Patient engagement in designing, conducting, and disseminating clinical pain research: IMMPACT recommended considerations

ABSTRACT

In the traditional clinical research model, patients are typically involved only as participants. However, there has been a shift in recent years highlighting the value and contributions that patients bring as members of the research team, across the clinical research lifecycle. It is becoming increasingly evident that to develop research that is both meaningful to people who have the targeted condition and is feasible, there are important benefits of involving patients in the planning, conduct, and dissemination of research from its earliest stages. In fact, research funders and regulatory agencies are now explicitly encouraging, and sometimes requiring, that patients are engaged as partners in research. Although this approach has become commonplace in some fields of clinical research, it remains the exception in clinical pain research. As such, the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials convened a meeting with patient partners and international representatives from academia, patient advocacy groups, government regulatory agencies, research funding organizations, academic journals, and the biopharmaceutical industry to develop consensus recommendations for advancing patient engagement in all stages of clinical pain research in an effective and purposeful manner. This article summarizes the results of this meeting and offers considerations for meaningful and authentic engagement of patient partners in clinical pain research, including recommendations for representation, timing, continuous engagement, measurement, reporting, and research dissemination.

Intraoperative pharmacologic opioid minimisation strategies and patient-centred outcomes after surgery: a scoping review

BACKGROUND

Postoperative patient-centred outcome measures are essential to capture the patient's experience after surgery. Although a large number of pharmacologic opioid minimisation strategies (i.e. opioid alternatives) are used for patients undergoing surgery, it remains unclear which strategies are most promising in terms of patient-centred outcome improvements. This scoping review had two main objectives: (1) to map and describe evidence from clinical trials assessing the patient-centred effectiveness of pharmacologic intraoperative opioid minimisation strategies in adult surgical patients, and (2) to identify promising pharmacologic opioid minimisation strategies.

METHODS

We searched MEDLINE, Embase, CENTRAL, Web of Science, and CINAHL databases from inception to February 2023. We included trials investigating the use of opioid minimisation strategies in adult surgical patients and reporting at least one patient-centred outcome. Study screening and data extraction were conducted independently by at least two reviewers.

RESULTS

Of 24,842 citations screened for eligibility, 2803 trials assessed the effectiveness of intraoperative opioid minimisation strategies. Of these, 457 trials (67,060 participants) met eligibility criteria, reporting at least one patient-centred outcome. In the 107 trials that included a patient-centred primary outcome, patient wellbeing was the most frequently used domain (55 trials). Based on aggregate findings, dexmedetomidine, systemic lidocaine, and COX-2 inhibitors were promising strategies, while paracetamol, ketamine, and gabapentinoids were less promising. Almost half of the trials (253 trials) did not report a protocol or registration number.

CONCLUSIONS

Researchers should prioritise and include patient-centred outcomes in the assessment of opioid minimisation strategy effectiveness. We identified three potentially promising pharmacologic intraoperative opioid minimisation strategies that should be further assessed through systematic reviews and multicentre trials. Findings from our scoping review may be influenced by selective outcome reporting bias.

STUDY REGISTRATION

OSF - https://osf.io/7kea3.

Movement-evoked Pain versus Pain at Rest in Postsurgical Clinical Trials and in Meta-analyses: An Updated Systematic Review

BACKGROUND

Given the widespread recognition that postsurgical movement-evoked pain is generally more intense, and more functionally relevant, than pain at rest, the authors conducted an update to a previous 2011 review to re-evaluate the assessment of pain at rest and movement-evoked pain in more recent postsurgical analgesic clinical trials.

METHODS

The authors searched MEDLINE and Embase for postsurgical pain randomized controlled trials and meta-analyses published between 2014 and 2023 in the setting of thoracotomy, knee arthroplasty, and hysterectomy using methods consistent with the original 2011 review. Included trials and meta-analyses were characterized according to whether they acknowledged the distinction between pain at rest and movement-evoked pain and whether they included pain at rest and/or movement-evoked pain as a pain outcome. For trials measuring movement-evoked pain, pain-evoking maneuvers used to assess movement-evoked pain were tabulated.

RESULTS

Among the 944 included trials, 504 (53%) did not measure movement-evoked pain (vs. 61% in 2011), and 428 (45%) did not distinguish between pain at rest and movement-evoked pain when defining the pain outcome (vs. 52% in 2011). Among the 439 trials that measured movement-evoked pain, selection of pain-evoking maneuver was highly variable and, notably, was not even described in 139 (32%) trials (vs. 38% in 2011). Among the 186 included meta-analyses, 94 (51%) did not distinguish between pain at rest and movement-evoked pain (vs. 71% in 2011).

CONCLUSIONS

This updated review demonstrates a persistent limited proportion of trials including movement-evoked pain as a pain outcome, a substantial proportion of trials failing to distinguish between pain at rest and movement-evoked pain, and a lack of consistency in the use of pain-evoking maneuvers for movement-evoked pain assessment. Future postsurgical trials need to (1) use common terminology surrounding pain at rest and movement-evoked pain, (2) assess movement-evoked pain in virtually every trial if not contraindicated, and (3) standardize movement-evoked pain assessment with common, procedure-specific pain-evoking maneuvers. More widespread knowledge translation and mobilization are required in order to disseminate this message to current and future investigators.

EDITOR’S PERSPECTIVE

Association of peri-operative prescription of non-steroidal anti-inflammatory drugs with continued prescription of opioids after total knee arthroplasty: a retrospective claims-based cohort study

Non-steroidal anti-inflammatory drugs (NSAIDs) are one of the mainstays of multimodal pain management. While effective for acute pain control, recent pre-clinical evidence has raised concerns regarding an association between NSAIDs and chronic pain and potential opioid use. Our objective was to explore the association between peri-operative use of prescription NSAIDs and the need for continued opioid prescriptions lasting 90-180 days in previously opioid-naïve patients undergoing total knee arthroplasty. A database of health claims in the USA was used to identify all opioid-naïve adult patients who underwent primary knee arthroplasty between January 2010 and October 2021. We evaluated the magnitude of association between peri-operative prescription NSAID claims and claims for opioids at 90 days postoperatively using multivariable logistic regression models. Secondary outcomes included: the magnitude of association between peri-operative NSAID prescription and claims for opioids at 180 days postoperatively; and identifying other potential factors associated with opioid claims at 90 days postoperatively. After risk adjustment using multivariable logistic regression models in the 789,736-patient cohort, the adjusted odds ratio (95%CI) for a continuous claim of opioids at 90 and 180 days postoperatively among patients with a peri-operative NSAID prescription within 30 days was 1.32 (1.30-1.35), p < 0.001; and 1.12 (1.10-1.15), p < 0.001, respectively. This estimate of effect remained robust at 90 days after accounting for known potential confounders, including pre-existing knee pain and acute postoperative pain severity. Similar analysis of other pain medications (e.g. paracetamol) did not detect such an association. This population-based cohort study suggests that peri-operative prescription NSAID use may be associated with continued opioid prescription claims at 90 and 180 days after knee arthroplasty, even after adjusting for other observed covariates for continuous opioid claims. These novel findings can inform clinical decision-making for post-surgical pain management, risk-benefit discussions with patients and future research.

Effectiveness of dexmedetomidine during surgery under general anaesthesia on patient-centred outcomes: a systematic review and Bayesian meta-analysis protocol

INTRODUCTION

Dexmedetomidine is a promising pharmaceutical strategy to minimise opioid use during surgery. Despite its growing use, it is uncertain whether dexmedetomidine can improve patient-centred outcomes such as quality of recovery and pain.

METHODS AND ANALYSIS

We will conduct a systematic review and meta-analysis following the recommendations of the Cochrane Handbook for Systematic Reviews. We will search MEDLINE, Embase, CENTRAL, Web of Science and CINAHL approximately in October 2023. We will include randomised controlled trials evaluating the impact of systemic intraoperative dexmedetomidine on patient-centred outcomes. Patient-centred outcome definition will be based on the consensus definition established by the Standardised Endpoints in Perioperative Medicine initiative (StEP-COMPAC). Our primary outcome will be the quality of recovery after surgery. Our secondary outcomes will be patient well-being, function, health-related quality of life, life impact, multidimensional assessment of postoperative acute pain, chronic pain, persistent postoperative opioid use, opioid-related adverse events, hospital length of stay and adverse events. Two reviewers will independently screen and identify trials and extract data. We will evaluate the risk of bias of trials using the Cochrane Risk of Bias Tool (RoB 2.0). We will synthesise data using a random effects Bayesian model framework, estimating the probability of achieving a benefit and its clinical significance. We will assess statistical heterogeneity with the tau-squared and explore sources of heterogeneity with meta-regression. We have involved patient partners, clinicians, methodologists, and key partner organisations in the development of this protocol, and we plan to continue this collaboration throughout all phases of this systematic review.

ETHICS AND DISSEMINATION

Our systematic review does not require research ethics approval. It will help inform current clinical practice guidelines and guide development of future randomised controlled trials. The results will be disseminated in open-access peer-reviewed journals, presented at conferences and shared among collaborators and networks.

PROSPERO REGISTRATION NUMBER

CRD42023439896.

