans; therefore, a continuous infusion of fentanyl may be a rational regimen in dogs, even if duration of infusion is extended.

Etomidate-remifentanil is more suitable for monitored anesthesia care during gastroscopy in older patients than propofol-remifentanil

Background

This prospective and randomized study was designed to compare safety, potential complications, and patient and examiner satisfaction of 2 anesthetic combinations – etomidate-remifentanil and propofol-remifentanil – in elderly patients undergoing diagnostic gastroscopy.

Material/Methods

A group of 720 patients, aged 60–80 years, scheduled for diagnostic gastroscopy under sedation were prospectively randomized. After 0.4–0.6 μg kg⁻¹ of remifentanil was infused, etomidate or propofol was administered. Patients in the etomidate group received doses of etomidate at 0.1–0.15 mg kg⁻¹ followed by 4–6 mg. Patients in the propofol group received doses of propofol at 1–2 mg kg⁻¹ followed by 20–40 mg. Physiological indexes were evaluated for the 715 of 720 patients that completed the treatment. The onset time, duration time, and discharge time were recorded. Physicians, anesthetists, and patients were surveyed to assess their satisfaction.

Results

Systolic pressure and diastolic pressure decreased significantly after the procedure in the propofol group (P<0.001). The average heart rate was significantly lower in the propofol group (P<0.05). No periods of desaturation (SpO₂ <95%) were observed in either group. The onset time was earlier in the etomidate group (P=0.00). All adverse events, with the exception of myoclonus, were greater in the propofol group, and physician and patient satisfaction in both groups was similar.

Conclusions

Etomidate-remifentanil administration for sedation and analgesia during gastroscopy resulted in more stable hemodynamic responses and less adverse events in older patients.

Awake craniotomy: A qualitative review and future challenges

Neurosurgery in awake patients incorporates newer technologies that require the anesthesiologists to update their skills and evolve their methodologies. They need effective communication skills and knowledge of selecting the right anesthetic drugs to ensure adequate analgesia, akinesia, along with patient satisfaction with the anesthetic conduct throughout the procedure. The challenge of providing adequate anesthetic care to an awake patient for intracranial surgery requires more than routine vigilance about anesthetic management.

Short-term use of remifentanil during endotracheal extubation for prophylactic analgesia in neurosurgical patients after craniotomy (SURE after Craniotomy Study): a study protocol and statistical analysis plan for a randomised controlled trial

INTRODUCTION

Acute pain is common during the endotracheal extubation period, and is related to complications and adverse outcomes. Patients with delayed extubation after craniotomy are vulnerable to pain and complications of extubation. However, pain control during extubation is still inadequate. Remifentanil, a new opioid with rapid onset and short duration of action, provides adequate analgesia during procedures with minimal effect of respiratory depression.

METHODS AND ANALYSIS

The study is a prospective, randomised, double-blinded, controlled parallel-group design. Patients with delayed extubation after intracranial surgery are screened daily. Adult patients ready for extubation are enrolled and assigned randomly to one of the two treatment study groups, labelled as the 'Remi group' or 'Saline group'. Patients in the Remi group receive an intravenous bolus dose of remifentanil 0.5 μg/kg over 60 s followed by a continuous infusion 0.05 μg/kg/min for 20 min. Patients in the Saline group receive an intravenous infusion of 0.9% sodium chloride at a volume and rate equal to that of remifentanil. Pain intensity is measured by the visual analogue scale (VAS) pain score. Adverse events during drug infusion are documented and reported. Patients will be followed up until hospital discharge, death or 60 days after the trial intervention on a first come, first served basis. Details of the incidence of reintubation and reoperation within 72 h after extubation, length of stay in the intensive care unit and hospital and mortality are collected. The primary end point is the incidence of severe pain (defined as a VAS pain score more than 5 cm) during the periextubation period (defined as the period of time from immediately before extubation to 20 min after extubation).

ETHICS AND DISSEMINATION

The study was approved by the Institutional Review Board (IRB) of the Beijing Tiantan Hospital, Capital Medical University. The study findings will be disseminated through peer-reviewed publications and conference presentations.

TRIAL REGISTRATION NUMBER

ClinicalTrials (NCT): ChiCTR-PRC-13003879.

