Remifentanil for general anaesthesia: a systematic review

Total intravenous anaesthesia with high-dose remifentanil does not aggravate postoperative nausea and vomiting and pain, compared with low-dose remifentanil: a double-blind and randomized trial

The study was designed to investigate postoperative nausea and vomiting (PONV) in low- and high-dose remifentanil regimens for total intravenous anaesthesia (TIVA) in adult female patients with American Society of Anaesthesiologists physical status classification I undergoing local breast excision. Propofol and remifentanil 5 ng·mL⁻¹ (L group) or 10 ng·mL⁻¹ (H group) were administered for anaesthesia induction and maintenance. Propofol was titrated within range of 0.1 μg·mL⁻¹ to maintain bispectral index (BIS) values between 40 and 60. Haemodynamic parameters during the intra- and postoperative periods and 24 h postoperative visual analogue scale (VAS) and PONV were evaluated. Each group with 63 patients was analyzed. The H group showed higher use of remifentanil and lower use of propofol, with similar recovery time. Mean systemic arterial blood pressure (MBP), heart rate, and BIS did not differ significantly before and after endotracheal intubation in the H group. However, significant increases in MBP and BIS were apparent in the L group. Postoperative VAS, PONV incidence and scale, and Rhodes index did not differ significantly between the two groups. In conclusion, TIVA with high-dose remifentanil did not aggravate PONV with similar postoperative pain, compared with low-dose remifentanil. Furthermore, high-dose remifentanil showed more haemodynamic stability after endotracheal intubation. This trial is registered with KCT0000185.

Prophylactic effect of ephedrine to reduce hemodynamic changes associated with anesthesia induction with propofol and remifentanil

BACKGROUND

One of the complications of anesthesia induction with propofol is a substantial decrease in arterial blood pressure and heart rate (HR), which can be intensified by adding remifentanil. This study aimed to assess the prophylactic effects of two doses of ephedrine to control the hypotension and bradycardia caused by anesthesia induced with propofol and remifentanil.

MATERIALS AND METHODS

A total of 150 patients candidate for short-term minor elective orthopedic and ophthalmic surgery under general anesthesia were randomized to three groups receiving normal saline, low dose ephedrine (0.07 mg/kg) or high dose ephedrine (0.15 mg/kg). Anesthesia was induced in all groups with propofol 2.5 mg/kg and remifentanil 3 μg/kg. No neuromuscular blocking agent was used. Patients' hemodynamic status was assessed in the following four steps: Immediately before, 2 min after induction of anesthesia, as well as 1 and 5 min after intubation.

RESULTS

A total of 143 patients consisting of 46 patients in the low dose ephedrine (0.07 mg/kg) group, 49 patients in the high dose ephedrine (0.15 mg/kg) group and 48 controls completed the trial. In all three groups, after induction of anesthesia, significant decreases occurred in the mean systolic, diastolic and mean arterial pressures, as well as in the mean HR. This decline was highest in the control group and lowest in the high dose ephedrine (0.15 mg/kg) group.

CONCLUSION

Our findings suggest that the administration of high dose ephedrine (0.15 mg/kg) may have a significant effect in preventing hypotension and bradycardia after anesthesia induction with propofol and remifentanil.

[Comparison of two opioids with different kinetics for intravenous analgesia in outpatient multiple third molar avulsions]

INTRODUCTION

We had for aim to compare the effects of intra-operative opioid analgesia according to the drug kinetics.

PATIENTS AND METHODS

We conducted a prospective, controlled, randomized, double-blinded trial including 60 patients scheduled for ambulatory multiple third molar avulsion. The general anesthesia, performed with propofol and analgesia was a target-controlled infusion of either remifentanil or sufentanil. The anesthesia was set to reach an optimal bispectral index and adjusted to a clinical target throughout the procedure. The main endpoints were: postoperative request for morphine and other opioids; postoperative pain; postoperative adverse effects of opioids.

RESULTS

In the post-operative care unit (French acronym PACU), patients who received remifentanil were extubated earlier (17 vs. 26 min.), but had more pain and required twice more morphine for analgesia (6 vs. 3 mg), than those who had received sufentanil. However, the need for post-surgery oral opioid intake was greater in the sufentanil group, so the overall postoperative opioid consumption and patient satisfaction were identical in both groups. The time spent in the PACU was also identical for both groups.

DISCUSSION

Using an ultra-short kinetic opioid such as remifentanil does not seem useful, since the shorter delay before extubation is compensated by a greater need for morphine in the PACU.

Intrathecal administration of roscovitine prevents remifentanil-induced postoperative hyperalgesia and decreases the phosphorylation of N-methyl-D-aspartate receptor and metabotropic glutamate receptor 5 in spinal cord

