High post surgical opioid requirements in Crohn's disease are not due to a general change in pain sensitivity

Gastrointestinal pain: A systematic review of temporal summation of pain paradigms and outcomes

BACKGROUND AND OBJECTIVE

Since targeted treatment for gastrointestinal pain is elusive, identifying the mechanistic underpinning of this pain type is important. Facilitation of spinal neuronal responses underpins certain pain types, and the psychophysical temporal summation of pain (TSP) paradigm provides a proxy measure of spinal facilitatory processes. Our aim was to systematically review whether facilitated TSP is a feature of gastrointestinal pain in patients with, or pain-free people experiencing experimentally induced, gastrointestinal pain.

DATABASES AND DATA TREATMENT

EMBASE, MEDLINE, PsychInfo, CINAHL, and Web of Science were systematically searched, from inception to July 2023, for human studies reporting TSP paradigm outcomes in the context of gastrointestinal pain. The Appraisal tool for Cross-Sectional studies was used for quality assessment and applied independently by two researchers.

RESULTS

Fifteen papers consisting of cross-sectional (n = 6), case-control (n = 8), and retrospective cohort (n = 1) studies, were included. Thirteen studies investigated TSP in people with gastrointestinal pain with (n = 5) or without (n = 8) defined pathology. Two studies evoked TSP by repetitive gut stimulation in people undergoing abdominal medical procedures. Preliminary evidence showed that facilitated TSP correlated with the presence of functional gastrointestinal pain in women, and those with a history of trauma. No effect was observed in people with inflammatory bowel disease, although it was often unclear if they experienced pain.

CONCLUSIONS

It is not possible to conclude whether facilitated TSP is a feature of gastrointestinal pain. We recommend that subgroup findings are corroborated and that TSP paradigms are standardized in order that direct comparisons between studies may be made.

SIGNIFICANCE STATEMENT

Evidence indicated that pain facilitatory processes, as evidenced by a facilitated TSP outcome, contribute to functional gastrointestinal pain in women and those with a history of trauma. However, heterogeneity of study populations and paradigms precluded statistical synthesis and findings would need be corroborated. Studies exploring facilitatory processes in people with inflammatory bowel diseases did not report significant results, but pain is not a given in these conditions and, conversely, may be driven by peripheral inflammation during active disease. This should be taken in consideration in future explorations.

REGISTRATION REVIEW

PROSPERO CRD42022341845.

Are catechol-O-methyltransferase gene polymorphisms genetic markers for pain sensitivity after all? - A review and meta-analysis

The catechol-O-methyltransferase (COMT) gene has arguably been the designated pain sensitivity gene for nearly two decades. However, the literature provides inconsistent evidence. We performed several meta-analyses including k = 31 samples and n = 4631 participants thereby revealing small effects of rs4680 on pain thresholds in fibromyalgia, headache and across chronic pain conditions. Moreover, rs4680 effects were found across pain patients when affected, but not unaffected, body sites were assessed. No effect was detected for any other SNP investigated. Importantly, our results corroborate earlier findings in that we found a small effect of COMT haplotypes on pain sensitivity. Our review and meta-analysis contribute to the understanding of COMT-dependent effects on pain perception, provide insights into research issues and offer future directions. The results support the theory that rs4680 might only impact behavioural measures of pain when descending pain modulatory pathways are sufficiently challenged. After all, COMT polymorphisms are genetic markers of pain sensitivity, albeit with some limitations which are discussed with respect to their implications for research and clinical significance.

Predictive factors of postoperative fentanyl consumption in patients with inflammatory bowel disease: a retrospective cohort study

Background

Patients with inflammatory bowel disease (IBD), including Crohn’s disease and ulcerative colitis, might present difficulties in achieving postoperative analgesia. Prior studies have suggested that patients with IBD undergoing major abdominal surgery require higher doses of perioperative opioids than do patients without IBD. Considering patients with IBD potentially require high-dose opioids, identifying those requiring higher opioid doses will allow clinicians to optimize the perioperative opioid dose and avoid insufficient pain management or complications of opioid overdose. Therefore, we conducted this study to identify predictive factors that might influence postoperative opioid consumption in patients with IBD.

