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

Low-dose remifentanil as an adjunct analgesic is not associated with clinically important opioid-induced hyperalgesia: secondary analysis from a randomized controlled trial

BACKGROUND

Remifentanil, as the primary opioid or in high doses, is associated with opioid-induced hyperalgesia. We assessed outcomes of pain and opioid use with low-dose remifentanil as an adjunct analgesic after same-day surgeries.

METHODS

This prospective cohort study was nested within a randomized controlled trial showing no difference in achieving satisfactory analgesia in the postanesthetic care unit with morphine or hydromorphone. Primary outcomes were pain scores in the postanesthetic care unit and 24 hours after surgery between patients who received remifentanil (R group) or those who received non-remifentanil opioid regimens (C group). We also evaluated pain scores in the day surgical unit, dose of long-acting opioids, and need for non-steroidal anti-inflammatory drugs. The association of remifentanil dose with outcomes was explored using linear regression.

RESULTS

Patients in both groups (R=276, C=126) had comparable baseline characteristics. There were no differences in maximum postanesthetic care unit pain scores or average pain scores 24 hours after surgery: mean difference 0.3 (95% CI -0.9 to 0.2) and 0.4 (95% CI -1.7 to 0.9), respectively. In the R group, the dose of long-acting opioids in postanesthetic care unit was higher: mean difference 0.97 mg (95% CI 0.2 to 1.7) intravenous morphine equivalents, p=0.01. Adjusted analyses indicated that higher doses of remifentanil (25 mcg increments) were associated with higher maximum pain scores in day surgical unit: 0.23 units (95% CI 0.05 to 0.41), p=0.01; higher average pain scores 24 hours after surgery: 0.25 units (95% CI 0.036 to 0.46), p=0.02; and higher long-acting opioid doses in postanesthetic care unit: 0.14 mg intravenous morphine equivalents (95% CI 0.02 to 0.25), p=0.02.

CONCLUSION

Opioid-induced hyperalgesia and increased opioid requirement after low-dose remifentanil use is unlikely to be clinically significant.

TRIAL REGISTRATION NUMBER

NCT02223377.

Remifentanil-induced inflammation in microglial cells: Activation of the PAK4-mediated NF-κB/NLRP3 pathway and onset of hyperalgesia

BACKGROUND

The perioperative use of remifentanil is associated with postoperative hyperalgesia, which can impair recovery and extend hospitalization. Recent studies have revealed that microglia-mediated activation of the NLRP3 inflammasome plays a critical role in opioid-induced hyperalgesia, with NF-κB acting as a pivotal activation point for NLRP3. Despite these findings, the specific molecular mechanisms underlying remifentanil-induced postoperative hyperalgesia remain unclear. This study aims to develop a model of remifentanil-induced hyperalgesia and investigate the molecular mechanisms, focusing on the NF-κB/NLRP3 pathway, using both in vitro and in vivo approaches.

METHOD

We established a remifentanil-induced hyperalgesia model and performed proteomic analysis to identify differential protein expression in the spinal cord tissue of rats. NLRP3 or PAK4 antagonists were administered intrathecally in vivo, and mechanical pain thresholds in the hind paws were measured using Von Frey testing. In vitro, we applied NLRP3 or PAK4 inhibitors or used lentivirus infection to silence PAK4, NF-κB, and NLRP3 genes. Protein expression was assessed through immunohistochemistry, immunofluorescence, and Western blotting. Additionally, ELISA was performed to measure IL-1β and IL-18 levels, and RT-qPCR was conducted to evaluate the transcription of target genes.

RESULTS

Proteomic analysis revealed that remifentanil upregulates PAK4 protein in spinal cord tissue two hours after the surgery. In addition, remifentanil induces morphological changes in the spinal cord dorsal horn, characterized by increased expression of PAK4, p-p65, NLRP3 and Iba-1 proteins, which in turn leads to elevated IL-1β and IL-18 levels and an inflammatory response. Intrathecal injection of NLRP3 or PAK4 inhibitors mitigates remifentanil-induced hyperalgesia and associated changes. In vitro, downregulation of PAK4 inhibits the increase in PAK4, p-p65, NLRP3 and Caspase-1 induced by LPS. Conversely, the downregulation of NLRP3 does not impact the levels of PAK4 and p-p65 proteins, aligning with the in vivo results and suggesting that PAK4 acts as an upstream signaling molecule of NLRP3.

CONCLUSION

Remifentanil can increase PAK4 expression in spinal cord dorsal horn cells by activating the NF-κB/NLRP3 pathway and mediating microglial activation, thereby contributing to postoperative hyperalgesia.

Remifentanil-induced hyperalgesia: the current state of affairs

Remifentanil-induced hyperalgesia (RIH) is a part of a general opioid-induced hyperalgesia (OIH) syndrome, seemingly resulting from abrupt cessation of continuous remifentanil infusion at rates equal or exceeding 0.3 mcg/kg/min. The intricate mechanisms of its development are still not completely understood. However, hyperactivation of the N -methyl d -aspartate receptor system, descending spinal facilitation and increased concentration of dynorphin (a κ-opioid ligand) are commonly proposed as possible mechanisms. Several ways of prevention and management have been suggested, such as slow withdrawal of remifentanil infusion, the addition of propofol, pretreatment with or concomitant administration of ketamine, buprenorphine, cyclooxygenase-2 inhibitors (NSAIDs), methadone, dexmedetomidine. In clinical and animal studies, these strategies exhibited varying success, and many are still being investigated.

