Addition of liposomal bupivacaine to standard bupivacaine versus standard bupivacaine alone in the supraclavicular brachial plexus block: a randomized controlled trial.

BACKGROUND: The analgesic effect of adding liposomal bupivacaine to standard bupivacaine in supraclavicular brachial plexus block is not known. We hypothesized that addition of liposomal bupivacaine would reduce acute postoperative pain compared to standard bupivacaine alone. METHODS: A randomized controlled trial was conducted. Patients and outcome assessors were blinded. Eighty patients undergoing distal radial fracture fixation under regional anesthesia with supraclavicular brachial plexus block were randomized into two groups. The liposomal bupivacaine (LB-BPB) group received 10ml of 0.5% plain bupivacaine immediately followed by 10ml of 1.33% liposomal bupivacaine (n=40). The standard bupivacaine (S-BPB) group received 20ml of 0.5% plain bupivacaine (n=40). The primary outcome was weighted area under curve (AUC) numerical rating scale (NRS) pain score at rest over the first 48 hours after surgery. Secondary outcomes included AUC scores for pain with movement, overall benefit with analgesia score (OBAS) and other functional scores. RESULTS: For the primary outcome, LB-BPB group was associated with statistically significantly lower AUC pain score at rest (0.6 vs 1.4, p-value < 0.001) in the first 48 hours. Of the secondary outcomes, no difference between treatment groups reached statistical significance with the exception of AUC score for pain with movement (2.3 vs 3.7, adjusted p-value < 0.001) and OBAS (1.1 vs 1.7, adjusted p-value = 0.020) in the first 48 hours, as well as NRS pain score at rest (0.5 vs 1.9, adjusted p-value < 0.001) and with movement (2.7 vs 4.9, adjusted p-value < 0.001) on postoperative day (POD) 1. Differences in NRS pain scores on POD2, POD3 and POD4 did not reach the level of statistical significance. There were no statistically significant differences in sensory function. CONCLUSION: Liposomal bupivacaine given via supraclavicular brachial plexus block reduced pain at rest in the early postoperative period.

A validation study of the Cantonese Chinese version of short form McGill pain questionnaire 2 in Cantonese-speaking patients with chronic pain in Hong Kong.

OBJECTIVE: The study tests the reliability and validity of the Cantonese Chinese version of Short Form McGill Pain Questionnaire 2 (SF-MPQ-2-CC). METHODS: The original Short Form McGill Pain Questionnaire (SF-MPQ-2) was translated into Cantonese Chinese version. Cantonese-speaking chronic pain patients from three pain centers in Hong Kong were recruited and asked to complete SF-MPQ-2-CC, validated Chinese versions of Identification Pain questionnaire (ID Pain), Pain Catastrophizing Scale (PCS), and Short Form Health Survey (SF-36) for evaluation of convergent and divergent validity, 2 weeks apart for evaluation of internal consistency. RESULTS: A total of 333 and 197 participants completed the first and second set of questionnaires, respectively. SF-MPQ-2-CC was shown to have excellent internal consistency, with an overall Cronbach's alpha value of 0.933. The overall correlation coefficient was 0.875 that shows good test-retest reliability. Construct validity was evaluated using confirmatory factor analysis, where a seconder-order factor model demonstrated a good fit with our data (χ2 = 826.51, p < 0.001, CFI = 0.92, TLI = 0.908, RMSEA = 0.097; SRMR = 0.063; error terms adjusted). SF-MPQ-2-CC also showed good convergent validity with Chinese versions of ID Pain (neuropathic pain) and PCS (continuous pain), and divergent validity was shown by a negative correlation with Chinese version of SF-36. CONCLUSIONS: Our study demonstrated that SF-MPQ-2-CC is a valid and reliable pain assessment tool for Cantonese-speaking patients in Hong Kong with a wide range of chronic pain conditions. It also helps to identify the presence of neuropathic pain and negative pain cognition among respondents.

Molecular Mechanisms and Pathophysiological Pathways of High-Fat Diets and Caloric Restriction Dietary Patterns on Pain.