Aspiration Induced by Remifentanil

Background:

Remifentanil is widely used for monitored anesthesia care in spontaneously breathing patients. However, the authors’ previous studies have shown that remifentanil induces subjective swallowing difficulties, which may increase the risk of aspiration.

Methods:

Twenty-five healthy volunteers participated in a double-blind, randomized, crossover trial at the University Hospital in Örebro, Örebro, Sweden. The volunteers were studied on two different occasions during which they received either remifentanil with an effect-site target concentration of 3 ng/ml or saline over 1 h. A radionuclide tracer was infused simultaneously into the nasopharynx at a rate of 0.1 ml/min. Aspiration was determined by lung scans, and subjective swallowing difficulties and grip strength were evaluated. The primary outcome was the difference in occurrence of aspiration between remifentanil and placebo treatments. The secondary outcomes were differences in swallowing difficulty and grip strength and the association between aspiration and swallowing difficulty.

Results:

During remifentanil and placebo infusion, 48 and 12% of the volunteers aspirated, respectively, difference: 36% (95% CI, 10 to 62%). A similar significant difference was found for swallowing difficulties but not for the association between aspiration and swallowing. No difference was found in grip strength between the two treatments.

Conclusions:

Remifentanil infusion at concentrations used in monitored anesthesia care increases the incidence of aspiration. However, the subjective swallowing difficulty induced by remifentanil is not indicative of the aspiration risk.

Dose requirements of remifentanil for intubation in nonparalyzed Chinese children

BACKGROUND

The objective of this study was to determine ED50 and ED95 of remifentanil for intubation combined with propofol in nonparalyzed Chinese children.

METHODS

Forty-seven American Society of Anesthesiologists Class I children aged 4-11 years weighing 14-33.5 kg underwent general anesthesia with 2.5 mg·kg(-1) of intravenous propofol followed by remifentanil in Wenzhou, China. The initial dose of remifentanil was 2.5 μg·kg(-1) injected over 60 s. Intubation was attempted 30 s after the completion of remifentanil injection. Level of difficulty to intubate was graded on a scoring system. If the initial intubation condition was deemed satisfactory, subsequent remifentanil doses were decreased by 0.25 μg·kg(-1). If the intubating condition was deemed unsatisfactory, subsequent remifentanil doses were increased by 0.25 μg·kg(-1). Mean arterial pressure, heart rate, and pulse oximetry were documented before and after induction, immediately after intubation, and 1 min after intubation.

RESULTS

The ED50 of remifentanil used to render a satisfactory intubating condition used in combination with 2.5 mg·kg(-1) of propofol in nonparalyzed Chinese children was 2.30 μg·kg(-1) (95% confidence interval: 2.28-2.31 μg·kg(-1)), and the ED95 is 2.75 μg·kg(-1) (95% confidence interval: 2.59-3.35 μg·kg(-1)). These doses were lower than previously reported.

CONCLUSION

When used in combination with 2.5 mg·kg(-1) of intravenous propofol, ED50 and ED95 of remifentanil for adequate intubation in nonparalyzed children were lower than previously reported, at 2.30 and 2.75 μg·kg(-1), respectively.

Assessment of the effect of ketamine in combination with remifentanil on postoperative pain

BACKGROUND AND OBJECTIVES

The combination of ketamine and remifentanil seems to be associated with better analgesia and duration. The aim of this study was to evaluate whether a ketamine-remifentanil combination promotes improved postoperative analgesia.

METHODS

Prospective, randomized, double blind study of 40 patients undergoing video laparoscopic cholecystectomy. Anesthesia was performed with remifentanil, propofol, atracurium, and 50% oxygen. Group 1 (GI) patients received remifentanil (0.4 mcg.kg(-1).min(-1)) and ketamine (5 mcg.kg(-1).min(-1)) and Group 2 (G2) received remifentanil (0.4 mcg.kg(-1).min(-1)) and saline solution. Morphine 0.1mg.kg(-1) was administered at the end of the procedure, and postoperative pain was treated with morphine via PCA. We evaluated the severity of postoperative pain by a numerical scale from zero to 10 during 24 hours. We registered the time to the first analgesic supplementation, amount of morphine used in the first 24 hours, and adverse effects.

