Remifentanil produces vasorelaxation in isolated rat thoracic aorta strips

Cardiac Arrest during Temporary Clipping for Ruptured Internal Carotid Artery Aneurysm: A Case Report

Mechanical stimulation of the trigeminal nerve during craniofacial, skull base, or dental surgeries may cause bradycardia, hypotension, or cardiac arrest. This phenomenon is called trigeminal cardiac reflex (TCR). We encountered a rare case of a patient who experienced sinus arrest due to temporary clipping of the intracranial carotid artery during the clipping of a ruptured aneurysm. We discuss possible reasons for the occurrence of TCR in this case. A man in his 30s with no medical history presented with a sudden-onset headache. Computed tomography revealed a subarachnoid hemorrhage in the basal cistern and left Sylvian fissure. Angiography revealed a saccular aneurysm of the left internal carotid-anterior choroidal artery. A left frontotemporal craniotomy and dural incision were performed, followed by a trans-Sylvian approach. Cardiac arrest occurred twice during the temporary clipping of the intracranial carotid artery. After surgery, we performed a cardiac ultrasound echo and a 1-week Holter electrocardiogram. Neither showed abnormalities. No arrhythmia or cardiac events were observed over a one and half-year follow-up period. The cardiac arrest might have been triggered by the stimulation of the trigeminal nerve in the internal carotid artery. The repeated and anatomical features of this case suggest that TCR triggered cardiac arrest. The high probability that cardiac arrest was induced by trigeminal nerve stimulation should be considered during the temporary clipping of the internal carotid artery. However, the predisposing factors and exact underlying mechanisms for these arrhythmias remain unknown and require further investigation.

Prevention of trigeminocardiac reflex-induced severe bradycardia during cerebral aneurysm clipping surgery by topical anesthesia of the dura surface and atropine administration: a case report

BACKGROUND

Trigeminocardiac reflex (TCR) by stimulation of the sensory branch of the trigeminal nerve induces transient bradycardia and hypotension. We report a case in which light mechanical stimulation to the dura mater during brain surgery induced severe bradycardia.

CASE PRESENTATION

A 77-year-old woman with bradycardia-tachycardia syndrome was scheduled for clipping of an unruptured left middle cerebral artery aneurysm. General anesthesia was performed with propofol, remifentanil, and rocuronium. Before starting surgery, the function of the pyramidal tract was examined by motor evoked potential. Transcranial electric stimulation for motor evoked potential induced atrial fibrillation and tachycardia. Continuous administration of landiolol was started and verapamil was used for tachycardia. During detachment of the dura mater from the bone, an electrocardiogram suddenly showed sinus arrest for 6 s. Immediately after the manipulation was interrupted, a junctional rhythm appeared. However, light touch to the dura mater induced severe bradycardia again, and atropine was therefore administered. In addition, the dura surface was anesthetized with topical lidocaine infiltration. After that, light touch-induced bradycardia was prevented.

CONCLUSIONS

We experienced a case of severe bradycardia during surgery due to TCR caused by light mechanical stimulation to the dura mater. Topical anesthesia of the dura surface and atropine administration were effective for preventing TCR-induced bradycardia.

Effects of remote ischemic preconditioning on regional cerebral oxygen saturation in patients in the beach chair position during shoulder surgery: A double-blind randomized controlled trial

STUDY OBJECTIVE

The beach chair position for shoulder surgery induces cerebral hypoperfusion. We evaluated the effects of remote ischemic preconditioning (RIPC) prior to surgery to ameliorate cerebral desaturation in a double-blind randomized fashion.

DESIGN

Blinded, prospective, randomized study.

SETTING

Operating room & postoperative recovery room, tertiary university hospital.

PATIENTS

Seventy patients scheduled for shoulder surgery were recruited. After excluding 7 patients according to the exclusion criteria, 63 patients were randomized into two groups (control and RIPC).

INTERVENTIONS

Remote ischemic preconditioning was applied by briefly inflating a tourniquet on the thigh three times just after inducing anesthesia in the RIPC group.