Methods

This single-center, historical cohort study reviewed the medical records of all patients admitted to the IBD center of our institution for surgery and who used intravenous fentanyl patient-controlled analgesia (PCA) after open abdominal surgery between June 2013 and April 2017. Ultimately, 179 patients were enrolled in the analysis. Variables expected to influence and/or represent pain, analgesia, inflammation, disease condition, and extent of surgery were selected as potential explanatory variables for predicting postoperative opioid consumption. Multivariable linear regression analysis was used to examine the effect of independent variables on postoperative fentanyl consumption.

Results

Of the nine predictive variables selected using the stepwise-selection method, eight were significant. Intraoperative fentanyl consumption, current smoking, ulcerative colitis, administration of biologics during the month before surgery, and the use of supplementary analgesics had a significant increasing effect on postoperative fentanyl consumption, whereas droperidol concentration in the PCA solution, age, and diabetes mellitus had a significant decreasing effect. Preoperative use of opioids was a non-significant variable. The adjusted coefficient of determination was 0.302.

Conclusions

Intraoperative fentanyl consumption, current smoking, ulcerative colitis, administration of biologics during the month before surgery, and the use of supplementary analgesics had a significant increasing effect, whereas droperidol concentration in the PCA solution, age, and diabetes mellitus had a significant decreasing effect on postoperative fentanyl consumption. These factors should be considered when adopting postoperative intravenous fentanyl PCA administration for patients with IBD.

Trial registration

Registry: UMIN Clinical Trials Registry.

Clinical Trial Number: UMIN000031198.

Date of registration: February 8, 2018.

Comparison of outcome after right colectomy with an enhanced recovery programme in patients with inflammatory bowel disease and patients operated on for other conditions: a monocentric retrospective study

PURPOSE

Enhanced recovery programmes (ERPs) after surgery reduce postoperative complications and hospital stay. Patients with inflammatory bowel disease (IBD) often present risk factors for postoperative complications. This accounts for reluctance to include them in ERPs. We compared outcome after right colectomy with an ERP in IBD and non-IBD patients.

METHODS

In our GRACE colorectal surgery database comprising 508 patients, we analysed patients scheduled for right colectomy (n = 160). Adherence to the protocol, postoperative complications and length of hospital stay of IBD patients (n = 45) were compared with those of non-IBD patients (n = 115). Data (mean ± SD, median [IQR], count (%)) were compared by Student's t, Mann-Whitney U and chi-square tests when appropriate; p < 0.05 taken as statistically significant.

RESULTS

IBD patients were significantly younger (38.9 ± 13.8 vs. 58.9 ± 18.5 years, p < 0.001) and had lower BMI (23.0 ± 5.0 vs. 25.1 ± 5.0 kg m^-2, p < 0.01). Adherence to ERP was similar in the two groups. Resumption of eating on the day of the operation was less well tolerated (73.3% vs. 85.2%, p < 0.05) and postoperative pain (p < 0.001) was greater in IBD patients. The incidence of postoperative complications (13.3% vs. 17.3%) and the length of hospital stay (3 [3-4.5] vs. 3 [2-5] days) were comparable in IBD and non-IBD patients, respectively.

CONCLUSION

The management of IBD patients in an ERP is not only feasible but also indicated. These patients benefit as much from ERP as non-IBD patients.

Symptoms of central sensitization in patients with inflammatory bowel diseases: a case-control study examining the role of musculoskeletal pain and psychological factors

OBJECTIVES

Musculoskeletal (MSK) pain is a common complaint in patients with inflammatory bowel diseases (IBD). MSK pain in IBD has previously demonstrated association with symptoms of central sensitization; however it is uncertain whether these symptoms are influenced simply by the presence of MSK pain and/or IBD. Primary aim of this study was to investigate whether symptoms of central sensitization differed across three groups: IBD patients with and without MSK pain and healthy controls. Secondary aim was to investigate between-group differences for measures of somatosensory functioning.

METHODS

Cross-sectional study was performed on adults with IBD. Assessments included: central sensitization inventory (CSI), pressure pain threshold, temporal summation, conditioned pain modulation, perceived stress, affect style, anxiety, depression, and pain catastrophizing. One-way analyses of variance and covariance were used to investigate between-group differences for measures of central sensitization and potential confounding by psychological factors.