N-methyl-D-aspartate receptor (NMDAR) and metabotropic glutamate receptor 5 (mGluR5) play an important role in nociceptive processing and central sensitization. Our previous study showed that tyrosine phosphorylation of NMDAR subunit 2B (NR2B) at Tyr1472 in spinal dorsal horn contributes to the postoperative hyperalgesia induced by remifentanil. Cyclin-dependent kinase 5 (Cdk5) has been implicated in synaptic plasticity, learning, memory and pain signaling via regulating the phosphorylation of NMDAR and mGluR5. In the present study, a rat model of postoperative pain was used to investigate the role of Cdk5 in spinal dorsal horn in remifentanil-induced hyperalgesia and the intervention of pretreatment with Cdk5 inhibitor roscovitine. Intraoperative infusion of remifentanil (0.04 mg/kg, subcutaneous) significantly enhanced mechanical allodynia and thermal hyperalgesia induced by plantar incision during the postoperative period (each lasting between 2 h and 48 h), which were attenuated by pretreatment with roscovitine. Correlated with the pain behavior changes, Western blotting revealed that there was a significant increase in the expression of Cdk5 and its activator p35/p25, and further the kinase activity of Cdk5 in spinal dorsal horn after intraoperative infusion of remifentanil. The phosphorylation of NR2A at Ser1232, the phosphorylation of NR2B at Tyr1472 and the phosphorylation of mGluR5 at Ser1167 were also significantly up-regulated. Furthermore, these increases were attenuated by pretreatment with roscovitine. These results suggested that Cdk5 may contribute to remifentanil-induced postoperative hyperalgesia via regulating the phosphorylation of NMDAR and mGluR5 in spinal dorsal horn. These findings provide experimental evidence for the further application of Cdk5 inhibitor in preventing remifentanil-induced hyperalgesia.

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.

Comparison of Remifentanil and Low-Dose Fentanyl for Fast-Track Cardiac Anesthesia: A Prospective Randomized Study

<p><b>Background:</b> Different anesthetic techniques have been used for fast tracking in cardiac anesthesia. Remifentanil, with its unique pharmacokinetic profile, could be an ideal drug for fast tracking. Possible limitations of remifentanil are rapid onset of postoperative pain after discontinuation of the drug infusion, which may increase the risk of an ischemic event. We conducted this randomized study to compare the efficacy of remifentanil versus low doses of fentanyl in fast-track cardiac anesthesia. It has been hypothesized that remifentanil would provide a safe anesthesia with no impact on myocardial function and with positive effects on extubation time and mobilization.</p><p><b>Methods:</b> We compared the postoperative course of patients, the remifentanil group (RG) and the low-dose fentanyl group (LDFG), in whom remifentanil and low-dose fentanyl, respectively, were used for fast-track cardiac anesthesia. The study was designed as a prospective randomized study. The primary outcomes were changes in the cardiac index and creatine kinase MB fraction (CKMB), extubation times, mobilization times, and lengths of stay in the intensive care unit (ICU) and the hospital. Frequency of myocardial infarction (MI), reoperations due to excessive bleeding, renal impairment, and cerebral complications were registered as well.</p><p><b>Results:</b> Seventy-one patients were enrolled in the study, and 7 were excluded due to difficult airway, bleeding, and technical difficulties. The RG comprised 33 patients and the LDFG comprised of 31 patients. There were no differences between the groups in terms of age, Euroscore, types of surgery, extracorporeal circulation, and aortic cross-clamp time. We did not find significant difference in cardiac index, CKMB, extubation times, mobilization times, length of stay in the ICU and in the hospital between the groups. Postoperative complications such as MI, rates of reoperations, renal and cerebral complications and incidence of atrial fibrillation did not show any significant differences.</p><p><b>Conclusions:</b> Remifentanil fast-track anesthesia for cardiac patients has no negative impact on myocardial function. Both remifentanil and low-dose fentanyl are equally effective and safe for fast-track cardiac anesthesia. The study did not highlight any statistical superiority of remifentanil anesthesia over low-dose fentanyl anesthesia.</p>

Remifentanil has a minimal direct effect on sinoatrial node pacemaker activity in the Guinea pig heart

BACKGROUND

Whereas remifentanil administration is associated with severe bradycardia, it has yet to be fully investigated whether the negative chronotropic action of remifentanil is mediated by its direct action on sinoatrial (SA) node pacemaker activity in the heart versus indirect results of enhanced vagal activity.

METHODS

We examined the effects of remifentanil and fentanyl on the spontaneous action potentials of guinea pig SA node cells at concentrations of 5, 10, 100, and 1000 nM using the amphotericin B-perforated whole-cell patch-clamp technique. Isolated guinea pig hearts were perfused in a Langendorff mode with 5, 10, 100, and 1000 nM remifentanil.

RESULTS

The spontaneous firing rate and diastolic depolarization rate (DDR) of the SA node action potentials were 189.1 ± 14.8 /min and 74.1 ± 2.9 mV/s (n = 8), respectively, under control conditions, and were not significantly affected by exposure to 5 nM (P = 1.0 for both spontaneous firing rate and DDR; n = 6), 10 nM (P = 0.62 for spontaneous firing rate, P = 0.99 for DDR; n = 6), or 100 nM (P = 0.23 for spontaneous firing rate, P = 0.38 for DDR; n = 6) remifentanil. However, 1000 nM remifentanil modestly but significantly decreased the spontaneous firing rate (P = 0.0087) and DDR (P = 0.0072, n = 6). Remifentanil did not affect the heart rate of isolated Langendorff-perfused guinea pig hearts at concentrations of 5 nM (P = 0.98), 10 nM (P = 0.35), or 100 nM (P = 0.24) but significantly reduced the heart rate at 1000 nM (P < 0.0001). Fentanyl did not affect the spontaneous firing rate and DDR at concentrations of 5 nM (P = 1.0 for both spontaneous firing rate and DDR) and 10 nM (P = 0.62 for spontaneous firing rate, P = 0.79 for DDR), but it significantly reduced both at 100 nM (P = 0.00038 for spontaneous firing rate, P = 0.0080 for DDR) and 1000 nM (P < 0.0001 for both spontaneous firing rate and DDR).