Treating pain in patients with Ehlers-Danlos syndrome : Multidisciplinary management of a multisystemic disease

BACKGROUND

The clinical picture of people with Ehlers-Danlos syndromes (EDS) is complex and involves a variety of potential causes of pain. This poses major challenges to patients and healthcare professionals alike in terms of diagnosis and management of the condition.

OBJECTIVES

The aim of the article was to provide an overview of the specific pain management needs of patients with EDS and address their background.

MATERIAL AND METHODS

A selective literature search was performed to highlight the current state of research on pain management in EDS patients.

RESULTS

Affected patients require multimodal pain management considering their individual needs, disease-specific features, and comorbidities.

CONCLUSION

Medical awareness and evidence need to be further improved to enhance the medical care situation of these patients with complex needs.

Ultrasound-guided pericapsular nerve group (PENG) block for early analgesia in elderly patients with hip fractures: a single-center prospective randomized controlled study

BACKGROUND

The aim of this study was to compare the efficacy of ultrasound-guided PENG (pericapsular nerve group) block and drug therapy with intravenous flurbiprofen for early analgesia in elderly patients with hip fractures after hospitalization.

METHODS

This is a single-center, observer-blinded, prospective, randomized, controlled trial. A total of 41 elderly patients (aged 60 or older) with hip fractures were enrolled in the current study. Patients were randomly assigned to two groups: Group P (ultrasound-guided PENG block, 20 mL of 0.375% ropivacaine) and Group F (intravenous flurbiprofen 50 mg). The primary outcome measure was the dynamic (passive straight leg raising 15°) NRS (numerical rating scale 0 to 10) pain scores at different time points. The secondary outcomes were the static NRS scores at different time points, the number of rescue analgesia sessions, patient satisfaction, and the incidence of complications.

RESULTS

Patients in the two groups had comparable baseline characteristics. The group P had lower dynamic and static NRS scores at 15 min, 30 min, 6 h, and 12 h after intervention (P<0.05) than the group F. The highest NRS pain scores in the group P were still lower than the NRS scores in the group F at 30 min-12 h (Group F: 5.57±1.54 vs. Group P: 3.00±1.12, P<0.001), and there was no significant difference between the two groups at 12-24 h (Group F: 6.35±1.79 vs. Group P: 5.90±1.83, P>0.05). The group P had higher satisfaction scores (Group P: 9 (9,9) vs. Group F: 8 (7,8), P<0.001). There was no statistically significant difference in the number of rescue analgesics at 0-12 h or 12-24 h or the incidence of complications between the groups.

CONCLUSIONS

Compared with intravenous flurbiprofen, ultrasound-guided PENG block provides better early analgesic effects in elderly patients with hip fractures, and a PENG block is safe for elderly patients with hip fractures after hospitalization. Trial registration This study was registered in the Chinese Clinical Trial Testing Center (ID: ChiCTR2200062400).

Trajectory of pain threshold and its association with acute pain after thoracic surgery: a prospective observational study

BACKGROUND

Postoperative analgesic management is an ongoing challenge. The pain threshold (PT) is an objective index that reflects the body's sensitivity to pain and can be used for quantitative pain assessment. We hypothesized that the PT is correlated with postoperative pain and can thus be used to guide postoperative pain management.

METHODS

This study involved 93 patients who underwent thoracoscopic surgery from December 2019 to February 2020. The PT was measured with transcutaneous electrical stimulation before surgery (T0) and at 1 h (T1), 6 h (T6), and 24 h (T24) after surgery. The visual analogue scale (VAS) score was used to evaluate the severity of postoperative pain at the same time. The PT variation (PTV) after surgery was calculated as the ratio of the postoperative PT to preoperative PT.

RESULTS

The postoperative PT was higher than the preoperative PT and showed a downward trend within 24 h after surgery; the PTV also showed a downward trend within 24 h after surgery. PT-T1 was negatively correlated with VAS-T1 at rest and during motion (rest: VAS-T1r = - 0.274, P = 0.008; motion: VAS-T1r = - 0.298, P = 0.004). PTV-T1 was negatively correlated with VAS-T1 during motion (r = - 0.213, P = 0.04). Lower VAS-T1 scores (< 4) at rest and during motion were associated with higher PT-T1 (rest: t = 2.452, P = 0.016; motion: t = 2.138, P = 0.035). The intraoperative sufentanil dose was associated with a postoperative increase in PTV-T1. Increased rescue analgesic administration was associated with PTV elevation. However, the incidence of dizziness in patients with moderate PTV-T24 was lower than that in patients with high or low PTV-T24 (χ2 = 8.297, P = 0.015).

CONCLUSIONS

The postoperative PT was higher than the preoperative PT and showed a downward trend within 24 h after surgery; PTV also showed a downward trend within 24 h after surgery. The PT and PTV were negatively correlated with the pain intensity at rest and during motion and were associated with perioperative analgesic consumption and the incidence of adverse events.