Randomized, double-blind, controlled trial of a combination of alpha-lipoic acid and pregabalin for neuropathic pain: the PAIN-CARE trial

ABSTRACT

We compared a combination of the nonsedating antioxidant, alpha-lipoic acid (ALA), with the sedating anticonvulsant, pregabalin, vs each monotherapy to treat neuropathic pain due to peripheral neuropathies. In this randomized, double-blind, 3-period crossover trial, participants received oral ALA, pregabalin, and their combination-each for 6 weeks. The primary outcome was mean daily pain intensity at maximal tolerated doses (MTD); secondary outcomes included quality of life (SF-36), sleep (Medical Outcomes Study-Sleep Scale), adverse effects, drug doses, and other measures. Of 55 participants randomized (20-diabetic neuropathy, 19-small fiber neuropathy, and 16-other neuropathies), 46 completed 2 periods, and 44 completed 3. At MTD, the primary outcome of mean pain intensity (0-10) was 5.32 (standard error, SE = 0.18), 3.96 (0.25), 3.25 (0.25), and 3.16 (0.25) at baseline, ALA, pregabalin, and combination, respectively ( P < 0.01 for ALA vs combination and pregabalin). Treatment differences were similar in subgroups with diabetic neuropathy and with other neuropathies. SF-36 total scores (higher number indicates better quality of life) were 66.6 (1.88), 70.1 (1.88), and 69.4 (1.87) with ALA, pregabalin, and combination ( P < 0.05 for ALA vs combination and pregabalin). At MTD, there were no statistically significant treatment differences in adverse effects or drug doses. This trial demonstrates superiority of pregabalin vs ALA but provides no evidence to suggest added benefit of combining ALA with pregabalin to treat neuropathic pain.

Patient Expectations and Therapeutic Alliance Affect Pain Reduction Following Lidocaine Infusion in an Interdisciplinary Chronic Pain Clinic

Pain experience is affected by both ascending nociceptive signals and descending modulation. Expectations can affect pain experience and augment treatment-induced analgesia through descending inhibitory modulation of pain. This open-label, prospective cohort study examined the association between participant expectation ratings and pain reduction in adult participants with chronic pain receiving an intravenous lidocaine infusion. We aimed to explore whether: 1) participants' expectations of treatment efficacy were associated with pain reduction over 8 weeks after infusion; and 2) participants' therapeutic alliance was associated with expectations and/or pain reduction. We recruited 70 participants with chronic pain scheduled for lidocaine infusion. Study measures included pain intensity (pre-treatment, post-treatment, and daily for 8 weeks), treatment expectations (EXPECT), and therapeutic alliance (Trust in Physician and Working Alliance Inventory-Short Revised). Baseline treatment expectations were significantly correlated with pain reduction (r = .42, P < .01). Therapeutic alliance was significantly correlated with expectations (r = .27, P < .05) and pain reduction (r = .38, P < .01). This study quantifies the contribution of: 1) treatment expectations; and 2) therapeutic alliance to the magnitude of lidocaine-induced pain reduction. Results generate the hypothesis that focused efforts to augment treatment expectations and therapeutic alliance could serve to improve pain treatment outcomes. PERSPECTIVE: This study evaluates the relationship between pain reduction and ratings of: 1) treatment expectations; and 2) therapeutic alliance following an intravenous lidocaine infusion. Results generate the hypothesis that focused efforts to augment treatment expectations and therapeutic alliance could serve to improve pain treatment outcomes.

Self-Reported Pain Treatment Practices Among U.S. and Canadian Adults: Findings From a Population Survey

Background and Objectives

Pain treatments and their efficacy have been studied extensively. Yet surprisingly little is known about the types of treatments, and combinations of treatments, that community-dwelling adults use to manage pain, as well as how treatment types are associated with individual characteristics and national-level context. To fill this gap, we evaluated self-reported pain treatment types among community-dwelling adults in the United States and Canada. We also assessed how treatment types correlate with individuals' pain levels, sociodemographic characteristics, and country of residence, and identified unique clusters of adults in terms of treatment combinations.

Research Design and Methods

We used the 2020 "Recovery and Resilience" United States-Canada general online survey with 2 041 U.S. and 2 072 Canadian community-dwelling adults. Respondents selected up to 10 pain treatment options including medication, physical therapy, exercise, etc., and an open-ended item was available for self-report of any additional treatments. Data were analyzed using descriptive, regression-based, and latent class analyses.

Results

Over-the-counter (OTC) medication was reported most frequently (by 55% of respondents, 95% CI 53%-56%), followed by "just living with pain" (41%, 95% CI 40%-43%) and exercise (40%, 95% CI 38%-41%). The modal response (29%) to the open-ended item was cannabis use. Pain was the most salient correlate, predicting a greater frequency of all pain treatments. Country differences were generally small; a notable exception was alcohol use, which was reported twice as often among U.S. versus Canadian adults. Individuals were grouped into 5 distinct clusters: 2 groups relied predominantly on medication (prescription or OTC), another favored exercise and other self-care approaches, one included adults "just living with" pain, and the cluster with the highest pain levels employed all modalities heavily.

Discussion and Implications

Our findings provide new insights into recent pain treatment strategies among North American adults and identify population subgroups with potentially unmet need for more adaptive and effective pain management.

Research objectives and general considerations for pragmatic clinical trials of pain treatments: IMMPACT statement

ABSTRACT

Many questions regarding the clinical management of people experiencing pain and related health policy decision-making may best be answered by pragmatic controlled trials. To generate clinically relevant and widely applicable findings, such trials aim to reproduce elements of routine clinical care or are embedded within clinical workflows. In contrast with traditional efficacy trials, pragmatic trials are intended to address a broader set of external validity questions critical for stakeholders (clinicians, healthcare leaders, policymakers, insurers, and patients) in considering the adoption and use of evidence-based treatments in daily clinical care. This article summarizes methodological considerations for pragmatic trials, mainly concerning methods of fundamental importance to the internal validity of trials. The relationship between these methods and common pragmatic trials methods and goals is considered, recognizing that the resulting trial designs are highly dependent on the specific research question under investigation. The basis of this statement was an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) systematic review of methods and a consensus meeting. The meeting was organized by the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership. The consensus process was informed by expert presentations, panel and consensus discussions, and a preparatory systematic review. In the context of pragmatic trials of pain treatments, we present fundamental considerations for the planning phase of pragmatic trials, including the specification of trial objectives, the selection of adequate designs, and methods to enhance internal validity while maintaining the ability to answer pragmatic research questions.

Do "central sensitization" questionnaires reflect measures of nociceptive sensitization or psychological constructs? A systematic review and meta-analyses

ABSTRACT

Central sensitization (CS) is defined as an increased nociceptive responsiveness due to sensitization of neurons in the central nervous system, usually the result of prolonged nociceptive input or a disease state associated with noxious inputs (eg, polyarthritis). The concept of CS has recently been adopted in clinical assessments of chronic pain, but its diagnosis in humans may now include a wide range of hypervigilant responses. The purpose of this review is to ascertain whether self-report questionnaires linked with CS are associated with enhanced nociceptive responses or whether they measure sensitivity in a broader sense (ie, emotional responses). According to our published, PROSPERO-registered review protocol (CRD42021208731), a predefined search of studies that involve the Central Sensitization Inventory (CSI) or Pain Sensitivity Questionnaire (PSQ), correlated with either nociceptive sensory tests or emotional hypervigilance was conducted on MEDLINE, PsycINFO, and Web of Science. Correlations between the CSI or PSQ with our primary outcomes were extracted and meta-analysed. A review of 66 studies totalling 13,284 participants found that the CSI (but not the PSQ) strongly correlated with psychological constructs: depression, anxiety, stress, pain catastrophising, sleep, and kinesiophobia. The CSI and PSQ showed weak or no correlations with experimental measures of nociceptive sensitivity: pain thresholds, temporal summation, or conditioned pain modulation. The PSQ did, however, correlate strongly with phasic heat and tonic cold pain tests. The studies reviewed did not provide sufficient evidence that self-report measures reflect a canonical understanding of CS. The CSI more closely reflects psychological hypervigilance than increased responsiveness of nociceptive neurons.

Prevalence of postoperative pain after hospital discharge: systematic review and meta-analysis

Assessment and management of postoperative pain after hospital discharge is very challenging. We conducted a systematic review to synthesize available evidence on the prevalence of moderate-to-severe postoperative pain within the first 1 to 14 days after hospital discharge. The previously published protocol for this review was registered in PROSPERO. MEDLINE and EMBASE databases were searched until November 2020. We included observational postsurgical pain studies in the posthospital discharge setting. The primary outcome for the review was the proportion of study participants with moderate-to-severe postoperative pain (eg, pain score of 4 or more on a 10-point Numerical Rating Scale) within the first 1 to 14 days after hospital discharge. This review included 27 eligible studies involving a total of 22,108 participants having undergone a wide variety of surgical procedures. The 27 studies included ambulatory surgeries (n = 19), inpatient surgeries (n = 1), both ambulatory and inpatient surgeries (n = 4), or was not specified (n = 3). Meta-analyses of combinable studies provided estimates of pooled prevalence rates of moderate-to-severe postoperative pain ranging from 31% 1 day after discharge to 58% 1 to 2 weeks after discharge. These findings suggest that moderate-to-severe postoperative pain is a common occurrence after hospital discharge and highlight the importance of future efforts to more effectively evaluate, prevent, and treat postsurgical pain in patients discharged from the hospital.

