Pain
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Cold stimuli of varying intensities were randomly applied to upper middle incisors of 12 healthy young subjects for a mean duration of 2 min by individually adapted thermodes the temperatures of which ranged from +30 degrees C to -30 degrees C. The subjects were asked to rate the magnitude of their pain sensations during application of the stimuli by means of a linear potentiometer according to a category scale. After each stimulus, they were asked to describe the quality of their pain sensations. ⋯ This was described as a dull, burning pain which was difficult to localize. The human pain ratings are compared to recordings of intradental nerve fibres in the cat and, under the assumption that the response behaviour of human pulpal nerve fibres is comparable to that of the cat, we hypothesize that the first pain component is evoked by intradental A delta fibres exhibiting their typical phasic response behaviour and firing during the initial steep temperature decrease. After some seconds, intradental temperature reached values sufficient to evoke C-fibre activity associated with the second pain component.
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This study characterized the excitatory (nociceptive) and desensitizing (antinociceptive) properties of the natural pungent substances, capsaicin (CAP) and resiniferatoxin (RTX) instilled in the bladder (intravesical, i.ves.) via an indwelling cannula in awake, freely moving rats. The incidence of 9 behaviors was scored for 10 min following i.ves. vehicle or RTX (1.0 nmol). Abdominal licking and head-turning occurred significantly more often in RTX-treated rats compared to vehicle controls, whereas head-grooming, locomotion, rearing and biting did not differ between the two groups. ⋯ This study demonstrates that repeated application of both CAP and RTX into the bladder produces behavioral effects indicative of local sensory afferent desensitization. I.ves. CAP and RTX appear to produce their excitatory and desensitizing effects via a common mechanism, which is dependent on cation channel activation.(ABSTRACT TRUNCATED AT 400 WORDS)
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This study examined the effects of increasing the number of assessments on the reliability and validity of measures of average pain intensity. Two hundred chronic pain patients completed 2 weeks of hourly pain ratings. ⋯ Also, and as expected, the results indicate that a single rating of pain intensity is not adequately reliable or valid as a measure of average pain. However, a composite pain intensity score calculated from an average of 12 ratings across 4 days demonstrated adequate reliability and excellent validity as a measure of the average pain in this sample of chronic pain patients.(ABSTRACT TRUNCATED AT 250 WORDS)
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparative local anaesthetic blocks in the diagnosis of cervical zygapophysial joint pain.
The utility of randomised, double-blind, controlled, comparative local anaesthetic blocks for the diagnosis of cervical, zygapophysial joint pain was studied in 47 patients with chronic neck pain following whiplash injury. Each patient was investigated with radiologically controlled blocks of the medial branches of the cervical, dorsal rami to anaesthetise the target cervical, zygapophysial joint. The blocks were performed using either lignocaine or bupivacaine, randomly allocated, and the patients' responses were assessed in a double-blind fashion. ⋯ The durations of pain relief obtained from the anaesthetics were consistent with the known characteristics of these drugs with bupivacaine lasting significantly longer than lignocaine (P = 0.0003). A subgroup of 13 patients were identified with unexpected, prolonged responses to one or both of the anaesthetics. Comparative, diagnostic blocks are a valid technique in the identification of painful zygapophysial joints, and constitute an implementable alternative to normal saline controls.
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Comparative Study
Long-term intrathecal infusion of morphine and morphine/bupivacaine mixtures in the treatment of cancer pain: a retrospective analysis of 51 cases.
A retrospective analysis of 51 patients with cancer pain treated with a continuous i.t. morphine infusion through a tunnelled percutaneous catheter was undertaken. Because of insufficient pain relief with morphine only, 17 of these patients received a morphine/bupivacaine mixture. Pain relief subsequently improved significantly in 10 patients and a moderate improvement was present in 4 patients. ⋯ No serious complications, neurologic sequelae or meningitis occurred. It is concluded that long-term i.t. infusion of morphine through a tunnelled catheter can provide adequate pain relief in cancer patients with an acceptable risk-benefit ratio. The effects of long-term intrathecal co-administration of local anesthetics, especially bupivacaine, await further prospective evaluation.