The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Effects of intramuscular anesthesia on the expression of primary and referred pain induced by intramuscular injection of hypertonic saline.
Intramuscular injection of hypertonic saline produces pain in the belly of the injected muscle (primary pain) and, often, pain that projects distally (referred pain). While it is known that referred pain can be induced during complete sensory block of the distal site, there is little evidence as to whether the perception of referred pain depends on ongoing input from the primary stimulus. We assessed whether blocking the noxious input following the induction of pain blocks the primary but not the referred pain. A cannula was inserted into the tibialis anterior muscle in 15 subjects (8 male, 7 female). In a quasi-random crossover design conducted over 2 experimental sessions, each subject received a bolus intramuscular injection of .5 mL of 5% hypertonic saline, followed 90 seconds later by either: A) A second bolus injection or; B) An injection of 2 mL lignocaine through the same cannula. Protocol A was followed 60 seconds later by either a sham injection or an injection of lignocaine, while protocol B was followed 60 seconds later by either a sham injection or an injection of hypertonic saline. Subjects mapped the areas of primary and referred pain, and rated the intensities at these sites every 30 seconds until the cessation of pain. In all subjects, the area and intensity of primary pain rapidly disappeared within 7.5 minutes of intramuscular lignocaine injection (P < .02 relative to the nonanesthesia condition). With the exception of 2 subjects, in whom the referred pain continued in the absence of primary pain, the referred pain declined in parallel with local pain: the mean total pain intensity declined by 74% in both regions. We conclude that the maintenance of referred muscle pain usually depends on ongoing noxious inputs from the site of primary muscle pain. ⋯ Referred pain is a significant clinical problem, and commonly occurs with pain originating in muscle but not from skin. It is important to know the primary source of the pain so that treatment can be directed to this site rather to the site of referral.
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Randomized Controlled Trial
Personal values and pain tolerance: does a values intervention add to acceptance?
Previous research suggests that acceptance is a promising alternative to distraction and control techniques in successfully coping with pain. Acceptance interventions based upon Acceptance and Commitment Therapy (ACT) have been shown to lead to greater tolerance of acute pain as well as increased adjustment and less disability among individuals with chronic pain. However, in these previous intervention studies, the ACT component of values has either not been included or not specifically evaluated. The current study compares the effects of an ACT-based acceptance intervention with and without the values component among individuals completing the cold-pressor task. Results indicate that inclusion of the values component (n = 34) of ACT leads to significantly greater pain tolerance than acceptance alone (n = 30). Consistent with previous research, both conditions were associated with greater pain tolerance than control (n = 35). Despite the difference in tolerance, pain threshold did not differ, and participants in the control condition provided lower ratings of pain severity. The findings from this study support the important role of values and values clarification in acceptance-based interventions such as ACT, and provide direction for clinicians working with individuals with chronic pain conditions. ⋯ This article evaluates the additive effect of including a personalized-values exercise in an acceptance-based treatment for pain. Results indicate that values interventions make a significant contribution and improvement to acceptance interventions, which may be of interest to clinicians who provide psychological treatment to individuals with chronic pain.
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Randomized Controlled Trial
L2 spinal nerve-block effects on acute low back pain from osteoporotic vertebral fracture.