RESULTS

There was a decrease in pain severity between extubation and other times evaluated in G1 and G2. There was no significant difference in pain intensity between the groups. There was no difference between G1 (22±24.9 min) and G2 (21.5±28.1min) regarding time to first dose of morphine and dose supplement of morphine consumed in G1 (29±18.4mg) and G2 (25.1±13.3mg).

CONCLUSION

The combination of ketamine (5 mcg.kg(-1).min(-1)) and remifentanil (0.4mcg.kg(-1).min(-1)) for cholecystectomy did not alter the severity of postoperative pain, time to first analgesic supplementation or dose of morphine in 24hours.

Fentanyl-related compounds and derivatives: current status and future prospects for pharmaceutical applications

Fentanyl and its analogs have been mainstays for the treatment of severe to moderate pain for many years. In this review, we outline the structural and corresponding synthetic strategies that have been used to understand the structure-biological activity relationship in fentanyl-related compounds and derivatives and their biological activity profiles. We discuss how changes in the scaffold structure can change biological and pharmacological activities. Finally, recent efforts to design and synthesize novel multivalent ligands that act as mu and delta opioid receptors and NK-1 receptors are discussed.

Assessment of the effect of ketamine in combination with remifentanil on postoperative pain

BACKGROUND AND OBJECTIVES

The combination of ketamine and remifentanil seems to be associated with better analgesia and duration. The aim of this study was to evaluate whether a ketamine- remifentanil combination promotes improved postoperative analgesia.

METHODS

Prospective, randomized, double blind study of 40 patients undergoing video laparoscopic cholecystectomy. Anesthesia was performed with remifentanil, propofol, atracurium, and 50% oxygen. Group 1 (GI) patients received remifentanil (0.4 mcg.kg(-1).min(-1)) and ketamine (5 mcg.kg(-1).min(-1)) and Group 2 (G2) received remifentanil (0.4 mcg.kg(-1).min(-1)) and saline solution. Morphine 0.1 mg.kg(-1) was administered at the end of the procedure, and postoperative pain was treated with morphine via PCA. We evaluated the severity of postoperative pain by a numerical scale from zero to 10 during 24 hours. We registered the time to the first analgesic supplementation, amount of morphine used in the first 24 hours, and adverse effects.

RESULTS

There was a decrease in pain severity between extubation and other times evaluated in G1 and G2. There was no significant difference in pain intensity between the groups. There was no difference between G1 (22 ± 24.9 min) and G2 (21.5 ± 28.1 min) regarding time to first dose of morphine and dose supplement of morphine consumed in G1 (29 ± 18.4 mg) and G2 (25.1 ± 13.3 mg).

CONCLUSION

The combination of ketamine (5 mcg.kg(-1).min(-1)) and remifentanil (0.4 mcg.kg(-1).min(-1)) for cholecystectomy did not alter the severity of postoperative pain, time to first analgesic supplementation or dose of morphine in 24 hours.

Considerations for the use of short-acting opioids in general anesthesia

Anesthesiologists play a critical role in facilitating a positive perioperative experience and early recovery for patients. Depending on the kind of procedure or surgery, a wide variety of agents and techniques are currently available to anesthesiologists to administer safe and efficacious anesthesia. Notably, the fast-track or ambulatory surgery environment requires the use of agents that enable rapid induction, maintenance, and emergence combined with minimal adverse effects. Short-acting opioids demonstrate a safe and rapid onset/offset of effect; that short effect is both predictable and precise. It also ensures easier titration and reduced or rapidly reversed side effects. Due to their distinct pharmacokinetic and pharmacodynamic properties, and, in one case, rapid extra-hepatic clearance of remifentanil, these agents have several applications in general anesthesia.

Effects of remifentanil on processing of auditory stimuli: a combined MEG/EEG study

Remifentanil (Ultiva(®)) is a potent ultra-short acting mu-opioid receptor agonist used for perioperative pain treatment and anaesthesia. So far, it is not known how sensitive the cognitive processing of auditory perception elicited by the mismatch negativity (MMN) paradigm is to opioids. The present exploratory study investigated how the opioid remifentanil modulates different stages of auditory processing as reflected in the MMN(m) and P3a(m). We recorded electroencephalography (EEG) and magnetoencephalography (MEG) during auditory stimulation under remifentanil or placebo infusion in 20 healthy participants. For the MMN, a gender effect was found for tones deviating in frequency (± 10%) from the standard tone. Remifentanil increased the amplitude of the frequency MMN at F3 in females but not in males. No effect of treatment was found for the MMN(m) or the novel P3a(m). These results suggest that while the bottom-up stimulus change detection system for auditory stimuli appears to be relatively insensitive to opioids, the automatic attention switch caused by the change detection seems to be modulated by the opioid system in females. The multiple deviant paradigm including novel sounds is a promising tool for investigating pharmacological manipulation of different stages of auditory processing. Furthermore, combining the two techniques will yield more specific information about the drug effects on MMN(m).

