Hypoalgesia after exercises with painful vs. non-painful muscles in healthy subjects - a randomized cross-over study.

OBJECTIVES: Exercise-induced hypoalgesia (EIH) is a decrease in the pain sensitivity after exercise. Individuals with chronic pain show less EIH after one exercise session compared with pain-free individuals possibly due to pain in exercising muscles. The primary aim of this randomized controlled cross-over study was to compare the EIH response at the exercising thigh muscle following exercises performed with painful vs. non-painful muscles. Secondary aims were to explore if a reduced EIH response was confined to the painful muscle, and whether the muscle pain intensity and the EIH responses were negatively associated. METHODS: In two sessions, 34 pain-free participants received a painful (hypertonic saline, 5.8%) injection and a control (isotonic saline, 0.9%) injection in the right thigh muscle before performing a 3 min isometric wall squat exercise. Pressure pain thresholds (PPTs) were assessed at both thighs and the left neck/shoulder at baseline, after injections and after exercise. Pain intensities in the thighs were rated on numerical rating scales (NRS: 0-10). RESULTS: Hypertonic saline induced moderate thigh pain at rest (NRS: 4.6 ± 2.1) compared to the control injection (NRS: 0.3 ± 0.4; p<0.001). EIH at the thighs and neck/shoulder were not different between sessions (Injected thigh: 0 kPa; 95% CI: -51 to 52; Contralateral thigh: -6 kPa; 95% CI: -42 to 30; neck/shoulder: 19 kPa; 95% CI: -6 to 44). No significant associations between pain intensity ratings immediately after the Painful injection and EIH responses at any assessment sites were found (right thigh: ß=0.08, 95% CI: -12.95 to 20.64, p=0.64, left thigh: ß=-0.33, 95% CI: -27.86 to 0.44, p=0.06; neck/shoulder: ß=-0.18, 95% CI: -15.11 to 4.96, p=0.31). CONCLUSIONS: Pain in the area of an exercising muscle did not reduce local or systemic EIH responses. TRIAL REGISTRATION NUMBER: NCT04354948.

Testosterone replacement therapy of opioid-induced male hypogonadism improved body composition but not pain perception: a double-blind, randomized, and placebo-controlled trial.

BACKGROUND: Hypogonadism is prevalent during opioid treatment, but the effect of testosterone replacement treatment (TRT) on body composition, pain perception, and adrenal function is unclear. PURPOSE: To measure changes in body composition, pain perception, quality of life, and adrenal function after TRT or placebo in opioid-treated men with chronic non-malignant pain. METHODS: Double-blind, placebo-controlled study in 41 men (>18 years) with total testosterone <12 nmol/L were randomized to 24 weeks TRT (Testosterone undecanoate injection three times/6 months, n = 20) or placebo (placebo-injections, n = 21). OUTCOMES: Body composition (lean body mass and fat mass assessed by DXA), clinical pain intensity (numerical rating scale), and experimental pain perception (quantitative sensory assessment), quality of life (SF36), and adrenocorticotrophic hormone (ACTH) test. Data were presented as median (quartiles). Mann-Whitney tests were performed on delta values (24-0 weeks) between TRT and placebo. RESULTS: The median age was 55 years (46; 59) and total testosterone before intervention was 6.8 (5.0; 9.3) nmol/L. TRT was associated with change of testosterone levels: 12.3 (7.0; 19.9) nmol/L (P < 0.001 vs placebo), increased lean body mass: 3.6 (2.3; 5.0) kg vs 0.1 kg (-2.1; 1.5) during TRT vs placebo and decreased total fat mass: -1.2 (-3.1; 0.7) kg vs 1.2 kg (-0.9; 2.5) kg, both P < 0.003. Changed pain perception, SF36, and ACTH-stimulated cortisol levels were non-significantly changed during TRT compared with placebo. CONCLUSIONS: Six months of TRT improved body composition in men with opioid-induced hypogonadism without significant changes in outcomes of pain perception, quality of life, or adrenal function.

Chronic pain patients with possible co-morbid post-traumatic stress disorder admitted to multidisciplinary pain rehabilitation-a 1-year cohort study.

BACKGROUND: Although post-traumatic stress disorder (PTSD) is a common co-morbidity in chronic pain, little is known about the association between PTSD and pain in the context of chronic pain rehabilitation. OBJECTIVE: The aim of the present study was two-fold: (1) to investigate the association of a possible PTSD diagnosis with symptoms of pain, physical and mental functioning, as well as the use of opioids, and (2) to compare the outcome of multidisciplinary chronic pain rehabilitation for patients with a possible PTSD diagnosis at admission with patients without PTSD at admission. METHOD: A consecutively referred cohort of 194 patients completed a baseline questionnaire at admission covering post-traumatic stress, pain symptoms, physical and mental functioning, as well as self-reported sleep quality and cognitive difficulties. Medication use was calculated from their medical records. A total of 95 were admitted to further multidisciplinary treatment and included in the outcome study. RESULTS: A high prevalence of possible PTSD was found (26.3%). Patients with possible co-morbid PTSD experienced significantly poorer general and mental health, poorer sleep quality, and more cognitive problems as well as inferior social functioning compared to patients without PTSD. Possible co-morbid PTSD did not result in higher use of opioids or sedatives. Surprisingly, possible co-morbid PTSD at admission was not associated with lower levels of symptom reduction from pre- to post-treatment. CONCLUSIONS: Possible co-morbid PTSD in chronic pain is a major problem associated with significantly poorer functioning on several domains. Nevertheless, our results indicate that pain-related symptoms could be treated with success despite possible co-morbid PTSD. However, since PTSD was only measured at admission it is not known whether rehabilitation actually reduced PTSD.