Prevalence and correlates of prescription opioid use among US adults, 2019-2020

This study estimates the prevalence of prescription opioid use (POU) in the United States (US) in 2019-2020, both in the general population and specifically among adults with pain. It also identifies key geographic, demographic, and socioeconomic correlates of POU. Data were from the nationally-representative National Health Interview Survey 2019 and 2020 (N = 52,617). We estimated POU prevalence in the prior 12 months among all adults (18+), adults with chronic pain (CP), and adults with high-impact chronic pain (HICP). Modified Poisson regression models estimated POU patterns across covariates. We found POU prevalence of 11.9% (95% CI 11.5, 12.3) in the general population, 29.3% (95% CI 28.2, 30.4) among those with CP, and 41.2% (95% CI 39.2, 43.2) among those with HICP. Findings from fully-adjusted models include the following: In the general population, POU prevalence declined about 9% from 2019 to 2020 (PR = 0.91, 95% CI 0.85, 0.96). POU varied substantially across US geographic regions: It was significantly more common in the Midwest, West, and especially the South, where adults had 40% higher POU (PR = 1.40, 95% CI 1.26, 1.55) than in the Northeast. In contrast, there were no differences by rural/urban residence. In terms of individual characteristics, POU was lowest among immigrants and among the uninsured, and was highest among adults who were food insecure and/or not employed. These findings suggest that prescription opioid use remains high among American adults, especially those with pain. Geographic patterns suggest systemic differences in therapeutic regimes across regions but not rurality, while patterns across social characteristics highlight the complex, opposing effects of limited access to care and socioeconomic precarity. Against the backdrop of continuing debates about benefits and risks of opioid analgesics, this study identifies and invites further research about geographic regions and social groups with particularly high or low prescription opioid use.

Trial protocol for a multicenter randomized controlled trial to assess the efficacy and safety of intravenous ketamine for chronic daily headaches: the "KetHead" trial

BACKGROUND

Chronic daily headaches (CDH) are common and associated with significant morbidity, poor quality of life, and substantial burden on the healthcare system. CDH tends to be refractory to conventional medical management and/or patients cannot afford expensive treatments. It is stipulated that CDH share a mechanism of central sensitization in the trigeminocervical complex, mediated by activation of the N-methyl-D-aspartate (NMDA) receptors. Ketamine, a non-competitive NMDA antagonist, has been used in the treatment of chronic pain, but its role in CDH has not been completely established. This trial aims to evaluate the effect of high-dose IV ketamine infusions (compared to placebo) on the number of headache days at 28 days post-infusion.

METHODS

A multicenter, placebo-controlled, randomized controlled trial will be conducted with two parallel groups and blinding of participants and outcome assessors. The study will include 56 adults with a CDH diagnosis as per ICHD-3 criteria. Participants will be randomized (1:1) to either ketamine (1 mg. kg^-1 bolus followed by infusion of 1 mg. kg^-1. h^-1 for 6 h) or placebo (0.9% saline in the same volume and infusion rate as the trial medication) bolus and infusion for 6 h. The impact on the number of monthly headache days, headache intensity, physical activity, mood, sleep, quality of life, analgesic consumption, and adverse effects will be recorded at baseline, immediately post-infusion, and from 1 to 28 days, 29 to 56 days, and 57 to 84 days after the infusion DISCUSSION: Despite advancements in treatment, many patients continue to suffer from CDH. This trial investigates whether high-dose IV ketamine infusions can effectively and safely improve the CDH burden as compared to a placebo infusion. This treatment could become a safe, affordable, and widely available option for patients living with refractory headache.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05306899. Registered on April 1, 2022.

Intraoperative pharmacologic opioid minimisation strategies and patient-centred outcomes after surgery: a scoping review protocol

INTRODUCTION

For close to a century opioid administration has been a standard of care to complement anaesthesia during surgery. Considering the worldwide opioid epidemic, this practice is now being challenged and there is a growing use of systemic pharmacological opioid minimising strategies. Our aim is to conduct a scoping review that will examine clinical trials that have evaluated the impact of intraoperative opioid minimisation strategies on patient-centred outcomes and identify promising strategies.

METHODS AND ANALYSIS

Our scoping review will follow the framework developed by Arksey and O'Malley. We will search MEDLINE, Embase, CENTRAL, Web of Science and CINAHL from their inception approximately in March 2023. We will include randomised controlled trials, assessing the impact of systemic intraoperative pharmacologic opioid minimisation strategies on patient-centred outcomes. We define an opioid minimisation strategy as any non-opioid drug with antinociceptive properties administered during the intraoperative period. Patient-centred outcomes will be defined and classified based on the consensus definitions established by the Standardised Endpoints in Perioperative Medicine initiative (StEP-COMPAC group) and informed by knowledge users and patient partners. We will use a coproduction approach involving interested parties. Our multidisciplinary team includes knowledge users, patient partners, methodologists and knowledge user organisations. Knowledge users will provide input on methods, outcomes, clinical significance of findings, implementation and feasibility. Patient partners will participate in assessing the relevance of our design, methods and outcomes and help to facilitate evidence translation. We will provide a thorough description of available clinical trials, compare their reported patient-centred outcome measures with established recommendations and identify promising strategies.

ETHICS AND DISSEMINATION

Ethics approval is not required for the review. Our scoping review will inform future research including clinical trials and systematic reviews through identification of important intraoperative interventions. Results will be disseminated through a peer-reviewed publication, presentation at conferences and through our network of knowledge user collaborators.

REGISTRATION

Open Science Foundation (currently embargoed).

Optimizing and Accelerating the Development of Precision Pain Treatments for Chronic Pain: IMMPACT Review and Recommendations

Large variability in the individual response to even the most-efficacious pain treatments is observed clinically, which has led to calls for a more personalized, tailored approach to treating patients with pain (ie, "precision pain medicine"). Precision pain medicine, currently an aspirational goal, would consist of empirically based algorithms that determine the optimal treatments, or treatment combinations, for specific patients (ie, targeting the right treatment, in the right dose, to the right patient, at the right time). Answering this question of "what works for whom" will certainly improve the clinical care of patients with pain. It may also support the success of novel drug development in pain, making it easier to identify novel treatments that work for certain patients and more accurately identify the magnitude of the treatment effect for those subgroups. Significant preliminary work has been done in this area, and analgesic trials are beginning to utilize precision pain medicine approaches such as stratified allocation on the basis of prespecified patient phenotypes using assessment methodologies such as quantitative sensory testing. Current major challenges within the field include: 1) identifying optimal measurement approaches to assessing patient characteristics that are most robustly and consistently predictive of inter-patient variation in specific analgesic treatment outcomes, 2) designing clinical trials that can identify treatment-by-phenotype interactions, and 3) selecting the most promising therapeutics to be tested in this way. This review surveys the current state of precision pain medicine, with a focus on drug treatments (which have been most-studied in a precision pain medicine context). It further presents a set of evidence-based recommendations for accelerating the application of precision pain methods in chronic pain research. PERSPECTIVE: Given the considerable variability in treatment outcomes for chronic pain, progress in precision pain treatment is critical for the field. An array of phenotypes and mechanisms contribute to chronic pain; this review summarizes current knowledge regarding which treatments are most effective for patients with specific biopsychosocial characteristics.

Frequency and characteristics of patient exclusion criteria in Canadian multidisciplinary pain treatment facilities: a cross-sectional study

PURPOSE

A multidisciplinary approach is recommended for patients with complex chronic pain (CP). Many multidisciplinary pain treatment facilities (MTPFs) use patient exclusion criteria but little is known about their characteristics. The objective of this study was to describe the frequency and characteristics of exclusion criteria in public Canadian MTPFs.

METHODS

We conducted a cross-sectional study in which we defined an MPTF as a clinic staffed with professionals from three disciplines or more (including at least one medical specialty) and whose services were integrated within the facility. We disseminated a web-based questionnaire in 2017-2018 to the administrative leads of MPTFs across the country. They were invited to complete the questionnaire about the characteristics of their facilities. Data were analyzed using descriptive statistics and correlation measures.

RESULTS

A total of 87 MTPFs were included in the analyses. Half of them (52%) reported using three exclusion criteria or more. There was no significant association between the number of exclusion criteria and wait time for a first appointment or number of new consultations in the past year. Fibromyalgia and migraine were the most frequently excluded pain syndromes (10% and 7% of MPTFs, respectively). More than one MPTF out of four excluded patients with mental health disorders (30%) and/or substance use disorders (29%), including MPTFs with specialists in their staff.

CONCLUSIONS

Multidisciplinary pain treatment facility exclusion criteria are most likely to affect CP patients living with complex pain issues and psychosocial vulnerabilities. Policy efforts are needed to support Canadian MPTFs in contributing to equitable access to pain management.

Glial-modulating agents for the treatment of pain: protocol for a systematic review

INTRODUCTION

Evidence suggests a role for Central nervous system glia in pain transmission and in augmenting maladaptive opioid effects. Identification of drugs that modulate glia has guided the evaluation of glial suppression as a pain management strategy. This planned systematic review will describe evidence of the efficacy and adverse effects of glial-modulating drugs in pain management.

METHODS AND ANALYSIS

A detailed search will be conducted on the Cochrane Central Register of Controlled Trials, Medline, and Embase from their inception until the date the final searches are run to identify relevant randomised controlled trials. The reference lists of retrieved studies, as well as online trial registries, will also be searched. English language, randomised, double-blind trials comparing various glial-modulating drugs with placebo and/or other comparators, with participant-reported pain assessment, will be included. Two reviewers will independently evaluate studies for eligibility, extract data and assess trial quality and potential bias. Risk of bias will be assessed using criteria outlined in the Cochrane Handbook for Systematic Review of Interventions. Primary outcomes for this review will include any validated measure of pain intensity and/or pain relief. Dichotomous data will be used to calculate risk ratio and number needed to treat or harm. The quality of evidence will be assessed using Grading of Recommendations Assessment, Development and Evaluation.

ETHICS AND DISSEMINATION

This systematic review does not require formal ethics approval. The findings will be disseminated through peer-reviewed publications and conference presentations.

PROSPERO REGISTRATION NUMBER

CRD42021262074.

