Effects of an Intraoperative Intravenous Bolus Dose of Dexmedetomidine on Remifentanil-Induced Postinfusion Hyperalgesia in Patients Undergoing Thyroidectomy: A Double-Blind Randomized Controlled Trial

Determining the optimum dose of remifentanil in combination with propofol for total intravenous anaesthesia in hysteroscopy under Narcotrend and SPI monitoring

Background

Outpatient hysteroscopic surgery requires patients to be anaesthetised and recover quickly, and the drugs used must be safe and effective. Remifentanil is typically co-administered with propofol as total intravenous anaesthesia (TIVA) for hysteroscopy because of its favourable pharmacokinetic and pharmacodynamic properties. However, the optimal dose of remifentanil when co-administered with propofol without neuromuscular blocking agents (NMBAs) has not been established.

Objectives

In this sequential dose-finding study, the 90% effective dose (ED90) of remifentanil effect-site concentration (Ce) combined with propofol without NMBAs during outpatient hysteroscopy was calculated to minimise the side effects of using higher doses.

Design

This sequential dose-finding study was conducted in August 2022.

Methods

Forty patients who underwent outpatient hysteroscopy under TIVA were included in the study. With a biased coin up-and-down design, the initial remifentanil Ce was established at 2 ng/mL, and the subsequent remifentanil dosage was determined based on the reaction of the previous patient. The primary outcome was a remifentanil Ce that resulted in successful TIVA by maintaining a Narcotrend index < 60, surgical pleth index (SPI) < 50, and without patient movement throughout hysteroscopy. Secondary outcomes included rates of hypotension-related symptoms and interventions, drug consumption, post-anaesthesia care unit (PACU)-estimated visual analogue scale (VAS) and Ramsay sedation scores, modified Aldrete scores, and other adverse effects of anaesthesia. The ED90 and 95% confidence intervals (CI) were estimated using isotonic regression methods and bootstrapping.

Results

For TIVA without NMBAs during outpatient hysteroscopy, the ED90 Ce of remifentanil combined with propofol was determined to be 2.75 ng/mL (95% CI, 2.50-3.00 ng/mL). The incidence of peri-operative adverse effects of anaesthesia was relatively low. All the patients had satisfactory VAS, Ramsay sedation, and modified Aldrete scores in the PACU.

Conclusion

Remifentanil at a Ce of 2.75 ng/mL is recommended for TIVA combined with propofol in outpatient hysteroscopic surgery.

Trial registration

http://www.chictr.org.cn (ChiCTR2200062284; 31/7/2022).

Comparing subjective quality of recovery between remimazolam- and propofol-based total intravenous anesthesia for surgical procedures: a meta-analysis

BACKGROUND

Remimazolam is a novel ultra-short-acting benzodiazepine that has been recently introduced as an alternative to propofol for general anesthesia. While both agents have been compared in terms of safety and efficacy, their relative effects on postoperative quality of recovery (QoR) remain unclear. Therefore, this meta-analysis aimed to compare the effects of remimazolam and propofol on subjective QoR in surgical patients who underwent general anesthesia.

METHODS

Medline, Embase, Google Scholar, and the Cochrane Central Register of Controlled Trials were searched from inception to May 28, 2024 to identify randomized controlled trials comparing remimazolam and propofol in terms of postoperative QoR. The Cochrane risk-of-bias tool (RoB 2) was used to assess study quality. QoR score on postoperative day (POD) 1 (primary outcome), QoR scores on PODs 2-3, QoR dimensions, time to loss of consciousness, other recovery characteristics, and rescue analgesia requirement were evaluated using random-effects meta-analyses.

