A new way of thinking about pains

Beyond the chronic pain stage: default mode network perturbation depends on years lived with back pain

ABSTRACT

Research has indicated that the default mode network (DMN) is perturbated in patients with chronic pain when compared with healthy controls, and this perturbation is correlated with the duration of pain during the chronic pain stage. It remains unclear whether DMN adaptations manifest during the subacute pain stage and progress over time because of the duration of pain experience, rather than being a specific correlate of the chronic pain stage. Furthermore, information regarding whether these adaptations are related to cognitive processes of adaptation is lacking. To this end, we examined the DMN in 31 patients with chronic back pain (CBP), 77 patients with subacute back pain (SBP), as well as 39 healthy pain-free controls (HC) applying a graph-theoretic network approach on functional resting-state magnetic resonance imaging. Beyond the comparison between groups, we used a linear analysis considering the years lived with pain (YLP) across all patients with back pain and additionally performed a mediation analysis of the role of cognitive pain coping. In line with previous studies, we found significant DMN perturbation in CBP compared with HC. However, this did not apply to the comparison of CBP with SBP. Instead, we observed a positive correlation between DMN perturbation and YLP. This was significantly mediated by coping attitudes towards pain. Default mode network perturbation may thus reflect neural adaptation processes to pain experience rather than a single correlate of the chronic pain stage and be modulated by cognitive adaption. This points to potentially underinvestigated significant adaptation processes that could enable more fine-grained patient stratification.

The concept of nociplastic pain-where to from here?

ABSTRACT

Nociplastic pain, a third mechanistic pain descriptor in addition to nociceptive and neuropathic pain, was adopted in 2017 by the International Association for the Study of Pain (IASP). It is defined as "pain that arises from altered nociception" not fully explained by nociceptive or neuropathic pain mechanisms. Peripheral and/or central sensitization, manifesting as allodynia and hyperalgesia, is typically present, although not specific for nociplastic pain. Criteria for possible nociplastic pain manifesting in the musculoskeletal system define a minimum of 4 conditions: (1) pain duration of more than 3 months; (2) regional, multifocal or widespread rather than discrete distribution of pain; (3) pain cannot entirely be explained by nociceptive or neuropathic mechanisms; and (4) clinical signs of pain hypersensitivity present in the region of pain. Educational endeavors and field testing of criteria are needed. Pharmacological treatment guidelines, based on the three pain types, need to be developed. Currently pharmacological treatments of nociplastic pain resemble those of neuropathic; however, opioids should be avoided. A major challenge is to unravel pathophysiological mechanisms driving altered nociception in patients suffering from nociplastic pain. Examples from fibromyalgia would include pathophysiology of the peripheral as well as central nervous system, such as autoreactive antibodies acting at the level of the dorsal root ganglia and aberrant cerebral pain processing, including altered brain network architecture. Understanding pathophysiological mechanisms and their interactions is a prerequisite for the development of diagnostic tests allowing for individualized treatments and development of new strategies for prevention and treatment.

Perioperative Risk Factors for Persistent Postsurgical Pain After Inguinal Hernia Repair: Systematic Review and Meta-Analysis

Persistent postsurgical pain (PPSP) is one of the most bothersome and disabling long-term complications after inguinal hernia repair surgery. Understanding perioperative risk factors that contribute to PPSP can help identify high-risk patients and develop risk-mitigation approaches. The objective of this study was to systematically review and meta-analyze risk factors that contribute to PPSP after inguinal hernia repair. The literature search resulted in 303 papers included in this review, 140 of which were used for meta-analyses. Our results suggest that younger age, female sex, preoperative pain, recurrent hernia, postoperative complications, and postoperative pain are associated with a higher risk of PPSP. Laparoscopic techniques reduce the PPSP occurrence compared to anterior techniques such as Lichtenstein repair, and tissue-suture techniques such as Shouldice repair. The use of fibrin glue for mesh fixation was consistently associated with lower PPSP rates compared to tacks, staples, and sutures. Considerable variability was observed with PPSP assessment and reporting methodology in terms of study design, follow-up timing, clarity of pain definition, as well as pain intensity or interference threshold. High or moderate risk of bias in at least one domain was noted in >75% of studies. These may limit the generalizability of our results. Future studies should assess and report comprehensive preoperative and perioperative risk factors for PPSP adjusted for confounding factors, and develop risk-prediction models to drive stratified PPSP-mitigation trials and personalized clinical decision-making. PERSPECTIVE: This systematic review and meta-analysis summarizes the current evidence on risk factors for persistent pain after inguinal hernia repair. The findings can help identify patients at risk and test personalized risk-mitigation approaches to prevent pain. PROSPERO REGISTRATION: htttps://www.crd.york.ac.uk/prospero/display_record.php?RecordID=154663.