Pain perception provides evolutionary advantages by enhancing the probability of survival, but chronic pain continues to be a significant global health concern in modern society. Various factors are associated with pain alteration. Accumulating evidence has revealed that obesity correlates with enhanced pain perception, especially in chronic pain individuals. Existing dietary patterns related to obesity are primarily high-fat diets (HFD) and calorie restriction (CR) diets, which induce or alleviate obesity separately. HFD has been shown to enhance nociception while CR tends to alleviate pain when measuring pain outcomes. Herein, this review mainly summarizes the current knowledge of the effects of HFD and CR on pain responses and underlying molecular mechanisms of the immunological factors, metabolic regulation, inflammatory processes, Schwann cell (SC) autophagy, gut microbiome, and other pathophysiological signaling pathways involved. This review would help to provide insights on potential nonpharmacological strategies of dietary patterns in relieving pain.

Analgesic Effect of Buprenorphine for Chronic Noncancer Pain: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

BACKGROUND: Buprenorphine is a partial agonist at the µ-opioid receptor and an antagonist at the delta and kappa opioid receptors. It has high affinity and low intrinsic activity at the µ-opioid receptor. Buprenorphine demonstrates no ceiling effect for clinical analgesia, but demonstrates this for respiratory depression and euphoria. It may provide effective analgesia while producing less adverse effects, making it a promising opioid analgesic. A systematic review and meta-analysis were performed to examine the analgesic efficacy of buprenorphine for patients with chronic noncancer pain. METHODS: PubMed, MEDLNE, Embase, and the Cochrane Library were searched up to January 2022. Randomized controlled trials were included if they compared buprenorphine versus placebo or active analgesic in patients with chronic noncancer pain, where pain score was an outcome. Nonrandomized controlled trials, observational studies, qualitative studies, case reports, and commentaries were excluded. Two investigators independently performed the literature search, study selection, and data collection. A random-effects model was used. The primary outcome was the effect of buprenorphine on pain intensity in patients with chronic noncancer pain based on standardized mean difference (SMD) in pain score. Quality of evidence was assessed using the Grade of Recommendations Assessment, Development, and Evaluation (GRADE) approach. RESULTS: Two separate literature searches were conducted for patients with and without opioid use disorder (OUD). Only one study met the search criteria for those with OUD. Fourteen randomized controlled trials were included for those without OUD. Buprenorphine was associated with reduced pain score (SMD = -0.368, P < .001, I 2 = 89.37%) compared to placebo or active analgesic. Subgroup meta-analyses showed statistically significant differences in favor of buprenorphine versus placebo (SMD = -0.404, P < .001), for chronic low back pain (SMD = -0.383, P < .001), when administered via the transdermal route (SMD = -0.572, P = .001), via the buccal route (SMD = -0.453, P < .001), with length of follow-up lasting <12 weeks (SMD = -0.848, P < .05), and length of follow-up lasting 12 weeks or more (SMD = -0.415, P < .001). There was no significant difference when compared to active analgesic (SMD = 0.045, P > .05). Quality of evidence was low to moderate. CONCLUSIONS: Buprenorphine was associated with a statistically significant and small reduction in pain intensity compared to placebo. Both the transdermal and buccal routes provided pain relief. There was more evidence supporting its use for chronic low back pain.

Efficacy of Peripheral Nerve Field Stimulation for the Management of Chronic Low Back Pain and Persistent Spinal Pain Syndrome: A Narrative Review.

OBJECTIVES: Various approaches have been developed with a view to treating the back pain component in patients with chronic low back pain (CLBP) and persistent spinal pain syndrome (PSPS). Emerging evidence shows that peripheral nerve field stimulation (PNFS) may be an efficacious therapeutic modality against axial low back pain. Hence, the aim of the review was to evaluate the analgesic efficacy and safety of PNFS, when used alone or as an adjunct to spinal cord stimulation (SCS), for managing CLBP and PSPS. MATERIALS AND METHODS: A comprehensive search for clinical studies on PNFS and PNFS + SCS used for the management of CLBP and/or PSPS was performed using PubMed, EMBASE, MEDLINE via Proquest, and Web of Science. RESULTS: A total of 15 studies were included, of which four were randomized controlled trials (RCTs), nine were observational studies, and two were case series. For patients receiving PNFS, a significant decrease in back pain intensity and analgesic consumption, together with a significant improvement in physical functioning, was observed upon implant of the permanent system. Meanwhile, the addition of PNFS to SCS in refractory cases was associated with a significant reduction in back and leg pain, respectively. CONCLUSIONS: This review suggests that PNFS, when used alone or in combination with SCS, appears to be effective in managing back pain. However, high-quality evidence that supports the long-term analgesic efficacy and safety is still lacking. Hence, RCTs with a larger patient population and of a longer follow-up duration are warranted.