RESULTS

This meta-analysis included 13 studies published between 2022 and 2024 involving 1,418 patients. QoR was evaluated using either the QoR-15 (10 studies) or QoR-40 (3 studies) questionnaire. The pooled results indicated no significant difference in the QoR scores on POD 1 (standardized mean difference: 0.02, 95% confidence interval [CI]: - 0.20, 0.23, P = 0.88, I2 = 73%) and PODs 2-3 between remimazolam and propofol. Furthermore, no significant differences were observed in QoR dimensions, length of postanesthesia care unit (PACU) stay, and time to extubation as well as in the risks of agitation and postoperative nausea and vomiting. Patients administered remimazolam exhibited slower anesthetic induction (mean difference (MD): 32.27 s) but faster recovery of consciousness (MD: - 1.60 min) than those administered propofol. Moreover, remimazolam was associated with a lower risk of rescue analgesia requirement in the PACU (risk ratio: 0.62, 95% CI: 0.43, 0.89, P = 0.009, I2 = 0%) but not in the ward.

CONCLUSION

Remimazolam is a potential alternative to propofol for general anesthesia as it offers similar QoR to the latter and has advantages in terms of consciousness recovery and immediate postoperative analgesia requirement.

Remifentanil-induced hyperalgesia in healthy volunteers: a systematic review and meta-analysis of randomized controlled trials

ABSTRACT

Recent literature suggests that the withdrawal of remifentanil (RF) infusion can be associated with hyperalgesia in clinical and nonclinical settings. We performed a systematic review and a meta-analysis of randomized controlled trials with cross-over design, to assess the effect of discontinuing RF infusion on pain intensity and areas of hyperalgesia and allodynia in healthy volunteers. Nine studies were included. The intervention treatment consisted in RF infusion that was compared with placebo (saline solution). The primary outcome was pain intensity assessment at 30 ± 15 minutes after RF or placebo discontinuation, assessed by any pain scale and using any quantitative sensory testing. Moreover, postwithdrawal pain scores were compared with baseline scores in each treatment. Secondary outcomes included the areas (% of basal values) of hyperalgesia and allodynia. Subjects during RF treatment reported higher pain scores after discontinuation than during treatment with placebo [standardized mean difference (SMD): 0.50, 95% confidence interval (CI): 0.03-0.97; P = 0.04, I 2 = 71%]. A significant decrease in pain scores, compared with baseline values, was found in the placebo treatment (SMD: -0.87, 95% CI: -1.61 to -0.13; P = 0.02, I 2 = 87%), but not in the RF treatment (SMD: -0.28, 95% CI: -1.18 to 0.62; P = 0.54, I 2 = 91%). The area of hyperalgesia was larger after RF withdrawal (SMD: 0.55; 95% CI: 0.27-0.84; P = 0.001; I 2 = 0%). The area of allodynia did not vary between treatments. These findings suggest that the withdrawal of RF induces a mild but nonclinically relevant degree of hyperalgesia in HVs, likely linked to a reduced pain threshold.

Effects of an intraoperative intravenous Bolus Dose of Dexmedetomidine on postoperative catheter-related bladder discomfort in male patients undergoing transurethral resection of bladder tumors: a randomized, double-blind, controlled trial

PURPOSE

To investigate whether the effect of intravenous bolus doses of dexmedetomidine on postoperative catheter-related bladder discomfort (CRBD) was dose-dependent in male patients undergoing transurethral resection of bladder tumors (TURBT).

METHODS

The study protocol was registered at the Chinese Clinical Trial Registry (ChiCTR 2,000,034,657, date of registration: July 14, 2020). Adult male patients were randomized to one of four groups: placebo (Group C); dexmedetomidine 0.2 µg/kg (Group D 0.2); dexmedetomidine 0.5 µg/kg (Group D 0.5); or dexmedetomidine 1 µg/kg (Group D 1). The primary outcome was the incidence of moderate-to-severe CRBD at 0, 1, 6, 24, and 48 h postoperatively.

