Intra-operative remifentanil might influence pain levels in the immediate post-operative period after major abdominal surgery

Postoperative pain after different doses of remifentanil infusion during anaesthesia: a meta-analysis

BACKGROUND

This meta-analysis aimed to explore the correlation between the different doses of remifentanil-based anaesthesia and postoperative pain in randomised trials.

METHODS

The electronic databases including PubMed, Cochrane, clinical trial registries, and Google Scholar were searched up to November 2022 for randomised controlled trials (RCTs) that assessed the dose dependent efficacy of remifentanil for postoperative pain intensity and hyperalgesia.

RESULTS

31 studies involving 2019 patients were included for analysis. Compared with the high remifentanil dose administration, patients in low doses showed less postoperative pain intensity at 1-2 h (weighted mean differences (WMD): 0.60, 95% CI, 0.05 to 1.15), 3-8 h (WMD: 0.38, 95% CI, 0.00 to 0.75), 24 h (WMD: 0.26, 95% CI, 0.04 to 0.48) and 48 h (WMD: 0.32, 95% CI, 0.09 to 0.55). Remifentanil-free regimen failed to decrease the pain score at 24 h (WMD: 0.10, 95% CI, -0.10 to 0.30) and 48 h (WMD: 0.15, 95% CI, -0.22 to 0.52) in comparison with remifentanil-based anaesthesia. After excluding trials with high heterogeneity, the dose of the remifentanil regimen was closely correlated with the postoperative pain score (P=0.03). In addition, the dose of the remifentanil regimen was not associated with the incidence of postoperative nausea and vomiting (PONV) (P=0.37).

CONCLUSIONS

Our meta-analysis reveals that the low dose of remifentanil infusion is recommendable for general anaesthesia maintenance. No evidence suggests that remifentanil-free regimen has superiority in reducing postoperative pain. Moreover, remifentanil doesn't have a dose dependent effect in initiating PONV.

TRIAL REGISTRATION

The protocol of present study was registered with PROSPERO (CRD42022378360).

Total opioid-free general anaesthesia can improve postoperative outcomes after surgery, without evidence of adverse effects on patient safety and pain management: A systematic review and meta-analysis

BACKGROUND

Opioid-based treatment is used to manage stress responses during surgery and postoperative pain. However, opioids have both acute and long-term side effects, calling for opioid-free anaesthetic strategies. This meta-analysis compares adverse events, postoperative recovery, discharge time from post-anaesthesia care unit, and postoperative pain, nausea, vomiting, and opioid consumption between strict opioid-free and opioid-based general anaesthesia.

METHODS

We conducted a systematic review and meta-analysis. We searched PubMed, Embase, Cinahl, Cochrane Library, selected reference lists, and Google Scholar. We included randomised controlled trials (RCTs) published between January 2000 and February 2021 with at least one opioid-free study arm, i.e. no opioids administered preoperatively, during anaesthesia induction, before skin closure, or before emergence from anaesthesia.

RESULTS

The study comprised 1934 patients from 26 RCTs. Common interventions included laparoscopic gynaecological surgery, upper gastrointestinal surgery, and breast surgery. There is firm evidence that opioid-free anaesthesia significantly reduced adverse postoperative events (OR 0.32, 95% CI 0.22 to 0.46, I²  = 56%, p < 0.00001), mainly driven by decreased nausea (OR 0.27, (0.17 to 0.42), p < 0.00001) and vomiting (OR 0.22 (0.11 to 0.41), p < 0.00001). Postoperative opioid consumption was significantly lower in the opioid-free group (-6.00 mg (-8.52 to -3.48), p < 0.00001). There was no significant difference in length of post-anaesthesia care unit stay and overall postoperative pain between groups.

CONCLUSIONS

Opioid-free anaesthesia can improve postoperative outcomes in several surgical settings without evidence of adverse effects on patient safety and pain management. There is a need for more evidence-based non-opioid anaesthetic protocols for different types of surgery as well as postoperative phases.