Propofol total intravenous anaesthesia versus inhalational anaesthesia for acute postoperative pain in patients with morphine patient-controlled analgesia: a large-scale retrospective study with covariate adjustment.

BACKGROUND: To compare the postoperative analgesic effect of propofol total intravenous anaesthesia (TIVA) versus inhalational anaesthesia (GAS) in patients using morphine patient-controlled analgesia (PCA). METHODS: A retrospective cohort study was performed in a single tertiary university hospital. Adult patients who used PCA morphine after general anaesthesia across 15 types of surgeries were included. Patients who received propofol TIVA were compared to those who had inhalational anaesthesia. Primary outcomes assessed were postoperative numerical rating scale (NRS) pain scores and postoperative opioid consumption. RESULTS: Data from 4202 patients were analysed. The overall adjusted NRS pain scores were significantly lower in patients who received propofol TIVA at rest (GEE: ß estimate of the mean on a 0 to 10 scale = -0.56, 95% CI = (-0.74 to -0.38), p < 0.001; GAS as reference group) and with movement (ß estimate = -0.89, 95% CI = (-1.1 to -0.69), p < 0.001) from postoperative days (POD) 1-3. Propofol TIVA was associated with lower overall adjusted postoperative morphine consumption (ß estimate = -3.45, 95% CI = (-4.46 to -2.44), p < 0.001). Patients with propofol TIVA had lower adjusted NRS pain scores with movement for hepatobiliary/pancreatic (p < 0.001), upper gastrointestinal (p < 0.001) and urological surgeries (p = 0.005); and less adjusted postoperative morphine consumption for hepatobiliary/pancreatic (p < 0.001), upper gastrointestinal (p = 0.006) and urological surgeries (p = 0.002). There were no differences for other types of surgeries. CONCLUSION: Propofol TIVA was associated with statistically significant, but small reduction in pain scores and opioid consumption in patients using PCA morphine. Subgroup analysis suggests clinically meaningful analgesia possibly for hepatobiliary/pancreatic and upper gastrointestinal surgeries. TRIAL REGISTRATION: This study is registered at ClinicalTrials.gov ( NCT03875872 ).

Characterization of acute pain-induced behavioral passivity in mice: Insights from statistical modeling.

Affective-motivational disturbances are highly inconsistent in animal pain models. The reproducibility of the open-field test in assessing anxiety, malaise or disability remains controversial despite its popularity. While traumatic, persistent or multiregional pain models are commonly considered more effective in inducing negative affect or functional impairment, the early psychobehavioral changes before pain chronification are often underexplored. Here, we aimed to clarify the fundamental relationship between hypernociception and passive distress-like behavior using a model of transient inflammatory pain. To minimize latent confounders and increase data consistency, male C57BL/6N mice were habituated to the open-field arena 6 times before receiving the unilateral intraplantar injection of prostaglandin E2 (PGE2) or vehicle. Open-field (40-min exploration) and nociceptive behavior were evaluated repeatedly along the course of hypernociception in both wild-type and transgenic mice with a known pronociceptive phenotype. To reduce subjectivity, multivariate open-field behavioral outcomes were analyzed by statistical modeling based on exploratory factor analyses, which yielded a 2-factor solution. Within 3 hr after PGE2 injection, mice developed significantly reduced center exploration (factor 1) and a marginally significant increase in their habituation tendency (factor 2), which were not apparent in vehicle-injected mice. The behavioral passivity generally improved as hypernociception subsided. Therefore, transient inflammatory irritation is sufficient to suppress mouse open-field exploratory activity. The apparent absence of late affective-motivational changes in some rodents with prolonged hypernociception may not imply a lack of preceding or underlying neuropsychological alterations. Procedural pain after invasive animal experiments, however small, should be assessed and adequately controlled as a potential research confounder.

Preoperative dexamethasone for pain relief after total knee arthroplasty: A randomised controlled trial.