Patient engagement partnerships in clinical trials (PEP-CT): protocol for the systematic development and testing of patient partner and investigator decision aids

INTRODUCTION

Building capacity to improve sex/gender knowledge and strengthen patient engagement in clinical trials requires training and support. The overall goal of this 2-year project is to refine, translate and evaluate two web-based open-access patient and investigator decision aids aimed to improve patient engagement partnerships in clinical trials.

METHODS AND ANALYSIS

Two decision aids were designed in Phase 1 of this programme of research and this protocol describes a subsequent sequential phased approach to refine/translate (Phase 2A) and conduct alpha/usability (Phase 2B) and beta/field (Phase 3) testing. Decision aid development is guided by the International Patient Decision Aid Standards, User-Centred Design, Ottawa Decision-Support Framework and the Ottawa Model of Research Use. We have integrated patient-oriented research methods by engaging patient partners across all phases of our programme of research. Decision aids will first be refined and then translated to French (Phase 2A). Eight iterative cycles of semistructured interviews with 40 participants (20 patient partners and 20 investigators) will be conducted to determine usability (Phase 2B). A pragmatic pre/post pilot study design will then be implemented for field/beta testing using another purposive sample of 80 English-speaking and French-speaking participants (40 patients and 40 investigators). The samples are purposive to ensure an equal representation of English-speaking and French-speaking participants and an equal representation of men and women. Since sex and/or gender differences in utilisation and effectiveness of decision aids have not been previously reported, Phase 3 outcomes will be reported for the total sample and separately for men and women.

ETHICS AND DISSEMINATION

Ethics approval has been granted from the University of Toronto (41109, 28 September 2021). Informed consent will be obtained from participants. Dissemination will include co-authored publications, conference presentations, educational national public forums, fact sheets/newsletters, social media sharing and videos/webinars.

Risk factors for persistent pain after breast and thoracic surgeries: a systematic literature review and meta-analysis

ABSTRACT

Persistent postsurgical pain (PPSP) is common after breast and thoracic surgeries. Understanding which risk factors consistently contribute to PPSP will allow clinicians to apply preventive strategies, as they emerge, to high-risk patients. The objective of this work was to systematically review and meta-analyze the literature on risk factors of PPSP after breast and thoracic surgeries. A systematic literature search using Ovid Medline, Cochrane Central Register of Controlled Trials, Cumulative Index to Nursing and Allied Health Literature, Embase, PsycINFO, and Scopus databases was conducted. Study screening with inclusion and exclusion criteria, data extraction, and risk of bias assessment was performed independently by 2 authors. The data for each surgical group were analyzed separately and meta-analyzed where possible. The literature search yielded 5584 articles, and data from 126 breast surgery and 143 thoracic surgery articles were considered for meta-analysis. In breast surgery, younger age, higher body mass index, anxiety, depression, diabetes, smoking, preoperative pain, moderate to severe acute postoperative pain, reoperation, radiotherapy, and axillary lymph node dissection were the main factors associated with higher risk of PPSP. In thoracic surgery, younger age, female sex, hypertension, preoperative pain, moderate to severe acute postoperative pain, surgical approach, major procedure, and wound complications were associated with PPSP. This systematic review demonstrated certain consistent risk factors of PPSP after breast and thoracic surgeries, as well as identified research gaps. Understanding the factors that increase susceptibility to PPSP can help selectively allocate resources to optimize perioperative care in high-risk patients and help develop targeted, risk-stratified interventions for PPSP prevention.

Evaluating the stability of opioid efficacy over 12 months in patients with chronic noncancer pain who initially demonstrate benefit from extended release oxycodone or hydrocodone: harmonization of Food and Drug Administration patient-level drug safety study data

ABSTRACT

Opioids relieve acute pain, but there is little evidence to support the stability of the benefit over long-term treatment of chronic noncancer pain. Previous systematic reviews consider only group level published data which did not provide adequate detail. Our goal was to use patient-level data to explore the stability of pain, opioid dose, and either physical function or pain interference in patients treated for 12 months with abuse deterrent formulations of oxycodone and hydrocodone. All available studies in the Food and Drug Administration Document Archiving, Reporting, and Regulatory Tracking System were included. Patient-level demographics, baseline data, exposure, and outcomes were harmonized. Individual patient slopes were calculated from a linear model of pain, physical function, and pain interference to determine response over time. Opioid dose was summarized by change between baseline and the final month of observation. Patients with stable or less pain, stable or lower opioid dose, and stable or better physical function (where available) met our prespecified criteria for maintaining long-term benefit from chronic opioids. Of the complete data set of 3192 patients, 1422 (44.5%) maintained their pain level and opioid dose. In a secondary analysis of 985 patients with a measured physical function, 338 (34.3%) maintained their physical function in addition to pain and opioid dose. Of 2040 patients with pain interference measured, 788 (38.6%) met criteria in addition. In a carefully controlled environment, about one-third of patients successfully titrated on opioids to treat chronic noncancer pain demonstrated continued benefit for up to 12 months.

Weight bearing as a measure of disease progression in experimental autoimmune encephalomyelitis

Motor disability in multiple sclerosis is often modeled using experimental autoimmune encephalomyelitis (EAE) and assessed using the clinical score (CS), an observer-dependent tool that can lead to potential bias. The Advanced Dynamic Weight Bearing (ADWB) system was evaluated as an observer-independent measurement of EAE symptoms. ADWB detected weight shifts onto the front paws as mice develop hindlimb motor disability. CS and ADWB were strongly correlated, indicated that these measures are comparable and suggesting that ADWB may be an appropriate observer-independent tool for the assessment of EAE progression.

A scoping review of the diurnal variation in the intensity of neuropathic pain

BACKGROUND

Recent studies suggest that neuropathic pain exhibit a daily diurnal pattern with peak levels usually in the late afternoon to evening and trough in the morning hours, although literature on this topic has been sparse. This scoping review examines current evidence on the chronobiology of neuropathic pain in both animal models and in humans with neuropathic pain.

METHOD

Literature search was conducted on major medical databases for relevant articles on chronobiology of neuropathic pain in both animal models and in humans with neuropathic pain. Data extracted include details of specific animal models or specific neuropathic pain conditions in humans, methods and timing of assessing pain severity, and specific findings of diurnal variation in pain intensity or its surrogate markers.

RESULTS

Thirteen animal and eight human studies published between 1976 to 2020 were included in the analysis. Seven out of 13 animal studies reported specific diurnal variation in pain intensity, with five of the seven studies reporting a trend towards increased sensitivity to mechanical allodynia or thermal hyperalgesia in the late light to dark phase. All eight studies on human subjects reported a diurnal variation in the intensity of neuropathic pain where there was an increase in pain intensity through the day with peaks in late evening and early night hours.

CONCLUSIONS

Studies included in this review demonstrated a diurnal variation in the pattern of neuropathic pain that is distinct from the pattern for nociceptive pain. These findings have implications for potential therapeutic strategies for neuropathic pain.

Research approaches for evaluating opioid sparing in clinical trials of acute and chronic pain treatments: Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials recommendations

ABSTRACT

Randomized clinical trials have demonstrated the efficacy of opioid analgesics for the treatment of acute and chronic pain conditions, and for some patients, these medications may be the only effective treatment available. Unfortunately, opioid analgesics are also associated with major risks (eg, opioid use disorder) and adverse outcomes (eg, respiratory depression and falls). The risks and adverse outcomes associated with opioid analgesics have prompted efforts to reduce their use in the treatment of both acute and chronic pain. This article presents Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) consensus recommendations for the design of opioid-sparing clinical trials. The recommendations presented in this article are based on the following definition of an opioid-sparing intervention: any intervention that (1) prevents the initiation of treatment with opioid analgesics, (2) decreases the duration of such treatment, (3) reduces the total dosages of opioids that are prescribed for or used by patients, or (4) reduces opioid-related adverse outcomes (without increasing opioid dosages), all without causing an unacceptable increase in pain. These recommendations are based on the results of a background review, presentations and discussions at an IMMPACT consensus meeting, and iterative drafts of this article modified to accommodate input from the co-authors. We discuss opioid sparing definitions, study objectives, outcome measures, the assessment of opioid-related adverse events, incorporation of adequate pain control in trial design, interpretation of research findings, and future research priorities to inform opioid-sparing trial methods. The considerations and recommendations presented in this article are meant to help guide the design, conduct, analysis, and interpretation of future trials.

Long-term opioid use in seniors following hip and knee arthroplasty in Ontario: a historical cohort study

PURPOSE

Canadian seniors who undergo hip and knee arthroplasty often experience significant postoperative pain, which could result in persistent opioid use. We aimed to document the impact of preoperative opioid use and other characteristics on postoperative opioid prescriptions in elderly patients following hip and knee replacement before widespread dissemination of opioid reduction strategies.

METHODS

We conducted a historical cohort study to evaluate postoperative opioid use in patients over 65 yr undergoing primary total hip and knee replacement over a ten-year period from 1 April 2006 to 31 March 2016, using linked de-identified Ontario administrative data. We determined the use of preoperative opioids and the duration of postoperative opioid prescriptions (short-term [1-90 days], prolonged [91-180 days], chronic [181-365 days], or undocumented).

RESULTS

The study included 49,638 hip and 85,558 knee replacement patients. Eighteen percent of hip and 21% of knee replacement patients received an opioid prescription within 90 days before surgery. Postoperatively, 51% of patients filled opioid prescriptions for 1-90 days, while 24% of hip and 29% of knee replacement patients filled prescriptions between 6 and 12 months, with no impact of preoperative opioid use. Residence in long-term care was a significant predictor of chronic opioid use (hip: odds ratio [OR], 2.64; 95% confidence interval [CI], 1.93 to 3.59; knee: OR, 2.46; 95% CI, 1.75 to 3.45); other risk factors included female sex and increased comorbidities.

