Clinical Pain Studies Research Articles

Clinical study of palmar foot pain in 30 polo ponies with forelimb lameness in Thailand

Palmar foot pain is an important chronic problem that impairs the abilities of sport horses. Though there are several research on different types of horses, there is a lack of information regarding polo horses, which are known for using in unique sport. Therefore, this research aimed to find the prevalence of palmar foot pain in polo ponies with forelimb lameness in Thailand. The horses included in this study were 30 Argentine polo ponies: 10 geldings and 20 mares, aged from 7 to 20 years old. All were barefoot and had not exercised for at least 2 months. The ponies underwent lameness examination procedures with subjective and objective evaluation, including a trot on a straight line, left and right lunging, a full forelimb flexion test and a toe wedge test. Close inspections of hoof conformation, hoof percussion and hoof testing were done before performing a palmar digital nerve block. The result showed that 25 (83.33%) of 30 polo ponies had forelimb lameness, which can be divided into 56.7% with unilateral forelimb lameness, and 26.7% with bilateral forelimb lameness. There were 17 (56.7%) polo ponies that responded positively to the full flexion test and 25 (83.33%) that responded positively to the hoof tester and percussion at the frog area. However, only 9 ponies (30%) were positive to palmar nerve block. In conclusion, this study reveals a notable incidence of forelimb lameness and palmar foot pain. Understanding palmar foot pain prevalence is vital for further equine health management.

Video-Based versus On-Site Neonatal Pain Assessment in Neonatal Intensive Care Units: The Impact of Video-Based Neonatal Pain Assessment in Real-World Scenario on Pain Diagnosis and Its Artificial Intelligence Application.

Neonatal pain assessment (NPA) represents a huge global problem of essential importance, as a timely and accurate assessment of neonatal pain is indispensable for implementing pain management. To investigate the consistency of pain scores derived through video-based NPA (VB-NPA) and on-site NPA (OS-NPA), providing the scientific foundation and feasibility of adopting VB-NPA results in a real-world scenario as the gold standard for neonatal pain in clinical studies and labels for artificial intelligence (AI)-based NPA (AI-NPA) applications. A total of 598 neonates were recruited from a pediatric hospital in China. This observational study recorded 598 neonates who underwent one of 10 painful procedures, including arterial blood sampling, heel blood sampling, fingertip blood sampling, intravenous injection, subcutaneous injection, peripheral intravenous cannulation, nasopharyngeal suctioning, retention enema, adhesive removal, and wound dressing. Two experienced nurses performed OS-NPA and VB-NPA at a 10-day interval through double-blind scoring using the Neonatal Infant Pain Scale to evaluate the pain level of the neonates. Intra-rater and inter-rater reliability were calculated and analyzed, and a paired samples t-test was used to explore the bias and consistency of the assessors' pain scores derived through OS-NPA and VB-NPA. The impact of different label sources was evaluated using three state-of-the-art AI methods trained with labels given by OS-NPA and VB-NPA, respectively. The intra-rater reliability of the same assessor was 0.976-0.983 across different times, as measured by the intraclass correlation coefficient. The inter-rater reliability was 0.983 for single measures and 0.992 for average measures. No significant differences were observed between the OS-NPA scores and the assessment of an independent VB-NPA assessor. The different label sources only caused a limited accuracy loss of 0.022-0.044 for the three AI methods. VB-NPA in a real-world scenario is an effective way to assess neonatal pain due to its high intra-rater and inter-rater reliability compared to OS-NPA and could be used for the labeling of large-scale NPA video databases for clinical studies and AI training.

Postoperative acute pain management with duloxetine as compared to placebo: A systematic review with meta-analysis of randomized clinical trials.