Pains Revisited

OBJECTIVES

The management of pain patients has not evolved as rapidly as envisioned when IASP was founded almost 50 years ago. We sought to identify factors that could contribute to this situation, with a focus on concepts of pain and the education of pain physicians.

METHODS

Relevant literature describing new strategies for diagnosing and managing patients with high-impact chronic pain was reviewed.

RESULTS

It appears that the acute-chronic dichotomy has outlived its usefulness and pains should be identified as of peripheral origin or due to central processing errors. Pains of peripheral origin and those of central processing errors require different diagnostic and therapeutic strategies.

DISCUSSION

Peripheral treatments and opioids are not effective for central pains. When the cause of the pain lies in the central nervous system, a more centrally focused approach is needed to minimize wasteful pursuit of peripheral causes. The education and training of pain physicians should reflect the skills needed to address these 2 very different clinical problems.

Acupoint Stimulation for Pain Control in Enhanced Recovery After Surgery: Systematic Review and Meta-Analysis

Introduction: Postoperative pain control is a challenge in enhanced recovery after surgery (ERAS). The current study reviewed the efficacy and safety of incorporating acupoint stimulation for postoperative pain control in ERAS. Methods: Ten databases for relevant randomized controlled trials (RCTs) published in English or Mandarin Chinese were searched from 1997 to 2022. The quality of each article was appraised using the Cochrane Collaboration Risk of Bias Criteria and the modified Jadad Scale. The primary outcome was pain control, measured using the visual analog scale 24 h after surgery. Results: Eleven trials met the eligibility criteria and were included in the study. Acupoint stimulation was found more effective than control treatments in terms of pain intensity (standardized mean difference [SMD] -0.94; 95% confidence interval [CI] -1.35 to -0.53), analgesic drug consumption (SMD -1.87; 95% CI -2.98 to -0.75), postoperative nausea (PON; SMD 0.31; 95% CI 0.13 to 0.73), postoperative vomiting (POV; SMD 0.57; 95% CI 0.11 to 2.92), and PON and POV (PONV; SMD 0.29; 95% CI 0.16 to 0.53). The Zusanli (ST36) and Neiguan (PC6) were the most-used acupoints in the included trials (8/11). The reported adverse reaction was only one case of bruising. Discussion: Acupoint stimulation improved pain control in patients undergoing ERAS more than control treatments. The findings provide an evidence-based premise for incorporating acupoint stimulation into ERAS strategies. More rigorous RCTs are needed in the future.

Impact of homeostatic body hydration status, evaluated by hemodynamic measures, on different pain sensitization paths to a chronic pain syndrome

Contrasting findings on the mechanisms of chronic pain and hypertension development render the current conventional evidence of a negative relationship between blood pressure (BP) and pain severity insufficient for developing personalized treatments. In this interdisciplinary study, patients with fibromyalgia (FM) exhibiting clinically normal or elevated BP, alongside healthy participants were assessed. Different pain sensitization responses were evaluated using a dynamic 'slowly repeated evoked pain' (SREP) measure, as well as static pain pressure threshold and tolerance measures. Cardiovascular responses to clino-orthostatic (lying-standing) challenges were also examined as acute re- and de-hydration events, challenging cardiovascular and cerebrovascular homeostasis. These challenges involve compensating effects from various cardiac preload or afterload mechanisms associated with different homeostatic body hydration statuses. Additionally, hair cortisol concentration was considered as a factor with an impact on chronic hydration statuses. Pain windup (SREP) and lower pain threshold in FM patients were found to be related to BP rise during clinostatic (lying) rehydration or orthostatic (standing) dehydration events, respectively. These events were determined by acute systemic vasoconstriction (i.e., cardiac afterload response) overcompensating for clinostatic or orthostatic cardiac preload under-responses (low cardiac output or stroke volume). Lower pain tolerance was associated with tonic blood pressure reduction, determined by permanent hypovolemia (low stroke volume) decompensated by permanent systemic vasodilation. In conclusion, the body hydration status profiles assessed by (re)activity of systemic vascular resistance and effective blood volume-related measures can help predict the risk and intensity of different pain sensitization components in chronic pain syndrome, facilitating a more personalized management approach.

The Pharmacological Treatment of Neuropathic Pain in Children

The International Association for the Study of Pain (IASP) defines neuropathic pain as pain caused by a lesion or disease of the somatosensory nervous system. It is characterized as a clinical condition in which diagnostic studies reveal an underlying cause of an abnormality in the peripheral or central nervous system. Many common causes of neuropathic pain in adults are rare in children. The purpose of this focused narrative review is, to 1) provide an overview of neuropathic pain in children, 2) highlight unique considerations related to the diagnosis and mechanisms of neuropathic pain in children, and 3) perform a comprehensive analysis of the pharmacological treatments available. We emphasize that data for routine use of pharmacological agents in children with neuropathic pain are largely inferred from adult literature with little research performed on pediatric populations, yet have clear evidence of harms to pediatric patients. Based on these findings, we propose risk mitigation strategies such as utilizing topical treatments whenever possible, assessing pain phenotyping to guide drug class choice, and considering pharmaceuticals in the broader context of the multidisciplinary treatment of pediatric pain. Furthermore, we highlight important directions for future research on pediatric neuropathic pain treatment.