RESULTS

The incidence of moderate-to-severe CRBD was significantly lower in Group D 0.5 and Group D 1 than in Group C at 0 h (13% vs. 40%, P = 0.006; 8% vs. 40%, P = 0.001), 1 h (15% vs. 53%, P < 0.001; 13% vs. 53%, P < 0.001), and 6 h (10% vs. 32%, P = 0.025; 8% vs. 32%, P = 0.009) postoperatively. Compared with baseline, both the MAP and HR were significantly lower in Group D 1 at 1 min ([94 ± 15] vs. [104 ± 13] mm Hg, P = 0.003; [64 ± 13] vs. [73 ± 13] bpm, P = 0.001) and 30 min ([93 ± 10] vs. [104 ± 13] mm Hg, P < 0.001; [58 ± 9] vs. [73 ± 13] bpm, P < 0.001) postextubation.

CONCLUSION

The effect of intravenous bolus doses of dexmedetomidine on postoperative CRBD was dose-independent, whereas intravenous administration of 0.5 µg/kg dexmedetomidine reduced the early postoperative incidence of CRBD with minimal side effects.

TRIAL REGISTRATION

Clinical trial number and registry URL: ChiCTR 2,000,034,657, http://www.chictr.org.cn , date of registration: July 14, 2020.

Microglial Nrf2/HO-1 signaling gates remifentanil-induced hyperalgesia via suppressing TRPV4-mediated M1 polarization

Remifentanil-induced hyperalgesia (RIH) represents a significant clinical challenge due to the widespread use of opioids in pain management. However, the molecular and cellular mechanisms underlying RIH remain elusive. This study aimed to unravel the role of spinal cord microglia, focusing on the Nrf2/HO-1 signaling pathway and TRPV4 channels in the development of RIH. We used both in vivo and in vitro models to investigate the activation state of spinal cord microglia, the expression of TRPV4 channels, and the modulation of the Nrf2/HO-1 pathway under remifentanil exposure. In addition, we evaluated the potential therapeutic effects of dexmedetomidine, a perioperative α2-adrenergic agonist, on RIH and its related molecular pathways. Our results revealed a prominent role of spinal cord microglia in RIH, demonstrating an apparent microglial M1 polarization and increased TRPV4 channel expression. A notable observation was the downregulation of the Nrf2/HO-1 pathway, which was associated with increased neuroinflammation and mechanical allodynia. By upregulating or overexpressing Nrf2, we confirmed its ability to inhibit TRPV4 and thereby attenuate RIH-associated mechanical allodynia, M1 polarization, and neuroinflammation. Encouragingly, dexmedetomidine demonstrated therapeutic potential by positively modulating the Nrf2-TRPV4 nexus, attenuating mechanical allodynia, and reducing microglial inflammation. Our research highlights the critical role of spinal cord microglia in RIH mediated by the Nrf2-TRPV4 axis. The ability of dexmedetomidine to modulate this axis suggests its potential as an adjunctive therapy to remifentanil in mitigating RIH. Further studies are imperative to explore the broader implications and practical applicability of our findings.

Perioperative analgesia in the elderly

The administration of analgesic drugs in elderly patients should take into account age-related physiological changes, loss of efficiency of homeostatic mechanisms, and pharmacological interactions with chronic therapies. Underestimation of pain in patients with impaired cognition is often linked to difficulties in pain assessment. In the preoperative phase, it is essential to assess the physical status, cognitive reserve, and previous chronic pain conditions to plan effective analgesia. Furthermore, an accurate pharmacological history of the patient must be collected to establish any possible interaction with the whole perioperative analgesic plan. The use of analgesic drugs with different mechanisms of action for pain relief in the intraoperative phase is a crucial step to achieve adequate postoperative pain control in older adults. The combined multimodal and opioid-sparing strategy is strongly recommended to reduce side effects. The use of various adjuvants is also preferable. Moreover, the implementation of non-pharmacological approaches may lead to faster recovery. High-quality postoperative analgesia in older patients can be achieved only with a collaborative interdisciplinary team. The aim of this review is to highlight the perioperative pain management strategies in the elderly with a special focus on intraoperative pharmacological interventions.