Duloxetine has been used as an adjunct in multimodal analgesia for acute postoperative pain in clinical studies. This meta-analysis aims to conclude whether oral duloxetine, when given perioperatively, is any better than a placebo in managing postoperative pain. Effects of duloxetine on postoperative pain scores, time to first rescue analgesia, postoperative rescue analgesia consumption, side effects attributable to duloxetine, and patient satisfaction profile were assessed. MEDLINE, Web of Science, EMBASE, Scholar Google, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched with keywords including "Duloxetine" AND "postoperative pain", "Duloxetine" AND "acute pain" and with "Duloxetine" till October 2022. This meta-analysis included randomized clinical trials in which perioperative duloxetine 60 mg per oral was administered not more than 7 days before surgery and for at least 24 after surgery but not more than 14 days after surgery. All RCTs in which the comparator is placebo and outcomes related to analgesic efficacy like pain scores, opioid consumption, and side effects of duloxetine until 48 h postoperatively were included. Data were extracted from the studies and a risk of bias summary was formed using the Cochrane Collaboration tool. Effect sizes were given as standardized mean differences for continuous outcomes and risk ratios (RR) by the Mantel-Haenszel test for the categorical outcome. Confirmation of publication bias was done by Egger's regression test (p < 0.05). If publication bias or heterogeneity was detected, the trim-and-fill method was used to calculate the adjusted effect size. Sensitivity analysis was done by leaving one out method after excluding the study with a high risk of bias. Subgroup analysis was done based on the type of surgery and gender. The study was prospectively registered in the PROSPERO under the registration number CRD42019139559. 29 studies with 2043 patients met the inclusion criteria and were reviewed for this meta-analysis. Postoperative pain scores at 24 h [Std. Mean Difference (95% CI); -0.69 (-1.07, -0.32)] and at 48 h [-1.13 (-1.68, -0.58)] are significantly less with duloxetine (p-value < 0.05). Time to first rescue analgesia was significantly more in patients where duloxetine was administered [1.27 (1.10, 1.45); p-value > 0.05]. Opioid consumption up to 24 h [-1.82 (-2.46, -1.18)] and 48 h [-2.48 (-3.46, -1.50)] was significantly less (p-value < 0.05) in patients who received duloxetine. Complications and recovery profiles were similar in patients receiving either duloxetine or a placebo. Based on GRADE findings, we conclude that there is low to moderate evidence to advocate the use of duloxetine for managing postoperative pain. Further trials are needed to replicate or refute these results based on robust methodology.

On determining the mechanical nociceptive threshold in pigs: a reliability study.

A pressure algometer is a valuable tool for assessing the mechanical nociceptive threshold (MNT) in clinical pain studies. Recent research has turned to large animal models of pain because of the closer anatomy and physiology to humans. Although the reliability and usefulness of the MNT have been extensively validated in humans, similar data from large animals is still sparse. Therefore, the aim of the current study was to evaluate the reliability (within- and between-session) of MNT in the forelimb of pigs using a pressure algometer. Nine animals were used (23-40 kg), and MNTs were measured at both the right and left limbs at three different sessions, with three repetitions per session. The intraclass correlation coefficient (ICC) was used as a metric for relative reliability. The standard error of measurement (SEM) and coefficient of variation (CV) was used to assess absolute reliability. Systematic bias was also evaluated. The average ICC was found to be 0.71 and 0.45 for the between-session and within-session, respectively. CV ranged from 17.9% to 20.5%, with a grand average of 19.1%. The grand average SEM was 249.5 kPa (16.6%). No systematic differences were found for the MNT between sessions, which suggests that there was no habituation to the stimulus. The reliability indices obtained in this study are comparable to results obtained in other species or anatomical regions and substantiate the use of the pressure algometer as a valuable tool to investigate the nociceptive system in pigs and translation to the human nociceptive withdrawal reflex.

Efficacy of Essential Oils in Relieving Cancer Pain: A Systematic Review and Meta-Analysis.

Over 80% of patients affected by cancer develops cancer-related pain, one of the most feared consequences because of its intractable nature, particularly in the terminal stage of the disease. Recent evidence-based recommendations on integrative medicine for the management of cancer pain underline the role of natural products. The present systematic review and meta-analysis aims at appraising for the first time the efficacy of aromatherapy in cancer pain in clinical studies with different design according to the most updated Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020 recommendations. The search retrieves 1002 total records. Twelve studies are included and six are eligible for meta-analysis. The present study demonstrates significant efficacy of the use of essential oils in the reduction of the intensity of pain associated with cancer (p < 0.00001), highlighting the need for earlier, more homogeneous, and appropriately designed clinical trials. Good certainty body of evidence is needed for effective and safe management of cancer-related pain using essential oils by establishment of a step-by-step preclinical-to-clinical pathway to provide a rational basis for clinical use in integrative oncology. PROSPERO registration: CRD42023393182.

Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks−American Pain Society−American Academy of Pain Medicine Pain Taxonomy Diagnostic Criteria for Acute Needle Pain

Needle procedures are among the most common causes of pain and distress for individuals seeking health care. While needle pain is especially problematic for children needle pain and associated fear also has significant impact on adults and can lead to avoidance of appropriate medical care. Currently there is not a standard definition of needle pain. A taxonomy, or classification system, for acute needle pain would aid research efforts and enhance clinical care. To meet this need, the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks public−private partnership with the U.S. Food and Drug Administration, the American Pain Society, and the American Academy of Pain Medicine formed the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks−American Pain Society−American Academy of Pain Medicine Pain Taxonomy initiative. One of the goals of this initiative was to develop taxonomies for acute pain disorders, including needle pain. To accomplish this, a working group of experts in needle pain was convened. Based on available literature and expert opinion, the working group used a 5-dimenional structure (diagnostic criteria, common features, modulating factors, impact and/or functional consequences, and putative mechanisms) to develop an acute pain taxonomy that is specific needle pain. As part of this, a set of 4 diagnostic criteria, with 2 modifiers to account for the influence of needle associated fear, are proposed to define the types of acute needle pain. PerspectiveThis article presents a taxonomy for acute needle pain. This taxonomy could help to standardize definitions of acute pain in clinical studies of patients undergoing needle procedures.

Exploring pain interference with motor skill learning in humans: A systematic review.

Motor learning underpins successful motor skill acquisition. Although it is well known that pain changes the way we move, it's impact on motor learning is less clear. The aim of this systematic review was to synthesize evidence on the impact of experimental and clinical pain on task performance and activity-dependent plasticity measures across learning and explore these findings in relation to different pain and motor learning paradigms. Five databases were searched: Web of Science, Scopus, MEDLINE, Embase and CINAHL. Two reviewers independently screened the studies, extracted data, and assessed risk of bias using the Cochrane ROB2 and ROBIN-I. The overall strength of evidence was rated using the GRADE guidelines. Due to the heterogeneity of study methodologies a narrative synthesis was employed. Twenty studies were included in the review: fifteen experimental pain and five clinical pain studies, covering multiple motor paradigms. GRADE scores for all outcome measures suggested limited confidence in the reported effect for experimental pain and clinical pain, on motor learning. There was no impact of pain on any of the task performance measures following acquisition except for 'accuracy' during a tongue protrusion visuomotor task and 'timing of errors' during a motor adaptation locomotion task. Task performance measures at retention, and activity dependent measures at both acquisition and retention showed conflicting results. This review delivers a detailed synthesis of research studies exploring the impact of pain on motor learning. This is despite the challenges provided by the heterogeneity of motor learning paradigms, outcome measures and pain paradigms employed in these studies. The results highlight important questions for further research with the goal of strengthening the confidence of findings in this area.

Gabapentin inhibits the analgesic effects and nerve regeneration process induced by hepatocyte growth factor (HGF) in a peripheral nerve injury model: Implication for the use of VM202 and gabapentinoids for peripheral neuropathy

Hepatocyte growth factor (HGF) is a multifunctional protein that plays a critical role in the angiogenic, neurotrophic, antifibrotic, and antiapoptotic activities of various cell types. It has been previously reported that intramuscular injection of pCK-HGF-X7 (or VM202), a plasmid DNA designed to express both native isoforms of human HGF (Pyun et al., 2010), significantly reduced the level of neuropathic pain in clinical studies as well as in a variety of animal models. In clinical studies, it has been observed that pCK-HGF-X7 appeared to give much higher pain-relieving effects in subjects not taking pregabalin or gabapentin, α2δ1 calcium channel blockers frequently prescribed for reducing pain in patients with diabetic peripheral neuropathy. In this study, we tested the effects of gabapentin on HGF-mediated pain reduction and nerve regeneration in vivo. Consistent with the data from clinical studies, gabapentin administration inhibited the pain reduction and axon regeneration effects mediated by HGF expression from pCK-HGF-X7. In the context of nerve regenerative effects, treatment with gabapentin or EGTA, a Ca2+ chelator, inhibited HGF-mediated axon outgrowth of injured sciatic nerves in vivo. Taken together, i.m. injection of HGF-encoding plasmid DNA ameliorated pain symptoms and enhanced the regeneration of injured nerves, and these therapeutic effects of HGF were significantly hindered by gabapentin treatment, suggesting the possible involvement of Ca2+ in the pro-regenerative activities of native HGF derived from treatment with pCK-HGF-X7.