BACKGROUND: Corticosteroids can reduce pain but the optimal dose and safety profiles are still uncertain. OBJECTIVE: This study aimed to evaluate two different doses of dexamethasone for pain management and their side effects after total knee arthroplasty. DESIGN: A prospective randomised, controlled trial. SETTING: A tertiary teaching hospital in Hong Kong. PATIENTS: One hundred and forty-six patients were randomly allocated to one of three study groups. INTERVENTIONS: Before operation, patients in group D8, D16 and P received dexamethasone 8 mg, dexamethasone 16 mg and placebo (0.9% saline), respectively. MAIN OUTCOME MEASURES: The primary outcome was postoperative pain score. Secondary outcomes were opioid consumption, physical parameters of the knees and side effects of dexamethasone. RESULTS: Compared with placebo, group D16 patients had significantly less pain during maximal active flexion on postoperative day 3 [-1.3 (95% CI, -2.2 to -0.31), P = 0.005]. There was also a significant dose-dependent trend between pain scores and dexamethasone dose (P = 0.002). Compared with placebo, patients in group D16 consumed significantly less opioid [-6.4 mg (95% CI, -11.6 to -1.2), P = 0.025] and had stronger quadriceps power on the first three postoperative days (all P < 0.05). They also had significantly longer walking distance on postoperative day 1 [7.8 m ([95% CI, 0.85 to 14.7), P = 0.023] with less assistance during walking on the first two postoperative days (all P < 0.029) and significantly better quality-of-recovery scores on postoperative day 1 (P = 0.018). There were significant dose-dependent trends between all the above parameters and dexamethasone dose (all P < 0.05). No significant differences were found in the incidence of chronic pain or knee function 3, 6 and 12 months postoperatively. CONCLUSION: Dexamethasone 16 mg given before total knee arthroplasty led to a reduction in postoperative pain, less opioid consumption, stronger quadriceps muscle power, better mobilisation and better overall quality-of-recovery after operation. No long-term improvement in reduction in pain and function of the knee was found. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02767882.

Changes in Prevalence, Outcomes, and Help-seeking Behavior of Chronic Pain in an Aging Population Over the Last Decade.

BACKGROUND: Chronic pain is expected to increase as the population ages. This study aimed to investigate the changes in prevalence, patterns, and help-seeking behavior of chronic pain and prevalence of neuropathic pain of an aging population in Hong Kong. METHODS: A cross-sectional, telephone interview with a structured questionnaire was conducted in a randomly selected sample of adults with acute or chronic pain of any kind in the general population to estimate the prevalence of chronic and neuropathic pain, and to describe sociodemographics and help-seeking behavior. Results were compared with a similar study conducted in 1999. RESULTS: Totally, 1,570 people were interviewed. Chronic pain was experienced by 28.7% of all respondents, compared to 10.8% in 1999. Joint (45.5%), muscle (27.1%), and back (25.2%) pain were the most common, similar to findings in 1999. Of those with chronic pain, 83.1% reported pain in more than one body site (63.4% in 1999, P = 0.0023). More respondents reported their average pain as being intense (51.57% vs. 33.0% in 2013 and 1999, respectively, P = 0.0098). A downward trend of respondents taking medications for chronic pain (34.9% in 2013 vs. 47.6% in 1999, P = 0.019) was seen. Neuropathic pain was present in 9.03% of the population and 14.7% of chronic pain sufferers. CONCLUSION: The prevalence of neuropathic pain in Hong Kong is high and is described here for the first time. The number of chronic pain sufferers has tripled in the past decade. Significant changes in the patterns and help- seeking behavior of chronic pain sufferers are also seen.

Cardioprotection from emulsified isoflurane postconditioning is lost in rats with streptozotocin-induced diabetes due to the impairment of Brg1/Nrf2/STAT3 signalling.

Isoflurane postconditioning (IsoPostC) attenuates myocardial ischaemia/reperfusion injury (IRI). Signal transducer and activator of transcription-3 (STAT3) is critical in ischaemic postconditioning cardioprotection, which can be regulated by the Brahma-related gene (Brg1) and nuclear factor-erythroid 2-related factor 2 (Nrf2), although they are both reduced in diabetic hearts. We hypothesized that reduced Brg1/Nrf2 and STAT3 activation may jeopardize IsoPostC-mediated cardioprotection in diabetic hearts. In the present study, Langendorff-perfused, non-diabetic (control) and 8-week-old streptozotocin-induced Type 1 diabetic rat hearts were subjected to 30 min of global ischaemia and 120 min of reperfusion without or with IsoPostC, which was achieved by administering emulsified isoflurane (2.0%, v/v) in Krebs-Henseleit (KH) solution immediately at the onset of reperfusion for 10 min and switching to KH solution perfusion alone thereafter. Cultured H9C2 cells were exposed to normal glucose (NG, 5.5 mM) or high glucose (HG, 30 mM) and subjected to hypoxia/reoxygenation (HR) in the presence or absence of IsoPostC. Diabetic rats displayed larger post-ischaemic myocardial infarction and more severe haemodynamic dysfunction, associated with increased myocardial oxidative stress and reduced cardiac Brg1, Nrf2 and STAT3 phosphorylation/activation (p-STAT3), compared with controls. These changes were reversed/prevented by IsoPostC in control but not in diabetic rats. In H9C2 cells exposed to NG but not HG, IsoPostC significantly attenuated HR-induced cellular injury and superoxide anion production with increased Brg1, Nrf2 and p-STAT3. These beneficial effects of IsoPostC were abolished by Brg1, Nrf2 or STAT3 gene knockdown. Brg1 or Nrf2 gene knockdown abolished IsoPostC-induced STAT3 activation. N-acetylcysteine restored Brg1, Nrf2 and p-STAT3, and IsoPostC-induced protection in H9C2 cells exposed to HG and HR. In conclusion, IsoPostC confers cardioprotection through Brg1/Nrf2/STAT3 signalling, and impairment of this pathway may be responsible for the loss of IsoPostC cardioprotection in diabetes.