MEASUREMENTS

The changes in regional cerebral oxygen saturation, hemodynamic values, laboratory values, and serum levels of cytokines including interleukin (IL)-1β, IL-6, IL-10 and transforming growth factor-β were measured.

MAIN RESULTS

The remote ischemic preconditioning group had higher regional cerebral oxygen saturation just after establishment of the beach chair position (P = 0.002) and lower cerebral desaturation (P = 0.007) during operation than the control group. Hemodynamic and laboratory values did not differ between the groups. There were no significant intergroup differences in cytokine levels.

CONCLUSION

Remote ischemic preconditioning before surgery ameliorates cerebral desaturation in patients in the beach chair position during shoulder surgery. Trial Registry Number: KCT0001384 (http://cris.nih.go.kr).

The use of remifentanil in critically ill patients undergoing percutaneous dilatational tracheostomy: A prospective randomized-controlled trial

Remifentanil was a μ-agonist, with a rapid onset, a powerful narcotic analgesic activity and a fast nonspecific esterases hydrolyzation and theoretically an ideal opioid for percutaneous dilatational tracheostomy (PDT). The present study discussed use of remifentanil in critically ill patients undergoing PDT. Ninety-nine patients were randomly assigned to the propofol/remifentanil group (PR group, n = 49) or the propofol group (P group, n = 50). Two patients (one in P group and one in PR group) were excluded and transferred to surgical way of tracheostomy because of uncontrolled bleeding. The primary outcomes were critical care pain observation (CPOT) scores during PDT; hemodynamic response and side effects, such as bleeding and muscle rigidity (MR). CPOT scores in P group were significantly higher than in PR group during incision and dilation stages (P < 0.05 and P < 0.01). Systolic blood pressure had a significant drop after a bolus of remifentanil in PR group compared with patients in P group (P < 0.056). The incidence of MR was significantly higher in PR group than in P group (P < 0.05). Recovery time in PR group was significantly shorter than in P group (P < 0.05). The occurrence of tachycardia, bleeding, vomiting, and nausea had no statistically differences in both groups. Patients in PR group were undergoing shorter recovery time and better experience of pain in PDT compared with patients in P group, but MR seemed to be higher in PR group. Remifentanil seemed to be a safe and effective opioid used in critically ill patients undergoing PDT.

Effects of RMF on BKCa and Kv channels in basilar arterial smooth‑muscle cells of SHR

The current study observed the effects and investigated the mechanism of remifentanil (RMF) on the isolated cerebral basilar arteries of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. A pressure myograph system was used to observe and compare the effects of different concentrations of RMF (10⁻¹⁰-10⁻⁵ mol/l) on the diameter changes of freshly isolated cerebral basilar arteries, which have been pre-shrunk by phenylephrine (PE), an endothelium-independent vasoconstrictor. Vascular smooth-muscle cells of the cerebral basilar artery (BASMCs) were freshly obtained via enzymolysis. BKCa (large-conductance calcium-activated potassium channels) current (I_BKCa) and Kv (voltage-gated potassium channels) current (I_Kv) were recorded using a whole-cell patch-clamp technique. The changes in I_BKCa and I_Kv produced by different concentrations of RMF (10⁻¹⁰ to 10⁻⁵ mol/l) on the two types of rats with the holding potential of −40 mV were observed and compared. The cerebral basilar arteries of the SHR and WKY rats were relaxed by RMF in a concentration-dependent manner (P<0.05; n=5). At the same concentration, the diastolic effect of RMF on SHR was weaker than that observed in WKY rats (P<0.05, n=5). When the rats were pre-perfused with 10⁻³ mol/l of the BKCa channel blocker tetraethylammonium (TEA), the diastolic amplitudes of RMF in SHR and WKY rats were decreased, and the fitting curves shifted down (P<0.05; n=7 and 6, respectively). However, no statistically significant difference was observed with 10⁻³ mol/l of the Kv channel blocker 4-aminopyridine (4-AP; n=6 and 9, respectively; P>0.05). Outward currents were increased by RMF in both BASMCs of SHR and WKY rats in a voltage- and dose-dependent manner (P<0.05; n=6). At the same concentration, the effect of RMF on the outward currents in BASMCs of WKY rats was stronger than that on SHR (P<0.05; n=6). The enhancing effect of RMF can be partially blocked by either 10⁻³ mol/l TEA (P<0.05; n=6) or 10⁻³ mol/l 4-AP (P<0.05 or 0.01; n=6 and 9, respectively) however can be totally blocked by the mixture of TEA and 4-AP (P<0.05, n=7). RMF served a diastolic role in the cerebral basilar arteries of rats in a dose-dependent manner, likely by activating the BKCa and Kv channels. However, SHR demonstrated a less pronounced diastolic reaction to RMF than that observed in WKY rats.