Clinical Study of Pain in Right Iliac Fossa

Background: To study the clinical profile of pain in right iliac fossa.&#x0D; Methods: 100 patients with signs and symptoms of right iliac fossa mass admitted in Hospital were identified and were studied by taking detailed clinical history, physical examination and were subjected to various investigations like x ray erect abdomen, chest x-ray, contrast x-ray .&#x0D; Result: In this study of out of 100 cases, 71.00% of cases were related to appendicular pathology either in the form of appendicular mass or appendicular abscess. There were 9.00% cases of Ileocaecal tuberculosis.&#x0D; Conclusion: Appendicular lump remains the most common cause for right iliac fossa pain. Ileocaecal tuberculosis is one of the most important differential diagnoses for pain abdomen.&#x0D; Keywords: Appendicitis, , Right Iliac Fossa Mass, Pain

Keratinocyte Biomarkers Distinguish Painful Diabetic Peripheral Neuropathy Patients and Correlate With Topical Lidocaine Responsiveness.

This study investigated quantifiable measures of cutaneous innervation and algesic keratinocyte biomarkers to determine correlations with clinical measures of patient pain perception, with the intent to better discriminate between diabetic patients with painful diabetic peripheral neuropathy (PDPN) compared to patients with low-pain diabetic peripheral neuropathy (lpDPN) or healthy control subjects. A secondary objective was to determine if topical treatment with a 5% lidocaine patch resulted in correlative changes among the quantifiable biomarkers and clinical measures of pain perception, indicative of potential PDPN pain relief. This open-label proof-of-principle clinical research study consisted of a pre-treatment skin biopsy, a 4-week topical 5% lidocaine patch treatment regimen for all patients and controls, and a post-treatment skin biopsy. Clinical measures of pain and functional interference were used to monitor patient symptoms and response for correlation with quantitative skin biopsy biomarkers of innervation (PGP9.5 and CGRP), and epidermal keratinocyte biomarkers (Nav1.6, Nav1.7, CGRP). Importantly, comparable significant losses of epidermal neural innervation (intraepidermal nerve fibers; IENF) and dermal innervation were observed among PDPN and lpDPN patients compared with control subjects, indicating that innervation loss alone may not be the driver of pain in diabetic neuropathy. In pre-treatment biopsies, keratinocyte Nav1.6, Nav1.7, and CGRP immunolabeling were all significantly increased among PDPN patients compared with control subjects. Importantly, no keratinocyte biomarkers were significantly increased among the lpDPN group compared with control. In post-treatment biopsies, the keratinocyte Nav1.6, Nav1.7, and CGRP immunolabeling intensities were no longer different between control, lpDPN, or PDPN cohorts, indicating that lidocaine treatment modified the PDPN-related keratinocyte increases. Analysis of the PDPN responder population demonstrated that increased pretreatment keratinocyte biomarker immunolabeling for Nav1.6, Nav1.7, and CGRP correlated with positive outcomes to topical lidocaine treatment. Epidermal keratinocytes modulate the signaling of IENF, and several analgesic and algesic signaling systems have been identified. These results further implicate epidermal signaling mechanisms as modulators of neuropathic pain conditions, highlight a novel potential mode of action for topical treatments, and demonstrate the utility of comprehensive skin biopsy evaluation to identify novel biomarkers in clinical pain studies.

