Blood pressure-related pain modulation in fibromyalgia: Differentiating between static versus dynamic pain indicators

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.

Algometry for the assessment of central sensitisation to pain in fibromyalgia patients: a systematic review

INTRODUCTION

The pathophysiology of fibromyalgia (FM) is related to central sensitisation (CS) to pain. Algometry allows assessing CS based on dynamic evoked pain. However, current algometrýs protocols require optimising, unifying and updating.

OBJECTIVES

1) identify the dynamic pain measures used most frequently to effectively assess CS processes in FM, and 2) consider the future of the algometry assessing CS in these patients.

METHODS

Cochrane Collaboration guidelines and PRISMA statements were followed. The protocol was registered in PROSPERO database (ID: CRD42021270135). The selected articles were evaluated using the Cochrane risk of bias (ROB) assessment tool. The PubMed, Scopus, and Web of Science databases were searched.

RESULTS

Thirty-four studies were selected, including measures such as temporal summation of pain (TSP), aftersensations (AS), spatial summation of pain (SSP), the noxious flexion reflex (NFR) threshold, conditioned pain modulation (CPM), cutaneous silent period (CuSP), and slowly repeated evoked pain (SREP); and evoked pain combined with neuroimaging. Each measure offered various advantages and limitations. According to ROB, 28 studies were of low quality, 3 of moderate quality, and 3 of high quality.

CONCLUSIONS

Several pain indicators have been demonstrated to successfully examine CS involvement in FM in the last years. Algometry, especially when it involves diverse body sites and tissues, might provide further insight into (1) the evaluation of psychological factors known to influence pain experience, (2) new dynamic pain indicators, and (3) the simultaneous use of certain neuroimaging techniques. Further research clarifying the mechanisms underlying some of these measures, and homogenisation and optimisation of the algometrýs protocols, are needed. KEY MESSAGESAlgometry allows for assessing Central Sensitisation by applying dynamic evoked pain.The future of algometry could relapse in its combination with neuroimaging.Recently-emerged pain indicators should be considered for algometrýs new protocols.

Fibromyalgia: Associations Between Fat Infiltration, Physical Capacity, and Clinical Variables

Background

Obesity is a risk factor for the development of fibromyalgia (FM) and generally most studies report increased Body Mass Index (BMI) in FM. Obesity in FM is associated with a worse clinical presentation. FM patients have low physical conditioning and obesity further exacerbates these aspects. Hitherto studies of FM have focused upon a surrogate for overall measure of fat content, ie, BMI. This study is motivated by that ectopic fat and adipose tissues are rarely investigated in FM including their relationships to physical capacity variables. Moreover, their relationships to clinical variables including are not known. Aims were to 1) compare body composition between FM and healthy controls and 2) investigate if significant associations exist between body composition and physical capacity aspects and important clinical variables.

Methods

FM patients (n = 32) and healthy controls (CON; n = 30) underwent a clinical examination that included pressure pain thresholds and physical tests. They completed a health questionnaire and participated in whole-body magnetic resonance imaging (MRI) to determine body composition aspects.

Results

Abdominal adipose tissues, muscle fat, and BMI were significantly higher in FM, whereas muscle volumes of quadriceps were smaller. Physical capacity variables correlated negatively with body composition variables in FM. Both body composition and physical capacity variables were significant regressors of group belonging; the physical capacity variables alone showed stronger relationships with group membership. A mix of body composition variables and physical capacity variables were significant regressors of pain intensity and impact in FM. Body composition variables were the strongest regressors of blood pressures, which were increased in FM.

Conclusion

Obesity has a negative influence on FM symptomatology and increases the risk for other serious conditions. Hence, obesity, dietary habits, and physical activity should be considered when developing clinical management plans for patients with FM.

Circadian Variation of Blood Pressure in Patients with Chronic Musculoskeletal Pain: A Cross-Sectional Study

The aim of this study was to analyze the impact of circadian variation of blood pressure (BP) in patients with chronic musculoskeletal pain (CPM). A further purpose was to study differences in circadian variation of BP between genders and the correlation between BP circadian variation and pain. We performed a cross-sectional, observational study in which seventy-five participants with CMP participated. Circadian variation in BP was calculated using the diurnal/nocturnal BP ratio, and all participants used validated self-measurement BP devices. The Numeric Pain Rating Scale was used to assess pain perception. All circadian BP values from participants who suffered from CPM followed pathologic cardiovascular parameters (BP ratio < 10%). When comparing BP ratios between genders, statistically significant differences were found (p = 0.011). BP itself did not correlate with pain in any subgroup. Circadian variations of BP in those suffering from CMP are shown and new possibilities of research and treatment are proposed.