CONCLUSIONS

Clinically relevant concentrations (nanomolar order concentrations) of remifentanil do not produce significant direct effects on intrinsic cardiac automaticity; thus, suggesting that remifentanil-induced bradycardia in the clinical setting is independent of its direct cardiac effects.

Comparison of intraoperative blood loss during spinal surgery using either remifentanil or fentanyl as an adjuvant to general anesthesia

Background

Remifentanil enhances intraoperative hemodynamic stability, suggesting that it may decrease intraoperative blood loss when included as an adjuvant to general anesthesia. This retrospective study compared intraoperative blood loss during spinal surgery in patients administered either remifentanil or fentanyl as an opioid adjuvant.

Methods

We reviewed clinical and surgical data from 64 consecutive laminoplasty or laminectomy patients treated at National Hospital Organization Zentsuji Hospital between April 2010 and March 2011. Patients received either remifentanil (n = 35) or fentanyl (n = 29) as an opioid analgesic during general anesthesia. In addition to intraoperative blood loss, indices of hemodynamic stability, including heart rate as well as systolic, mean, and diastolic blood pressure (BP), were compared over the entire perioperative period between remifentanil and fentanyl groups.

Results

The remifentanil group exhibited significantly lower intraoperative arterial BP than the fentanyl group. Intraoperative blood loss was also significantly lower in the remifentanil group (125 ± 67 mL vs. 165 ± 82 mL, P = 0.035).

Conclusions

Intraoperative blood loss during spinal surgery was decreased in patients who received remifentanil as an opioid adjuvant, possibly because of lower intraoperative BP. A larger-scale prospective randomized controlled trial is warranted to confirm our results and to test whether remifentanil can decrease intraoperative blood loss during other surgical procedures.

General anaesthetic considerations for haemostasis in orbital surgery

Orbital surgery is often conducted in areas with limited exposure where vital structures are tightly crowded together. A bloodless field is paramount in orbital surgery for the proper identification of normal and pathologic tissue and even minimal bleeding can obscure the surgical field, making surgery more difficult and increasing the risk of complications. Surgery for highly vascular orbital lesions is an additional situation where maintaining an adequate surgical field is often challenging but paramount. The role of the anaesthetist in controlling surgical blood loss has been increasingly recognized in the last few decades. Various techniques including hypotensive anaesthesia have been described, but the control of intraoperative bleeding does not rely on a single particular technique, but a series of well-designed interventions that result in optimal conditions. An understanding of the anaesthetic considerations pertinent to haemostasis is invaluable for oculoplastic surgeons. Additionally, with the growing use of endonasal approaches to medial wall decompression and accessing the medial orbit, it has become increasingly important that orbital surgeons understand the anaesthetic requirements of their colleagues in other disciplines.

The impact of remifentanil on incidence and severity of postoperative nausea and vomiting in a university hospital-based ambulatory surgery center: a retrospective observation study

Background

Ambulatory surgery, including short-stay surgery, has become a common choice in clinical practice. For the success of ambulatory surgery, perioperative care with safe and effective anesthesia and postoperative analgesia, which can reduce the occurrence of postoperative nausea and vomiting (PONV), is essential. The effect of remifentanil on the occurrence and severity of PONV has not been thoroughly examined, particularly, in an ambulatory surgery setting. Here, we investigate whether remifentanil influences the occurrence and severity of PONV in a university hospital-based ambulatory unit.

Methods

We retrospectively analyzed a total of 1,765 cases of patients who had undergone general anesthesia at our ambulatory surgery unit. Parameters, such as occurrence and severity of nausea, vomiting or retching, use of antiemetic drugs, amount of postoperative analgesic and patient satisfaction, were extracted from the records and analyzed between the groups that received and not received remifentanil.

Results

Within 565 patients of the RF group, 39 patients (6.6%) experienced nausea, 7 patients (1.2%) experienced vomiting or retching, and 10 patients (1.8%) were given antiemetic; in addition, the maximum VAS value for nausea was 12.1 mm. In 1,200 patients of the non RF group, 102 patients (8.5%) experienced nausea, 19 patients (1.6%) experienced vomiting or retching, and 34 patients (2.8%) were given antiemetic, and the maximum VAS value was 13.2 mm. There were no statistically significant differences between the two groups.

Conclusions

Our results indicate that remifentanil did not increase the occurrence of PONV in patients within the ambulatory surgery unit.

Implementation of a fast-track-pathway including analgo-sedation with local anaesthesia for outpatient varicose vein surgery: a cohort study

Objective

To evaluate the clinical and economical impact of a fast-track anaesthesia protocol in the management of primary varicose vein (VV) surgery.

Methods

Over a 10-month period (from 1 December 2009 to 30 September 2011), all patients eligible for open VV surgery ( N = 176) were enrolled in a fast-track clinical pathway including titrated analgo-sedation combined with local anaesthesia. This fast-track cohort was compared with a historical cohort undergoing similar procedures and receiving general anaesthesia (GA) or spinal anaesthesia (SA) (between 1 December 2009 to 30 September 2011, N = 200). The length of stay in the operating facilities and postoperative recovery areas were reported and hospital costs were estimated. In addition, the occurrence of adverse events and unplanned hospital admission were compared between the two consecutive periods.

Results

Patients characteristics and surgical procedure were not different in the two cohorts. After implementation of the fast-track pathway, the incidence of postoperative adverse events decreased from 41% to 2.3%, with no need for overnight hospital stay (0% versus 7%). The reduction in anaesthesia-controlled time (-47%) and in postoperative recovery time (-61%) were associated with an increased operating capacity (1 extra case per day) and with substantial cost-savings (mean reduction of €312 per case, P < 0.001).