Regenerative medicine for the treatment of chronic low back pain: a narrative review.

Low back pain (LBP) is a common and important clinical problem. In addition to pain, patients are also affected by personal, social, and economic burdens. Intervertebral disc (IVD) degeneration is a common cause of LBP, further increasing the patient's morbidity and medical costs. The limitations of current treatment strategies for long-term pain relief mean that increasing attention has been paid to regenerative medicine. We carried out a narrative review to explore the roles of four types of regenerative medicine for treating LBP: marrow-derived stem cells, growth factors, platelet-rich plasma, and prolotherapy. Marrow-derived stem cells are regarded as an ideal cell source for IVD regeneration. Growth factors may stimulate the synthesis of extracellular matrix and attenuate or reverse the degenerative process in IVD, while platelet-rich plasma, which contains multiple growth factors, is thought to be a promising alternative therapy for IVD degeneration. Prolotherapy can initiate the body's inflammatory healing response to repair injured joints and connective tissues. This review summarizes the mechanisms, in vitro and in vivo studies, and clinical applications of these four types of regenerative medicine in patients with LBP.

Use of pain-related gene features to predict depression by support vector machine model in patients with fibromyalgia.

The prevalence rate of depression is higher in patients with fibromyalgia syndrome, but this is often unrecognized in patients with chronic pain. Given that depression is a common major barrier in the management of patients with fibromyalgia syndrome, an objective tool that reliably predicts depression in patients with fibromyalgia syndrome could significantly enhance the diagnostic accuracy. Since pain and depression can cause each other and worsen each other, we wonder if pain-related genes can be used to differentiate between those with major depression from those without. This study developed a support vector machine model combined with principal component analysis to differentiate major depression in fibromyalgia syndrome patients using a microarray dataset, including 25 fibromyalgia syndrome patients with major depression, and 36 patients without major depression. Gene co-expression analysis was used to select gene features to construct support vector machine model. The principal component analysis can help reduce the number of data dimensions without much loss of information, and identify patterns in data easily. The 61 samples available in the database were not enough for learning based methods and cannot represent every possible variation of each patient. To address this issue, we adopted Gaussian noise to generate a large amount of simulated data for training and testing of the model. The ability of support vector machine model to differentiate major depression using microarray data was measured as accuracy. Different structural co-expression patterns were identified for 114 genes involved in pain signaling pathway by two-sample KS test (p < 0.001 for the maximum deviation D = 0.11 > D critical = 0.05), indicating the aberrant co-expression patterns in fibromyalgia syndrome patients. Twenty hub gene features were further selected based on co-expression analysis to construct the model. The principal component analysis reduced the dimension of the training samples from 20 to 16, since 16 components were needed to retain more than 90% of the original variance. The support vector machine model was able to differentiate between those with major depression from those without in fibromyalgia syndrome patients with an average accuracy of 93.22% based on the expression levels of the selected hub gene features. These findings would contribute key information that can be used to develop a clinical decision-making tool for the data-driven, personalized optimization of diagnosing depression in patients with fibromyalgia syndrome.

Individual-level and neighborhood-level shifts in mortality patterns among drug poisoning deaths in a high-density Asian city: a territory-wide, case-only analysis.