The Effect of Pneumoperitoneum-induced Hypertension During Laparoscopic Cholecystectomy Under General Anesthesia on Postoperative Pain: A Randomized Clinical Trial

Background: Acute postoperative pain is a significant cause of morbidities. This study aimed to evaluate the effect of intraoperative blood pressure during laparoscopic cholecystectomy under general anesthesia on postoperative pain in patients without underlying disorders. Methods: In this randomized clinical trial, 72 patients undergoing general anesthesia for elective laparoscopic cholecystectomy were randomly assigned into two groups: Group A with higher than baseline preoperative blood pressure (MAP allowed to increase up to 20% higher than baseline MAP by inducing pneumoperitoneum) and group B with normal to low blood pressure (MAP deliberately controlled at a tight limit from normal baseline MAP values to 20% less than baseline by titrating TNG infusion). The Visual Analog Scale (VAS) after 2, 8, 12, and 24 hours of surgery, and the total dose of meperidine used to manage postoperative pain were recorded and compared between the two groups. Results: The pain scores in group A were significantly lower than group B (P = 0.001). The postoperative analgesia request time was different between the two groups (P = 0.53). During the first 24 hours, the total meperidine consumption dose in group A was significantly lower than in group B (P = 0.001). Conclusions: High intraoperative blood pressure may affect the postoperative pain after laparoscopic cholecystectomy and lead to less postoperative pain score and analgesic requirements.

Effectiveness of Acceptance and Commitment Therapy in Central Pain Sensitization Syndromes: A Systematic Review

OBJECTIVES

Acceptance and commitment therapy (ACT) is considered by the American Psychological Association as an evidence-based treatment for a variety of disorders, including chronic pain. The main objective of the present systematic review was to determine the effectiveness of ACT in patients with central pain sensitization syndromes (CPSS).

METHODS

This systematic review was conducted according to the guidelines of the Cochrane Collaboration and PRISMA statements. The protocol was registered in advance in the Prospective Register of Systematic Reviews (PROSPERO) international database. The selected articles were evaluated using the Cochrane risk of bias (ROB) assessment tool. The PubMed, Scopus, and Web of Science databases were searched.

RESULTS

The literature search identified 21 studies (including investigations of fibromyalgia syndrome, irritable bowel syndrome, and migraine) eligible for the systematic review. There were no studies regarding the effectiveness of ACT for chronic tension-type headache (CTTH), interstitial cystitis (IC), or temporomandibular disorder (TMD). The evaluation of ROB showed that 12 of the selected studies were of low quality, 5 were of moderate quality, and 4 were high quality. ACT reduces some clinical symptoms, such as anxiety, depression, and pain. This positive effect of ACT might be mediated by pain acceptance, psychological flexibility, optimism, self-efficacy, or adherence to values. ACT showed better results in comparison to non-intervention (e.g., "waiting list") conditions, as well as pharmacological and psychoeducational interventions. It is not entirely clear whether extended ACT treatments are more advantageous than briefer interventions.

CONCLUSIONS

There are few studies about the effectiveness of ACT on CPSS. However, ACT seems to reduce subjective CPSS symptoms and improve the health-related quality of life of these patients. The absence of studies on the effectiveness of ACT in CTTH, IC, and TMD, indicate the pressing need for further ACT studies in these CPSS.

Blood pressure-related hypoalgesia: a systematic review and meta-analysis

OBJECTIVE

Spontaneous or experimentally induced high blood pressure (BP) is associated with reduced pain perception, known as BP-related hypoalgesia. Despite its clinical implications, such as the interference with early detection of myocardial infarction in 'at risk' groups, the size of the association between high BP and pain has not yet been quantified. Moreover, the distinct association between high BP and physiological or psychological components of pain has not yet been considered so far. The aim of this study was to overcome this gap by performing separate meta-analyses on nociceptive response versus quantifiable perceptual measures of pain in relation to high BP.

METHODS

PubMed and Web of Knowledge databases were searched for English language studies conducted in humans. Fifty-nine studies were eligible for the analyses. Pooled effect sizes (Hedges' g) were compared. Random effect models were used. Results show that higher BP is significantly associated with lower nociceptive response (g = 0.38; k = 6) and reduced pain perception, assessed by quantifiable measures (g = 0.48; k = 59).

RESULTS

The association between BP and pain perception, derived from highly heterogeneous studies, was characterized by significant publication bias. BP assessment, pain assessment, site of pain stimulation, percentage of female participants in the sample, and control for potential confounders were significant moderators.

CONCLUSION

Current meta-analytic results confirm the presence of BP-related hypoalgesia and point towards the need for a better understanding of its underlying mechanisms.