RESULTS

Study participants (n=66) were age/gender matched across three study groups. Between-group differences were solely demonstrated for CSI scores [F(2,63)=19.835, p<0.001, r=0.62], with IBD patients with MSK pain demonstrating the highest CSI scores and healthy controls the lowest. After controlling for individual psychological features, post hoc comparisons indicated that CSI scores were significantly different between-groups (p≤0.025) after controlling for most psychological variables, with the exception of perceived stress (p=0.063) and pain catastrophizing (p=0.593).

CONCLUSIONS

IBD patients as a whole demonstrated significantly greater symptoms of central sensitization compared to healthy controls. However, IBD patients with persistent MSK pain demonstrated the greatest symptoms of central sensitization compared to patients without MSK pain and healthy controls. Between-group differences for CSI in IBD patients with MSK were not confounded by psychological features.

IMPLICATIONS

Study results indicate that persistent MSK pain in IBD represents patients with greater central sensitization symptomology. This increased symptomology is suggestive of underlying mechanisms related to central sensitization, highlighting patient potentially at risk for worse pain experiences.

Transient receptor potential ankyrin 1 promoter methylation and peripheral pain sensitivity in Crohn's disease

Background

Crohn’s disease is a chronic inflammatory disorder of the gastrointestinal tract associated with abdominal pain and diarrhea. Pain caused by Crohn’s disease likely involves neurogenic inflammation which seems to involve the ion channel transient receptor potential ankyrin 1 (TRPA1). Since the promoter methylation of TRPA1 was shown to influence pain sensitivity, we asked if the expression of TRPA1 is dysregulated in patients suffering from Crohn’s disease.

The methylation rates of CpG dinucleotides in the TRPA1 promoter region were determined from DNA derived from whole blood samples of Crohn patients and healthy participants. Quantitative sensory testing was used to examine pain sensitivities.

Results

Pressure pain thresholds were lower in Crohn patients as compared to healthy participants, and they were also lower in females than in males. They correlated inversely with the methylation rate at the CpG − 628 site of the TRPA1 promoter. This effect was more pronounced in female compared to male Crohn patients. Similar results were found for mechanical pain thresholds. Furthermore, age-dependent effects were detected. Whereas the CpG − 628 methylation rate declined with age in healthy participants, the methylation rate in Crohn patients increased. Pressure pain thresholds increased with age in both cohorts.

Conclusions

The TRPA1 promoter methylation appears to be dysregulated in patients suffering from Crohn’s disease, and this effect is most obvious when taking gender and age into account. As TRPA1 is regarded to be involved in pain caused by neurogenic inflammation, its aberrant expression may contribute to typical symptoms of Crohn’s disease.

Randomized Clinical Trial Comparing Laparoscopic Versus Ultrasound-Guided Transversus Abdominis Plane Block in Minimally Invasive Colorectal Surgery

BACKGROUND

Transversus abdominis plane block may improve analgesia after colorectal surgery; however, techniques remain unstandardized and results are conflicting.

OBJECTIVE

The purpose of this study was to compare laparoscopic and ultrasound-guided transversus abdominis plane block with no block in minimally invasive colorectal surgery.

DESIGN

This was a randomized controlled trial.

SETTINGS

The study was conducted at an urban teaching hospital.

PATIENTS

Patients undergoing laparoscopic colorectal surgery were included.

INTERVENTIONS

The intervention included 2:2:1 randomization to laparoscopic, ultrasound-guided, or no transversus abdominis plane block.

MAIN OUTCOME MEASURES

Morphine use in the first 24 hours after surgery was measured.

RESULTS

The study cohort included 107 patients randomly assigned to laparoscopic (n = 41), ultrasound-guided (n = 45), or no transversus abdominis plane block (n = 21). Mean age was 50.4 years (SD ± 18 y), and 50 patients (47%) were men. Laparoscopic transversus abdominis plane block was superior to ultrasound-guided (p = 0.007) and no transversus abdominis plane block (p = 0.007), with median (interquartile range) total morphine used in the first 24 hours postoperatively of 17.6 mg (6.6-33.9 mg), 34.0 mg (16.4-44.4 mg), and 31.6 mg (18.4-44.4 mg). At 48 hours, laparoscopic transversus abdominis plane block remained superior to ultrasound-guided (p = 0.03) and no transversus abdominis plane block (p = 0.007) with median (interquartile range) total morphine used at 48 hours postoperatively of 26.8 mg (15.5-45.8 mg), 44.0 mg (27.6-70.0 mg), and 60.8 mg (34.8-78.8 mg). Mean hospital stay was 5.1 ± 3.1 days without any intergroup differences. Overall complications were similar between groups.