Postoperative Pain Management in Pediatric Spinal Fusion Surgery for Idiopathic Scoliosis

This article reviews and summarizes current evidence and knowledge gaps regarding postoperative analgesia after pediatric posterior spine fusion for adolescent idiopathic scoliosis, a common procedure that results in severe acute postoperative pain. Inadequate analgesia may delay recovery, cause patient dissatisfaction, and increase chronic pain risk. Despite significant adverse effects, opioids are the analgesic mainstay after scoliosis surgery. However, growing emphasis on opioid minimization and enhanced recovery has increased adoption of multimodal analgesia (MMA) regimens. While opioid adverse effects remain a concern, MMA protocols must also consider risks and benefits of adjunct medications. We discuss use of opioids via different administration routes and elaborate on the effect of MMA components on opioid/pain and recovery outcomes including upcoming regional analgesia. We also discuss risk for prolonged opioid use after surgery and chronic post-surgical pain risk in this population. Evidence supports use of neuraxial opioids at safe doses, low-dose ketorolac, and methadone for postoperative analgesia. There may be a role for low-dose ketamine in those who are opioid-tolerant or have chronic pain, but the evidence for preoperative gabapentinoids and intravenous lidocaine is currently insufficient. There is a need for further studies to evaluate pediatric-specific optimal MMA dosing regimens after scoliosis surgery. Questions remain regarding how best to prevent acute opioid tolerance, opioid-induced hyperalgesia, and chronic postsurgical pain. We anticipate that this timely update will enable clinicians to develop efficient pain regimens and provide impetus for future research to optimize recovery outcomes after spine fusion.

Femoral versus Multiple Nerve Blocks for Analgesia after Total Knee Arthroplasty

BACKGROUND

The PROSPECT (Procedure-Specific Postoperative Pain Management) Group recommended a single injection femoral nerve block in 2008 as a guideline for analgesia after total knee arthroplasty. Other authors have recommended the addition of sciatic and obturator nerve blocks. The lateral femoral cutaneous nerve is also involved in pain syndrome following total knee arthroplasty. We hypothesized that preoperative blocking of all four nerves would offer superior analgesia to femoral nerve block alone.

METHODS

This is a prospective, randomized, controlled, and observer-blinded clinical study. A total of 107 patients were randomly assigned to one of three groups: a femoral nerve block group, a multiple nerve block group, and a control group. All patients were treated postoperatively using patient-controlled intravenous analgesia with morphine. Pain intensity at rest, during flexion and extension, and morphine consumption were compared between groups over three days.

RESULTS

A total of 90 patients completed the study protocol. Patients who received multiple nerve blocks experienced superior analgesia and had reduced morphine consumption during the postoperative period compared to the other two groups. Pain intensity during flexion was significantly lower in the "blocks" groups versus the control group. Morphine consumption was significantly higher in the control group.

CONCLUSIONS

Pain relief after total knee arthroplasty immediately after surgery and on the first postoperative day was significantly superior in patients who received multiple blocks preoperatively, with morphine consumption significantly lower during this period. A preoperative femoral nerve block alone produced partial and insufficient analgesia immediately after surgery and on the first postoperative day. (Clinical trial registration number (NIH): NCT01303120).

Intrathecal morphine versus intravenous opioid administration to impact postoperative analgesia in hepato-pancreatic surgery: a randomized controlled trial

PURPOSE

Inadequate analgesia following abdominal surgery may affect outcome. Data in patients undergoing liver surgery suggested that postoperative coagulopathy might delay epidural catheter removal. Thus, alternative analgesic techniques should be evaluated.

METHODS

We compared the analgesic efficacy of intraoperative intrathecal morphine [single injection 4 µg/kg before skin incision (ITM group, n = 23)] to intravenous opioids [iv remifentanil infusion during surgery followed by i.v. bolus of morphine, 0.15 mg/kg before the end of surgery (IVO group, n = 26)]. Forty-nine adult patients undergoing elective open resection of liver or pancreas lesions in the Tel Aviv Medical Center were randomized into the two analgesic protocols. Postoperatively both groups received i.v. morphine via a patient-controlled analgesia pump. Follow-up was till the 3rd postoperative day (POD).

RESULTS

There was no significant difference in demographics and intraoperative data between groups. The primary outcome, pain scores on movement, was significantly worse in the IVO group when compared with the ITM group at various time points till POD3. In the secondary outcomes - need for rescue drugs - the IVO group required significantly more rescue morphine boluses. Complication related to the analgesia and recovery parameters were similar between groups.