Effects of remifentanil on the esophagogastric junction and swallowing

BACKGROUND

A recent study demonstrated that reflux is associated with impaired pressure augmentation in the esophagogastric junction (EGJ), caused by diaphragmal contractions during inspiration. It is unknown whether this augmentation is influenced by opioids. Swallowing difficulties can be a poorly recognised side effect of remifentanil. Here, we investigated whether remifentanil influences inspiratory EGJ augmentation and evaluated subjective swallowing difficulties induced by remifentanil. We also used the peripheral opioid receptor antagonist methylnaltrexone to evaluate whether these effects are centrally or peripherally mediated.

METHODS

Ten healthy volunteers participated in a double-blind, randomised, cross-over trial at the University Hospital in Örebro, Sweden. They were studied on two different occasions, during which they were randomly assigned to receive either methylnaltrexone 0.15 mg/kg or saline subcutaneously 30 min before the target-controlled infusion of remifentanil of 3 ng/mL. EGJ pressures were measured by high-resolution manometry. Swallowing difficulties were assessed when volunteers performed dry swallows. The outcomes were the differences in EGJ pressures at baseline and during remifentanil infusion and with methylnaltrexone vs. placebo. Differences in swallowing difficulties before and during remifentanil, and with methylnaltrexone vs. placebo were also recorded.

RESULTS

Remifentanil decreased the inspiratory EGJ augmentation and induced swallowing difficulties. No statistically significant differences between methylnaltrexone and placebo occasions were found.

CONCLUSIONS

Remifentanil may increase risk for gastroesophageal reflux by decreasing the inspiratory EGJ augmentation. The clinical significance of remifentanil-induced swallowing difficulties is to be studied further. Given the limited sample size, it cannot be concluded whether these effects are centrally or peripherally mediated.

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

Background

Desflurane 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.

Methods

Twenty-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.

Results

We 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.

Conclusions

In 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.

Intravenous boluses of fentanyl, 1 μg kg⁻¹, and remifentanil, 0.5 μg kg⁻¹, give similar maximum ventilatory depression in awake volunteers

BACKGROUND

The relative respiratory effects of fentanyl and remifentanil, administered as i.v. bolus, have not previously been studied. We determined what remifentanil bolus dose gave the same maximum depression of ventilation as 1 µg kg(-1) of fentanyl.

METHODS

Twelve healthy volunteers rebreathed in a system designed to dampen variations in end-tidal carbon dioxide tension PE'CO2 so that measurements would be obtained at similar levels of CO(2) stimulation. The minute ventilation was measured before (V(preinj)) and after injection (V(nadir)) of fentanyl, 1 µg kg(-1), and remifentanil, 0.25, 0.5, and 1 µg kg(-1). The remifentanil doses were plotted against V(nadir)/V(preinj) in a log-probit diagram to determine what amount gave the same maximum ventilatory depression as the fentanyl dose.

RESULTS

V(nadir) was [median (inter-quartile range)] 51 (38-64)% of V(preinj) after fentanyl, and 70 (61-77), 50 (46-56), and 29 (24-38)%, respectively, after remifentanil. The nadir occurred 5.0 (4.4-7.0) min after fentanyl, and 3.8 (2.7-4.6), 2.9 (2.7-3.2), and 3.0 (2.7-3.2) min after remifentanil injection. PE'CO2 at ventilation nadir was 6.26 (5.98-6.62) kPa after fentanyl, and 6.18 (6.12-6.50), 6.11 (5.91-6.45), and 6.11 (5.93-6.45) kPa after remifentanil 0.25, 0.5, and 1 µg kg(-1), respectively. A remifentanil dose of 0.47 (0.42-0.62) µg kg(-1) was equidepressant to 1 µg kg(-1) of fentanyl. Fifteen minutes after fentanyl injection, the median minute ventilation was 30-40% less than after injection of remifentanil, 0.25 and 0.5 µg kg(-1) (P<0.05).