Sufentanil attenuates impairment of the endothelium-dependent vasodilation induced by hypoxia-reoxygenation in the rat coronary artery

Sufentanil has been used broadly in cardiac surgery, but the mechanisms by which it modulates coronary vascular tone after ischemia-reperfusion injury are largely unknown. Effects of sufentanil on coronary tone and on the relaxation of rat coronary arteries (CAs) in response to endothelium-dependent (acetylcholine) and endothelium-independent (sodium nitroprusside) relaxing agents in the presence of hypoxia-reoxygenation (H/R) was studied in an in vitro organ chamber setup. Sufentanil (10^-7-10^-4 mol/L) relaxed rat CA rings in endothelium-dependent and endothelium-independent manners. In endothelium-intact rings, preincubation of H/R-treated CAs with sufentanil (10^-5 mol/L) significantly increased the acetylcholine response, but did not augment sodium nitroprusside-induced relaxation. Sufentanil-mediated potentiation of acetylcholine-induced relaxation was not affected by a nitric oxide synthase inhibitor or by intermediate- or small-conductance Ca²⁺-activated K⁺ channel blockers. However, potentiation was abolished by iberiotoxin (100 nmol/L), a selective inhibitor of large-conductance Ca²⁺-activated K⁺ channels, as well as Rp-cAMPS (30 μmol/L), a cyclic AMP-dependent protein kinase (PKA) inhibitor. Sufentanil induced endothelium-dependent and endothelium-independent relaxation and attenuated H/R-induced impairment of endothelium-dependent vasodilation in the rat CAs. The potentiating effect of sufentanil may involve activation of large-conductance Ca²⁺-activated K⁺ channels via cAMP-dependent mechanisms.

Cardioprotective Effects of Remifentanil in a Sympathetic Hyperactivity Model in Rabbits

OBJECTIVE

In this study, the antiarrhythmic and anti-ischemic effects of a 6 μg kg(-1) min(-1) infusion dose of remifentanil are investigated in a central sympathetic hyperactivity model in rabbits.

METHODS

In this study, 18 New Zealand rabbits were used. The subjects were randomly divided into three groups (n=6) and received 10 μmol L(-1) glutamate intracerebroventricularly to provide the central sympathetic hyperactivity. In group 1, 10 μmol L(-1) glutamate was used; in group 2, 1 h before L-glutamate injection, 40 mg kg(-1) N (omega)-nitro-L-arginine methyl ester was intravenously (iv) administered; and in group 3, also 1 h before L-glutamate injection, 40 mg kg(-1) N (omega)-nitro-L-arginine methyl ester was iv administered. A 6 μg kg(-1) min(-1) dose of remifentanil infusion was administered 5 min before L-glutamate injection. Heart rate, systolic arterial pressure and mean arterial pressure were measured and recorded. Within 15 min of the intracerebroventricular L-glutamate injection, premature ventricular complexes, bigeminy ventricular arrhythmia, ventricular tachycardia, ST-segment shift and T-wave inversions were recorded.

RESULTS

When incidences of heart rate, rate pressure product, premature ventricular complexes and bigeminy ventricular arrhythmia were compared between groups, significant differences were not determined. Mean arterial pressure was more significantly increased in group 2 than in the other groups (p<0.05). Ventricular tachycardia, ST-segment shift and T-wave inversions were significantly lower in group 3 than in groups 1 and 2 (p<0.05).