Oral efficacy of Δ(9)-tetrahydrocannabinol and cannabidiol in a mouse neuropathic pain model

The psychoactive and non-psychoactive constituents of cannabis, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), have synergistic analgesic efficacy in animal models of neuropathic pain when injected systemically. However, the relevance of this preclinical synergy to clinical neuropathic pain studies is unclear because many of the latter use oral administration. We therefore examined the oral effectiveness of these phytocannabinoids and their interactions in a mouse chronic constriction injury (CCI) model of neuropathic pain. THC produced a dose-dependent reduction in mechanical and cold allodynia, but also induced side-effects with similar potency. CBD also reduced allodynia, albeit with lower potency than THC, but did not produce cannabinoid-like side-effects at any dose tested. Combination THC:CBD produced a dose-dependent reduction in allodynia, however, it displayed little to no synergy. Combination THC:CBD produced substantial, synergistic side-effects which increased with the proportion of CBD. These findings demonstrate that oral THC and CBD, alone and in combination, have analgesic efficacy in an animal neuropathic pain model. Unlike prior systemic injection studies, combination THC:CBD lacks analgesic synergy when delivered orally. Furthermore, both THC and combination THC:CBD display a relatively poor therapeutic window when delivered orally. This suggests that CBD provides a safer, albeit lower efficacy, oral treatment for nerve injury induced neuropathic pain than THC-containing preparations.This article is part of the special issue on ‘Cannabinoids’.

A neuroimaging biomarker for sustained experimental and clinical pain.

Sustained pain is a major characteristic of clinical pain disorders, but it is difficult to assess in isolation from co-occurring cognitive and emotional features in patients. In this study, we developed a functional magnetic resonance imaging signature based on whole-brain functional connectivity that tracks experimentally induced tonic pain intensity and tested its sensitivity, specificity and generalizability to clinical pain across six studies (total n = 334). The signature displayed high sensitivity and specificity to tonic pain across three independent studies of orofacial tonic pain and aversive taste. It also predicted clinical pain severity and classified patients versus controls in two independent studies of clinical low back pain. Tonic and clinical pain showed similar network-level representations, particularly in somatomotor, frontoparietal and dorsal attention networks. These patterns were distinct from representations of experimental phasic pain. This study identified a brain biomarker for sustained pain with high potential for clinical translation.

Bioavailability of subcutaneous and intramuscular administrated buprenorphine in New Zealand White rabbits

BackgroundBuprenorphine is one of the most used analgesics for postoperative pain in rabbits. The recommended dose in rabbits (0.01–0.05 mg/kg) is the same for intravenous (IV), intramuscular (IM), and subcutaneous (SC) administration, despite lack of pharmacokinetic data. Five male and five female New Zealand White rabbits (mean ± SD body weight 3.1 ± 0.3 kg) were administered 0.05 mg/kg buprenorphine by the IV, IM and SC routes and 0.1 mg/kg by the SC route, in a cross-over design with two-week wash-out periods between treatments. Blood was collected before, and up to 8 h post buprenorphine injection, for determination of serum levels by UPHLC-MS/MS.ResultsThe area under the time concentration curve (AUC0-t) was lower after SC (398 ± 155 ng/mL/min) than IM (696 ± 168 ng/mL/min, p < 0.001) and IV (789 ± 189 ng/mL/min, p < 0.001) administration. The maximum serum concentration was lower after SC (2.2 ± 1.4 ng/mL) than after IM (11 ± 3.2 ng/mL) administration (p < 0.001). The bioavailability was lower after SC (50 ± 19%) than after IM (95 ± 21%) administration (p = 0.006). The elimination half-life was longer after SC (260 ± 120 min) than after IM (148 ± 26 min, p = 0.002) as well as IV (139 ± 33 min) injection (p < 0.001). An increase in the SC dose from 0.05 to 0.1 mg/kg resulted in an increase in the area under the time concentration curve of 50% in female (p = 0.022) and 165% in male rabbits (p < 0.001). The bioavailability did not change in the females (36 ± 14%, p = 0.6), whereas it increased in the males (71 ± 23%, p = 0.008).ConclusionsThe lower bioavailability of 0.05 mg/kg buprenorphine after SC administration could explain the lack of efficacy seen in clinical pain studies in rabbits, using this route. For immediate pain relief, IV or IM administration is therefore be recommended, whereas SC administration may be useful to sustain analgesic serum levels, once efficient pain relief has been achieved. The current data do not support an increase in dose to compensate for the lower SC bioavailability.