CONCLUSIONS

Fentanyl, 1 µg kg(-1), and remifentanil, 0.5 µg kg(-1), gave similar maximum ventilatory depression. The onset of and recovery from ventilatory depression were faster with remifentanil.

Comparison between local anaesthesia with remifentanil and total intravenous anaesthesia for operative hysteroscopic procedures in day surgery

BACKGROUND

This study aimed at comparing total i.v. anaesthesia (TIVA) with monitored anaesthesia care (MAC) during day-surgery operative hysteroscopy regarding: operation time, time to mobilization and discharge, and patient satisfaction.

METHODS

Ninety-one healthy women were randomized to MAC with paracervical local anaesthesia and remifentanil or to TIVA with propofol and remifentanil. Time from arrival to leaving the operating theatre, time from arrival in the recovery room to mobilization and discharge readiness, and patient satisfaction with MAC and TIVA were observed.

RESULTS

Time from arrival to leaving the operating theatre showed no significant difference between groups (P=0.6). The time to mobilization {MAC: 53 min [inter-quartile range (IQR) 40-83], TIVA: 69 min (IQR 52-96) (P=0.017)} and the total time from arrival to discharge readiness [MAC: 118 min (IQR 95-139), TIVA: 138 (IQR 120-158) (P=0.0009)] were significantly reduced for patients in the MAC group. More patients in the MAC group 45 (91.8%) than in the TIVA group 24 (64.9%) responded positively to the question: would you like to receive the same kind of anaesthesia for a similar procedure in the future? (P=0.003).

CONCLUSIONS

Paracervical local anaesthesia combined with remifentanil is suitable for operative hysteroscopy in day surgery.

Use of remifentanil and alfentanil in endotracheal intubation: a comparative study

Background:

Opioids, such as alfentanil, are used to facilitate endotracheal intubation without the use of neuromuscular blocking agents in patients undergoing elective surgery.

Objectives:

The goal of this study was to evaluate the endotracheal intubation conditions when remifentanil or alfentanil was used with propofol without the application of neuromuscular blocking agents.

Patients and Methods:

One hundred American Society of Anesthesiologists (ASA) grade I patients scheduled for elective surgery were enrolled in this prospective, randomized, triple-blinded study. The patients were randomized to group A (alfentanil) or R (remifentanil). In group A, alfentanil (50 mcg/kg) was intravenously injected over 10 seconds, and after 45 seconds or at the occurrence of apnea, propofol (2 mg/kg) was intravenously injected over 5 seconds. Thirty seconds after the administration of propofol, laryngoscopy and endotracheal intubation were attempted. In group R, remifentanil (5 mcg/kg) was administered instead of alfentanil. Intubation conditions, including ease of laryngoscopy, patency of the vocal cords, jaw relaxation, limb movement (1-4 score), and also, demographic data were evaluated.

Results:

There were no demographic data differences between groups (age, weight, and sex). Further, laryngoscopy, jaw relaxation, and limb movement scores were similar in the R and A groups and there were no significant differences, but vocal cords were significantly more patent in group R than those in group A (P = 0. 028).

Conclusions:

The results of this study showed that remifentanil, similar to alfentanil, provided excellent conditions for endotracheal intubation when used with propofol for the induction of anesthesia; however, remifentanil improved the patency of the vocal cords to a greater extent than alfentanil.

The efficiency of IV PCA with remifentanil and ketorolac after laparoscopic-assisted vaginal hysterectomy

BACKGROUND

This randomized, double-blinded clinical study was designed to evaluate the efficiency and safety of remifentanil with ketorolac for IV PCA after laparoscopic-assisted vaginal hysterectomy.

METHODS

Eighty patients were randomly allocated into four groups. Group R received IV PCA using only remifentanil at a basal rate of 0.025 µg/kg/min and a bolus of 0.375 µg/kg. Group RK1 received IV PCA using remifentanil at a basal rate of 0.015 µg/kg/min and a bolus of 0.225 µg/kg. Group RK2 received IV PCA using remifentanil at a basal rate of 0.0075 µg/kg/min and a bolus of 0.1125 µg/kg. Group F received IV PCA using fentanyl at a basal rate of 0.3 µg/kg/h and a bolus of 0.075 µg/kg. In addition, ketorolac at a basal rate of 0.04 mg/kg/h and a bolus of 0.01 mg/kg was added to Group RK1, RK2, and F. All PCA conditions had a lock out period of 15 minutes. Pulse rate, systolic and diastolic BP, sedation score, visual analogue scale (VAS), and PONV score were recorded at 1, 3, 6, 12, and 24 hours after the operation. Total opioid use and the patients' number for rescue analgesic drug were also collected.

