Pain
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Randomized Controlled Trial Clinical Trial
A multi-faceted workplace intervention for low back pain in nurses' aides: a pragmatic stepped wedge cluster randomised controlled trial.
This study established the effectiveness of a workplace multifaceted intervention consisting of participatory ergonomics, physical training, and cognitive-behavioural training (CBT) for low back pain (LBP). Between November 2012 and May 2014, we conducted a pragmatic stepped wedge cluster randomised controlled trial with 594 workers from eldercare workplaces (nursing homes and home care) randomised to 4 successive time periods, 3 months apart. The intervention lasted 12 weeks and consisted of 19 sessions in total (physical training [12 sessions], CBT [2 sessions], and participatory ergonomics [5 sessions]). ⋯ The linear mixed models yielded significant effects on LBP days of -0.8 (95% confidence interval [CI], -1.19 to -0.38), LBP intensity of -0.4 (95% CI, -0.60 to -0.26), and bothersomeness days of -0.5 (95% CI, -0.85 to -0.13) after the intervention compared with the control group. This study shows that a multifaceted intervention consisting of participatory ergonomics, physical training, and CBT can reduce LBP among workers in eldercare. Thus, multifaceted interventions may be relevant for improving LBP in a working population.
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The neurobiological mechanisms underlying chronic pain associated with cancers are not well understood. It has been hypothesized that factors specifically elevated in the tumor microenvironment sensitize adjacent nociceptive afferents. We show that parathyroid hormone-related peptide (PTHrP), which is found at elevated levels in the tumor microenvironment of advanced breast and prostate cancers, is a critical modulator of sensory neurons. ⋯ We also observed an increase in plasma membrane TRPV1 protein levels after exposure to PTHrP, leading to upregulation in the proportion of TRPV1-responsive neurons, which was dependent on the activity of PKC and Src kinases. Furthermore, co-injection of PKC or Src inhibitors attenuated PTHrP-induced thermal but not mechanical hypersensitivity. Altogether, our results suggest that PTHrP and mild acidic conditions could induce constitutive pathological activation of sensory neurons through upregulation of TRPV1 function and trafficking, which could serve as a mechanism for peripheral sensitization of nociceptive afferents in the tumor microenvironment.
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Mechanical allodynia, a cardinal symptom of persistent pain, is associated with the unmasking of usually blocked local circuits within the superficial spinal or medullary dorsal horn (MDH) through which low-threshold mechanical inputs can gain access to the lamina I nociceptive output neurons. Specific interneurons located within inner lamina II (IIi) and expressing the gamma isoform of protein kinase C (PKCγ⁺) have been shown to be key elements for such circuits. However, their morphologic and electrophysiologic features are still unknown. ⋯ In addition, at least 2 morphologically and functionally different subpopulations of PKCγ⁺ interneurons can be identified: central and radial PKCγ⁺ interneurons. The former exhibit a lower membrane input resistance, rheobase and, thus, action potential threshold, and less PKCγ⁺ immunoreactivity than the latter. These 2 subpopulations might thus differently contribute to the gating of dorsally directed circuits within the MDH underlying mechanical allodynia.
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Painful peripheral neuropathy due to the antiretroviral therapy used to treat HIV is one of the most prevalent side effects occurring in at least 30% of patients living with this infection. We have evaluated the electrophysiological and behavioral effects of d4T and ddC on peripheral large and small nerve fibers in male rats treated with d4T (Sprague-Dawley, 50 mg/kg, twice within 1 week), ddC (Wistar, 50 mg/kg, 3 times per week for 3 weeks), or vehicle. The effect of the interventions was assessed using behavioral measures of mechanical sensitivity, conventional nerve conduction studies, and microneurographic single nerve C-fiber recordings. ⋯ No relationship could be established between measures of spontaneous activity in C-nociceptors and the results of the behavioral tests. Our results show that both models of antiretroviral-induced neuropathy differ in their effects on peripheral nerves. However, both groups present abnormal spontaneous activity in mechanoinsensitive C-nociceptors that can be used as a model for pharmacological intervention.