LIMITATIONS

Treatment teams were not blinded and there was operator dependence of techniques and variable timing of the blocks.

CONCLUSIONS

Laparoscopic transversus abdominis plane block is superior to ultrasound-guided and no transversus abdominis plane block in achieving pain control and minimizing opioid use in the first 24 hours after colorectal surgery. A large, multicenter, randomized trial is needed to confirm our findings. See Video Abstract at http://links.lww.com/DCR/A822.

Pain management in patients with inflammatory bowel disease: translational approaches from bench to bedside

Abdominal pain is a common symptom in patients with inflammatory bowel disease (IBD) that negatively affects quality of life and can lead to increased health-seeking behavior. Although abdominal pain has been traditionally attributed to inflammation, there is growing literature demonstrating the existence of functional abdominal pain in patients with IBD, of which there are a variety of potential causes. Thus, when approaching a patient with IBD who has abdominal pain, in addition to IBD-related complications (e.g., inflammation/stricture), it is important to screen for related contributors, including peripheral factors (visceral hypersensitivity, bacterial overgrowth, and bowel dysmotility) and centrally mediated neurobiological and psychosocial underpinnings. These central factors include psychological symptoms/diagnoses, sleep disturbance, and stress. Opioid-induced hyperalgesia (e.g., narcotic bowel syndrome) is also growing in recognition as a potential central source of abdominal pain. This review draws from clinical studies and animal models of colitis and abdominal pain to consider how knowledge of these potential etiologies can be used to individualize treatment of abdominal pain in patients with IBD, including consideration of potential novel treatment modalities for the future. Accurate assessment of the source(s) of pain in patients with IBD can help guide appropriate diagnostic workup and use of disease-modifying therapy.

Association of OPRM1 A118G variant with risk of morphine-induced respiratory depression following spine fusion in adolescents

The μ1 opioid receptor (OPRM1) genetic variant A118G results in decreased μ-receptor binding potential in the brain and increases morphine requirement. We hypothesized that OPRM1 A118G polymorphism will affect morphine-induced respiratory depression (MIRD) risk in children receiving morphine. A prospective genotype-blinded study was conducted in 88 healthy adolescents (11-18 years; 67% female, 85% Caucasian) who underwent spine fusion for scoliosis. They were followed for 48 h postoperatively for MIRD, pain scores, morphine consumption and use of analgesic adjuvants. Patients were genotyped for OPRM1 A118G variant-76% were wild type (AA) and 24% heterozygous/homozygous for variant (AG/GG). Multivariable logistic regression showed that the risk of MIRD in patients with AA genotype was significantly higher (odds ratio 5.6, 95% CI: 1.4-37.2, P=0.030). Presence of G allele was associated with higher pain scores (effect size 0.73, P=0.045). This novel association is an important step toward predicting MIRD susceptibility and personalizing morphine use.

µ-opioid receptor gene variant OPRM1 118 A>G: a summary of its molecular and clinical consequences for pain

The human µ-opioid receptor variant 118 A>G (rs1799971) has become one of the most analyzed genetic variants in the pain field. At the molecular level, the variant reduces opioid receptor signaling efficiency and expression, the latter probably via a genetic-epigenetic interaction. In experimental settings, the variant was reproducibly associated with decreased effects of exogenous opioids. However, this translates into very small clinical effects (meta-analysis of 14 studies: Cohen's d = 0.096; p = 0.008), consisting of slightly higher opioid dosing requirements in peri- and post-operative settings. An effect can neither be maintained for chronic analgesic therapy nor for opioid side effects. It seems unlikely that further studies will reveal larger effect sizes and, therefore, further analyses appear unwarranted. Thus, due to its small effect size, the SNP is without major clinical relevance as a solitary variant, but should be regarded as a part of complex genotypes underlying pain and analgesia.