CONCLUSION

Despite a main goal of joint arthroplasty being relief of pain, seniors commonly remained on postoperative opioids, even if not receiving opioids before surgery. Opioid reduction strategies need to be implemented at the surgical, primary physician, long-term care, and patient levels. These findings form a basis for future investigations following implementation of opioid reduction approaches.

Cryoanalgesia for postsurgical pain relief in adults: A systematic review and meta-analysis

Background

Despite advances in pain management, postoperative pain continues to be an important problem with significant burden. Many current therapies have dose-limiting adverse effects and are limited by their short duration of action. This review examines the evidence for the efficacy and safety of cryoanalgesia in postoperative pain.

Materials and methods

This review was registered in PROSPERO and prepared in accordance with PRISMA. MEDLINE, EMBASE, and Cochrane databases were searched until July 2020. We included randomized controlled trials (RCTs) of adults evaluating perioperatively administered cryoanalgesia for postoperative pain relief.

Results

Twenty-four RCTS were included. Twenty studies examined cryoanalgesia for thoracotomy, two for herniorrhaphy, one for nephrectomy and one for tonsillectomy. Meta-analysis was performed for thoracic studies. We found that cryoanalgesia with opioids was more efficacious than opioid analgesia alone for acute pain (mean difference [MD] 2.32 units, 95 % confidence interval [CI] -3.35 to -1.30) and persistent pain (MD 0.81 units, 95 % CI -1.10 to -0.53) after thoracotomy. Cryoanalgesia with opioids also resulted in less postoperative nausea compared to opioid analgesia alone (relative risk [RR] 0.23, 95 % CI 0.06 to 0.95), but there was no difference in atelectasis (RR 0.38, 95 % CI 0.07 to 2.17).

Conclusion

Heterogeneity in comparators and outcomes were important limitations. In general, reporting of adverse events was incomplete and inconsistent. Many studies were over two decades old, and most were limited in how they described their methodology. Considering the potential, larger RCTs should be performed to better understand the role of cryoanalgesia in postoperative pain management.

General risks of harm with cannabinoids, cannabis, and cannabis-based medicine possibly relevant to patients receiving these for pain management: an overview of systematic reviews

ABSTRACT

The growing demand for improved pain treatments together with expanding legalization of, and access to, cannabinoids, cannabis, and cannabis-based medicines has intensified the focus on risk-benefit considerations in pain management. Given limited harms data from analgesic clinical trials, we conducted an overview of systematic reviews focused on all harms possibly relevant to patients receiving cannabinoids for pain management. This PROSPERO-registered, PRISMA-compliant systematic overview identified 79 reviews, encompassing over 2200 individual reports about psychiatric and psychosocial harms, cognitive/behavioral effects, motor vehicle accidents, cardiovascular, respiratory, cancer-related, maternal/fetal, and general harms. Reviews, and their included studies, were of variable quality. Available evidence suggests variable associations between cannabis exposure (ranging from monthly to daily use based largely on self-report) and psychosis, motor vehicle accidents, respiratory problems, and other harms. Most evidence comes from settings other than that of pain management (eg, nonmedicinal and experimental) but does signal a need for caution and more robust harms evaluation in future studies. Given partial overlap between patients receiving cannabinoids for pain management and individuals using cannabinoids for other reasons, lessons from the crisis of oversupply and overuse of opioids in some parts of the world emphasize the need to broadly consider harms evidence from real-world settings. The advancement of research on cannabinoid harms will serve to guide optimal approaches to the use of cannabinoids for pain management. In the meantime, this evidence should be carefully examined when making risk-benefit considerations about the use of cannabinoids, cannabis, and cannabis-based medicine for chronic pain.

Cannabinoids, cannabis, and cannabis-based medicines for pain management: an overview of systematic reviews

ABSTRACT

Cannabinoids, cannabis, and cannabis-based medicines (CBM) are increasingly used to manage pain, with limited understanding of their efficacy and safety. We assessed methodological quality, scope, and results of systematic reviews of randomised controlled trials of these treatments. Several search strategies sought self-declared systematic reviews. Methodological quality was assessed using both AMSTAR-2 and techniques important for bias reduction in pain studies. Of the 106 articles read, 57 were self-declared systematic reviews, most published since 2010. They included any type of cannabinoid, cannabis, or CBM, at any dose, however administered, in a broad range of pain conditions. No review examined the effects of a particular cannabinoid, at a particular dose, using a particular route of administration, for a particular pain condition, reporting a particular analgesic outcome. Confidence in the results in the systematic reviews using AMSTAR-2 definitions was critically low (41), low (8), moderate (6), or high (2). Few used criteria important for bias reduction in pain. Cochrane reviews typically provided higher confidence; all industry-conflicted reviews provided critically low confidence. Meta-analyses typically pooled widely disparate studies, and, where assessable, were subject to potential publication bias. Systematic reviews with positive or negative recommendation for use of cannabinoids, cannabis, or CBM in pain typically rated critically low or low (24/25 [96%] positive; 10/12 [83%] negative). Current reviews are mostly lacking in quality and cannot provide a basis for decision-making. A new high-quality systematic review of randomised controlled trials is needed to critically assess the clinical evidence for cannabinoids, cannabis, or CBM in pain.

Cannabinoids, cannabis, and cannabis-based medicine for pain management: a systematic review of randomised controlled trials

ABSTRACT

Cannabinoids, cannabis, and cannabis-based medicines (CBMs) are increasingly used to manage pain, with limited understanding of their efficacy and safety. We summarised efficacy and adverse events (AEs) of these types of drugs for treating pain using randomised controlled trials: in people of any age, with any type of pain, and for any treatment duration. Primary outcomes were 30% and 50% reduction in pain intensity, and AEs. We assessed risk of bias of included studies, and the overall quality of evidence using GRADE. Studies of <7 and >7 days treatment duration were analysed separately. We included 36 studies (7217 participants) delivering cannabinoids (8 studies), cannabis (6 studies), and CBM (22 studies); all had high and/or uncertain risk of bias. Evidence of benefit was found for cannabis <7 days (risk difference 0.33, 95% confidence interval 0.20-0.46; 2 trials, 231 patients, very low-quality evidence) and nabiximols >7 days (risk difference 0.06, 95% confidence interval 0.01-0.12; 6 trials, 1484 patients, very low-quality evidence). No other beneficial effects were found for other types of cannabinoids, cannabis, or CBM in our primary analyses; 81% of subgroup analyses were negative. Cannabis, nabiximols, and delta-9-tetrahydrocannabinol had more AEs than control. Studies in this field have unclear or high risk of bias, and outcomes had GRADE rating of low- or very low-quality evidence. We have little confidence in the estimates of effect. The evidence neither supports nor refutes claims of efficacy and safety for cannabinoids, cannabis, or CBM in the management of pain.

International Association for the Study of Pain Presidential Task Force on Cannabis and Cannabinoid Analgesia: research agenda on the use of cannabinoids, cannabis, and cannabis-based medicines for pain management

ABSTRACT

The President of the International Association for the Study of Pain established a task force on cannabis and cannabinoid analgesia to systematically examine the evidence on (1) analgesic pharmacology of cannabinoids and preclinical evidence on their efficacy in animal models of injury-related or pathological persistent pain; (2) the clinical efficacy of cannabis, cannabinoids, and cannabis-based medicines for pain; (3) harms related to long-term use of cannabinoids; as well as (4) societal issues and policy implications related to the use of these compounds for pain management. Here, we summarize key knowledge gaps identified in the task force outputs and propose a research agenda for generating high-quality evidence on the topic. The systematic assessment of preclinical and clinical literature identified gaps in rigor of study design and reporting across the translational spectrum. We provide recommendations to improve the quality, rigor, transparency, and reproducibility of preclinical and clinical research on cannabis and cannabinoids for pain, as well as for the conduct of systematic reviews on the topic. Gaps related to comprehensive understanding of the endocannabinoid system and cannabinoid pharmacology, including pharmacokinetics and drug formulation aspects, are discussed. We outline key areas where high-quality clinical trials with cannabinoids are needed. Remaining important questions about long-term and short-term safety of cannabis and cannabinoids are emphasized. Finally, regulatory, societal, and policy challenges associated with medicinal and nonmedicinal use of cannabis are highlighted, with recommendations for improving patient safety and reducing societal harms in the context of pain management.

Efficacy and Safety of Drug Combinations for Chronic Pelvic Pain: Protocol for a Systematic Review

Background

Chronic pelvic pain with various etiologies and mechanisms affects men and women and is a major challenge. Monotherapy is often unsuccessful for chronic pelvic pain, and combinations of different classes of medications are frequently prescribed, with the expectation of improved outcomes. Although a number of combination trials for chronic pelvic pain have been reported, we are not aware of any systematic reviews of the available evidence on combination drug therapy for chronic pelvic pain.

Objective

We have developed a protocol for a systematic review to evaluate available evidence of the efficacy and safety of drug combinations for chronic pelvic pain.

Methods

This systematic review will involve a detailed search of randomized controlled trials investigating drug combinations to treat chronic pelvic pain in adults. The databases searched will include the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and EMBASE from their inception until the date the searches are run to identify relevant studies. The primary outcome will be pain relief measured using validated scoring tools. Secondary outcomes, where reported, will include the following: adverse events, serious adverse events, sexual function, quality of life, and depression and anxiety. Methodological quality of each included study will be assessed using the Cochrane Risk of Bias Tool.