Patient Assisted Intervention for Neuropathy: Comparison of Treatment in Real Life Situations (PAIN-CONTRoLS)

Cryptogenic sensory polyneuropathy (CSPN) is a common generalized slowly progressive neuropathy, second in prevalence only to diabetic neuropathy. Most patients with CSPN have significant pain. Many medications have been tried for pain reduction in CSPN, including antiepileptics, antidepressants, and sodium channel blockers. There are no comparative studies that identify the most effective medication for pain reduction in CSPN. To determine which medication (pregabalin, duloxetine, nortriptyline, or mexiletine) is most effective for reducing neuropathic pain and best tolerated in patients with CSPN. From December 1, 2014, through October 20, 2017, a bayesian adaptive, open-label randomized clinical comparative effectiveness study of pain in 402 participants with CSPN was conducted at 40 neurology care clinics. The trial included response adaptive randomization. Participants were patients with CSPN who were 30 years or older, with a pain score of 4 or greater on a numerical rating scale (range, 0-10, with higher scores indicating a higher level of pain). Participant allocation to 1 of 4 drug groups used the utility function and treatment's sample size for response adaptation randomization. At each interim analysis, a decision was made to continue enrolling (up to 400 participants) or stop the whole trial for success (80% power). Patient engagement was maintained throughout the trial, which helped guide the study and identify ways to communicate and disseminate information. Analysis was performed from December 11, 2015, to January 19, 2018. Participants were randomized to receive nortriptyline (n = 134), duloxetine (n = 126), pregabalin (n = 73), or mexiletine (n = 69). The primary outcome was a utility function that was a composite of the efficacy (participant reported pain reduction of ≥50% from baseline to week 12) and quit (participants who discontinued medication) rates. Among the 402 participants (213 men [53.0%]; mean [SD] age, 60.1 [13.4] years; 343 White [85.3%]), the utility function of nortriptyline was 0.81 (95% bayesian credible interval [CrI], 0.69-0.93; 34 of 134 [25.4%] efficacious; and 51 of 134 [38.1%] quit), of duloxetine was 0.80 (95% CrI, 0.68-0.92; 29 of 126 [23.0%] efficacious; and 47 of 126 [37.3%] quit), pregabalin was 0.69 (95% CrI, 0.55-0.84; 11 of 73 [15.1%] efficacious; and 31 of 73 [42.5%] quit), and mexiletine was 0.58 (95% CrI, 0.42-0.75; 14 of 69 [20.3%] efficacious; and 40 of 69 [58.0%] quit). The probability each medication yielded the highest utility was 0.52 for nortriptyline, 0.43 for duloxetine, 0.05 for pregabalin, and 0.00 for mexiletine. This study found that, although there was no clearly superior medication, nortriptyline and duloxetine outperformed pregabalin and mexiletine when pain reduction and undesirable adverse effects are combined to a single end point. ClinicalTrials.gov Identifier: NCT02260388.

The Pain Assessment in Impaired Cognition scale (PAIC15): A multidisciplinary and international approach to develop and test a meta‐tool for pain assessment in impaired cognition, especially dementia

Over the last decades, a considerable number of observational scales have been developed to assess pain in persons with dementia. The time seems ripe now to build on the knowledge and expertize implemented in these scales to form an improved, "best-of" meta-tool. The EU-COST initiative "Pain in impaired cognition, especially dementia" aimed to do this by selecting items out of existing observational scales and critically re-assessing their suitability to detect pain in dementia. This paper reports on the final phase of this collaborative task. Items from existing observational pain scales were tested for "frequency of occurrence (item difficulty)," "reliability" and "validity." This psychometric testing was carried out in eight countries, in different healthcare settings, and included clinical as well as experimental pain conditions. Across all studies, 587 persons with dementia, 27 individuals with intellectual disability, 12 Huntington's disease patients and 59 cognitively healthy controls were observed during rest and movement situations or while receiving experimental pressure pain, respectively. The psychometric outcomes for each item across the different studies were evaluated within an international and multidisciplinary team of experts and led a final selection of 15 items (5x facial expressions, 5x body movements, 5x vocalizations). The final list of 15 observational items have demonstrated psychometric quality and clinical usefulness both in their former scales and in the present international evaluation; accordingly, they qualified twice to form a new internationally agreed-on meta-tool for Pain Assessment in Impaired Cognition, the PAIC-15 scale. Using a meta-tool approach by building on previous observational pain assessment scales and putting the items of these scales through rigorous empirical testing (using experimental as well as clinical pain studies in several European countries), we were able to identify the best items for pain assessment in individuals with impaired cognition. These selected items form the novel PAIC15 scale (pain assessment in impaired cognition, 15 items).