Efficacy and safety of flurbiprofen‑axetil combined with nalbuphine pretreatment on remifentanil‑induced postoperative hyperalgesia: A randomized clinical trial

Remifentanil-induced hyperalgesia (RIH) is a common and complicated issue in patients undergoing laparoscopic cholecystectomy (LC), which significantly reduces patient satisfaction. The present trial was designed to clarify the individual and combined effects of flurbiprofen-axetil and nalbuphine on remifentanil-induced hyperalgesia. This randomized double-blind clinical trial included 120 adult patients who underwent LC at The Second People's Hospital of Wuhu. The individuals were randomized into a flurbiprofen-axetil group (F group), nalbuphine group (N group), flurbiprofen-axetil combined with nalbuphine group (FN group) and saline group (S group). The four groups were given flurbiprofen-axetil (50 mg, iv.), nalbuphine (0.1 mg/kg, iv.), flurbiprofen-axetil (50 mg, iv.) combined with nalbuphine (0.1 mg/kg, iv.) or normal saline respectively prior to skin incision. The primary outcome was the postoperative mechanical pain thresholds at the inner forearm and peri-incisional area. The secondary outcomes were the visual analog scale (VAS) and Ramsay sedation scale at 0.5, 1, 4 and 24 h after surgery, and any other adverse events. The pain threshold of the medial forearm in the FN group did not differ from that in the F and N groups at 24 h after surgery (P=0.310 and P=0.910, respectively). However, the pain threshold around the incision in FN group was significantly lower than that in F and N groups 24 h after surgery (P=0.001). The VAS of the F group, N group and FN group were all significantly lower than that in the S group at 0.5, 1 and 24 h after surgery (P<0.001). No significant differences were observed in the incidence of adverse events between the four groups. Single flurbiprofen-axetil and single nalbuphine effectively prevented RIH 24 h after surgery in LC. The combination of the two analgesic drugs, with different mechanisms of action, was not superior to single therapy. The present study was registered with the Chinese Clinical Trial Registry (registration no. ChiCTR2100045347).

Pharmacological interventions for preventing opioid-induced hyperalgesia in adults after opioid-based anesthesia: a systematic review and network meta-analysis

Background: Opioid-induced hyperalgesia (OIH) is an adverse event of prolonged opioid use that increases pain intensity. The optimal drug to prevent these adverse effects is still unknown. We aimed to conduct a network meta-analysis to compare different pharmacological interventions for preventing the increase in postoperative pain intensity caused by OIH. Methods: Several databases were searched independently for randomized controlled trials (RCTs) comparing various pharmacological interventions to prevent OIH. The primary outcomes were postoperative pain intensity at rest after 24 h and the incidence of postoperative nausea and vomiting (PONV). Secondary outcomes included pain threshold at 24 h after surgery, total morphine consumption over 24 h, time to first postoperative analgesic requirement, and shivering incidence. Results: In total, 33 RCTs with 1711 patients were identified. In terms of postoperative pain intensity, amantadine, magnesium sulphate, pregabalin, dexmedetomidine, ibuprofen, flurbiprofen plus dexmedetomidine, parecoxib, parecoxib plus dexmedetomidine, and S (+)-ketamine plus methadone were all associated with milder pain intensity than placebo, with amantadine being the most effective (SUCRA values = 96.2). Regarding PONV incidence, intervention with dexmedetomidine or flurbiprofen plus dexmedetomidine resulted in a lower incidence than placebo, with dexmedetomidine showing the best result (SUCRA values = 90.3). Conclusion: Amantadine was identified as the best in controlling postoperative pain intensity and non-inferior to placebo in the incidence of PONV. Dexmedetomidine was the only intervention that outperformed placebo in all indicators. Clinical Trial Registration: https://www.crd.york.ac. uk/prospero/display_record.php?, CRD42021225361.