Slowly repeated evoked pain (SREP) as a central sensitization marker in episodic migraine patients

Migraine headache is a pain condition characterized by severe and recurrent unilateral head pain. Among other mechanisms, central pain sensitization processes seem to be involved in the disorder. An experimental protocol based on slowly repeated evoked pain (SREP) has been shown to indicate pain sensitization in fibromyalgia patients and differentiate these patients from healthy individuals and rheumatoid arthritis patients. This study examined SREP sensitization in migraine patients and explored its potential usefulness as a central sensitization marker. The SREP protocol was administered to 40 episodic migraine (EM) patients not currently experiencing a headache and 40 healthy controls. SREP consisted of a series of 9 suprathreshold painful pressure stimuli of 5 s duration and a 30 s interstimulus interval. SREP sensitization was indexed by the increase in pain ratings across the stimuli. Pain threshold, pain tolerance and temporal summation of pain were also assessed. SREP sensitization was observed in EM, but not in healthy individuals (p < .001). SREP differentiated between EM and healthy individuals with up to 75% diagnostic accuracy. Pain threshold, pain tolerance and temporal summation of pain did not show significant discriminative ability. An SREP index value of 0.5 was the most sensitive cut-off for detecting central pain sensitization when prioritizing diagnostic sensitivity (0.88). Results provide evidence for SREP as a possible central sensitization marker with potential clinical utility in migraine patients. Inclusion of SREP in Quantitative Sensory Testing protocols may enhance the assessment of altered pain modulation in different pain conditions.

Development and Validation of a Predictive Model of Pain Modulation Profile to Guide Chronic Pain Treatment: A Study Protocol

Introduction: Quantitative sensory testing is frequently used in research to assess endogenous pain modulation mechanisms, such as Temporal Summation (TS) and Conditioned Pain Modulation (CPM), reflecting excitatory and inhibitory mechanisms, respectively. Numerous studies found that a dysregulation of these mechanisms is associated with chronic pain conditions. In turn, such a patient's “profile” (increased TS and/or weakened CPM) could be used to recommend different pharmacological treatments. However, the procedure to evaluate these mechanisms is time-consuming and requires expensive equipment that is not available in the clinical setting. In this study, we aim to identify psychological, physiological and socio-demographic markers that could serve as proxies to allow healthcare professionals to identify these pain phenotypes in clinic, and consequently optimize pharmacological treatments.

Method: We aim to recruit a healthy participant cohort (n = 360) and a chronic pain patient cohort (n = 108). Independent variables will include psychological questionnaires, pain measurements, physiological measures and sociodemographic characteristics. Dependent variables will include TS and CPM, which will be measured using quantitative sensory testing in a single session. We will evaluate one prediction model and two validation models (for healthy and chronic pain participants) using multiple regression analysis between TS/CPM and our independent variables. The significance thresholds will be set at p = 0.05, respectively.

Perspectives: This study will allow us to develop a predictive model to compute the pain modulation profile of individual patients based on their biopsychosocial characteristics. The development of the predictive model is the first step toward the overarching goal of providing clinicians with a set of quick and cheap tests, easily applicable in clinical practice to orient pharmacological treatments.

Addition of Slowly Repeated Evoked Pain Responses to Clinical Symptoms Enhances Fibromyalgia Diagnostic Accuracy

OBJECTIVE

Fibromyalgia is a chronic pain syndrome characterized by central sensitization. A novel protocol based on slowly repeated evoked pain (SREP) appears to be a useful marker of pain sensitization in fibromyalgia patients. Whether SREP enhances diagnostic accuracy beyond key clinical symptoms that characterize fibromyalgia has not been examined.

METHODS

Fifty fibromyalgia patients, 30 rheumatoid arthritis patients, and 50 healthy individuals were evaluated to assess clinical pain, as well as fatigue, insomnia, pain catastrophizing, and negative mood. The SREP protocol consisted of a series of nine low-intensity painful pressure stimuli of five seconds' duration with 30-second interstimulus intervals. SREP sensitization was indexed by increases in pain intensity ratings across stimuli.

RESULTS

SREP sensitization was observed in fibromyalgia but not in rheumatoid arthritis or healthy individuals. As expected, fibromyalgia patients exhibited a more negative psychosocial profile than did rheumatoid arthritis patients and healthy individuals. SREP was positively associated with clinical pain, fatigue, insomnia, and catastrophizing, but not with negative mood. SREP discriminated fibromyalgia cases from rheumatoid arthritis and healthy individuals even when current clinical pain was included in the analysis. Combining fatigue, insomnia, and SREP led to near perfect diagnostic accuracy (99%) in differentiating fibromyalgia from healthy individuals and 86.3% accuracy in discriminating fibromyalgia from rheumatoid arthritis.

CONCLUSIONS

These results provide further evidence of SREP as a marker of pain sensitization in fibromyalgia and suggest that it captures aspects of fibromyalgia not fully captured by clinical features. Combining SREP with assessment of clinical features could potentially improve fibromyalgia diagnosis.