RESULTS

The groups did not differ in PONV score and hemodynamic changes. The VAS in Group RK2 was high compared with the other groups. In addition, the sedation score was high in Group R.

CONCLUSIONS

The additional ketorolac administration in remifentanil IV PCA had remifentanil sparing effects and reduced sedation among the side effects. Further studies will be needed to evaluate the precise and adequate dosage of ketorolac.

[Perioperative anesthesia management of extended partial liver resection. Pathophysiology of hepatic diseases and functional signs of hepatic failure]

The importance of partial liver resection as a therapeutic option to cure hepatic tumors has increased over the last decades. This has been influenced on the one hand by advances in surgical and anesthetic management resulting in a reduced mortality after surgery and on the other hand by an increased incidence of hepatocellular carcinoma. Nowadays, partial resection of the liver is performed safely and as a routine operation in specialized centers. This article describes the pathophysiological changes secondary to liver failure and assesses the perioperative management of patients undergoing partial or extended liver resection. It looks in detail at the preoperative assessment, the intraoperative anesthetic management including fluid management and techniques to reduce blood loss as well as postoperative analgesia and intensive care therapy.

Salvinorin A produces cerebrovasodilation through activation of nitric oxide synthase, κ receptor, and adenosine triphosphate-sensitive potassium channel

BACKGROUND

Salvinorin A is a nonopioid, selective κ opioid-receptor agonist. Despite its high potential for clinical application, its pharmacologic profile is not well known. In the current study, we hypothesized that salvinorin A dilates pial arteries via activation of nitric oxide synthase, adenosine triphosphate-sensitive potassium channels, and opioid receptors.

METHODS

Cerebral artery diameters and cyclic guanosine monophosphate in cortical periarachnoid cerebrospinal fluid were monitored in piglets equipped with closed cranial windows. Observation took place before and after salvinorin A administration in the presence or absence of an opioid antagonist (naloxone), a κ opioid receptor-selective antagonist (norbinaltorphimine), nitric oxide synthase inhibitors (N(G)-nitro-L-arginine and 7-nitroindazole), a dopamine receptor D2 antagonist (sulpiride), and adenosine triphosphate-sensitive potassium and Ca-activated K channel antagonists (glibenclamide and iberiotoxin). The effects of salvinorin A on the constricted cerebral artery induced by hypocarbia and endothelin were investigated. Data were analyzed by repeated measures ANOVA (n = 5) with statistical significance set at a P value of less than 0.05.

RESULTS

Salvinorin A induced immediate but brief vasodilatation that was sustained for 30 min via continual administration every 2 min. Vasodilatation and the associated cyclic guanosine monophosphate elevation in cerebrospinal fluid were abolished by preadministration N(G)-nitro-L-arginine, but not 7-nitroindazole. Although naloxone, norbinaltorphimine, and glibenclamide abolished salvinorin A-induced cerebrovasodilation, this response was unchanged by iberiotoxin and sulpiride. Hypocarbia and endothelin-constricted pial arteries responded similarly to salvinorin A, to the extent observed under resting tone.

CONCLUSIONS

Salvinorin A dilates cerebral arteries via activation of nitric oxide synthase, adenosine triphosphate-sensitive potassium channel, and the κ opioid receptor.