CONCLUSION

Remifentanil (6 μg kg(-1) min(-1) for 5 min of infusion) prevented life-threatening ventricular tachycardia and electrocardiographic signs of myocardial ischemia in a model of arrhythmia resulting from the association of central sympathetic overactivity.

Remifentanil use in pediatric scoliosis surgery-an effective alternative to morphine (a retrospective study)

PURPOSE

The unique properties of remifentanil make it ideal for pediatric use despite a lack of wide randomized clinical trials and fear of adverse events due to its high potency. We aimed to consolidate preliminary conclusions regarding the efficacy of remifentanil use in pediatric scoliosis surgery.

MATERIALS AND METHODS

The medical charts of children with idiopathic scoliosis who underwent primary spinal fusion between 1998 and 2007 at a large tertiary university-affiliated hospital were retrospectively reviewed and divided into two groups according to anesthetic regime (remifentanil vs. morphine). Demographic, surgery-related details and immediate postoperative course were recorded and compared.

RESULTS

All 36 remifentanil children were extubated shortly after termination of surgery, compared to 2 of the 84 patients in the morphine group. The remaining patients in the morphine group were extubated hours after surgery [5.4 hours; standard deviation (SD) 1.7 hours]. Six remifentanil children were spared routine intensive care hospitalization (vs. 2 morphine children-significant difference). Shorter surgeries [5.6 hours (SD 1.82 hours) vs. 7.14 hours (SD 2.15 hours); p=0.0004] were logged for the remifentanil group. To achieve controlled hypotension during surgery, vasodilator agents were used in the morphine group only. A comparison of early postoperative major or minor complication rates (including neurological and pulmonary complications) between the two groups yielded no significant differences.

CONCLUSION

Remifentanil use can shorten operating time and facilitate earlier spontaneous ventilation and extubation, with less of a need for intensive care hospitalization and no increase in significant complications.

Flurbiprofen axetil provides a prophylactic benefit against mesenteric traction syndrome associated with remifentanil infusion during laparotomy

PURPOSE

Mesenteric traction syndrome (MTS) is caused by PGI(2) release during abdominal procedures and is often observed during abdominal surgery. We have demonstrated that MTS occurs more frequently in cases using remifentanil than in those that are not. The aim of this study was to assess the prophylactic benefit of flurbiprofen axetil on MTS in patients undergoing abdominal surgery using remifentanil.

METHODS

Thirty ASA physical status I and II patients were enrolled. They were scheduled to undergo abdominal surgery under general anesthesia with remifentanil and were randomly assigned to receive flurbiprofen axetil (group F) or saline (group C) preoperatively (n = 15 each). MTS was defined according to our simplified diagnostic criteria. Arterial blood pressure and heart rate were recorded, and the plasma 6-keto-PGF(1α) (a stable metabolite of PGI(2)) concentration was measured just before skin incision and at 20 and 60 min after skin incision (T(0), T(20), T(60)) to confirm the diagnosis of MTS.

RESULTS

Twelve of 15 (80%) patients developed MTS in group C, whereas only 1 of 15 (6.7%) patients in group F developed MTS. At T(20), the group C patients showed significantly lower arterial blood pressure (P < 0.05) and a faster heart rate (P < 0.01) than those in group F. The mean plasma 6-keto-PGF(1α) concentration was significantly elevated in group C at T(20) (P < 0.01), whereas the plasma 6-keto-PGF(1α) level remained low throughout the observation period in group F.

CONCLUSIONS

We found that preoperative administration of flurbiprofen axetil reduced the incidence of MTS during abdominal surgery with remifentanil analgesia.

A cardiovascular monitoring system used in conscious cynomolgus monkeys for regulatory safety pharmacology: Part 2: Pharmacological validation

INTRODUCTION

This project addresses the validation study design of a test system using a telemetered non-human primate model for cardiovascular safety pharmacology evaluation.

