Articles: pain.
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Randomized Controlled Trial Comparative Study Clinical Trial
Postoperative analgesia after circumcision. A randomized comparison between caudal analgesia and intramuscular morphine in boys.
A randomised blind comparison between caudal analgesia (1.5 mg/kg bupivacaine) and intramuscular morphine (0.15 mg/kg) is reported. Forty boys were studied. Caudal analgesia is shown to be significantly better than morphine by means of a linear analogue scale designed to quantify behaviour immediately after operation.
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Electrical potentials evoked by 5 intensities of painful dental stimulation were recorded at the scalp. During testing, volunteers indicated subjective painfulness by verbal pain ratings and visual analogue scales. Evoked potentials (EPs) to each intensity, observed between 50 and 400 msec, were characterized by 4 waveform components. ⋯ In contrast, the amplitudes of the two later components were associated with subjective painfulness but not with stimulus intensity. A strong linear relationship was observed between subjective painfulness and peak-to-peak amplitude for the EP component observed between 175 and 260 msec. The data suggest that the earlier EP components may reflect sensory transmission processes while the later components indicate brain activity when pain is perceived.
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Comparative Study
Diffuse noxious inhibitory controls (DNIC). II. Lack of effect on non-convergent neurones, supraspinal involvement and theoretical implications.
(1) Diffuse noxious inhibitory controls (DNIC) were tested for their effect on noxious only, non-noxious and proprioceptive cells in the dorsal horn of the intact anaesthetized rat. Unlike convergent neurones, as described in the previous paper, there was no effect of DNIC on these neurones. ⋯ Thus the neuronal substrate for DNIC must involve supraspinal structures. (3) Because of the level of firing in convergent neurones induced by hair and touch receptors, presumably constantly and randomly activated in the freely moving animal, a noxious message arriving at higher centres may be partly masked by this background noise. On the basis of the known role of convergent neurones in nociception, we propose the following mechanism which may interpret this paradoxical convergence: two pools of convergent neurones are influenced by a painful peripheral stimulation, one segmental pool being activated whilst the remaining population of cells is inhibited; the "contrast" between the messages from these two pools may well produce a significant pain signalling output from the convergent dorsal horn cells. (4) These results and their theoretical implications are discussed with regard to the concept of the "analgesic system", certain clinical observations and the paradoxical pain relieving effects of counterirritation and some forms of acupuncture.