A comprehensive LC-MS-based quantitative analysis of fentanyl-like drugs in plasma and urine

Fentanyl, norfentanyl, alfentanil, sufentanil, remifentanil and 3-methylfentanyl are potent, short-acting, synthetic narcotic analgesics that are not revealed in standard opiate immunoassays. In this article, a fully validated analytical method for the determination of these fentanyl-type compounds in plasma and urine is presented, consisting of a liquid-liquid extraction followed by a LC-MS/MS analysis using electrospray ionisation in the positive ionisation mode. Fentanyl-d(5) and norfentanyl-d(5) were used as internal standards. The lower LOQ in plasma and urine was 0.1 ng/mL for fentanyl, norfentanyl, alfentanil, remifentanil and 3-methylfentanyl, and 0.2 ng/mL for sufentanil. The method proved linear over a concentration range of 0.2-50 ng/mL for sufentanil and 0.1-50 ng/mL for all other analytes, with correlation coefficients of 0.998 or better. The analytical procedure showed excellent selectivity and precision (all CVs below 15%) for all analytes. Accuracy was good, except for sufentanil, where deviations of more than 15% from nominal concentrations were observed. No matrix effects were observed, and stability of stock and internal standard solutions was within acceptability limits.

Effect of remifentanil on consumption of sevoflurane in entropy monitored general anesthesia

BACKGROUND

Monitoring of anesthetic depth is important for successful general anesthesia. It is well known that entropy or BIS monitoring assisted titration of anesthetic drugs decreases their consumption. This study evaluated the effect of remifentanil on consumption of sevoflurane during entropy monitored general anesthesia.

METHODS

Patients were randomly assigned to two groups. The R group was administered 0.1 µg/kg/min of remifentanil and inhaled sevoflurane, while the S group was administered only inhaled sevoflurane. Anesthesia was maintained using sevoflurane with nitrous oxide, and entropy was monitored. In both groups, the concentration of sevoflurane was adjusted to keep the state entropy (SE) value between 40 and 60. End-tidal sevoflurane concentration (ET), entropy value, systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were measured at 5 minute intervals, during a 25 minute period after intubation, skin suture and the end of surgery.

RESULTS

ET was significantly lower in the R group than the S group. There were no significant differences in entropy value between R and S groups.

CONCLUSIONS

Entropy monitored titration of sevoflurane with remifentanil administration decreased ET with stable hemodynamics.

Refined induction of anesthesia with remifentanil after bolus propofol administration in Landrace/Large White swine

The authors report a prospective randomized blind study in which they used a refined anesthetic technique in male Landrace/Large White swine (n = 125 pigs, 19 ± 2 kg, 10-15 weeks old). The animals were first premedicated with ketamine, midazolam and atropine and then given a dose of 1, 2, 3, 4 or 5 μg remifentanil per kg body weight (dose amounts were randomly assigned) after a bolus dose of propofol. The authors assessed the intubation conditions (e.g., jaw relaxation and other parameters) 20 min after premedication and then 5 min after anesthesia induction. All animals that received each of the different remifentanil dose amounts were successfully intubated in less than 30 s. No animal developed apnea during intubation or experienced substantial reductions in heart rate or blood pressure (> 25%) between the two time points (20 min after premedication and 5 min after anesthesia induction). Overall intubation conditions were significantly better in animals that received 5 μg remifentanil per kg body weight than in animals that received other dose amounts (P < 0.001). The average time to intubation was significantly shorter for animals that received 5 μg remifentanil per kg body weight than for animals that received any of the other dose amounts (P < 0.001). The authors concluded that for this study, 5 μg remifentanil per kg body weight resulted in excellent intubating conditions in this swine breed.

Dose of remifentanil for minimizing the cardiovascular changes to tracheal intubation in pediatric patients

Background

The purpose of this study was to investigate a dosage of remifentanil for attenuating cardiovascular changes during anesthetic induction in pediatric anesthesia.

Methods

We examined the effect of remifentanil on the cardiovascular responses to intubation in 90 children ASA 1 patients, aged 4-15 years, randomly allocated to receive 1.0 ug/kg remifentanil as a bolus (R 1), or 1.5 ug/kg remifentanil (R 1.5), or 2.0 ug/kg remifentanil (R 2). Before induction, IV midazolam 0.05 mg/kg was given for sedation. After glycoppylorate 5 ug/kg, thiopental 4.0 mg/kg was injected within 10 seconds and followed by remifentanil. Following check the unconsciousness, patients were received rocuronium 0.6 mg/kg and tracheal intubation were performed 90s later, and anesthesia was maintained with 2% sevoflurane in air/oxygen. Systolic arterial pressure (SAP), mean arterial pressure (MAP) and heart rate (HR) were measured at before induction of anesthesia (B), before, just after and at 1, and 3 minutes after tracheal intubation.