Pharmacogenetics of OPRM1

Pharmacogenetic research has the potential to explain the variation in treatment efficacy within patient populations. Understanding the interaction between genetic variation and medications may provide a method for matching patients to the most effective therapeutic options and improving overall patient outcomes. The OPRM1 gene has been a target of interest in a large number of pharmacogenetic studies due to its genetic and structural variation, as well as the role of opioid receptors in a variety of disorders. The mu-opioid receptor (MOR), encoded by OPRM1, naturally regulates the analgesic response to pain and also controls the rewarding effects of many drugs of abuse, including opioids, nicotine, and alcohol. Genetic variants in OPRM1, particularly the non-synonymous polymorphism A118G, have been repeatedly associated with the efficacy of treatments for pain and various types of dependence. This review focuses on the current understanding of the pharmacogenetic impact of OPRM1, primarily with regard to the treatment of pain and addiction.

Pharmacogenetics of opiates in clinical practice: the visible tip of the iceberg

Opioids are the cornerstone of analgesic therapy and are used as a substitution therapy for opiate addiction. Interindividual variability in response to opioids is a significant challenge in the management of pain and substitution. Therefore, treatment with opioids requires a careful individualization of dosage to achieve an appropriate balance of efficacy and adverse effects and, consequently, avoid toxicity, particularly respiratory depression, sedation and for some, cardiac ventricular fibrillations. Many studies have investigated the association between genetic factors and the variability of response to opioids. Variants in genes encoding proteins implied in opioid pharmacokinetics (absorption, distribution, metabolism, excretion and toxicity), together with those implied in opioids direct and indirect pharmacodynamics (genes of opioid receptors and monoaminergic systems), are the most studied. Many association studies have not been replicated. The purpose of this article is to summarize pharmacogenetic data associated with some opioids frequently encountered in managed care settings.

Catechol-O-methyltransferase gene polymorphism and chronic human pain: a systematic review and meta-analysis

In human studies, low COMT (catechol-O-methyltransferase) activity has been associated with increased sensitivity to acute clinical preoperative or postoperative pain. We explored the association between the COMT genotype and three chronic pain conditions: migrainous headache, fibromyalgia, or chronic widespread pain and chronic musculoskeletal pain. Furthermore, we evaluated whether COMT genotype affects the efficacy of opioids in chronic pain. After a systematic literature review, we carried out meta-analyses on the three chronic pain conditions. The efficacy of opioids was evaluated using a systematic review only. The meta-analyses showed that fibromyalgia or chronic widespread pain is the only type of chronic pain that could be associated with the COMT single nucleotide polymorphism rs4680 (Val158Met). Met158, which results in the low-activity variant of COMT, is the risk allele. In chronic clinical pain, the effect of the COMT polymorphism depends on the pain condition. Low COMT activity is not associated with migrainous headache or chronic musculoskeletal pain conditions, but it may increase the risk for fibromyalgia or chronic widespread pain. Low COMT activity increases opioid receptors and enhances opioid analgesia and adverse effects in some cancer pains. Findings from animal studies that have utilized COMT inhibitors elucidate the mechanism behind these findings. In rodent pain models, COMT inhibitors are pronociceptive, except for neuropathic pain models, where nitecapone was found to be antiallodynic. The complex interplay between enhanced adrenergic and dopaminergic activity in different parts of the nociceptive system probably explains the complicated actions of low COMT activity.

Endogenous opiates and behavior: 2009

This paper is the 32nd consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2009 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Personalized therapy in pain management: where do we stand?

Genomic variations influencing response to pharmacotherapy of pain are currently under investigation. Drug-metabolizing enzymes represent a major target of ongoing research in order to identify associations between an individual’s drug response and genetic profile. Polymorphisms of the cytochrome P450 enzymes (CYP2D6) influence metabolism of codeine, tramadol, hydrocodone, oxycodone and tricyclic antidepressants. Blood concentrations of some NSAIDs depend on CYP2C9 and/or CYP2C8 activity. Genomic variants of these genes associate well with NSAIDs’ side effect profile. Other candidate genes, such as those encoding (opioid) receptors, transporters and other molecules important for pharmacotherapy in pain management, are discussed; however, study results are often equivocal. Besides genetic variants, further variables, for example, age, disease, comorbidity, concomitant medication, organ function as well as patients’ compliance, may have an impact on pharmacotherapy and need to be addressed when pain therapists prescribe medication. Although pharmacogenetics as a diagnostic tool has the potential to improve patient therapy, well-designed studies are needed to demonstrate superiority to conventional dosing regimes.