CONCLUSIONS

The findings suggest that a single dose of ITM before hepatic/pancreatic surgery may offer better postoperative pain control than i.v. opioid administration during surgery. This beneficial effect is maintained throughout the first three PODs and is not associated with a higher complication rate; neither did it influence recovery parameters. ITM provides an appropriate alternative to i.v. morphine during major abdominal surgery.

Morphine amplifies mechanical allodynia via TLR4 in a rat model of spinal cord injury

Central neuropathic pain (CNP) is a pervasive, debilitating problem that impacts thousands of people living with central nervous system disorders, including spinal cord injury (SCI). Current therapies for treating this type of pain are ineffective and often have dose-limiting side effects. Although opioids are one of the most commonly used CNP treatments, recent animal literature has indicated that administering opioids shortly after a traumatic injury can actually have deleterious effects on long-term health and recovery. In order to study the deleterious effects of administering morphine shortly after trauma, we employed our low thoracic (T13) dorsal root avulsion model (Spinal Neuropathic Avulsion Pain, SNAP). Administering a weeklong course of 10mg/kg/day morphine beginning 24h after SNAP resulted in amplified mechanical allodynia. Co-administering the non-opioid toll-like receptor 4 (TLR4) antagonist (+)-naltrexone throughout the morphine regimen prevented morphine-induced amplification of SNAP. Exploration of changes induced by early post-trauma morphine revealed that this elevated gene expression of TLR4, TNF, IL-1β, and NLRP3, as well as IL-1β protein at the site of spinal cord injury. These data suggest that a short course of morphine administered early after spinal trauma can exacerbate CNP in the long term. TLR4 initiates this phenomenon and, as such, may be potential therapeutic targets for preventing the deleterious effects of administering opioids after traumatic injury.

Differential Postoperative Effects of Volatile Anesthesia and Intraoperative Remifentanil Infusion in 7511 Thyroidectomy Patients: A Propensity Score Matching Analysis

Although remifentanil is used widely by many clinicians during general anesthesia, there are recent evidences of opioid-induced hyperalgesia as an adverse effect. This study aimed to determine if intraoperative remifentanil infusion caused increased pain during the postoperative period in patients who underwent a thyroidectomy. A total of 7511 patients aged ≥ 20 years, who underwent thyroidectomy between January 2009 and December 2013 at the Asan Medical Center were retrospectively analyzed. Enrolled patients were divided into 2 groups: group N (no intraoperative remifentanil and only volatile maintenance anesthesia) and group R (intraoperative remifentanil infusion including total intravenous anesthesia and balanced anesthesia). Following propensity score matching analysis, 2582 patients were included in each group. Pain scores based on numeric rating scales (NRS) were compared between the 2 groups at the postoperative anesthetic care unit and at the ward until 3 days postoperation. Incidences of postoperative complications, such as nausea, itching, and shivering were also compared. The estimated NRS pain score on the day of surgery was 5.08 (95% confidence interval [CI] 4.97-5.19) in group N patients and 6.73 (95% CI 6.65-6.80) in group R patients (P < 0.001). There were no statistically significant differences in NRS scores on postoperative days 1, 2, and 3 between the 2 groups. Postoperative nausea was less frequent in group R (31.4%) than in group N (53.5%) (P < 0.001). However, the incidence of itching was higher in group R (4.3%) than in group N (0.7%) (P < 0.001). Continuous infusion of remifentanil during general anesthesia can cause higher intensity of postoperative pain and more frequent itching than general anesthesia without remifentanil infusion immediately after thyroidectomy. Considering the advantages and disadvantages of continuous remifentanil infusion, volatile anesthesia without opioid may be a good choice for minor surgeries, such as thyroidectomy.