Results

SAP and HR were increased than B values in the three groups just after intubation (P < 0.05). The percentage increases of SAP and HR were 30% and 30% of B values, respectively, in R 1; 19% and 24% in R 1.5; 10% and 22% in R 2. There were significant differences between R 2 group and other two groups in SAP and HR (P < 0.05).

Conclusions

In pediatric anesthesia, a bolus injection of 2 ug/kg remifentanil (R 2) was a dosage to attenuate the cardiovascular responses after intubation in pediatric patients.

Severe bradycardia during suspension laryngoscopy performed after tracheal intubation using a direct laryngoscope with a curved blade -A case report-

There are a few reports about bradycardia or asystole caused by direct laryngoscopy. However, we encountered severe bradycardia in response to suspension laryngoscopy for laryngeal polypectomy after safely completing tracheal intubation using a direct laryngoscope with a curved blade. The tip of the curved blade of the direct laryngoscope is positioned at the vallecula (between the base of the tongue and the pharyngeal surface of the epiglottis) during tracheal intubation, while the blade tip of the suspension laryngoscope lifts the laryngeal surface of the epiglottis or supraglottic area during surgery. Therefore, suspension laryngoscopy can be said more vagotonic than curved-blade direct laryngoscopy. Because of the possibility of bradycardia induced by suspension laryngoscopy, clinicians must be careful about severe bradycardia even after safely completing intubation using direct laryngoscopy.

Intraoperative hyperventilation vs remifentanil during electrocorticography for epilepsy surgery - a case report

BACKGROUND

Traditionally, intraoperative intracranial electroen-cephalography-recordings are limited to the detection of the irritative zone defined by interictal spikes. However, seizure patterns revealing the seizure onset zone are thought to give better localizing information, but are impractical due to the waiting time for spontaneous seizures. Therefore, provocation by seizure precipitants may be used with the precaution that spontaneous and provoked seizures may not be identical.

OBJECTIVE

We present evidence that hyperventilation induced and drug induced focal seizures may arise from different brain regions in the same patient.

METHODS

Hyperventilation and ultra short acting opioid remifentanil were used separately as intraoperative precipitatants of seizure patterns, while recording from subdural and intraventricular electrodes in a patient with temporal lobe epilepsy. Two different ictal onset zones appeared in response to hyperventilation and remifentanil. Both zones were resected and the patient has remained essentially seizure free for 1 year. Furthermore, this is the first description of hyperventilation used as an intraoperative seizure precipitant in human focal epilepsy.

Analgesia during abdominal aortic aneurysm endovascular repair: remifentanil vs. fentanyl-midazolam--a randomized controlled trial

BACKGROUND AND OBJECTIVE

Endovascular repair offers a less surgically invasive procedure for abdominal aortic aneurysms but nevertheless, still requires analgesic sedative cover to ensure an acceptable level of patient comfort and cardiorespiratory stability. The peculiarity of this kind of operation is that painful stimuli are concentrated in specific moments separated by intervals devoid of pain, so the insurgence of pain can be predicted and prevented with a bolus of analgesic, making a continuous infusion not essential, but potentially useful in achieving a better analgesic stability. The primary objective of the study was pain control measured by Visual Analogue Scale; secondary endpoints were cardiorespiratory stability and an acceptable level of sedation.

METHODS

The sedative analgesic protocols of two groups of randomly allocated patients, undergoing abdominal aortic aneurysm endovascular repair, were compared. The experimental group received remifentanil infusion (0.03-0.1 microg kg min) and the control group received intravenous doses of fentanyl and midazolam (1-3 microg kg and 0.05-0.1 mg kg, respectively).

RESULTS

Fifty patients were investigated out of 60 enrolled. There were no relevant differences concerning cardiorespiratory stability and level of sedation, but pain levels were significantly lower in the experimental group: mean Visual Analogue Scale 0.35+/-0.40 vs. 1.49+/-0.62 (P<0.001) and area under the curve 17.48+/-5.09 vs. 33.05+/-8.19 (P<0.001).

CONCLUSION

Both techniques were shown to be safe and most importantly effective in offering cardiovascular stability and analgesia for American Society of Anaesthesiologists III-IV patients undergoing endovascular abdominal aortic aneurysm repair. However, remifentanil continuous infusion proved to offer significantly more stable pain control compared with the currently used combination fentanyl-midazolam.