METHODS

In addition to non-pharmacological validation including installation and operation qualifications, performance qualification (locomotor activity and cardiovascular evaluations) was completed on free-moving cynomolgus monkeys by quantifying the degree of cardiovascular response measured by the telemetric device to various positive control drugs following their intravenous administration. Remifentanil (0.0005, 0.001, 0.002, 0.004, 0.008 and 0.016 mg/kg) was given to induce bradycardia and hypotension. Medetomidine (0.04 mg/kg) was used to induce an initial phase of hypertension followed by hypotension and bradycardia. Esmolol (0.5, 1.0 and 2.0 mg/kg) was used to induce bradycardia. Dopamine (0.002, 0.008, 0.01, 0.02, 0.03 and 0.05 mg/kg/min) was infused over 30 min to induce an increase in arterial and pulse pressures and tachycardia. Amiodarone (0.4, 0.8 and 1.6 mg/kg/min) was infused over 10 min to induce QT interval prolongation. Potassium chloride (0.08 mEq/kg/min) was infused for periods of less than 30 min to induce electrocardiographic (EKG) changes characteristic of hyperkalemia. Reliability was evaluated over 60 days.

RESULTS

Monitoring with a reference methodology and the telemetry system was important in order to evaluate precision and accuracy of the test system. Positive control drugs produced a wide range of cardiovascular effects with different amplitudes, which were useful in identification of the limits of the test system.

DISCUSSION

Reference monitoring methods and selection of a battery of positive control drugs are important to ensure proper test system validation. Drugs inducing not only QT prolongation but also positive and negative chronotropic effects, positive and negative systemic arterial pressure changes and ECG morphology alterations were useful to identify test system limitations during performance qualification. ECG data processing at significantly elevated heart rates revealed that a trained observer should review all cardiac cycles evaluated by computer.

Remifentanil-induced mechanical responses and membrane potential changes in human umbilical arteries

BACKGROUND

The aim of this study was to evaluate the characteristic features of the mechanical responses and membrane potential changes induced by remifentanil in human umbilical arteries (HUAs). The ionic mechanisms underlying the electrophysiological responses were pharmacologically assessed using two K(+) channel blockers.

METHODS

Thirty-eight HUAs were obtained. Contraction-relaxation, membrane potential changes and electrical responses of the HUAs were recorded.

RESULTS

Remifentanil produced concentration-dependent relaxation in both endothelium-intact and endothelium-denuded HUA rings. Remifentanil produced a significantly greater relaxation response in intact than in denuded HUA rings. In endothelium-intact rings, pre-treatment with L-nitroarginine [N(w)-NITRO-(L)-ARGININE (L-NO-ARG)] or indomethacin decreased the degree of remifentanil-induced relaxation. Remifentanil (10(-9)-10(-6) mol/l) produced a transient concentration-dependent membrane hyperpolarization, which was not decreased by pre-treatment with L-NO-ARG or indomethacin. It also produced a small concentration-dependent hyperpolarization in the presence of charybdotoxin or tetraethylammonium.

CONCLUSION

In both endothelium-intact and endothelium-denuded HUAs, remifentanil induces concentration-dependent vasorelaxation and simultaneously releases nitric oxide, prostaglandins and possibly an endothelium-derived hyperpolarizing factor. In addition, it produces hyperpolarization in a dose-dependent manner. Hyperpolarization induced by remifentanil involves the activation of Ca(2+)-dependent and Ca(2+)-independent potassium channels regulated by intracellular Ca(2+).

Effect of cooling on the responses of human saphenous vein to fentanyl, remifentanil and sufentanil

We studied the vasodilatory effects of fentanyl, remifentanil and sufentanil on the human saphenous vein strips at 37, 32 and 28 degrees C. Fentanyl produced concentration-dependent relaxation of human saphenous vein strips precontracted with 5-hydroxytryptamine (5-HT) at every temperature studied. Compared with vein strips at 37 degrees C, relaxant responses to each one concentration of fentanyl were significantly reduced at 32 and 28 degrees C. Remifentanil relaxed vein strips in a concentration-dependent way and the relaxation for all concentrations were significantly greater at 32 and 28 degrees C compared with 37 degrees C. Sufentanil produced concentration-dependent relaxation in saphenous vein strips precontracted with 5-HT. These relaxant responses were similar at 32 degrees C compared with 37 degrees C. When bath temperature was lowered from 37 to 28 degrees C, the relaxant responses to sufentanil were significantly reduced. In summary, the present study suggests that cooling reduces the relaxation caused by fentanyl and sufentanil on human saphenous veins but augments the relaxation with remifentanil. The augmented vasodilatory effect of remifentanil with cooling may be useful on systemic vascular resistance and organ preservation under hypothermic conditions like cardiopulmonary bypass surgery.