The therapeutic potential of interleukin-10 in neuroimmune diseases

Neuroimmune diseases have diverse symptoms and etiologies but all involve pathological inflammation that affects normal central nervous system signaling. Critically, many neuroimmune diseases also involve insufficient signaling/bioavailability of interleukin-10 (IL-10). IL-10 is a potent anti-inflammatory cytokine released by immune cells and glia, which drives the regulation of a variety of anti-inflammatory processes. This review will focus on the signaling pathways and function of IL-10, the current evidence for insufficiencies in IL-10 signaling/bioavailability in neuroimmune diseases, as well as the implications for IL-10-based therapies to treating such problems. We will review in detail four pathologies as examples of the common etiologies of such disease states, namely neuropathic pain (nerve trauma), osteoarthritis (peripheral inflammation), Parkinson's disease (neurodegeneration), and multiple sclerosis (autoimmune). A number of methods to increase IL-10 have been developed (e.g. protein administration, viral vectors, naked plasmid DNA, plasmid DNA packaged in polymers to enhance their uptake into target cells, and adenosine 2A agonists), which will also be discussed. In general, IL-10-based therapies have been effective at treating both the symptoms and pathology associated with various neuroimmune diseases, with more sophisticated gene therapy-based methods producing sustained therapeutic effects lasting for several months following a single injection. These exciting results have resulted in IL-10-targeted therapeutics being positioned for upcoming clinical trials for treating neuroimmune diseases, including neuropathic pain. Although further research is necessary to determine the full range of effects associated with IL-10-based therapy, evidence suggests IL-10 may be an invaluable target for the treatment of neuroimmune disease. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.

Assessment of morphine-induced hyperalgesia and analgesic tolerance in mice using thermal and mechanical nociceptive modalities

Opioid-induced hyperalgesia and tolerance severely impact the clinical efficacy of opiates as pain relievers in animals and humans. The molecular mechanisms underlying both phenomena are not well understood and their elucidation should benefit from the study of animal models and from the design of appropriate experimental protocols.

We describe here a methodological approach for inducing, recording and quantifying morphine-induced hyperalgesia as well as for evidencing analgesic tolerance, using the tail-immersion and tail pressure tests in wild-type mice. As shown in the video, the protocol is divided into five sequential steps. Handling and habituation phases allow a safe determination of the basal nociceptive response of the animals. Chronic morphine administration induces significant hyperalgesia as shown by an increase in both thermal and mechanical sensitivity, whereas the comparison of analgesia time-courses after acute or repeated morphine treatment clearly indicates the development of tolerance manifested by a decline in analgesic response amplitude. This protocol may be similarly adapted to genetically modified mice in order to evaluate the role of individual genes in the modulation of nociception and morphine analgesia. It also provides a model system to investigate the effectiveness of potential therapeutic agents to improve opiate analgesic efficacy.

Intraoperative use of remifentanil and opioid induced hyperalgesia/acute opioid tolerance: systematic review

INTRODUCTION

The use of opioids has been increasing in operating room and intensive care unit to provide perioperative analgesia as well as stable hemodynamics. However, many authors have suggested that the use of opioids is associated with the expression of acute opioid tolerance (AOT) and opioid-induced hyperalgesia (OIH) in experimental studies and clinical observations in dose and/or time dependent exposure even when used within the clinically accepted doses. Recently, remifentanil has been used for pain management during anesthesia as well as in the intensive care units because of its rapid onset and offset.

OBJECTIVES

Search of the available literature to assess remifentanil AOT and OIH based on available published data.

METHODS

We reviewed articles analyzing remifentanil AOT and OIH, and focused our literature search on evidence based information. Experimental and clinical studies were identified using electronic searches of Medline (PubMed, Ovid, Springer, and Elsevier, ClinicalKey).

RESULTS

Our results showed that the development of remifentanil AOT and OIH is a clinically significant phenomenon requiring further research.

DISCUSSIONS AND CONCLUSIONS

AOT - defined as an increase in the required opioid dose to maintain adequate analgesia, and OIH - defined as decreased pain threshold after chronic opioid treatment, should be suspected with any unexplained pain report unassociated with the disease progression. The clinical significance of these findings was evaluated taking into account multiple methodological issues including the dose and duration of opioids administration, the different infusion mode, the co-administrated anesthetic drug's effect, method assessing pain sensitivity, and the repetitive and potentially tissue damaging nature of the stimuli used to determine the threshold during opioid infusion. Future studies need to investigate the contribution of remifentanil induced hyperalgesia to chronic pain and the role of pharmacological modulation to reverse this process.