Conclusions

Implementation of a fast-track pathway for outpatient VV surgery was successful, safe and efficient. Analgo-sedation combined with infiltrative anaesthesia (instead of GA or SA) contributed to increase the operating capacity and to reduce the workload of nursing personnel.

Antihyperalgesic effects of dexmedetomidine on high-dose remifentanil-induced hyperalgesia

Background

Dexmedetomidine is a highly selective α2 adrenergic agonist that has been shown to decrease the intensity of opioid-induced hyperalgesia (OIH). We aimed to investigate the antihyperalgesic effects of dexmedetomidine on high-dose remifentanil-induced hyperalgesia.

Methods

Ninety American Society of Anesthesiologists physical status I-II patients undergoing laparoscopically assisted vaginal hysterectomy (LAVH) were randomly assigned to one of the following three groups, each of which received either dexmedetomidine (an initial dose of 1.0 µg/kg for 10 min, followed by a continuous infusion of 0.7 µg/kg/hr) or placebo saline 15 min before the induction of anesthesia and intraoperative remifentanil infusion: group C received a placebo and 0.05 µg/kg/min remifentanil; group RH received a placebo and 0.3 µg/kg/min remifentanil; and group DRH received dexmedetomidine and 0.3 µg/kg/min remifentanil.

Results

The mechanical hyperalgesia threshold 24 hr after surgery was significantly lower in group RH than in the other two groups. Postoperative pain intensity using visual analog scale (VAS) and cumulative volume of a patient-controlled analgesia (PCA) containing morphine over 24 hr were significantly greater in group RH than in group DRH. The time to the first postoperative analgesic requirement was significantly shorter in group RH than in the other two groups. The desflurane requirement was significantly greater in group C than in the other groups. The frequency of hypotension and bradycardia was significantly higher, but shivering and postoperative nausea and vomiting were significantly lower in group DRH than in the other two groups.

Conclusions

High-doses of remifentanil induced hyperalgesia, which presented a decreased mechanical hyperalgesia threshold, enhanced pain intensity, a shorter time to first postoperative analgesic requirement, and greater morphine consumption, but dexmedetomidine efficiently alleviated those symptoms. Dexmedetomidine may be a novel and effective treatment option for preventing or attenuating OIH.

Remifentanil protects liver against ischemia/reperfusion injury through activation of anti-apoptotic pathways

BACKGROUND

Remifentanil protects against ischemia/reperfusion (I/R)-induced organ injury, although its underlying mechanism remains elusive. This study was designed to examine the protective effect of remifentanil preconditioning, if any, against hepatic I/R injury in rats and the underlying mechanism involved.

MATERIALS AND METHODS

Adult Sprague-Dawley rats were randomly divided into sham operation (S group), ischemia/reperfusion (I/R group), and remifentanil preconditioning (R group) groups. Rats in the I/R group were subjected to a partial (70%) hepatic ischemia for 45 min, followed by 1 h, 3 h, and 6 h of reperfusion. Rats in the R group received venous injection of remifentanil (2 μg/kg/min) from 30 min prior to hepatic ischemia to the end of ischemia. Hepatic morphology and apoptosis were examined. Markers of liver damage, oxidative stress, and inflammation were evaluated. Mitochondrial function was assessed using mitochondrial membrane potential and appearance of mitochondrial swelling.

RESULTS

Compared with the S group, rats in the I/R group displayed a massive degenerative death in liver tissues and significantly enhanced cell apoptosis. Remifentanil preconditioning significantly reduced I/R-induced hepatocyte apoptosis. In addition, remifentanil protected against I/R-induced mitochondrial swelling and loss of membrane potential. Remifentanil preconditioning inhibited I/R-induced increases in tumor necrosis factor α, intercellular adhesion molecule 1, and nuclear factor κB p65 levels in liver tissues. Remifentanil preconditioning also inhibited the loss in superoxide dismutase and rise in malondialdehyde levels in liver tissues going through I/R injury.

CONCLUSIONS

Our data revealed that remifentanil preconditioning may turn on multiple cellular pathways in hepatocytes to protect the liver from I/R injury by alleviating hepatic apoptosis.

Effect of remifentanil on the hemodynamic responses and recovery profile of patients undergoing single jaw orthognathic surgery

The aim of this study was to compare fentanyl-based versus remifentanil-based anesthesia with regards to the intraoperative hemodynamic stress response and recovery profiles in patients undergoing Le Fort I osteotomy. Seventeen patients were randomly divided into two groups: patients in the F-group received 2 μg/kg fentanyl intravenously followed by an infusion of 0.03-0.06 μg/kg/min, while patients in the R-group received a 0.5 μg/kg bolus of remifentanil followed by an infusion of 0.0625-0.250 μg/kg/min. Mean arterial pressure and heart rate were recorded at the following points: before anesthetic induction, at endotracheal intubation, 5 min after intubation, at incision, just before the osteotomy, during the osteotomy, during the maxillary fracturing, at suturing, at extubation, 5 min after extubation, and then 15 and 30 min postoperatively. Heart rate and mean arterial pressure were significantly lower in the R-group in comparison to the F-group from t1 to t9 (P<0.05). All measured recovery times were significantly shorter in the R-group (P<0.05). The incidence of postoperative side effects was comparable between groups. Remifentanil-based anesthesia is an appropriate alternative to fentanyl during Le Fort I orthognathic surgery; it promotes hemodynamic stability, blunts the stress response to noxious stimuli, and provides a better recovery profile.