Results

The systematic review defined by this protocol is expected to synthesize available good quality evidence on combination drug therapy in chronic pelvic pain, which may help guide future research and treatment choices for patients and their health care providers.

Conclusions

This review will provide a clearer understanding of the efficacy and safety of combination pharmacological therapy for chronic pelvic pain.

Trial Registration

PROSPERO International Prospective Register of Systematic Reviews CRD42020192231; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=192231

International Registered Report Identifier (IRRID)

PRR1-10.2196/21909

Association between postsurgical pain and heart rate variability: protocol for a scoping review

INTRODUCTION

Surgical interventions can elicit neuroendocrine responses and sympathovagal imbalance, ultimately affecting cardiac autonomic function. Cardiac complications account for 30% of postoperative complications and are the leading cause of morbidity and mortality following non-cardiac surgery. One cardiovascular parameter, heart rate variability (HRV), has been found to be predictive of postoperative morbidity and mortality. HRV is defined as variation in time intervals between heartbeats and is affected by cardiac autonomic balance. Furthermore, altered HRV has been shown to predict cardiovascular events in non-surgical settings. In multiple studies, experimentally induced pain in healthy humans leads to reduced HRV suggesting a causal relationship. In a different studies, chronic pain has been associated with altered HRV, however, in the setting of clinical pain conditions, it remains unclear how much HRV impairment is due to pain itself versus autonomic changes related to analgesia. We aim to review the available evidence describing the association between postsurgical pain and HRV alterations in the early postoperative period.

METHODS AND ANALYSIS

We will conduct a scoping review of relevant studies using detailed searches of MEDLINE and EMBASE, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis. Included studies will involve participants undergoing non-cardiac surgery and investigate outcomes of (1) measures of pain intensity; (2) measures of HRV and (3) statistical assessment of association between #1 and #2. As secondary review outcomes included studies will also be examined for other cardiovascular events and for their attempts to control for analgesic treatment and presurgical HRV differences among treatment groups in the analysis. This work aims to synthesise available evidence to inform future research questions related to postsurgical pain and cardiac complications.

ETHICS AND DISSEMINATION

Ethics review and approval is not required for this review. The results will be submitted for publication in peer-reviewed journals.

Efficacy and Safety of N-acetylcysteine for the Management of Chronic Pain in Adults: A Systematic Review & Meta-analysis

OBJECTIVE

To assess the efficacy and safety of N-acetylcysteine in the treatment of chronic pain.

METHODS

A systematic search was carried out until April 2020 for clinical studies of N-acetylcysteine in the management of any persistent or recurrent chronic pain condition for adults ≥ 18 years old. Risk of Bias was assessed using the validated risk of bias tools. When appropriate, a meta-analysis using a random-effects model was performed, with a fixed-effect model for sensitivity analysis.

RESULTS

Nine studies (n = 863) were included (5 randomized controlled trials [RCTs], 2 open-label non-comparative studies and 2 comparative studies), that evaluated patients with sickle cell disease (3), complex regional pain syndrome (1), pelvic pain/endometriosis (2), rheumatoid arthritis (1), diabetic neuropathy (1), and chronic neuropathic pain (1). In the pooled analysis of 3 RCTs, N-acetylcysteine did not reduce pain intensities (SMD -0.21, 95% CI -0.33 to 0.75, random-effects), improve functional outcomes (SMD 0.21, 95% CI -0.33 to 0.75) or quality of life (SMD 0.60, 95% CI -4.44 to 5.64); however, sensitivity analysis with a fixed effect model demonstrated an effect for pain intensities and function. Due to adverse events being inconsistently reported, no conclusion could be made regarding safety of N-acetylcysteine in chronic pain.

CONCLUSIONS

While there is some evidence to indicate N-acetylcysteine may provide analgesic efficacy for certain pain conditions, there is insufficient evidence to provide definitive evidence on NAC in chronic pain management. Larger-size RCTs spanning a variety of chronic pain conditions are needed to determine N-acetylcysteine's role, if any, in pain medicine.

Prevalence of Postoperative Pain Following Hospital Discharge: Protocol for a Systematic Review

Background

Pain is one of the most common, feared, and unpleasant symptoms associated with surgery. However, there is a clear gap in patient care after surgical patients are discharged from hospital, resulting in poorly controlled postoperative pain. Inadequate pain management after discharge can have detrimental effects on quality of life and lead to the development of chronic postsurgical pain. The severity of postoperative pain before discharge is well described, but less emphasis has been placed on assessing pain at home after hospital discharge.

Objective

The objective of this review is to summarize the prevalence of moderate-to-severe postoperative pain within the first 1 to 14 days after hospital discharge.

Methods

A detailed search of epidemiological studies investigating postoperative pain will be conducted on MEDLINE and EMBASE from their inception until the date the searches are run. The primary outcome will be the proportion of patients reporting moderate-to-severe postoperative pain at rest and with movement within the first 1 to 14 days after hospital discharge. The secondary outcomes will include a comparison of postoperative pain after discharge between patients who underwent ambulatory and inpatient surgery, and adverse outcomes attributable to poor pain control after hospital discharge (eg, readmission to hospital, emergency room or other unplanned medical visits, or a decrease in quality of life).

Results

The protocol has been registered in PROSPERO (registration number CRD42020194346). The search strategies for MEDLINE and EMBASE have been completed. The final results are expected to be published in May 2021.

Conclusions

This systematic review is expected to synthesize evidence describing the prevalence of postoperative pain after hospital discharge. Available epidemiological evidence may help inform the magnitude of the problem of postoperative pain at home after hospital discharge.

Trial Registration

PROSPERO International Prospective Register of Systematic Reviews CRD42020194346; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=194346

International Registered Report Identifier (IRRID)

PRR1-10.2196/22437

Patient Engagement Partnerships in Clinical Trials: Development of Patient Partner and Investigator Decision Aids

BACKGROUND

A 2017 systematic review suggested patient engagement in clinical trials has been limited, with little active engagement in trial design or data analysis, interpretation or dissemination. Additionally, there remains limited sex/gender reporting in clinical trial research.

OBJECTIVES

The overall goal of this project was to disseminate sex/gender knowledge and build capacity for patient engagement in clinical trials. Specific objectives were to (1) create capacity and identify opportunities for patient engagement in clinical trials and sponsor- or investigator-led activities (e.g. clinical trial design and conduct); and (2) enhance new/early investigator sex/gender knowledge and skills related to patient-oriented research (POR).

METHODS

We used the Canadian Institutes of Health Research Strategy for Patient-Oriented Research (SPOR) Capacity Development Framework and the SPOR Patient Engagement Framework to guide three phases of this project: (1) conduct a scoping review using methods described by the Evidence for Policy and Practice Information (EPPI) and the Coordinating Centre at the Institute of Education (Phase 1); (2) host a 1-day POR consultation workshop (Phase 2); and (3) deliver a new/early investigator POR training day (Phase 3). Six electronic databases (CINAHL, MEDLINE, EMBASE, PsychInfo, the Cochrane Library, and AMED) were searched from 1996 using keywords and Medical Subject Heading (MeSH) terms in accordance with the International Association for Public Participation (IAP2) and the search criteria in the bibliographic databases. Standard approaches were used to search the grey literature.

RESULTS

A total of 79 studies and over 150 websites were subject to data abstraction by team members, capturing information on sex/gender and SPOR's patient engagement guiding principles of inclusiveness, support, mutual respect, and co-building. Results were presented to 32 key stakeholders at the consultation workshop and input was sought on next steps using nominal group techniques. Based on the plethora of existing POR resources, relevant POR information from the scoping review was collated into two decision aids (patient and investigator) to determine readiness to engage with/as a patient partner in a clinical trial. The decision aids were presented at a POR training day with 88 new/early investigators, clinicians, patient partners and decision makers. The decision aids showed 'good' usability, assessed using the System Usability Scale (SUS). Attendees thought the decision aids were engaging, they increased their understanding of sex/gender, patient engagement and POR, and they would recommend them to others. POR principles and practices were integrated across all phases of the project. Patient partners (1) identified research priorities/search terms; (2) collected/analyzed data; (3) designed the patient partner decision aid; and (4) disseminated the results through presentation.

CONCLUSION

Our digital patient partner and investigator decision aids are the first to provide information technology to deliver sex/gender, POR knowledge, and decision support beyond the traditional decision aids used for health screening and/or treatment decisions. The decision aids have the potential to make a significant contribution to Canada's Strategy for POR and support the collaborative efforts of patients and investigators to build a sustainable, accessible and equitable health care system.

Efficacy and Safety of Magnesium for the Management of Chronic Pain in Adults: A Systematic Review

Chronic pain is a highly prevalent and complex health problem that is associated with a heavy symptom burden, substantial economic and social impact, and also, very few highly effective treatments. This review examines evidence for the efficacy and safety of magnesium in chronic pain. The previously published protocol for this review was registered in International Prospective Register of Systematic Reviews (PROSPERO), MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) databases were searched until September 2018. We included randomized controlled trials (RCTs) comparing magnesium (at any dose, frequency, or route of administration) with placebo using participant-reported pain measures. A total of 9 RCTs containing 418 participants were included. Three studies examined neuropathic pain (62 participants), 3 examined migraines (190 participants), 2 examined complex regional pain syndrome (86 participants), and 1 examined low back pain with a neuropathic component (80 participants). Heterogeneity of included studies precluded any meta-analyses. No judgment could be made about safety because adverse events were inconsistently reported in the included studies. Evidence of analgesic efficacy from included studies was equivocal. However, reported efficacy signals in some of the included trials provide a rationale for more definitive studies. Future, larger-sized trials with good assay sensitivity and better safety assessment and reporting, as well as careful attention to formulations with optimal bioavailability, will serve to better define the role of magnesium in the management of chronic pain.