Elderly patients with osteoporosis sometimes experience lumbar vertebral fracture and may feel diffuse nonlocalized pain in the back, the lateral portion of the trunk, and the area surrounding the iliac crest. The pattern of sensory innervation of vertebral bodies remains unclear. Some sensory nerves from the L2 and L5 vertebral bodies may enter the paravertebral sympathetic trunks and reach the L2 dorsal root ganglion. Our randomized controlled study was to clarify the effect of L2 spinal nerve block on low back pain originating from acute osteoporotic lumbar vertebral fracture. Patients with low back pain originating from acute L3 or L4 osteoporotic vertebral fractures received a spinal nerve root block (L2 block group, n = 30) or subcutaneous injection (control, n = 30). Both groups received 1.5 mL of 1% lidocaine. The visual analog scale score, Roland Morris Disability Questionnaire, and Short Form questionnaire were examined before and after treatment. In both groups, spinal nerve blocks were significantly effective in alleviating low back pain (P < .05). One hour, 1 week, and 2 weeks after treatment, the visual analog scale score improved more in the L2 block group than in the control group (P < .05). From 1 month to 4 months after treatment, there were no significant differences in the pain scores between groups (P > .05). We conclude that L2 spinal nerve block for acute L3 or L4 osteoporotic vertebral body fracture was effective for 2 weeks, but it had no long-term effects on pain and social function. ⋯ L2 spinal nerve block treatment for L3 or L4 osteoporotic vertebral body fracture was effective. This results suggest that the L2 dorsal root ganglion may innervate the L3 and L4 vertebral bodies in humans. L2 spinal nerve block for lumbar osteoporotic vertebral fracture may be a useful strategy to treat acute low back pain.
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Mild knee pain is a common symptom in later life. Despite this fact, there are few data on the impact of it worsening or how individuals alter their appraisals and behavior when it becomes severe. We sought to describe the changes that accompany a substantial deterioration in characteristic knee pain. A nested case-control analysis of existing cohort data identified 57 adults aged over 50 years experiencing progression from mild to severe characteristic pain intensity 18 months later and compared them, before and after this transition, with 228 controls whose knee pain did not progress. Worsening knee pain was accompanied by a marked increase in pain frequency and extent, functional limitation, depressive symptoms, catastrophising, praying and hoping, and use of oral and topical analgesia. Most individuals consulted a general practitioner either during or after this episode. Although relatively rare, substantial deterioration in knee pain has a major impact on those affected. Timely presentation to primary care, addressing potentially unhelpful appraisals and coping strategies, reinforcing core nonpharmacological management, and future research to identify triggering events for substantial deterioration and loss of adequate pain control should be part of an agenda to improve care for this important minority of older adults with knee pain. ⋯ This article describes what happens when the common symptom of mild knee pain in later life becomes significantly worse. The results may help clinicians understand the health impact, changes in patient appraisal and coping, and treatments that typically accompany this change in symptoms.
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Randomized Controlled Trial Multicenter Study
Lacosamide in painful diabetic neuropathy: an 18-week double-blind placebo-controlled trial.
The efficacy and tolerability of oral lacosamide (200, 400, and 600 mg/day) was evaluated in patients with painful diabetic neuropathy in a double-blind, randomized, placebo-controlled trial. The primary target dose to be confirmed was lacosamide 400 mg/day. Efficacy was assessed by changes in pain scale scores from baseline, with changes over the last 4 weeks of the 12-week maintenance period regarded as the primary endpoint. Endpoint reductions in mean pain score were higher with all doses of lacosamide, reaching the level of significance with 400 mg/day (P = .05). Over the treatment period (titration + maintenance), pain relief was significantly higher than placebo with lacosamide 400 (P = .02) and 600 mg/day (P = .03). Lacosamide had an early-onset effect with significant reductions over placebo during the titration period. Nonparametric and mixed-model analysis approaches gave similar results, supporting significant efficacy at 400 mg/day. Secondary criteria such as Patient's Global Impression of Change, responder rates, and pain-free days provided additional support. Adverse events included dizziness, nausea, and headache. Incidence of cognitive and behavioral adverse events was low. This trial suggests that lacosamide has beneficial effects and may be a suitable treatment option for patients with diabetic neuropathic pain. ⋯ This study presents efficacy and safety results of a phase 3, double-blind, placebo-controlled trial of the anticonvulsant drug lacosamide in patients with painful diabetic neuropathy. Lacosamide treatment at a dose of 400 mg/day reduced diabetic neuropathic pain with a favorable safety and tolerability profile that may be suitable for patients with diabetes.