A multicentre, randomised, open-label, controlled trial evaluating equivalence of inhalational and intravenous anaesthesia during elective craniotomy

CONTEXT

A clear preference for intravenous or inhalational anaesthesia has not been established for craniotomy in patients without signs of cerebral hypertension.

OBJECTIVES

The NeuroMorfeo trial was designed to test equivalence of inhalational and intravenous anaesthesia maintenance techniques in the postoperative recovery of patients undergoing elective supratentorial surgery.

DESIGN

This trial is a multicentre, randomised, open-label, equivalence design. A balanced stratified randomisation scheme was maintained using a centralised randomisation service. Equivalence was tested using the two one-sided tests procedure.

SETTING

Fourteen Italian neuroanaesthesia centres participated in the study from December 2007 to March 2009.

PATIENTS

Adults, 18 to 75 years old, scheduled for elective supratentorial intracranial surgery under general anaesthesia were eligible for enrolment if they had a normal preoperative level of consciousness and no clinical signs of intracranial hypertension.

INTERVENTIONS

Patients were randomised to one of three anaesthesia maintenance protocols to determine if sevoflurane-remifentanil or sevoflurane-fentanyl were equivalent to propofol-remifentanil.

MAIN OUTCOME MEASURES

The primary outcome was the time to achieve an Aldrete postanaesthesia score of at least 9 after tracheal extubation. Secondary endpoints included haemodynamic parameters, quality of the surgical field, perioperative neuroendocrine stress responses and routine postoperative assessments.

RESULTS

Four hundred and eleven patients [51% men, mean age 54.8 (SD 13.3) years] were enrolled. Primary outcome data were available for 380. Median (interquartiles) times to reach an Aldrete score of at least 9 were 3.48 (2.02 to 7.56), 3.25 (1.21 to 6.45) and 3.32  min (1.40 to 8.33) for sevoflurane-fentanyl, sevoflurane-remifentanil and propofol-remifentanil anaesthesia respectively, which confirmed equivalence using the two one-sided tests approach. Between-treatment differences in haemodynamic variables were small and not clinically relevant. Urinary catecholamine and cortisol responses had significantly lower activation with propofol-remifentanil. Postoperative pain and analgesic requirements were significantly higher in the remifentanil groups.

CONCLUSION

Equivalence was shown for inhalational and intravenous maintenance anaesthesia in times to reach an Aldrete score of at least 9 after tracheal extubation. Haemodynamic variables, the quality of surgical field and postoperative assessments were also similar. Perioperative endocrine stress responses were significantly blunted with propofol-remifentanil and higher analgesic requirements were recorded in the remifentanil groups.

TRIAL REGISTRATION

Eudract 2007-005279-32.

The effect of anesthetic technique on recovery after orthognathic surgery: a retrospective audit

We audited the recovery characteristics of 51 patients who had undergone orthognathic maxillofacial surgery at a single center. Patients whose anesthesia had been maintained with intravenous propofol and remifentanil (n  =  21) had significantly higher pain scores during the first 4 hours after surgery than those whose anesthesia was maintained with volatile inhalational agents and longer-acting opioids (n  =  30) (P  =  .016). There was a nonsignificant trend towards shorter recovery times in the former group, while there were no differences in early postoperative opioid usage, hemodynamic parameters, or postoperative nausea and vomiting . Given that our data were collected retrospectively and without the ability to control for potential confounders, we interpret the results with caution. Notwithstanding these limitations, we believe this is the first report comparing the effects of different opioid-based anesthetic regimens on early recovery from orthognathic surgery, and we believe this report may be used as the starting point for a controlled study.

The effects of gabapentin on acute opioid tolerance to remifentanil under sevoflurane anesthesia in rats

BACKGROUND

Tolerance to remifentanil during sevoflurane anesthesia may blunt the ability of this drug to reduce anesthetic requirements. Gabapentin has been shown to be effective in reducing postoperative narcotic usage, a reduction that may be associated with a reduction in opioid-induced tolerance and hyperalgesia. We sought to determine whether gabapentin might prevent the observed acute opioid tolerance (AOT) produced by remifentanil in sevoflurane minimum alveolar concentration (MAC).

METHODS

Wistar rats were anesthetized with sevoflurane and the effects of gabapentin alone on sevoflurane MAC were determined at doses of 150 and 300 mg · kg(-1). In a second experiment, gabapentin 300 mg · kg(-1) was administered before remifentanil (120 and 240 μg · kg(-1) · h(-1)). The MAC was determined before gabapentin administration and 3 more times at 1.5-hour intervals after drug administration to assess AOT. MAC was determined from intratracheal gas samples using a sidestream gas analyzer; tail clamping was used as a supramaximal stimulus. Statistical analysis was performed with the 1-way analysis of variance test.

RESULTS

Remifentanil reduced MAC (2.5 ± 0.2%) by 16% ± 5% and 36% ± 6% (120 and 240 μg · kg(-1) · h(-1), respectively, P < 0.01) with a further reduction produced by coadministration with gabapentin 300 mg · kg(-1) to 39% ± 12% and 62% ± 14%, respectively (P < 0.01 versus remifentanil alone). Gabapentin given alone at 150 and 300 mg · kg(-1) reduced MAC by 26% (both doses, P < 0.01). AOT was observed with remifentanil and characterized by a lower degree of MAC reduction, approximately 1.5 hours later (P < 0.05). However, when remifentanil was administered with gabapentin, the AOT to remifentanil was not observed (P > 0.05).