Accessing care in multidisciplinary pain treatment facilities continues to be a challenge in Canada

BACKGROUND

Multidisciplinary pain treatment facilities (MPTFs) are considered the optimal settings for the management of chronic pain (CP). This study aimed (1) to determine the distribution of MPTFs across Canada, (2) to document time to access and types of services, and (3) to compare the results to those obtained in 2005-2006.

METHODS

This cross-sectional study used the same MPTF definition as in 2005-2006-that is, a clinic staffed with professionals from a minimum of three different disciplines (including at least one medical specialty) and whose services were integrated within the facility. A comprehensive search strategy was used to identify existing MPTFs across Canada. Administrative leads at each MPTF were invited to complete an online questionnaire regarding their facilities.

RESULTS

Questionnaires were completed by 104 MPTFs (response rate 79.4%). Few changes were observed in the distribution of MPTFs across Canada compared with 12 years ago. Most (91.3%) are concentrated in large urban cities. Prince Edward Island and the Territories still lack MPTFs. The number of pediatric-only MPTFs has nearly doubled but remains small (n=9). The median wait time for a first appointment in publicly funded MPTFs is about the same as 12 years ago (5.5 vs 6 months). Small but positive changes were also observed.

CONCLUSION

Accessibility to public MPTFs continues to be limited in Canada, resulting in lengthy wait times for a first appointment. Community-based MPTFs and virtual care initiatives to distribute pain services into regional and remote communities are needed to provide patients with CP with optimal care.

Chronic mechanical hypersensitivity in experimental autoimmune encephalomyelitis is regulated by disease severity and neuroinflammation

Chronic pain severely affects quality of life in more than half of people living with multiple sclerosis (MS). A commonly-used model of MS, experimental autoimmune encephalomyelitis (EAE), typically presents with hindlimb paralysis, neuroinflammation and neurodegeneration. However, this paralysis may hinder the use of pain behavior tests, with no apparent hypersensitivity observed post-peak disease. We sought to adapt the classic actively-induced EAE model to optimize its pain phenotype. EAE was induced with MOG_35-55/CFA and 100-600 ng pertussis toxin (PTX), and mice were assessed for mechanical, cold and thermal sensitivity over a 28-day period. Spinal cord tissue was collected at 14 and 28 days post-injection to assess demyelination and neuroinflammation. Only mice treated with 100 ng PTX exhibited mechanical hypersensitivity. Hallmarks of disease pathology, including demyelination, immune cell recruitment, cytokine expression, glial activation, and neuronal damage were higher in EAE mice induced with moderate (200 ng) doses of pertussis toxin, compared to those treated with low (100 ng) levels. Immunostaining demonstrated activated astrocytes and myeloid/microglial cells in both EAE groups. These results indicate that a lower severity of EAE disease may allow for the study of pain behaviors while still presenting with disease pathology. By using this modified model, researchers may better study the mechanisms underlying pain.

One-year Results of a Factorial Randomized Trial of Aspirin versus Placebo and Clonidine versus Placebo in Patients Having Noncardiac Surgery

BACKGROUND

The authors previously reported that perioperative aspirin and/or clonidine does not prevent a composite of death or myocardial infarction 30 days after noncardiac surgery. Moreover, aspirin increased the risk of major bleeding and clonidine caused hypotension and bradycardia. Whether these complications produce harm at 1 yr remains unknown.

METHODS

The authors randomized 10,010 patients with or at risk of atherosclerosis and scheduled for noncardiac surgery in a 1:1:1:1 ratio to clonidine/aspirin, clonidine/aspirin placebo, clonidine placebo/aspirin, or clonidine placebo/aspirin placebo. Patients started taking aspirin or placebo just before surgery; those not previously taking aspirin continued daily for 30 days, and those taking aspirin previously continued for 7 days. Patients were also randomly assigned to receive clonidine or placebo just before surgery, with the study drug continued for 72 h.

RESULTS

Neither aspirin nor clonidine had a significant effect on the primary 1-yr outcome, a composite of death or nonfatal myocardial infarction, with a 1-yr hazard ratio for aspirin of 1.00 (95% CI, 0.89 to 1.12; P = 0.948; 586 patients [11.8%] vs. 589 patients [11.8%]) and a hazard ratio for clonidine of 1.07 (95% CI, 0.96 to 1.20; P = 0.218; 608 patients [12.1%] vs. 567 patients [11.3%]), with effect on death or nonfatal infarction. Reduction in death and nonfatal myocardial infarction from aspirin in patients who previously had percutaneous coronary intervention at 30 days persisted at 1 yr. Specifically, the hazard ratio was 0.58 (95% CI, 0.35 to 0.95) in those with previous percutaneous coronary intervention and 1.03 (95% CI, 0.91to 1.16) in those without (interaction P = 0.033). There was no significant effect of either drug on death, cardiovascular complications, cancer, or chronic incisional pain at 1 yr (all P > 0.1).

CONCLUSIONS

Neither perioperative aspirin nor clonidine have significant long-term effects after noncardiac surgery. Perioperative aspirin in patients with previous percutaneous coronary intervention showed persistent benefit at 1 yr, a plausible sub-group effect.

AAAPT Diagnostic Criteria for Acute Knee Arthroplasty Pain

OBJECTIVE

The relationship between preexisting osteoarthritic pain and subsequent post-total knee arthroplasty (TKA) pain is not well defined. This knowledge gap makes diagnosis of post-TKA pain and development of management plans difficult and may impair future investigations on personalized care. Therefore, a set of diagnostic criteria for identification of acute post-TKA pain would inform standardized management and facilitate future research.

METHODS

The Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership with the US Food and Drug Administration (FDA), the American Pain Society (APS), and the American Academy of Pain Medicine (AAPM) formed the ACTTION-APS-AAPM Pain Taxonomy (AAAPT) initiative to address this goal. A multidisciplinary work group of pain experts was invited to conceive diagnostic criteria and dimensions of acute post-TKA pain.

RESULTS

The working group used contemporary literature combined with expert opinion to generate a five-dimensional taxonomical structure based upon the AAAPT framework (i.e., core diagnostic criteria, common features, modulating factors, impact/functional consequences, and putative mechanisms) that characterizes acute post-TKA pain.

CONCLUSIONS

The diagnostic criteria created are proposed to define the nature of acute pain observed in patients following TKA.

N-Methyl-D-Aspartate Antagonists and Steroids for the Prevention of Persisting Post-Surgical Pain After Thoracoscopic Surgeries: A Randomized Controlled, Factorial Design, International, Multicenter Pilot Trial

Purpose

We conducted a feasibility 2×2 factorial trial comparing N-methyl-D-aspartate (NMDA) antagonists (intravenous ketamine and oral memantine) versus placebo and intravenous steroids versus placebo, in patients having elective video-assisted thoracic surgery lobectomies, at St. Joseph's Hamilton, Canada, and Cleveland Clinic, Cleveland, USA. Our feasibility objectives were: 1) recruitment rate/week; 2) recruitment of ≥90% of eligible patients; and 3) >90% follow-up. Secondary objectives were incidence and intensity of persistent post-surgical pain (PPSP) and other clinical and safety outcomes.

Methods

Using computerized randomization, patients were allocated to one of four groups: NMDA active with steroid placebo; NMDA placebo with steroid active; both NMDA and steroid active; both NMDA and steroid placebo. Patients, health providers, and data analysts were blinded to allocation. Patients were followed for 3 months after randomization.

Results

The trial was initiated in May 2017 at Hamilton and, after subsequent regulatory and ethics approval, in April 2018 at Cleveland. The trial had to be stopped after only 1 month of recruitment in Cleveland because the packaged study medications (memantine) expired and we were unable to procure the dosage required. Among 41 eligible patients, 27 (66%) were randomized. The recruitment rate/week was 0.63, 95% confidence interval (CI): 0.47-0.79 in Hamilton; and 1, 95% CI: 0.83-1.17 in Cleveland. Follow-up was complete for all 24 patients (100%) in Hamilton, and 3 of 4 patients in Cleveland. In total, only 4 patients (15%), and 2 patients (7%) had persistent pain at rest and with movement, respectively. There were no significant differences between groups for other outcomes.

Conclusion

The trial had to be stopped prematurely due to non-availability of study medications. Trial feasibility objectives of recruiting 90% of eligible patients and recruiting at least one patient/week per site were not met. Consideration for protocol changes will be necessary for the full trial.

Trial Registration

NCT02950233.

Movement-Evoked Pain Versus Pain at Rest in Postsurgical Clinical Trials and Meta-Analyses: Protocol for a Follow-Up Systematic Review

Background

Postoperative pain is one of the most prevalent and disabling complications of surgery that is associated with personal suffering, delayed functional recovery, prolonged hospital stay, perioperative complications, and chronic postsurgical pain. Accumulating evidence has pointed to the important distinction between pain at rest (PAR) and movement-evoked pain (MEP) after surgery. In most studies including both measures, MEP has been shown to be substantially more severe than PAR. Furthermore, as MEP is commonly experienced during normal activities (eg, breathing, coughing, and walking), it has a greater adverse functional impact than PAR. In a previous systematic review conducted in 2011, only 39% of reviewed trials included MEP as a trial outcome and 52% failed to identify the pain outcome as either PAR or MEP. Given the recent observations of postsurgical pain trials that continue to neglect the distinction between PAR and MEP, this updated review seeks to evaluate the degree of progress in this area.

Objective

This updated review will include postsurgical clinical trials and meta-analyses in which the primary outcome was early postoperative pain intensity. The primary outcome for this review is the reporting of MEP (vs PAR) as an outcome measure for each trial and meta-analysis. Secondary outcomes include whether trials and meta-analyses distinguished between PAR and MEP.