Conditioning pain modulation reduces pain only during the first stimulation of thetemporal summation of pain paradigm in healthy participants.

Pro-nociceptive and anti-nociceptive mechanisms are commonly assessed in clinical and experimental pain studies, buttheir potential interaction is not well understood. Investigate the effect of conditioning pain modulation (CPM) on temporal summation of pain (TSP). Twenty healthy participants underwent cuff algometry assessment on the lower legs to establish the pressure pain tolerance threshold (PTT). For the TSP assessment, ten stimuli at the level of the PTT were delivered by computerised cuff inflations (1-s stimulation, 1-s break) while participants rated pain intensity on a 10-cm electronic visual analogue scale (VAS). This TSP paradigm was thenrepeated with a simultaneous conditioning stimulus induced by a cuff on the contralateral leg, inflated to a constant pressure corresponding to 30% (mild), 70% (moderate) or 100% (severe) of the PTT. These were assessed in a randomised order, with a fifteen-minute break between tests. A final TSP test without conditioning was reassessed at the end (post-recording). An interaction between stimuli (1-10) and repetition (p<0.05) was found for VAS scores. VAS scores for the first stimulus were decreased during 30%, 70%, and 100% conditioning intensities, compared to baselineand post-recordings (p<0.05). There was a significant increase in TSP during conditioning (p<0.05). There were no significant differences between baseline and post-recordings for any stimuli (p>0.05). The current study indicates that mild to severe stimuli administered by cuff algometry does not modulate summation effect of temporal summation of pain, which could indicate that pain facilitatory mechanisms are more potent compared with pain inhibitory mechanisms. Current knowledge on the interaction effect of pro and anti-nociceptive paradigms are the lacking. The current study indicates that conditioning pain modulation does not modulate thesummation effect of temporal summation of pain, when evaluated by computerized pressure algometry. This finding was independent of the mild, moderate and severe painful conditioning intensities.

(161) Enhanced Suprathreshold Heat Pain Sensitivity in Healthy Hispanic Relative to Non-Hispanic White Adults: A Preliminary Examination

While clinical pain studies in the U.S. have established that Hispanic Americans experience greater levels of pain and pain-related impairments compared to Non-Hispanic White Americans, the components of pain contributing to these disparities remain unclear. Although a number of previous studies have examined the pain sensitivity to standardized laboratory pain protocols in African Americans relative to Non-Hispanic White Americans, little work has extended to other ethnic groups, including Hispanic Americans. Therefore, to examine the role of ethnicity on pain sensitivity, the present study evaluated the effect of ethnicity in healthy Hispanic American and Non-Hispanic White American adults on self-report pain intensity to thermal-heat laboratory pain. Healthy Hispanic (n = 43, n female = 28) and Non-Hispanic White (n = 26, n female = 10) volunteers recruited through a psychology subject pool completed an ascending thermal-heat laboratory pain assessment comprised of four heat pulses at low (41°C), medium (44°C), and high (47°C) heat. After each pulse, participants verbally rated their pain intensity on a 0 to 10 numerical rating scale. A three-way mixed ethnicity X gender X temperature rating repeated measures ANOVA was conducted to reveal a statistically significant two-way interaction between temperature rating and ethnicity, F(1.833, 119.113) = 5.525, p = .006, partial η2 = .078. Given the small sample size, follow-up ANOVA comparisons revealed no differences in pain intensity ratings at the low and medium temperatures (p's > .16). However, at the high temperature, self-reported pain intensity was greater for Hispanics (M = 6.13, SD = 1.86) relative to Non-Hispanic Whites (M = 5.17, SD = 1.89), F(1, 67) = 4.252, p = .043, partial η2 = .060. Consistent with previous studies of laboratory pain disparities in ethnic minorities, these preliminary findings suggest that greater sensitivity to suprathreshold pain in Hispanics may contribute to disparities evidenced in Hispanic clinical pain.