BACKGROUND: The shifts in individual-level and neighborhood-level patterns of drug poisoning deaths in a high-density Asian city over time have been underestimated, although they provide essential information for community-based surveillance and interventions. METHODS: A case-only analysis with a 16-y, territory-wide, population-based registry in Hong Kong was applied to compare drug poisoning deaths from 2001 to 2010 with 2011 to 2016. Drug poisoning deaths, deaths from heroin and deaths from other opioids (codeine or morphine) were extracted (ICD codes: T36-T50, T40.1, T40.2). Binomial regressions were used to estimate the shifts in mortality patterns. RESULTS: Among 3069 drug poisoning deaths, a significant shift in mortality patterns was found despite a decreasing mortality trend in Hong Kong. Overall, drug poisoning deaths shifted towards middle-aged/young-old, widowed/divorced, economically active, white collar and non-local born. Since 2011, more deaths from heroin were in older ages and non-local born, but less were never married and economically inactive. More deaths from other opioids were middle-aged, young-old and divorced. In particular, most decedents shifted towards young-old, especially deaths from other opioids. Compared with deaths during 2001-2010, there were 3.72- and 6.50-fold more deaths from heroin and deaths from other opioids in those aged ≥60 y since 2021 (ORs: 3.72 [2.37, 5.86], 6.50 [3.97, 10.65]), respectively. Additionally, drug poisoning deaths shifted towards areas with less neighborhood deprivation (more high-education individuals and a mix of private/public housing residents), especially deaths from other opioids. CONCLUSION: Misuse of registered drugs (e.g. opioid pain relievers) could be a rising trend among vulnerable subpopulations in Hong Kong other than illegal drug use (heroin). Health officials should provide more advice and support on drug information. Specifically, an improved health system with education regarding the appropriate use of registered drugs for medical treatments should be provided to mid-/high-income and local-born individuals.

Central Endothelin-1 Confers Analgesia by Triggering Spinal Neuronal Histone Deacetylase 5 (HDAC5) Nuclear Exclusion in Peripheral Neuropathic Pain in Mice.

The rationale of spinal administration of endothelin-1(ET-1) mediated anti-nociceptive effect has not been elucidated. ET-1 is reported to promote nuclear effluxion of histone deacetylase 5 (HDAC5) in myocytes, and spinal HDAC5 is implicated in modulation of pain processing. In this study, we aimed to investigate whether central ET-1 plays an anti-nociceptive role by facilitating spinal HDAC5 nuclear shuttling under neuropathic pain. Here, we demonstrate that upregulating spinal ET-1 attenuated the nociception induced by partial sciatic nerve ligation surgery and this analgesic effect mediated by ET-1 was attenuated by intrathecal injection of endothelin A receptor selective inhibitor (BQ123) or by blocking the exportation of nuclear HDAC5 by adeno-associated viruses targeting neuronal HDAC5 (AVV-HDAC5 S259/498A Mutant). Notably, ET-1 administration increased spinal glutamate acid decarboxylases (GAD65/67) expression via initiating HDAC5 nuclear exportation and increased the acetylation of histone 3 at lysine 9 (Acetyl-H3K9) in the promotor regions of spinal Gad1 and Gad2 genes. This was reversed by blocking endothelin A receptor function or by inhibiting the spinal neuronal nuclear exportation of HDAC5. Therefore, inducing spinal GABAergic neuronal HDAC5 nuclear exportation may be a novel therapeutic approach for managing neuropathic pain. PERSPECTIVE: Neuropathic pain is intractable in a clinical setting, and epigenetic regulation is considered to contribute to this processing. Characterizing the anti-nociceptive effect of ET-1 and investigating the associated epigenetic mechanisms in animal models may lead to the development of new therapeutic strategies and targets for treating neuropathic pain.

Optimization of opioid utility in cancer pain populations.

In this era of crisis and controversy surrounding opioid therapy, we must remember that cancer patients entrust us with supporting them through what might be the most difficult, and oftentimes final, period of their life. The factors that affect the benefits and risks of opioid use in cancer patients and the non-cancer population are quite different. In fact, opioid-associated deaths are 10 times less likely in the former than the latter population, suggesting that a reluctance to initiate opioids in cancer patients can risk under treatment of complex pain. In this review, we outline the considerations and evidence-based practices required to manage the clinical situations that challenge the judicious use of opioids in patients with cancer. A comprehensive review that enable us to better understand and quantify the root causes of variability in pain control, as well as risks of opioid misuse or abuse, would arm healthcare providers with the tools they need to implement multi-modal approaches to treatment planning.

Analgesic Effects of Cannabinoids for Chronic Non-cancer Pain: a Systematic Review and Meta-Analysis with Meta-Regression.