The coronary and myocardial effects of remifentanil and sufentanil in the erythrocyte-perfused isolated rabbit heart

Remifentanil-induced hypotension may be associated with adverse ischemic myocardial events. Although these events can be easily attributed to a decrease in coronary pressure perfusion, we tested the hypothesis that remifentanil could directly affect coronary vasomotor tone. Therefore, we assessed intrinsic coronary and myocardial in vitro effects of remifentanil on a Langendorff's rabbit model and compared these effects with those provoked by similar intracoronary concentrations of sufentanil. Under general anesthesia, hearts from New Zealand rabbits were rapidly excised and mounted on an erythrocyte-perfused and isolated heart preparation. The hearts were then exposed to increasing concentrations (10-1000 nM) of either remifentanil (n = 10) or sufentanil (n = 8). Between each concentration, hearts were allowed to return to baseline status. The maximal coronary and myocardial effects of each concentration of both drugs were noted. Baseline values of coronary blood flow and myocardial performances were comparable between groups. Neither remifentanil nor sufentanil induced significant coronary and myocardial effects. These results suggest that myocardial ischemia, which may occur during remifentanil-induced hemodynamic disturbances, especially in cardiac patients, is only related to a decrease in coronary perfusion pressure provoked by peripheral hemodynamic changes.

Effects of General Anesthetics on Regulation of the Peripheral Vasculature

The heart is a passively filling pump in a circulatory system that is connected in series with distensible blood vessels. Therefore, systemic blood pressure and tissue perfusion depend upon adequate peripheral vascular tone as well as myocardial function. Likewise, pharmacologic agents that alter circulatory stability can affect one or both of these components. The generalized depressor effects of general anesthetics have been well known clinically for over 50 years. Moreover, there are many similarities in basic cellular regulatory mechanisms among the different tissue types, and general anesthetics are well known to distribute freely among the perfusion-rich tissues (eg, central nervous system, cardiovascular system, and renal system). Therefore, it is likely that the hemodynamic depression resulting from the systemic administration of anesthetics results from actions on regulatory mechanisms of the peripheral vasculature as well as on the heart. The peripheral vasculature is regulated by extrinsic neural, endothelial, and humoral mechanisms, which interact with each other as well as with intrinsic membrane and intracellular systems within the vascular smooth muscle cell. Different general anesthetics have been found to act on specific mechanisms at each of these levels. However, the large number and complexity of these known mechanisms, as well as the many anesthetic agents, has made it extremely difficult to determine which are significant in terms of the meaningful mechanisms that are responsible for anesthetic action, major side effects, or both. Current knowledge about the effects of general anesthetics on both the extrinsic intrinsic regulatory mechanisms of peripheral vascular control is reviewed.

Remifentanil: an update

PURPOSE OF REVIEW

Remifentanil has now reached maturity, as reflected by the increasing number of clinical papers relating to its use. Its position among anaesthetic drugs is now better understood, and this review will attempt to place it in the context of current clinical practice.

RECENT FINDINGS AND SUMMARY

Propofol reduces the initial distribution of remifentanil, leading to higher concentrations during induction. Propofol and remifentanil administered together at sedative doses display a major synergistic interaction on the respiratory drive. Remifentanil accelerates the penetration of sevoflurane to its site of effect. The risk of intraoperative awareness seems to be low when remifentanil is associated to very low concentrations of hypnotic drugs, but this field warrants further investigation. Acute tolerance to opioids and its prevention remain controversial.

SUMMARY

Remifentanil is the opioid of choice for tracheal intubation without muscle relaxants. It provides an alternative to regional anaesthesia in labour pain control. Target-controlled infusion may further improve the administration of remifentanil.