AAAPT Diagnostic Criteria for Acute Sickle Cell Disease Pain

Acute pain episodes are the most common complication in patients with sickle cell disease (SCD). Classically attributed to vaso-occlusion, recent insights suggest that chronic pain may also contribute to the pathogenesis of acute pain episodes, which adds complexity to their diagnosis and management. A taxonomy, or classification system, for acute pain in patients with SCD would aid research efforts and enhance clinical care. To meet this need, the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks public–private partnership with the U.S. Food and Drug Administration, the American Pain Society, and the American Academy of Pain Medicine formed the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks–American Pain Society–American Academy of Pain Medicine Pain Taxonomy initiative. One of the goals of this initiative was to develop taxonomies for acute pain disorders, including SCD. To accomplish this, a working group of experts in SCD and pain was convened. Based on available literature and expert opinion, the working group used a 5-dimenional structure (diagnostic criteria, common features, modulating factors, impact/functional consequences, and putative mechanisms) to develop an acute pain taxonomy that is specific to SCD. As part of this, a set of 4 diagnostic criteria, with 2 modifiers to account for the influence of chronic pain, are proposed to define the types of acute pain observed in patients with SCD. PerspectiveThis article presents a taxonomy for acute pain in patients with SCD. This taxonomy could help to standardize definitions of acute pain in clinical studies of patients with SCD.

A detailed clinical study of pain in 1957 participants with early/moderate Parkinson's disease

IntroductionThe causes of pain in early/moderate Parkinson's disease (PD) are not well understood. Although peripheral factors such as rigidity, reduced joint movements and poor posture may contribute towards the development of pain, central mechanisms including altered nociceptive processing may also be involved. MethodsWe performed a large clinical study to investigate potential factors contributing towards pain in early/moderate PD. We recruited 1957 PD participants who had detailed assessments of pain, motor and non-motor symptoms. The King's Parkinson's Pain scale was used to quantify different subtypes of pain. Results85% of participants reported pain (42% with moderate to severe pain). Pain influenced quality of life more than motor symptoms in a multiple regression model. Factors predicting overall pain severity included affective symptoms, autonomic symptoms, motor complications, female gender and younger age, but not motor impairment or disease duration. There was negligible correlation between the severity of motor impairment and the severity of musculoskeletal or dystonic pain as well as between the severity of OFF period motor problems and the severity of OFF period pain or OFF period dystonic pain. Features of central sensitization, including allodynia and altered pain sensation were common in this population. The use of drugs targeting central pain was very low. ConclusionsPain in early/moderate PD cannot be explained by peripheral factors. Central causes may play a much more important role than previously considered. These results should lead to a major shift in the investigation and management of this common and disabling symptom.

Clinical study of pain after inguinal hernia repair

Background: Chronic severe pain following inguinal hernia repair is a significant post-operative problem. Pain is a complex study subject, mostly defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage.Methods: Patients undergoing elective inguinal hernioplasty in the Hospital from March 2016 to March 2017 were included in the study. Seventy-eight patients were present for follow up for a period of 6 months. Patients presenting with obstructed/strangulated inguinal hernia were excluded from study.Results: Majority of our patients were male 97.43% with mean age 49.1 years (range 16-78 years). Table 8 shows the VAS scores of patients at six months following surgery. When patients were divided into groups of mild (1-3), moderate (4-7), and severe pain (&gt;7) on basis of VAS score, it was found that majority, 34.61%, had mild pain, 8.97% had moderate pain, and less than 1% had severe pain.Conclusions: In the present study, author found that chronic pain following inguinal hernia repair causes significant morbidity to patients and should not be ignored. All measures must be taken to suppress early postoperative pain and prevent complications as these lead to development of chronic pain.