There is growing interest in using cannabinoids for chronic pain. We performed a systematic review and meta-analysis of randomized controlled trials to evaluate the analgesic efficacy and adverse effects of cannabinoids for chronic non-cancer pain. PubMed, EMBASE, Web of Science, Cochrane CENTRAL and clinicaltrials.gov were searched up to December 2018. Information on the type, dosage, route of administration, pain conditions, pain scores, and adverse events were extracted for qualitative analysis. Meta-analysis of analgesic efficacy was performed. Meta-regression was performed to compare the analgesic efficacy for different pain conditions (neuropathic versus non-neuropathic pain). Risk of bias was assessed by The Cochrane Risk of Bias tool, and the strength of the evidence was assessed using the Grade of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Forty-three randomized controlled trials were included. Meta-analysis was performed for 33 studies that compared cannabinoids to placebo, and showed a mean pain score (scale 0-10) reduction of -0.70 (p < 0.001, random effect). Meta-regression showed that analgesic efficacy was similar for neuropathic and non-neuropathic pain (Difference = -0.14, p = 0.262). Inhaled, oral, and oromucosal administration all provided statistically significant, but small reduction in mean pain score (-0.97, -0.85, -0.45, all p < 0.001). Incidence of serious adverse events was rare, and non-serious adverse events were usually mild to moderate. Heterogeneity was moderate. The GRADE level of evidence was low to moderate. Pain intensity of chronic non-cancer patients was reduced by cannabinoids consumption, but effect sizes were small. Efficacy for neuropathic and non-neuropathic pain was similar.

Total Intravenous Anesthesia (TIVA) With Propofol for Acute Postoperative Pain: A Scoping Review of Randomized Controlled Trials.

Total intravenous anesthesia (TIVA) with propofol may improve acute postoperative pain control compared to inhalational anesthesia. The objective of this review was to comprehensively update and evaluate the existing literature on the analgesic efficacy of propofol TIVA. A systemized literature search for randomized controlled trials in adult patients was conducted in the PubMed and Cochrane CENTRAL (EMBASE source) databases up to August 2019. Clinical trials included compared propofol TIVA against inhalational isoflurane, sevoflurane, or desflurane. Only clinical trials that studied acute postoperative pain scores or analgesic consumption as a primary outcome were included. Sixteen randomized controlled trials were included. Surgical procedures evaluated included: radical gastrectomy, open vein stripping, breast cancer surgery, laparoscopic cholecystectomy, inguinal herniotomy, abdominoplasty, bariatric surgery, lumbar spine surgery, emergency neurosurgical operations, open and laparoscopic gynecological surgeries, and dental surgery. Propofol TIVA was associated with reduced postoperative pain scores and/or decreased opioid consumption in 9 out of 16 clinical trials. There was no difference in 5 clinical trials, and propofol TIVA was associated with worse analgesic outcomes in 2 trials. Propofol TIVA may improve acute postoperative analgesia after surgery, but different factors such as surgical procedures and anesthetic/analgesic techniques may influence its effectiveness.

Dysregulation of EAAT2 and VGLUT2 Spinal Glutamate Transports via Histone Deacetylase 2 (HDAC2) Contributes to Paclitaxel-induced Painful Neuropathy.

Effective treatments for chemotherapy-induced peripheral neuropathy (CIPN) remain unavailable. Given the significance of spinal cord glutamate transporters in neuronal plasticity and central sensitization, this study investigated the role of excitatory amino acid transporter 2 (EAAT2) and vesicular-glutamate transporter 2 (VGLUT2) in the development of paclitaxel-induced painful neuropathy. Paclitaxel (2 mg/kg, i.p., cumulative dose 8 mg/kg) induced long-lasting mechanical allodynia (>28 days) with increased glutamate concentration and decreased EAAT2 expression with no changes in GABA/glycine or VGAT (vesicular GABA transporter) in rat spinal dorsal horn. VGLUT2 expression was upregulated and coexpressed with enhanced synaptophysin, characterizing nociceptive afferent sprouting and new synapse formation of glutamatergic neurons in the spinal cord dorsal horn. HDAC2 and transcription factor YY1 were also upregulated, and their interaction and colocalization were confirmed following paclitaxel treatment using co-immunoprecipitation. Inhibition or knockdown of HDAC2 expression by valproic acid, BRD6688, or HDAC2 siRNA not only attenuated paclitaxel-induced mechanical allodynia but also suppressed HDAC2 upregulation, glutamate accumulation, and the corresponding changes in EAAT2/VGLUT/synaptophysin expression and HDAC2/YY1 interaction. These findings indicate that loss of the balance between glutamate release and reuptake due to dysregulation EAAT2/VGLUT2/synaptophysin cascade in the spinal dorsal horn plays an important role in the development of paclitaxel-induced neuropathic pain. HDAC2/YY1 interaction as a complex appears essential in regulating this pathway, which can potentially be a therapeutic target to relieve CIPN by reversing central sensitization of spinal nociceptive neurons.