CONCLUSIONS

Gabapentin reduced the sevoflurane MAC and enhanced the MAC reduction produced by remifentanil. This enhancement may limit AOT in rats.

Lipid-emulsion propofol less attenuates the regulation of body temperature than micro-emulsion propofol or sevoflurane in the elderly

PURPOSE

Anesthesia and surgery commonly cause hypothermia, and this caused by a combination of anesthetic-induced impairment of thermoregulatory control, a cold operation room environment and other factors that promote heat loss. All the general anesthetics markedly impair normal autonomic thermoregulatory control. The aim of this study is to evaluate the effect of two different types of propofol versus inhalation anesthetic on the body temperature.

MATERIALS AND METHODS

In this randomized controlled study, 36 patients scheduled for elective laparoscopic gastrectomy were allocated into three groups; group S (sevoflurane, n=12), group L (lipid-emulsion propofol, n=12) and group M (micro-emulsion propofol, n=12). Anesthesia was maintained with typical doses of the study drugs and all the groups received continuous remifentanil infusion. The body temperature was continuously monitored after the induction of general anesthesia until the end of surgery.

RESULTS

The body temperature was decreased in all the groups. The temperature gradient of each group (group S, group L and group M) at 180 minutes from induction of anesthesia was 2.5 ± 0.6°C, 1.6 ± 0.5°C and 2.3 ± 0.6°C, respectively. The body temperature of group L was significantly higher than that of group S and group M at 30 minutes and 75 minute after induction of anesthesia, respectively. There were no temperature differences between group S and group M.

CONCLUSION

The body temperature is maintained at a higher level in elderly patients anesthetized with lipid-emulsion propofol.

Remifentanil in cardiac surgery: a meta-analysis of randomized controlled trials

OBJECTIVE

The authors conducted a review of randomized controlled trials to identify advantages in clinically relevant outcomes in patients undergoing cardiac surgery with remifentanil.

DESIGN

Meta-analysis.

SETTING

Hospitals.

PARTICIPANTS

A total of 1,473 patients from 16 randomized trials.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULT

PubMed, BioMedCentral, and conference proceedings were searched (updated May 2010) for randomized trials that compared remifentanil with fentanyl or sufentanil in cardiac anesthesia. Four independent reviewers performed data extraction, with divergences resolved by consensus. Overall analysis showed that the use of remifentanil was associated with a significant reduction in postoperative mechanical ventilation (WMD = -139 min [-244, -32], p for effect = 0.01, p for heterogeneity < 0.001, I(2) = 89%); length of hospital stay (WMD = -1.08 days [-1.60, -0.57], p for effect < 0.0001, p for heterogeneity = 0.004, I(2) = 71%); and cardiac troponin-I release (WMD = -2.08 ng/mL [-3.93, -0.24], p for effect = 0.03, p for heterogeneity < 0.02, I(2) = 74%). No difference was noted in mortality (3/344 [0.87%] in the remifentanil group vs [1.06%] the control group, OR 0.76 [0.17-3.38], p for effect = 0.72, p for heterogeneity = 0.35, I(2) = 5%).

CONCLUSIONS

Remifentanil reduces cardiac troponin release, time of mechanical ventilation, and length of hospital stay in patients undergoing cardiac surgery.

An intraoperative small dose of ketamine prevents remifentanil-induced postanesthetic shivering

Patients undergoing gynecological laparotomy were randomized to receive either 0.5 mg/kg ketamine at induction of anesthesia followed by an infusion of 0.3 mg/kg/h until the end of surgery (ketamine group, n = 32), or an equivalent volume of normal saline (control group, n = 32). Anesthesia was maintained with IV propofol, a fixed infusion rate of remifentanil (0.25 μg/kg/min), and epidural ropivacaine. Postanesthetic shivering (PAS) was evaluated for 30 minutes after emergence. Intraoperative temperatures were similar between the 2 groups. The incidence of PAS was less frequent in the ketamine group (n = 2, 6%) compared with the control group (n = 12, 38%, P = 0.005). We conclude that, during the early recovery phase, intraoperative ketamine reduces remifentanil-induced PAS.

Delayed awakening following inadvertent high-dose remifentanil infusion in a 13 year old patient

We report the case of a 13 year old patient who received 3.0 mg of remifentanil during a 50-minute surgical procedure as a result of a dosage miscalculation. The patient failed to awaken at the conclusion of the procedure and showed signs of opioid overdose. She recovered spontaneously two hours later.

Long-term sedation in intensive care unit: a randomized comparison between inhaled sevoflurane and intravenous propofol or midazolam

PURPOSE

To evaluate efficacy and adverse events related to inhaled sevoflurane for long-term sedation compared with standard intravenous (i.v.) sedation with propofol or midazolam.

METHODS

Randomized controlled trial. Sixty intensive care unit (ICU) patients expected to require more than 24 h sedation were randomly assigned to one of three groups: group S, inhaled sevoflurane; group P, i.v. propofol; group M, i.v. midazolam. All patients also received i.v. remifentanil for goal-directed sedation (Ramsay scale and pain score) until extubation or for a maximum of 96 h. Primary end points were wake-up times and extubation delay from termination of sedative administration. Proportion of time within Ramsay score 3-4, i.v. morphine consumption at 24 h post extubation, hallucination episodes after end of sedation, adverse events, inorganic fluoride plasma levels, and ambient sevoflurane concentrations were recorded.