Nalmefene vs. dexmedetomidine for prevention of postoperative hyperalgesia in patients undergoing laparoscopic gynecological surgery with remifentanil infusion: A randomized double-blind controlled trial

Intraoperative remifentanil infusion may paradoxically induce post-surgical hyperalgesia. Dexmedetomidine reportedly reduces opioid-induced hyperalgesia. Nalmefene selectively reverses several side-effects of opioids without impairing analgesia. Herein, this randomized, double-blind controlled trial investigated whether nalmefene, dexmedetomidine, and both drugs combined prevent remifentanil-induced hyperalgesia. One hundred and fifty patients undergoing elective laparoscopic gynecological surgery under desflurane anesthesia randomly received either intraoperative sufentanil 0.20 μg kg^-1 (Group S), or remifentanil 0.20 μg kg^-1 min^-1 (Group R), or remifentanil and pre-anesthesia nalmefene 0.20 μg kg^-1 (Group N), or remifentanil and pre-anesthesia dexmedetomidine 0.50 μg kg^-1 (Group D), or remifentanil and the combination of dexmedetomidine 0.25 μg kg^-1 and nalmefene 0.10 μg kg^-1 (Group DN). The threshold of postoperative mechanical hyperalgesia (primary outcome) was measured with von Frey filaments. We also recorded pain intensity, analgesic consumptions, hyperalgesic area, and side-effects for 24 h postoperatively. Compared with Group S, remifentanil reduced hyperalgesic threshold on the forearm [mean 89.4 (SD 13.7) vs. 62.2 (10.7) g, p < 0.001] at postoperative 24 h. Pain threshold on the forearm at postoperative 24 h was significantly lower in Group R than in Groups N, D and DN [62.2 (10.7) vs. 71.1 (12.3), 72.4 (12.9) and 78.0 (13.8) g]. Compared with Group R, Postoperative pain intensity, analgesic consumption and hyperalgesic area were lower likewise in Groups D and DN. However, the incidence of intraoperative bradycardia was lower and post-anesthesia recovery time was shorter in Group DN than Group D. Preoperative therapy of dexmedetomidine and nalmefene combined attenuates postoperative hyperalgesia in patients undergoing laparoscopic gynecological surgery under desflurane-remifentanil anesthesia.

Suspected opioid-induced hyperalgesia in an infant following surgery: A case report

WHAT IS KNOWN AND OBJECTIVE

Opioids are commonly administered to infants having surgery. Opioid induced hyperalgesia (OIH) is a known adverse effect of opioids in adults but can be difficult to identify in infants.

CASE SUMMARY

A 3-month-old received high-dose fentanyl during anorectoplasty for imperforate anus. He had signs and symptoms of OIH immediately after surgery. His pain and agitation were difficult to manage but improved after he received ketamine.

WHAT IS NEW AND CONCLUSION

OIH should be considered in infants postoperatively when pain worsens despite administration of escalating doses of opioids. Ketamine can be an effective therapeutic for OIH.

Effect of ketorolac tromethamine combined with dezocine prior administration on hemodynamics and postoperative analgesia in patients undergoing laparoscopic hernia repair

OBJECTIVE

To observe the effect of Ketorolac tromethamine combined with dezocine prior administration on hemodynamics and postoperative sedation in patients undergoing laparoscopic hernia repair.

METHODS

100 male patients aged 60 to 80 years old, a line to elective laparoscopic inguinal hernia repair, were randomly divided into four groups: control group (Group A) and dezocine group (Group B), ketorolac tromethamine group (Group C), ketorolac tromethamine combined with dezocine group (Group D). Patients were administrated with 0.1 mg/kg dezocine in Group B, 0.5 mg/kg ketorolac in Group C, 0.1 mg/kg dezocine, and 0.5 mg/kg ketorolac in Group D, and with an equal dose of normal saline in group A. The heart rate (HR) and mean arterial pressure (MAP) of patients in 4 groups were recorded at each time point as follows, T0 (enter the operating room), T1 (before skin resection), 10 min after pneumoperitoneum (T2), mesh placement (T3), and laryngeal mask extraction (T4). Operation time, awakening time (time from drug withdrawal to consciousness recovery), the dosage of propofol, sufentanil, remifentanil, and intraoperative vasoactive drug dosage were recorded to compare. Visual analog scale score and sedation Ramsay score were evaluated 1, 6, 12, and 24 hours after extubation.