The effect of total intravenous anaesthesia with propofol on postoperative pain after third molar surgery: A double-blind randomized controlled trial.

BACKGROUND: Total intravenous anaesthesia (TIVA) with propofol may reduce pain after surgery compared with inhalational anaesthetic techniques. Whether propofol provides analgesic benefit may be influenced by the surgical procedure and anaesthetic/analgesic regime. Third molar surgery is a consistent and fairly standard surgical technique that provides a good model for postoperative pain. We investigated whether propofol TIVA or sevoflurane (SEVO) inhalational anaesthesia would produce better quality pain relief after third molar surgery. METHODS: In this double-blind, randomized controlled trial, patients scheduled for bilateral third molar surgery received propofol TIVA or SEVO inhalational anaesthesia. Postoperative numerical rating pain scores, analgesic consumption, adverse effects and global pain satisfaction were assessed. RESULTS: Data from 48 patients in each group were analysed. The area under curves for numerical rating scale pain scores were significantly lower in the propofol TIVA group at rest and during mouth opening between 1 and 72 hr after surgery (p = 0.013 at rest, p = 0.021 with mouth opening). There was no difference in postoperative analgesic consumption. Propofol TIVA was associated with less postoperative headache (p = 0.041 in the postoperative anaesthetic care unit, p = 0.036 in ward). There were no differences in other adverse effects including postoperative nausea and vomiting. Global pain satisfaction and level of postoperative discomfort at 24 hr after surgery were significantly better in the propofol TIVA group (p = 0.008 and p = 0.009, respectively). CONCLUSION: Propofol TIVA was associated with reduced postoperative pain after bilateral third molar surgery, but did not reduce postoperative analgesic consumption. SIGNIFICANCE: Choice of general anaesthetic technique can affect postoperative analgesia. The results of this study suggest that propofol TIVA improves postoperative pain and patient satisfaction after third molar surgery compared to inhalational anaesthesia.

Role of DLC2 and RhoA/ROCK pathway in formalin induced inflammatory pain in mice.

Deficiency of deleted in liver cancer 2 (DLC2), a novel domain to inhibit RhoA activity, plays an important role in inflammatory pain. However, the underlying mechanisms remain unclear. This study investigated the role of DLC2 and its downstream cascade of RhoA/ROCK in formalin-induced inflammatory pain using DLC2-knockout (DLC2-/-) mice and compared them with DLC2 wild-type (DLC2+/+) mice. Mechanical allodynia and thermal hyperalgesia were evaluated using von Frey filament aesthesiometer and Hargreaves test, respectively. The spinal cord dorsal horn (L3-L5) was selected for molecular and cellular identification by Western blot and immunofluorescence. DLC2-/- mice showed increased mechanical allodynia and thermal hyperalgesia. Expression of ROCK1, ROCK2 and IL-1ß was significantly higher in DLC2-/- mice. Intrathecal administration of RhoA inhibitor (C3 exoenzyme) or ROCK inhibitor (Y27632) significantly attenuated formalin-induced inflammatory hyperalgesia in DLC2-/- mice. ROCK2 and IL-1ß expression were reduced by C3 exoenzyme or Y27632. Spinal p38 activation was also inhibited by C3 exoenzyme or Y27632. Double-labelling immunofluorescence demonstrated co-localization of DLC2 with spinal dorsal microglia. The number of activated microglia in the spinal dorsal horn was significantly higher in DLC2-/- mice, but was reduced by Y27632. These findings indicate that DLC2 deficiency increased formalin-induced inflammatory hyperalgesia through regulating RhoA/ROCK2, and IL-1ß may be a downstream effector. Our results also suggest that RhoA/ROCK enhanced p38 activation plays an important role in formalin-induced inflammatory pain. The finding that DLC2 attenuated inflammatory pain through inhibiting RhoA/ROCK2 suggests that the DLC2/RhoA/ROCK2/p38/IL-ß pathway may be a potential therapeutic target to reduce inflammatory pain.