Pain
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In rats anaesthetized with urethane, we have investigated the response of neurones in the ventrobasal complex of the thalamus to noxious ischaemia of the tail, and to graded noxious thermal stimulation of the tail before and after ischaemia. In behavioural experiments conscious rats were exposed to the same experimental procedure. After ischaemia the threshold tail temperature required to elicit both a neuronal response and aversive behaviour in conscious rats, to thermal stimulation, was decreased significantly (P less than 0.01 paired t tests). ⋯ Most thalamic neurones responding to noxious thermal stimulation of the tail also increased firing rate during ischaemia. The latency of response of the thalamic neurones to ischaemia was 12.1 +/- 1.8 min and the latency of the behavioural response to the same stimulus was 11.9 +/- 2.1 min. Ventrobasal thalamic neurones, therefore, which responded to noxious thermal stimulation of the tail also responded to noxious ischaemia, and exhibited a neuronal correlate of post-ischaemic hyperalgesia which paralleled behavioural responses closely.
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Comparative Study
Cluster headache pain vs. other vascular headache pain: differences revealed with two approaches to the McGill Pain Questionnaire.
We compared cluster headache pain and other vascular (migraine and mixed) headache pain on pain intensity ratings and the McGill Pain Questionnaire (MPQ). Cluster headache sufferers reported not only more intense pain and more affective distress, but also different pain qualities than did migraine and mixed headache sufferers. The pain qualities that best distinguished cluster headaches from other vascular headaches were the presence of punctate pressure and thermal sensations and the absence of dull pain. ⋯ This finding may have occurred because MPQ subscale scores include an intensity component and do not provide information about specific pain qualities such as that provided by MPQ sensory items. These findings provide evidence that cluster headaches are characterized by distinct pain qualities and are not simply a more intense version of the same vascular headache pain experienced by migraine and mixed headache sufferers. They further suggest than when the MPQ is used to assess specific pain qualities, sensory items and not the sensory subscale are the preferred units for analysis.
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To establish inter-rater and test-retest reliability of use of a pressure algometer, 5 males and 5 females suffering from chronic fibromyalgia ('fibrositis'), and a normal group of 5 males and 5 females, were examined 2 times by each of 2 independent examiners, using 1 kg/sec rate of application, over 10 paired and typical 'tender points,' localized by skin marker. Tenderness thresholds of tender points were coded and analyzed using repeated measures ANOVA, for factors sex, normal/fibromyalgia, and side, rater, and time 1/time 2. There was significantly lower tenderness thresholds of tender points in fibromyalgia compared to normal subjects. ⋯ A 2-way ANOVA was conducted for summed and averaged scores for all tender and non-tender points, with factors normal/fibromyalgia and tender/non-tender; again, there was a large difference between normal and fibromyalgia subjects, and between tender and non-tender points. The interaction was small but significant, but there was a larger difference between fibromyalgia and normal subjects observed on non-tender points. The low tenderness threshold observed at the tender points of fibromyalgia patients may reflect a more generalized lowering of tenderness thresholds, seen at non-tender points as well.
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Comparative Study
Differential utility of medical procedures in the assessment of chronic pain patients.
Physicians are frequently called upon to evaluate patients with chronic pain to (1) establish the etiology, (2) determine the extent of impairment and disability, and (3) prescribe treatment. In many cases, there is little agreement as to what evaluation procedures should be used or how to weight and integrate these findings. Two studies were conducted to determine the domain of procedures pain specialists believe are most important in evaluation and the clinical utility of each. ⋯ The relevance of each of these procedures in the assessment of 100 pain patients was evaluated. Differential weights for each procedure derived from the survey were highly correlated with clinical practice. The results of the present studies provide a basis for development of a standardized assessment procedure that incorporates statistically derived weights to quantify medical findings.
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The postoperative analgesic effect of opiate premedication and local anaesthetic blocks was studied in 929 patients having orthopaedic surgery. The median time to first request for postoperative analgesia was less than 2 h when neither opiate premedication nor block was used; opiate premedication increased the time significantly to more than 5 h; local anaesthetic block produced a further significant increase to 8 h and opiate premedication used with local anaesthetic block extended the median time further to more than 9 h. ⋯ Age had no significant effect. Prolonging the time before more pain relief is required may be worthwhile for both patients and staff.