Prevalence of neuropathic pain according to the IASP grading system in patients with chronic non-malignant pain.

OBJECTIVE: The primary objective was to determine the prevalence of neuropathic pain according to the new International Association for the Study of Pain (IASP) grading system. The secondary objective was to compare the system classification of neuropathic pain with the classification of neuropathic pain according to a patient-administered screening questionnaire. SETTING: A Multidisciplinary Pain Center. SUBJECTS: One hundred twenty patients with a variety of chronic pain conditions referred to a multidisciplinary pain center. METHODS: Consecutively referred patients filled out the PainDETECT Questionnaire before the first consultation. During the first consultation, patients had pain history taken and bedside examination performed by a pain specialist. Patients were classified according to the score on the PainDETECT Questionnaire and graded according to the IASP grading system about the certainty of neuropathic pain. RESULTS: According to the IASP grading system, 22 patients (18.3%) classified as probable or definite neuropathic pain and 90 patients (75%) as unlikely neuropathic pain. According to the PainDETECT Questionnaire, 55 patients (45%) were classified as likely neuropathic pain and 13 patients (10.8%) as unlikely neuropathic pain. Eleven patients (20%) who were classified as neuropathic pain according to PainDETECT were also classified as probable or definite neuropathic pain by the new IASP grading system. CONCLUSIONS: According to the new IASP grading system, less than 20% of the patients referred to a multidisciplinary pain center fulfilled the criteria for neuropathic pain. The classification of neuropathic pain with the IASP system varies from the classification of neuropathic pain with the use of a self-administered screening questionnaire.

The traumatised chronic pain patient-Prevalence of posttraumatic stress disorder - PTSD and pain sensitisation in two Scandinavian samples referred for pain rehabilitation.

Introduction Correctly identifying chronic pain patients with posttraumatic stress disorder (PTSD) is important because the comorbidity of a chronic pain condition and PTSD is found to compromise treatment success. In addition, the existence of PTSD is associated with pain sensitisation, elevated levels of pain, and disability. Furthermore, the diagnostic criteria for PTSD has changed dramatically in the last two decades which has had a profound impact on the reported prevalence rates of PTSD in chronic pain samples. To our knowledge, no study has employed the DSM-IV criteria for estimating the prevalence of PTSD in chronic pain patients referred consecutively for multidisciplinary pain rehabilitation. Aim The aim of the present study was to assess the prevalence of significant traumatic stressors and PTSD in chronic pain patients referred consecutively to multidisciplinary pain rehabilitation. We wanted to investigate whether specific pain diagnoses were more related to PTSD than others. Moreover, we investigated the possible association of altered sensory processing (hypersensitivity or hyposensitivity) and PTSD. Methods Data were collected from two Scandinavian multidisciplinary pain centres (Denmark and Finland). All patients referred consecutively were assessed for PTSD and sensitisation at admission. A total of 432 patients were assessed, of which 304 (DK, N =220, female n = 144; FIN, N=84, female n = 44) were admitted and consented to participate. All patients had to be diagnosed with a non-malign chronic pain condition lasting for at least 6 months (median = 6.0 years). The Harvard Trauma Questionnaire was employed to measure PTSD symptoms, using the DSM-IV criteria. To measure altered sensory processing, anaesthetists performed quantitative sensory testing on admission. Patients were asked to report if cold, brush, and pinprick mechanical stimulation resulted in decreased or increased sensation or pain. Results stimulation resulted in decreased or increased sensation or pain. RESULTS: A high prevalence of PTSD was found in both consecutive samples. Using the DSM-IV criteria, 23% fulfilled the criteria for a possible PTSD diagnosis. There were no gender differences in PTSD. The three most reported traumatic events: traffic accidents, serious illness personally or in the family, and the actual loss of someone, were reported as the primary traumatic events by almost 50% of those with PTSD. No particular pain diagnosis was significantly related to PTSD. However, hypersensitivity to cold and hyposensitivity to brush were significantly associated with PTSD. Discussion The prevalence of PTSD in the present study was 23%. Earlier studies finding a lower prevalence rate of PTSD may reflect the use of older diagnostic criteria for PTSD or other estimates, for instance PTSD symptom cut-off scores. Conclusion The study emphasised the importance of screening all chronic pain patients for PTSD at admission for pain rehabilitation, using up to date diagnostic tools. Implications Untreated PTSD may exacerbate or maintain the pain condition and negatively affect outcome of pain rehabilitation.