Phosphorylated CaMKII levels increase in rat central nervous system after large-dose intravenous remifentanil

Background

Postoperative remifentanil-induced pain sensitization is common, but its molecular mechanism remains unclear. Calcium/calmodulin-dependent protein kinase II (CaMKII) has been shown to have a critical role in morphine-induced hyperalgesia. This study was designed to determine how CaMKII phosphorylation and protein expression levels change in the central nervous system of rats with remifentanil-induced hyperalgesia.

Material/Methods

Male Sprague-Dawley^® rats were exposed to large-dose (bolus of 6.0 μg/kg and 2.5 μg/kg/min for 2 hours) intravenous remifentanil to induce post-transfusion hyperalgesia. Levels of phosphorylated CaMKII (P-CaMKII) and total protein of CaMKII (T-CaMKII) were determined at different post-transfusion times by Western blot and immunostaining and were compared with controls.

Results

P-CaMKII increased significantly (P<0.05) at 0, 0.5, and 2 hours. However, P-CaMKII at 5 to 24 hours and T-CaMKII at 0 to 24 hours post-transfusion did not change significantly in rats’ spinal dorsal horn, hippocampus, or primary somatosensory (S1) cortex (n=6 per group). Similarly, immunostaining showed stronger P-CaMKII immunoreactants (P<0.05) and more P-CaMKII- positive cells (P<0.05) in the spinal dorsal horn, CA1 region of the hippocampus, and S1 cortex of rats 0.5 hours post-transfusion compared with the control group treated with 0.9% sodium chloride (n=3 per group).

Conclusions

These results suggest that a temporary rise in the P-CaMKII level in the central nervous system may correlate with remifentanil-induced pain sensitization in the postoperative period.

[Clonidine for remifentanil-induced hyperalgesia: a double-blind randomized, placebo-controlled study of clonidine under intra-operative use of remifentanil in elective surgery of the shoulder]

BACKGROUND

In the postoperative period, α2-adrenergic agonists have an opioid sparing effect. In a previous, experimental study, it was also shown that clonidine attenuates remifentanil-induced hyperalgesia. In this study, we examined under clinical conditions whether early administration of a single dose of clonidine can inhibit remifentanil-induced hyperalgesia in patients undergoing elective surgery of the shoulder and with continuous intraoperative use of remifentanil.

PATIENTS AND METHODS

In this study 40 patients received double-blind and randomized either 150 µg clonidine or placebo intravenously before skin incision. Anaesthesia was maintained with propofol and remifentanil (0.23 ± 0.09 µg/kg body weight/min) and morphine (0.1 mg/kg body weight) was administered 20 min before incision closure. Postoperatively, the patients were given a patient-controlled analgesia pump (PCA) with morphine.

RESULTS

Overall morphine consumption as well as overall assessment of pain with the visual analogue scale in the first 24 h postoperatively did not differ significantly between the groups. Isolated pain scores at 12 h and 24 h were significantly enhanced in the clonidine group (p<0.05).

CONCLUSION

An early single dose of 150 µg of clonidine did not reduce the postoperative morphine consumption and pain scores in patients undergoing elective surgery of the shoulder with remifentanil/propofol-based anaesthesia. After the effect of clonidine has presumably subsided the pain can even increase, therefore further studies with repetitive doses of clonidine should be carried out.

5-hydroxytryptamine type 3 receptor modulates opioid-induced hyperalgesia and tolerance in mice

BACKGROUND

Opioid-induced hyperalgesia (OIH) and tolerance are challenging maladaptations associated with opioids in managing pain. Recent genetic studies and the existing literature suggest the 5-hydroxytryptamine type 3 (5-HT3) receptor participates in these phenomena. The location of the relevant receptor populations and the interactions between the 5-HT3 system and other systems controlling OIH and tolerance have not been explored, however. We hypothesized that 5-HT3 receptors modulate OIH and tolerance, and that this modulation involves the control of expression of multiple neurotransmitter and receptor systems.

METHODS

C57BL/6 mice were exposed to a standardized 4-day morphine administration protocol. The 5-HT3 antagonist ondansetron was administered either during or after the conclusion of morphine administration. Mechanical testing was used to quantify OIH, and thermal tail-flick responses were used to measure morphine tolerance. In other experiments spinal cord and dorsal root ganglion tissues were harvested for analysis of messenger RNA concentrations by real-time polymerase chain reaction or immunochemistry analysis.

