Pain
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Randomized Controlled Trial Clinical Trial
Blinding effectiveness and association of pretreatment expectations with pain improvement in a double-blind randomized controlled trial.
Patient, provider, and clinical investigator expectations concerning treatments are believed to play important roles in patient response. This study examined the association of patient and research nurse/physician pretreatment expectations of pain relief with actual pain relief, the accuracy of patient and research nurse guesses about patient medication assignment, and changes in research nurse and patient pain relief expectations over the course of a randomized double-blind trial of amitriptyline versus an active placebo for patients with chronic pain and spinal cord injuries (SCI). Patient expectations of pain relief with amitriptyline were associated significantly with actual pain decrease for patients in the amitriptyline, but not placebo, condition. ⋯ The research nurse's, but not the patients', expectations of pain relief with amitriptyline decreased significantly over the course of the study. These findings have implications for future randomized controlled trials. Fully double-blind conditions are very difficult to achieve, and it is informative to assess patient and research clinician expectations and guesses regarding medication assignment.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparative study of electronic vs. paper VAS ratings: a randomized, crossover trial using healthy volunteers.
The visual analogue scale (VAS) is an established, validated, self-report measure usually consisting of a 10 cm line on paper with verbal anchors labeling the ends. Palmtop computers (PTCs also known as personal digital appliances) have incorporated VAS entry by use of a touch screen. However, the validity and psychophysical properties of the electronic VAS have never been formally compared with the conventional paper VAS. ⋯ The median of correlations comparing eVAS and pVAS ratings was 0.99 for verbal stimuli and 0.98 for sensory stimuli. Multivariate analyses showed equivalent stimuli to be rated much the same whether entered on paper VAS or PTC touch screen VAS (P < 0.0001). Support was found for the validity of the computer version of the VAS scale.
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Randomized Controlled Trial Clinical Trial
Anger and pain sensitivity in chronic low back pain patients and pain-free controls: the role of endogenous opioids.
The experience of anger (i.e. trait anger) and anger management style (i.e. anger-in, anger-out) are related to sensitivity to acute and chronic pain stimuli, although underlying mechanisms are unknown. This study tested whether anger variables are associated with impaired endogenous opioid antinociceptive activity, and whether these relationships differed between chronic pain patients and healthy normals. Forty-three chronic low back pain (LBP) sufferers and 45 pain-free normals received opioid blockade (8 mg naloxone i.v.) or placebo blockade (saline) in randomized, counterbalanced order in separate sessions. ⋯ Anger-out x LBP/normal interactions were non-significant, suggesting that links between anger-out and drug effects were similar for patients and normals. Controlling for depression did not eliminate the significant relationship between anger-out and drug effects. Findings suggest that anger-in and anger-out affect pain sensitivity through different mechanisms: only the effects of anger-out may be mediated by endogenous opioid dysfunction.
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Randomized Controlled Trial Clinical Trial
Sensory stimulation (TENS): effects of parameter manipulation on mechanical pain thresholds in healthy human subjects.
Transcutaneous electrical nerve stimulation (TENS) is a popular form of electrostimulation. Despite an extensive research base, there remains no consensus regarding the parameter selection required to achieve maximal hypoalgesic effects. The aim of this double blind, sham-controlled study was to investigate the relative hypoalgesic effects of different TENS parameters (frequency, intensity and stimulation site) upon experimentally induced mechanical pain. ⋯ Whilst high frequency, 'strong but comfortable' intensity, segmental stimulation produced comparable hypoalgesic levels during stimulation, this effect was not sustained post-stimulation. Stimulation at a combination of the two sites did not produce any greater hypoalgesic effects. These results may have implications for the clinical use of sensory stimulation.
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Comparative Study
Micromolar lidocaine selectively blocks propagating ectopic impulses at a distance from their site of origin.
Abnormal impulses caused by very slowly inactivating Na channels of peripheral nerve have been proposed to play a critical role in neuropathic pain. Low concentrations of local anesthetics, often effective in treating experimental and clinical neuropathic pain, are also known to potently suppress the long after-depolarizations induced by these persistently open Na channels. However, these drug actions on impulses that have propagated away from such sites are undetermined. ⋯ Tetrodotoxin also inhibited the induced spontaneous activity, but only at concentrations that also depressed the compound action potential spike. These findings show that low concentrations of lidocaine can restore normal firing patterns in nerve where hyperexcitability has been caused by delayed Na-channel inactivation, without acting directly at the site where ectopic impulses are generated. Thus, it appears that the pattern of abnormal activity rather than an abnormally gating Na channel per se can be a target for lidocaine's therapeutic action.