Methods

To be consistent with the 2011 review that we are updating, this review will again focus on randomized controlled trials and meta-analyses, from Medical Literature Analysis and Retrieval System Online and EMBASE databases, focusing on pain treatment after thoracotomy, knee arthroplasty, and hysterectomy in humans. Trials and meta-analyses will be characterized as to whether or not they assessed PAR and MEP; whether their pain outcome acknowledged the distinction between PAR and MEP; and, for trials assessing MEP, which pain-evoking maneuver(s) were used.

Results

Scoping review and pilot data extraction are under way, and the results are expected by March 2020.

Conclusions

It is our belief that every postsurgical analgesic trial should include MEP as an outcome measure. The previous 2011 review was expected to have an impact on more widespread assessment of MEP in subsequent postoperative pain treatment trials. Thus, the purpose of this follow-up review is to reevaluate the frequency of use of MEP as a trial outcome, compared with PAR, in more recently published postoperative pain trials.

Trial Registration

PROSPERO CRD42019125855; https://tinyurl.com/qw9dty8

International Registered Report Identifier (IRRID)

DERR1-10.2196/15309

Improving Study Conduct and Data Quality in Clinical Trials of Chronic Pain Treatments: IMMPACT Recommendations

The estimated probability of progressing from phase 3 analgesic clinical trials to regulatory approval is approximately 57%, suggesting that a considerable number of treatments with phase 2 trial results deemed sufficiently successful to progress to phase 3 do not yield positive phase 3 results. Deficiencies in the quality of clinical trial conduct could account for some of this failure. An Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials meeting was convened to identify potential areas for improvement in trial conduct in order to improve assay sensitivity (ie, ability of trials to detect a true treatment effect). We present recommendations based on presentations and discussions at the meeting, literature reviews, and iterative revisions of this article. The recommendations relate to the following areas: 1) study design (ie, to promote feasibility), 2) site selection and staff training, 3) participant selection and training, 4) treatment adherence, 5) data collection, and 6) data and study monitoring. Implementation of these recommendations may improve the quality of clinical trial data and thus the validity and assay sensitivity of clinical trials. Future research regarding the effects of these strategies will help identify the most efficient use of resources for conducting high quality clinical trials. PERSPECTIVE: Every effort should be made to optimize the quality of clinical trial data. This manuscript discusses considerations to improve conduct of pain clinical trials based on research in multiple medical fields and the expert consensus of pain researchers and stakeholders from academia, regulatory agencies, and industry.

Pharmacological interventions for the prevention of acute postoperative pain in adults following brain surgery

BACKGROUND

Pain following brain surgery can compromise recovery. Several pharmacological interventions have been used to prevent pain after craniotomy; however, there is currently a lack of evidence regarding which interventions are most effective.

OBJECTIVES

The objectives are to assess the effectiveness of pharmacological interventions for prevention of acute postoperative pain in adults undergoing brain surgery; compare them in terms of additional analgesic requirements, incidence of chronic headache, sedative effects, length of hospital stay and adverse events; and determine whether these characteristics are different for certain subgroups.

SEARCH METHODS

We searched MEDLINE, Embase, CINAHL, CENTRAL, Web of Science and two trial registries together with reference checking and citation searching on 28th of November 2018.

SELECTION CRITERIA

We included blinded and non-blinded, randomized controlled trials evaluating pharmacological interventions for the prevention of acute postoperative pain in adults undergoing neurosurgery, which had at least one validated pain score outcome measure.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures. We calculated mean differences for the primary outcome of pain intensity; any pain scores reported on a 0 to 100 scale were converted to a 0 to 10 scale.

MAIN RESULTS

We included 42 completed studies (3548 participants) and identified one ongoing study. Nonsteroidal anti-inflammatories (NSAIDs) Nonsteroidal anti-inflammatories (NSAIDs) reduce pain up to 24 hours (0 to 6 hours, MD -1.16, 95% CI -1.57 to -0.76; 12 hours, MD -0.62, 95% CI -1.11 to -0.14; 24 hours, MD -0.66, 95% CI -1.18 to -0.13; 6 studies, 742 participants; all high-quality evidence). Results for other outcomes were imprecise (additional analgesic requirements: MD 1.29 mg, 95% CI -5.0 to 2.46, 4 studies, 265 participants; nausea and vomiting RR 1.34, 95% CI 0.30 to 5.94, 2 studies, 345 participants; both low-quality evidence). Dexmedetomidine reduces pain up to 12 hours (0 to 6 hours, MD -0.89, 95% CI -1.27 to -0.51, moderate-quality evidence; 12 hours, MD -0.81, 95% CI -1.21 to -0.42, low-quality evidence). It did not show efficacy at 24 hours (MD -0.08, 95% CI -0.32 to 0.16; 2 studies, 128 participants; low-quality evidence). Dexmedetomidine may decrease additional analgesic requirements (MD -21.36 mg, 95% CI -34.63 to -8.1 mg, 2 studies, 128 participants, low-quality evidence). Results for other outcomes were imprecise (nausea and vomiting RR -0.43, 95% CI 0.06 to 3.08, 3 studies, 261 participants; hypotension RR 0.5, 95% CI 0.05 to 5.28, 3 studies, 184 participants; both low-quality evidence). Scalp blocks may reduce pain up to 48 hours (0 to 6 hours, MD -0.98, 95% CI -1.66 to -0.3, 10 studies, 414 participants; 12 hours, MD -0.95, 95% CI -1.53 to -0.37, 8 studies, 294 participants; 24 hours, MD -0.78, 95% CI -1.52 to -0.05, 9 studies, 433 participants, all low-quality evidence; 48 hours, MD -1.34, 95% CI -2.57 to -0.11, 4 studies, 135 participants, very low-quality evidence. When studies with high risk of bias were excluded, significance remained at 12 hours only. Scalp blocks may decrease additional analgesia requirements (SMD -1.11, 95% CI -1.97 to -0.25, 7 studies, 314 participants). Results for other outcomes were imprecise (nausea and vomiting RR 0.66, 95% CI 0.33 to 1.32, 4 studies, 165 participants, very low-quality evidence). Scalp Infiltration may reduce pain postoperatively but efficacy was inconsistent, with a significant effect at 12 and 48 hours only (12 hours, MD -0.71, 95% CI -1.34 to -0.08, 7 studies, 309 participants, low-quality evidence; 48 hours, MD - 1.09, 95% CI -2.13 to - 0.06, 3 studies, 128 participants, moderate-quality evidence). No benefit was observed at other times (0 to 6 hours, MD -0.64, 95% CI -1.28 to -0.00, 9 studies, 475 participants, moderate-quality evidence; 24 hours, MD -0.39, 95% CI -1.06 to 0.27,6 studies, 260 participants, low-quality evidence. Scalp infiltration may reduce additional analgesia requirements MD -9.56 mg, 95% CI -15.64 to -3.49, 6 studies, 345 participants, very low-quality evidence). When studies with high risk of bias were excluded, scalp infiltration lost the pain benefit at 12 hours and effects on additional analgesia requirements, but retained the pain-reducing benefit at 48 hours (MD -0.56, 95% CI -1.20 to -0.32, 2 studies, 100 participants, very low-quality evidence). Results for other outcomes were imprecise (nausea and vomiting, RR 0.74, 95% CI 0.48 to 1.41, 4 studies, 318 participants, low-quality evidence). Pregabalin or gabapentin may reduce pain up to 6 hours (2 studies, 202 participants), MD -1.15,95% CI -1.66 to -0.6, 2 studies, 202 participants, low-quality evidence). One study examined analgesic efficacy at 12 hours showing significant benefit. No analgesia efficacy was shown at later times (24 hours, MD -0.29, 95% CI -0.78 to -0.19; 48 hours, MD - 0.06, 95% CI -0.86 to 0.77, 2 studies, 202 participants, low-quality evidence). Additional analgesia requirements were not significantly less (MD -0.37 (95% CI -1.10 to 0.35, 3 studies, 234 participants, low-quality evidence). Risk of nausea and vomiting was significantly reduced (RR 0.51, 95% CI 0.29 to 0.89, 3 studies, 273 participants, low-quality evidence). Results for other outcomes were imprecise (additional analgesia requirements: MD -0.37, 95% CI -1.10 to 0.35, 3 studies, 234 participants, low-quality evidence). Acetaminophen did not show analgesic benefit (0 to 6 hours, MD -0.35, 95% CI -1.00 to 0.30; 12 hours, MD -0.51, 95% CI -1.04 to 0.03, 3 studies, 332 participants, moderate-quality evidence; 24 hours, MD -0.34, 95% CI -1.20 to 0.52, 4 studies, 439 participants, high-quality evidence). Results for other outcomes remained imprecise (additional analgesia requirements, MD 0.07, 95% CI -0.86 to 0.99, 4 studies, 459 participants, high-quality evidence; length of hospitalizations, MD -3.71, 95% CI -14.12 to 6.7, 2 studies, 335 participants, moderate-quality evidence).

AUTHORS' CONCLUSIONS

There is high-quality evidence that NSAIDs reduce pain up to 24 hours postoperatively. The evidence for reductions in pain with dexmedetomidine, pregabalin or gabapentin, scalp blocks, and scalp infiltration is less certain and of very low to moderate quality. There is low-quality evidence that scalp blocks and dexmedetomidine may reduce additional analgesics requirements. There is low-quality evidence that gabapentin or pregabalin may decrease nausea and vomiting, with the caveat that the total number of events for this comparison was low.