RESULTS

The results showed that (1) systemic or intrathecal injection of ondansetron significantly prevented and reversed OIH, but not local intraplantar injection; (2) systemic or intrathecal injection of ondansetron prevented and reversed tolerance; and (3) ondansetron blocked morphine-induced increases of multiple genes relevant to OIH and tolerance in dorsal root ganglion and spinal cord.

CONCLUSIONS

Morphine acts via a 5-HT3-dependent mechanism to support multiple maladaptations to the chronic administration of morphine. Furthermore, the use of 5-HT3 receptor antagonists may provide a new avenue to prevent or reverse OIH and tolerance associated with chronic opioid use.

Long-term potentiation in spinal nociceptive pathways as a novel target for pain therapy

Long-term potentiation (LTP) in nociceptive spinal pathways shares several features with hyperalgesia and has been proposed to be a cellular mechanism of pain amplification in acute and chronic pain states. Spinal LTP is typically induced by noxious input and has therefore been hypothesized to contribute to acute postoperative pain and to forms of chronic pain that develop from an initial painful event, peripheral inflammation or neuropathy. Under this assumption, preventing LTP induction may help to prevent the development of exaggerated postoperative pain and reversing established LTP may help to treat patients who have an LTP component to their chronic pain. Spinal LTP is also induced by abrupt opioid withdrawal, making it a possible mechanism of some forms of opioid-induced hyperalgesia. Here, we give an overview of targets for preventing LTP induction and modifying established LTP as identified in animal studies. We discuss which of the various symptoms of human experimental and clinical pain may be manifestations of spinal LTP, review the pharmacology of these possible human LTP manifestations and compare it to the pharmacology of spinal LTP in rodents.

[Opioid-induced pruritus. Mechanisms and treatment regimens]

Substantial progress has been achieved in recent years in research on the interaction between pain and pruritus. Over and above the known inhibition of pruritus by painful stimuli (e.g. scratching), a foundation for the explanation of opioid-induced pruritus was laid through the discovery of pruritus-specific neuronal processing channels. Although traditionally the degranulating effect of opioids on mast cells was assumed to be the essential mechanism, it is now clear that opioids can also induce itching at the spinal level. Neurons of the dorsal horn of the pain system inhibit spinal itch neurons. If this inhibition is weakened by opioids, the disinhibited itch neurons become active and mediate itching, without stimulation of the primary afferent peripheral nerves. Spinal triggering of itching is observed in particular by activation of mu-opioid receptors (mu-OR), while kappa-OR surprisingly suppress itch. The therapeutic implications of this interaction will be described.

[New substances and applications for postoperative pain therapy]

The onset of postoperative pain is the result of various pathophysiological mechanisms and depends on the type of surgery performed. Therefore, any adequate postoperative pain treatment requires multimodal and procedure-specific analgesia. In addition to reducing perioperative complications and improving patient comfort, optimal postoperative pain management also represents an important quality characteristic which can influence the patient in their choice of hospital. In the past 1-2 years, known groups of substances have been rediscovered for postoperative pain therapy (e.g., Gabapentin and Pregabalin, i.v. Lidocaine, Ketamine or glucocorticoids), while new substances (coxibe, oral oxycodone+naloxone) and applications have been developed. The present overview article discusses the advantages and disadvantages of these substances and analgesic methods, as well as their specific areas of application.

[Remifentanil-based intraoperative anaesthesia and postoperative pain therapy. Is there an optimal treatment strategy?]

Remifentanil is a synthetic opioid derivate with an agonist activity at mu-opioid receptors. The pharmacokinetic profile differs from other synthetic opioids. Remifentanil is rapidly metabolised by unspecific blood and tissue esterases and the metabolites have almost no intrinsic activity. According to its unique pharmacokinetic profile, remifentanil-based anaesthesia might be associated with a high level of postoperative pain, therefore, an appropriate postoperative pain management is an import aspect. In addition, remifentanil withdrawal induces a compensatory up-regulation of secondary messenger pathways, inducing hyperalgesia. This review provides a comprehensive summary of basic and clinical research concerning the intraoperative use of remifentanil and postoperative pain therapy. The relative contribution of rapid degradation and withdrawal-induced hyperalgesia to postoperative pain will be discussed. In addition, this review attempts to identify potential clinical implications and treatment strategies.