RESULTS

Forty-seven patients were analyzed. Wake-up time and extubation delay were significantly (P<0.01) shorter in group S (18.6 ± 11.8 and 33.6 ± 13.1 min) than in group P (91.3 ± 35.2 and 326.11 ± 360.2 min) or M (260.2 ± 150.2 and 599.6 ± 586.6 min). Proportion of time within desired interval of sedation score was comparable between groups. Morphine consumption during the 24 h following extubation was lower in group S than in groups P and M. Four hallucination episodes were reported in group P, five in group M, and none in group S (P=0.04). No hepatic or renal adverse events were reported. Mean plasma fluoride value was 82 μmol l(-1) (range 12-220 μmol l(-1)), and mean ambient sevoflurane concentration was 0.3 ± 0.1 ppm.

CONCLUSIONS

Long-term inhaled sevoflurane sedation seems to be a safe and effective alternative to i.v. propofol or midazolam. It decreases wake-up and extubation times, and post extubation morphine consumption, and increases awakening quality.

The effects of a single bolus of remifentanil on corrected QT interval change during sevoflurane induction

PURPOSE

Opioids may affect changes in the corrected QT interval (QTc) during anesthetic induction. This study examine whether a single bolus of remifentanil would prolong QTc after laryngeal mask airway (LMA) insertion during sevoflurane induction.

MATERIALS AND METHODS

Forty women of American Society of Anesthesiologists physical status 1 (ASA PS1) undergoing gynecological surgery were studied. All patients were induced using three vital capacity inhalation inductions with 5% sevoflurane. Two minutes after induction, the inspiratory concentration of sevoflurane was reduced to 2%. Using double-blinded randomization, patients were allocated into one of two groups, receiving either saline (placebo group, n = 20) or 0.25 μg.kg⁻¹ remifentanil (remifentanil group, n = 20) over a period of thirty seconds. Sixty seconds later, LMA insertion was performed. Recordings were taken with a 12-lead electrocardiogram at baseline, 2 min after induction and 1 and 3 min after LMA insertion. QTc was calculated by Bazett's formula. The mean arterial pressure (MAP) and heart rate (HR) were also measured at each time point.

RESULTS

The QTc interval was significantly prolonged in the placebo group as compared to the remifentanil group at 1 min after LMA insertion (467.8 ± 16.5 vs. 442.7 ± 21.3 ms, p < 0.001). However, there was no significant difference in QTc at 3 min after LMA insertion between the two groups. MAP and HR were significantly higher in the placebo group (p < 0.001).

CONCLUSION

A single bolus of remifentanil is safe method to attenuate prolonged QTc associated with insertion of LMA.

Remifentanil, a different opioid: potential clinical applications and safety aspects

IMPORTANCE OF THE FIELD

Opioids play an important role in every aspect of modern anesthetic practice. Remifentanil is an ultra-short-acting opioid featuring a unique pharmacokinetic profile allowing clinical versatility and improved control of its action. In this review, we assess the pharmacology of remifentanil, its clinical uses as well as safety issues on its action on the major organ systems and in particular clinical settings.

AREAS COVERED IN THIS REVIEW

A synthesis of evidence from a MEDLINE search for articles from 1993 to 2009 for available up-to-date information on remifentanil and its current applications and safety profile.

WHAT THE READER WILL GAIN

A synopsis of the unique pharmacokinetic properties of remifentanil and its action on major organ systems will provide insight on the safe and effective use of the drug in a variety of clinical settings.

TAKE HOME MESSAGE

Remifentanil is a valuable opioid in the armamentarium of the clinician, providing great clinical flexibility and safety but vigilance is required to avoid pitfalls.

Continuous infusion of two doses of remifentanil immediately after laparoscopic-assisted vaginal hysterectomy

Background

We evaluated the effect and safety of the immediate postoperative continuous infusion of remifentanil at two doses in patients undergoing laparoscopic-assisted vaginal hysterectomy (LAVH) with alfentanil-based patient-controlled analgesia (PCA).

Methods

The study enrolled 50 ASA physical status 1 or 2 patients scheduled to undergo LAVH. Anesthesia was maintained with sevoflurane-remifentanil-air. At the last skin suture, the sevoflurane was discontinued, and patients were randomized to receive remifentanil 0.05 µg/kg/min (group I) or 0.1 µg/kg/min (group II). PCA was started at the time of eye opening and response to a verbal command. In the recovery room, we monitored the mean arterial blood pressure (MAP), heart rate (HR), respiratory rate (RR), SpO₂, and bispectral index (BIS) at 5-minute intervals. Thirty minutes after starting PCA, the remifentanil was discontinued. Pain was assessed using a visual analog scale (0 = no pain; 100 = the worst possible pain) at 0, 5, 10, and 30 minutes after stopping the remifentanil infusion.

Results

The eye opening time, BIS, MAP, and HR did not differ significantly between the two groups, and pain scores were similar between the two groups. Respiratory depression (SpO₂ < 90% or RR < 8/min) did not occur in group I but did occur in three patients in group II.

Conclusions

Continuous remifentanil infusion (0.05 µg/kg/min) immediately postoperatively with alfentanil-based PCA had a similar effect as a 0.1 µg/kg/min infusion with respect to pain control without side effects. However, special attention must be given to respiratory depression.