RESULTS

There was no significant difference in operation time, anesthesia recovery time, sufentanil dosage, and vasoactive drugs among all groups. The amount of propofol in Group B and D was less than that in Group A and C (P < .05), and there was no difference between Group B and D, A and C (P > .05). The amount of remifentanil in Group B, C, and D was less than that in Group A (P < .05), and Group D was less than B and C (P < .05). After extubation, HR and MAP were significantly higher than before (P < .05). Compared with T0, HR and MAP increased in each group at T4, but MAP and HR in Group D increased the least (P < .05). There were significant differences between Group B, C, D, and A, MAP and HR fluctuated little during extubation (P < .05), but there was a significant difference between Group D and B, C (P < .05). Visual analog scale scores of Group B, C, and D were lower than those of A at 1, 6, and 12 hours after surgery (P < .05), and there was a significant difference between Group D, and B, C (P < .05). Ramsay scores in Group B and D were higher than those in A and C at 1 and 6 hours after the operation (P < .05). There was no difference in the incidence of adverse reactions among groups.

CONCLUSION

The prophylactic use of ketorolac tromethamine and dezocine before laparoscopic inguinal hernia repair can reduce hemodynamic disorder during anesthesia recovery, increase postoperative sedative and analgesic effects.

Effects of Preoperative Electroacupuncture on Remifentanil-Induced Post-Infusion Hyperalgesia in Patients Undergoing Thyroidectomy: A Double-Blind Randomized Controlled Trial

Objective

Electroacupuncture (EA) delivered one day before surgery could reduce postoperative pain. Remifentanil-induced post-infusion hyperalgesia (RPH) was occurred after exposure to high-dose remifentanil. This study aimed to investigate the effects of preoperative EA on RPH in patients undergoing thyroidectomy.

Methods

A total of 80 patients who were scheduled to undergo elective thyroidectomy were randomly assigned to two groups: an EA group and a sham EA (SEA) group. EA was delivered at the Zusanli (ST36) and Neiguan (PC6) acupoints 24 h before the surgery. To ensure uniformity across all patients, remifentanil was administered at the same set rate (0.3 μg/kg/min) to all patients. Mechanical pain thresholds were recorded by an electronic von Frey device around the skin incision and on the arm before surgery as well as at 30 min and 6, 24, and 48 h after surgery.

Results

At 30 min and 6 h after surgery, the EA group showed considerably greater mechanical pain thresholds surrounding the surgical site compared with the SEA group. At 30 min and 6 h after surgery, the patients in the SEA group showed a greater incidence of postoperative hyperalgesia surrounding the surgical site than those in the EA group. At 24 and 48 h after surgery, no significant differences were found between the two groups, although the pain intensity of the EA group was less than that of the SEA group. There were also no substantial differences between the two groups in the frequency of postoperative adverse reactions and rescue analgesia needed.

Conclusion

EA administered 24 h before surgery could alleviate RPH in patients undergoing thyroidectomy.

The Effect of Dexmedetomidine on Postanesthesia Care Unit Discharge and Recovery: A Systematic Review and Meta-Analysis

BACKGROUND

Current evidence on the effect of dexmedetomidine in early postoperative recovery is limited. We conducted a systematic review to evaluate the effect of dexmedetomidine on the length of stay (LOS) and recovery profile in postanesthesia care unit (PACU) patients.

METHODS

The study protocol is registered on International Prospective Register of Systematic Reviews (PROSPERO; CRD42021240559). No specific funding or support was received. We conducted searches in MEDLINE, Embase, PubMed, and Cochrane Library to March 31, 2021 for peer-reviewed randomized controlled studies comparing adult patients who received intravenous dexmedetomidine and placebo undergoing noncardiac, nonneurosurgical procedures under general anesthesia. All studies reporting statistics relating to the duration of stay in the recovery ward or PACU, the primary outcome, were included. We performed individual random-effect meta-analysis on the primary and secondary outcomes (time to extubation, emergence agitation, cough, pain, postoperative nausea and vomiting, shivering, residual sedation, bradycardia, and hypotension) using Stata version 17.0. Evidence was synthesized as mean difference (MD) and risk ratio (RR) for continuous and dichotomous variables, respectively. The quality of evidence was assessed using the revised Cochrane risk-of-bias tool for randomized trials (RoB 2) tool and Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

