Pain
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The effect of continuous subcutaneous (s.c.) infusion of ketamine on nerve injury pain was examined in patients with post-herpetic neuralgia. Five patients that reported pain relief after acute intravenous injection of ketamine were included in this open prospective study. Ketamine was administered continuously in increasing doses using a portable infusion pump (CADD-PLUS, Pharmacia), and the treatment period for each infusion rate (0.05, 0.075, 0.10, or 0.15 mg/kg/h) was 7 days and nights. ⋯ Itching and painful indurations at the injection site was the most bothersome side-effect and for this reason 1 patient discontinued treatment after 2 weeks. Other common side-effects were nausea, fatigue and dizziness. The present results show that continuous, spontaneous and evoked pain in patients with post-herpetic neuralgia is reduced by continuous s.c. infusion of ketamine, but is associated with intolerable side effects.
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Comparative Study
Effect of ketamine, an NMDA receptor inhibitor, in acute and chronic orofacial pain.
We examined the analgesic effect of racemic ketamine and its 2 enantiomers in 16 female patients (age: 20-29 years) suffering acute pain after oral surgery and in 7 female patients (age: 42-79 years) suffering chronic neuropathic orofacial pain. All 3 forms of ketamine consistently relieved postoperative pain, (S)-ketamine being 4 times more potent than (R)-ketamine. The analgesic effect was maximal 5 min after i.m. injection and lasted for about 30 min. ⋯ Relative to the analgesic effect (S)-ketamine caused more disturbing side effects than did (R)-ketamine. The mean serum concentration of each form of ketamine at the time of maximal effect was close to the approximate Kd value for PCP site occupancy by that particular form. This is in concert with the hypothesis that the effect of ketamine on acute nociceptive pain is due to N-methyl-D-aspartate (NMDA) receptor inhibition and adds to the evidence that NMDA receptors are important for the perception of acute, nociceptive pain in humans.(ABSTRACT TRUNCATED AT 250 WORDS)
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Improved methods for pain measurement have both theoretical and clinical importance. This study evaluated the Descriptor Differential Scale (DDS) of Pain Intensity, a recent methodology designed for assessing pain reports in clinical samples. Experiment 1 evaluated the sensitivity of the measure to small changes in electrocutaneous stimulation relative to a traditional visual analogue scale (VAS) of pain intensity. ⋯ Experiment 2 evaluated the performance of the measure in both experimental and clinical pain samples, as well as the similarity of item-response patterns in each of these samples. Results indicate that the DDS of Pain Intensity is sensitive to small changes in electrocutaneous stimulation, has consistent ratio-scale properties across two different psychophysical methods, and demonstrates similar item-response patterns across divergent experimental and clinical samples. The results support the validity of the sensory DDS as a measure of pain intensity.
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Spinal cord stimulation (SCS) is efficacious for pain due to injury of peripheral nerves, and therefore models of mononeuropathy appear to be particularly suitable for an experimental approach to the study of mechanisms underlying the clinical effect of this mode of treatment in chronic neuropathic pain. Virtually all previous experimental studies on SCS have utilized acute and nociceptive types of peripheral pain stimuli to explore the attenuating effects of SCS. In the present study we made use of the two models of supposedly painful neuropathy developed by Bennett and Xie (1988) and Seltzer et al. (1990) to explore the effect of SCS applied with stimulus parameters similar to those used in clinical practice. ⋯ The late, C fibre-mediated component was not influenced by SCS. The first component of the flexor reflex is conceivably mediated by A beta-fibre activation and it presumably corresponds to the withdrawal response induced by innocuous mechanical stimuli. The lack of effect of SCS on the late reflex component indicates that it selectively influences transmission of A-fibre activity. (ABSTRACT TRUNCATED AT 400 WORDS)
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The patient with a history of current opioid consumption presenting in the acute postoperative setting presents a challenge for pain management. Standard treatment dosages and strategies are often ineffective in providing pain relief. This retrospective case-control study reviews 4 years' experience of the Acute Pain Service (APS) at our institution providing care for 202 chronic pain and opioid-consuming (CPOC) patients, 6.6% of 3058 patients undergoing urologic, gynecologic, orthopedic and general surgical procedures. ⋯ EOA and B/F case studies showed similar results. Moderate sedation was experienced by 50% of CPOC patients receiving PCA. Differences in opioid usage, side effects, pain scores, sedation and prescribed treatment with anxiolytics were shown between CPOC patients and matched controls.(ABSTRACT TRUNCATED AT 250 WORDS)