The potential for mu-opioid receptor agonists to be anti-emetic in humans: a review of clinical data

In animal models of vomiting, mu-opioid (MOP, OP(3)) receptors mediate both emesis and anti-emesis. mu-receptors within the blood-brain barrier, mediating anti-emesis, are more rapidly accessible to lipid-soluble mu-opioid receptor agonists such as fentanyl than to morphine, and fentanyl has broad-spectrum anti-emetic effects in a number of species. Whether a similar situation exists in humans is not known. A search was performed for clinical studies comparing the emetic side effects of opioids administered peri-operatively in an attempt to identify differences between morphine and more lipid-soluble mu-receptor-selective agonists such as fentanyl. Overall, the evidence appears to suggest that fentanyl and other phenylpiperidines are associated with less nausea and vomiting than morphine, but not all studies support this, and fentanyl-like drugs are associated with nausea and vomiting per se. Good evidence, however, exists to show that fentanyl and alfentanil do not cause more nausea and vomiting than the ultra fast-acting remifentanil. Because remifentanil is cleared rapidly post-operatively, such trials suggest that the emetic side effects of fentanyl and alfentanil are minimal. The clinical evidence, although limited, is at least consistent with the possibility that central mu-opioid receptors may mediate anti-emesis in humans. It is possible that the role of mu-opioid agonists in anti-emesis may become clearer in the future as a result of the use of peripheral mu-opioid receptor antagonists.

Controlled hypotension for middle ear surgery: a comparison between remifentanil and magnesium sulphate

BACKGROUND

This prospective, randomized study was designed to compare remifentanil and magnesium sulphate during middle ear surgery in terms of postoperative pain and other complications.

METHODS

Eighty patients undergoing middle ear surgery were enrolled in the study. Patients were randomized into two groups of 40 to receive remifentanil (Group R) or magnesium sulphate (Group M) infusion. Propofol 2 mg kg(-1) was administered to induce anaesthesia, which was maintained using sevoflurane. Group R received a continuous infusion of remifentanil titrated between 3 and 4 ng ml(-1) using target-controlled infusion, whereas Group M received an i.v. magnesium sulphate bolus of 50 mg kg(-1) followed by a 15 mg kg(-1) h(-1) continuous infusion to maintain a mean arterial pressure (MAP) between 60 and 70 mm Hg. Haemodynamic variables, surgical conditions, postoperative pain, and adverse effects, such as postoperative nausea and vomiting (PONV) and shivering, were recorded.

RESULTS

Controlled hypotension was well maintained in both groups. MAP and heart rate were higher in Group R than in Group M after operation. Surgical conditions were not different between the two groups. Postoperative pain scores were significantly lower in Group M than in Group R (P<0.05). Seventeen patients in Group R (43%) and seven patients in Group M (18%) developed PONV (P=0.01).

CONCLUSIONS

Both magnesium sulphate and remifentanil when combined with sevoflurane provided adequate controlled hypotension and proper surgical conditions for middle ear surgery. However, patients administered magnesium sulphate had a more favourable postoperative course with better analgesia and less shivering and PONV.

Facial muscle activity, Response Entropy, and State Entropy indices during noxious stimuli in propofol-nitrous oxide or propofol-nitrous oxide-remifentanil anaesthesia without neuromuscular block

BACKGROUND

Entropy is an anaesthetic EEG monitoring method, calculating two numerical parameters: State Entropy (SE, range 0-91) and Response Entropy (RE, range 0-100). Low Entropy numbers indicate unconsciousness. SE uses the frequency range 0.8-32 Hz, representing predominantly the EEG activity. RE is calculated at 0.8-47 Hz, consisting of both EEG and facial EMG. RE-SE difference (RE-SE) can indicate EMG, reflecting nociception. We studied RE-SE and EMG in patients anaesthetized without neuromuscular blockers.

METHODS

Thirty-one women were studied in propofol-nitrous oxide (P) or propofol-nitrous oxide-remifentanil (PR) anaesthesia. Target SE value was 40-60. RE-SE was measured before and after endotracheal intubation, and before and after the commencement of surgery. The spectral content of the signal was analysed off-line. Appearance of EMG on EEG was verified visually.

RESULTS

RE, SE, and RE-SE increased during intubation in both groups. Elevated RE was followed by increased SE values in most cases. In these patients, spectral analysis of the signal revealed increased activity starting from low (<20 Hz) frequency area up to the highest measured frequencies. This was associated with appearance of EMG in raw signal. No spectral alterations or EMG were seen in patients with stable Entropy values.

CONCLUSIONS

Increased RE is followed by increased SE at nociceptive stimuli in patients not receiving neuromuscular blockers. Owing to their overlapping power spectra, the contribution of EMG and EEG cannot be accurately separated with frequency analysis in the range of 10-40 Hz.

[Procedural analgesia : concepts and practice]

The effect of severe pain and its hazardous stress-related cardiocirculatory consequences have been well documented for the perisurgical setting. Independently of surgical intervention however, even short and simple measures (e.g. thorax drain removal, repositioning a limb fracture) and longer diagnostic procedures such as MRI are potentially very painful or stressful to the patient. Though longer diagnostic procedures are frequently supported by systemic medication, short interventions regularly lack this aspect. Specific challenges result from the need to counteract sometimes great changes in pain intensity. Moreover procedural analgesia represents a multidisciplinary measure not restricted to anaesthesiology, as most of these measures are performed without anaesthesia. To avoid endangering the patient, the choice of drugs and patient monitoring have to meet certain professional and technical standards. Competence in respiratory management is of paramount importance. This paper outlines these requirements and serves as an orientation outside the anaesthesiological speciality.