RESULTS

Thirty-three studies including 2676 patients were eligible for analysis. All studies had low risk or some concerns of overall bias and provided low-to-high certainty evidence for all studied outcomes. Dexmedetomidine was not associated with a significantly increased PACU LOS (MD, 0.69 minute; 95% confidence interval [CI], -1.42 to 2.81 minutes). It was associated with a statistically but not clinically significant prolonged time to extubation (MD, 1 minute; 95% CI, 0.32-1.68 minutes). Dexmedetomidine was associated with significantly reduced incidence of emergence agitation (RR, 0.38; 95% CI, 0.29-0.52), cough (RR, 0.69; 95% CI, 0.61-0.79), pain (RR, 0.50; 95% CI, 0.32-0.80), postoperative nausea and vomiting (RR, 0.54; 95% CI, 0.33-0.86), and shivering (RR, 0.24; 95% CI, 0.12-0.49) in PACU. There was an increased incidence of hypotension (RR, 5.39; 95% CI, 1.12-5.89) but not residual sedation (RR, 1.23; 95% CI, 0.20-7.56) or bradycardia (RR, 5.13; 95% CI, 0.96-27.47) in the dexmedetomidine group.

CONCLUSIONS

The use of dexmedetomidine did not increase the duration of PACU LOS but was associated with reduced emergence agitation, cough, pain, postoperative nausea and vomiting, and shivering in PACU. There was an increased incidence of hypotension but not residual sedation or bradycardia in PACU.

Artesunate Reduces Remifentanil-induced Hyperalgesia and Peroxiredoxin-3 Hyperacetylation via Modulating Spinal Metabotropic Glutamate Receptor 5 in Rats

The experimental investigations on the pathogenesis of remifentanil-induced hyperalgesia (RIH) have been primarily conducted, but the effective treatment of RIH remains unclear. Recent reports highlight the necessity of ionotropic glutamate receptors in oxidative damage in spinal nociceptive transduction. Artesunate, the 1st-line anti-malaria drug, has been identified to be valid in removing superoxide in several pathological conditions. This study evaluated whether artesunate inhibits RIH via regulating metabotropic glutamate receptor 5 (mGluR5) and mitochondrial antioxidant enzyme peroxiredoxin-3 in rats. Artesunate was injected intrathecally 10 min before intravenous infusion of remifentanil (1 μg·kg^-1·min^-1 for 60 min) in rats. The antinociception of artesunate was verified by assessment of paw withdrawal mechanical threshold and paw withdrawal thermal latency. Spinal mGluR5 expression and peroxiredoxin-3 hyperacetylation were examined. Also, both the mGluR5 agonist DHPG and antagonist MPEP were utilized to explore the involvement of mGluR5 in the anti-hyperalgesic property of artesunate. Here, we found that artesunate (10 μg and 100 μg but not 1 μg) prevented RIH in a dose-dependent manner. Artesunate reduced remifentanil-related spinal over-expression of mGluR5 gene and protein, and hyperacetylation of peroxiredoxin-3. Intrathecal application of MPEP (10 nmol and 100 nmol but not 1 nmol) inhibited behavioral RIH and peroxiredoxin-3 acetylation. Moreover, hyperalgesia and peroxiredoxin-3 hyperacetylation were attenuated after the combination of artesunate (1 μg) and MPEP (1 nmol). Additionally, artesunate treatment reversed acute pain and peroxiredoxin-3 hyperacetylation following spinal exposure to DHPG. In conclusion, intrathecal injection of artesunate impairs RIH by down-regulating spinal mGluR5 expression and peroxiredoxin-3 hyperacetylation-mediated oxidative stress in rats.