Pain
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An experimental arthritis of the knee joint resulted in limping, guarding, and an increased response to heat stimuli (heat hyperalgesia). Spinal administration of the non-N-methyl-D-aspartate (non-NMDA) antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), significantly reduced the degree of peripheral inflammation, thermal and behavioral manifestations of arthritis. NMDA antagonists had no effect on the inflammation but did prevent the development of the heat hyperalgesia. Thus, central non-NMDA receptors play a major role in the development of peripheral inflammation while both non-NMDA and NMDA receptors are involved in the development of heat hyperalgesia.
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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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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.
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Case Reports
Hyperalgesia and myoclonus in terminal cancer patients treated with continuous intravenous morphine.
Eight cancer patients in the terminal stages of the disease treated with high doses of intravenous morphine developed hyperalgesia. All cases were retrospectively sampled from three different hospitals in Copenhagen. ⋯ Although only few clinical descriptions of the relationship between hyperalgesia/myoclonus and high doses of morphine are available, experimental support from animal studies indicates that morphine, or its metabolites, plays a causative role for the observed behavioural syndrome. The possible mechanisms are discussed and treatment proposals given suggesting the use of more efficacious opioids with less excitatory potency in these situations.