The journal of pain : official journal of the American Pain Society
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The functions of small fibers can be impaired in peripheral neuropathies, and screening tests for clinical use are required. To verify whether intraepidermal stimulation (IES) is useful for assessing the functions of Adelta fibers in the superficial layer, we investigated sensory thresholds and evoked cortical responses in healthy volunteers before and after a transdermal administration of lidocaine. Pain and tactile thresholds were studied using IES and transcutaneous electrical stimulation (TS), respectively, in 10 healthy volunteers before, and 1 hour, 3 hours, and 5 hours after a local anesthesia with lidocaine. Cortical potentials evoked with IES and TS were also studied in 12 healthy volunteers before and 5 hours after the anesthesia. Although the local anesthesia had no effect on the evoked potentials or the tactile threshold for TS, it markedly increased the pain threshold and almost abolished the evoked potentials for IES. These results suggest that IES is a sensitive tool for detecting functional changes of cutaneous Adelta fibers. ⋯ Compared with other methods of stimulation used to investigate Adelta fiber function, our method is easy to apply and less invasive and can stimulate any site of the body. Therefore, it should be useful as a screening test for patients with neuropathy.
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Randomized Controlled Trial
Capsaicin-induced central sensitization evokes segmental increases in trigger point sensitivity in humans.
This study investigated whether inducing central sensitization evokes segmental increases in trigger point pressure sensitivity. We evoked central sensitization at the C(5) segment and validated its presence via mechanical cutaneous sensitivity (brush allodynia) testing. Trigger point pressure sensitivity was quantified using the pain pressure threshold (PPT) value. A 50 cm(2) area of the C(5) dermatome at the right lateral elbow was pretreated with 45 degrees heat for 10 minutes. Test subjects (n = 20) then received topical capsaicin cream (0.075%; Medicis, Toronto, Canada) to the C(5) dermatome, whereas control subjects (n = 20) received a topical placebo cream (Biotherm Massage, Montreal, Canada). PPT readings were recorded from the infraspinatus (C(5,6)) and gluteus medius (L(4,5)S(1)) trigger points at zero (pre-intervention), 10, 20, and 30 minutes after intervention; all PPT readings were normalized to pre-intervention (baseline) values. The difference between the PPT readings at the 2 trigger point sites represents the direct influence of segmental mechanisms on the trigger point sensitivity at the infraspinatus site (PPT(seg)). Test subjects demonstrated statistically significant increases in Total Allodynia scores and significant decreases in PPT(seg) at 10, 20, and 30 minutes after application, when compared with control subjects. These results demonstrate that increases in central sensitization evoke increases in trigger point pressure sensitivity in segmentally related muscles. ⋯ Myofascial pain is the most common form of musculoskeletal pain. Myofascial trigger points play an important role in the clinical manifestation of myofascial pain syndrome. Elucidating the role of central sensitization in the pathophysiology of trigger points is fundamental to developing optimal strategies in the management of myofascial pain syndrome.
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Pain is a debilitating condition affecting millions each year, yet what predisposes certain individuals to be more sensitive to pain remains relatively unknown. Several psychological factors have been associated with pain perception, but the structural relations between multiple higher- and lower-order constructs and pain are not well understood. Thus, we aimed to examine the associations between pain perception using the cold pressor task (CPT), higher-order personality traits (neuroticism, negative affectivity, trait anxiety, extraversion, positive affectivity, psychoticism), and lower-order pain-related psychological constructs (pain catastrophizing [pre- and post-], fear of pain, anxiety sensitivity, somatosensory amplification, hypochondriasis) in 66 pain-free adults. Factor analysis revealed 3 latent psychological variables: pain- or body-sensitivity, negative affect/neuroticism, and positive affect/extraversion. Similarly, pain responses factored into 3 domains: intensity, quality, and tolerance. Regression and correlation analyses demonstrated that: 1) all the lower-order pain constructs (fear, catastrophizing, and hypochondriasis) are related through a single underlying latent factor that is partially related to the higher-order negative-valence personality traits; 2) pain- or body-sensitivity was more strongly predictive of pain quality than higher-order traits; and 3) the form of pain assessment is important-only qualitative pain ratings were significantly predicted by the psychological factors. ⋯ Consistent with the biopsychosocial model, these results suggest multiple pain-related psychological measures likely assess a common underlying factor, which is more predictive of qualitative than intensity pain ratings. This information may be useful for the development and advancement of pain assessments and treatments while considering the multidimensional nature of pain.
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This study investigated the association between effectiveness of ED pain treatment and race of patients, race of providers, and the concordance of patient and provider race, with a prospective, multicenter study of patients presenting to 1 of 20 US and Canadian EDs with moderate to severe pain. Primary outcome is a 2-point or greater reduction in pain intensity, measured with an 11-point verbal scale, considered the minimum clinically important reduction in pain intensity. A total of 776 patients were enrolled. The sample included 57% female, 44% white, 26% black, and 26% Hispanic. The physician was white in 85% of encounters. Arrival pain score (adjusted odds ratio, 1.14; 95% CI 1.06, 1.24), receipt of any ED analgesia (1.59; 95% CI 1.17, 2.17), and physician nonwhite race (1.68; 95% CI 1.10, 2.55) were significant predictors of clinically significant reduction in pain intensity in multivariate analysis. Nonwhite physicians achieved better pain control without using more analgesics. Future research should explore the determinants of this difference in patient response to pain treatment related to provider race including provider characteristics and training that were not measured in this study. This study provided no evidence supporting an effect of racial concordance on the primary outcome. ⋯ This article presents analysis of predictors of clinically important reduction in pain intensity among emergency department patients, finding nonwhite physicians achieving better pain relief with less analgesia. This finding should encourage researchers to investigate elements of the therapeutic relationship that may be enhanced to achieve better pain relief for patients.