[Nociplastic pain in research and practice : Overview of biopsychosocial principles, possibilities and difficulties]

Traditionally, two mechanistic pain categories were distinguished: nociceptive and neuropathic pain. After the definitions of these two mechanistic descriptors were refined more precisely in the International Association for the Study of Pain (IASP) taxonomy in 2011, a large group of patients remained whose pain could not be assigned to either of the two categories. Nociplastic pain was therefore proposed as a third mechanistic descriptor in 2016. This review article presents the current state of the integration of nociplastic pain into research and clinical practice. In particular, the possibilities and difficulties of applying this concept are addressed from a human and animal experimental research perspective.

Pain Management at the End of Life in the Emergency Department: A Narrative Review of the Literature and a Practical Clinical Approach

Access to pain management is a fundamental human right for all people, including those who are at the end of life (EOL). In end-stage patients, severe and uncontrolled pain is a common cause of admission to the emergency department (ED), and its treatment is challenging due to its complex, often multifactorial genesis. The aim of this narrative review was to identify the available literature on the management of severe EOL pain in the ED. The MEDLINE, SCOPUS, EMBASE, and CENTRAL databases were searched from inception to 1 April 2023 including randomised controlled trials, observational studies, systemic or narrative reviews, case reports, and guidelines on the management of EOL pain in the ED. A total of 532 articles were identified, and 9 articles were included (5 narrative reviews, 2 retrospective studies, and 2 prospective studies). Included studies were heterogeneous on the scales used and recommended for pain assessment and the recommended treatments. No study provided evidence for a better approach for EOL patients with pain in the ED. We provide a narrative summary of the findings and a review of the management of EOL pain in clinical practice, including (i) the identification of the EOL patients and unmet palliative care needs, (ii) a multidimensional, patient-centred assessment of the type and severity of pain, (iii) a multidisciplinary approach to the management of end-of-life pain, including an overview of non-pharmacological and pharmacological techniques; and (iv) the management of special situations, including rapid acute deterioration of chronic pain, breakthrough pain, and sedative palliation.

Applying the behavioural change wheel to guide the implementation of a biopsychosocial approach to musculoskeletal pain care

Achieving high value, biopsychosocial pain care can be complex, involving multiple stakeholders working synergistically to support the implementation of quality care. In order to empower healthcare professionals to assess, identify and analyse biopsychosocial factors contributing to musculoskeletal pain, and describe what changes are needed in the whole-of-system to navigate this complexity, we aimed to: (1) map established barriers and enablers influencing healthcare professionals' adoption of a biopsychosocial approach to musculoskeletal pain against behaviour change frameworks; and (2) identify behaviour change techniques to facilitate and support the adoption and improve pain education. A five-step process informed by the Behaviour Change Wheel (BCW) was undertaken: (i) from a recently published qualitative evidence synthesis, barriers and enablers were mapped onto the Capability Opportunity Motivation-Behaviour (COM-B) model and Theoretical Domains Framework (TDF) using "best fit" framework synthesis; (ii) relevant stakeholder groups involved in the whole-of-health were identified as audiences for potential interventions; (iii) possible intervention functions were considered based on the Affordability, Practicability, Effectiveness and Cost-effectiveness, Acceptability, Side-effects/safety, Equity criteria; (iv) a conceptual model was synthesised to understand the behavioural determinants underpinning biopsychosocial pain care; (v) behaviour change techniques (BCTs) to improve adoption were identified. Barriers and enablers mapped onto 5/6 components of the COM-B model and 12/15 domains on the TDF. Multi-stakeholder groups including healthcare professionals, educators, workplace managers, guideline developers and policymakers were identified as target audiences for behavioural interventions, specifically education, training, environmental restructuring, modelling and enablement. A framework was derived with six BCTs identified from the Behaviour Change Technique Taxonomy (version 1). Adoption of a biopsychosocial approach to musculoskeletal pain involves a complex set of behavioural determinants, relevant across multiple audiences, reflecting the importance of a whole-of-system approach to musculoskeletal health. We proposed a worked example on how to operationalise the framework and apply the BCTs. Evidence-informed strategies are recommended to empower healthcare professionals to assess, identify and analyse biopsychosocial factors, as well as targeted interventions relevant to various stakeholders. These strategies can help to strengthen a whole-of-system adoption of a biopsychosocial approach to pain care.

The history of pain measurement in humans and animals

Pain needs to be measured in order to be studied and managed. Pain measurement strategies in both humans and non-human animals have varied widely over the years and continue to evolve. This review describes the historical development of human and animal algesiometry.