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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sharp pain is conducted rapidly by myelinated delta A fibers and diffused pain slowly by nonmyelinated C fibers to pseudobipolar neurons in the posterior ganglion and from there to neurons located in the posterolateral horn of the spinal cord. From here on nociferous impulses are transmitted by excitatory peptides (e.g. substance P) or amino acids (e.g. glutamate, aspartate) through interconnecting neurons of the pain pathways, primarily on the contralateral side, to the brain stem and from there to the sensory cortex, where they are appreciated and acted upon. There are specific inhibitory receptors located on axon terminals, near to the release sites of the excitatory amino acids and peptides. Stimulation of these receptors by their appropriate ligands such as endogenous (e.g. enkephalis, endorphins) or exogenous opioids, clonidine, serotonin, somatostatin inhibits the release of excitatory neurotransmitters and relieves pain. There are at least 3 different opioid receptors, called mu-, kappa- and delta-receptors in the spinal cord. These can be differentiated from one another by their specific affinity toward different endogenous or exogenous opioids and the pure narcotic antagonist, naloxone. It appears that the nociferous impulses transmitted by parallel pathways equipped with different inhibitory receptors have to be integrated to produce pain sensation and partial inhibition of transmission in different pathways or complete inhibition in one of the pathways may relieve pain. In recent years the concept of "selective spinal analgesia" has been applied clinically for the relief of postoperative, obstetrical and chronic pain. At first it was expected that the intrathecal or peridural administration of morphine will produce analgesia without the side effects of systemically administered morphine. It soon became evident, however, that intrathecally and peridurally administered morphine after several hours of delay reaches the fourth ventricle and by stimulating mu-receptors may cause respiratory depression and other undesired effects (e.g. nausea, vomiting, pruritus). Several different approaches are being investigated for the production of selective spinal analgesia without side effects. They include: a. the use of more lipophilic, long-lasting opioids (e.g. lofentanil) which would be almost completely absorbed by the spinal cord and therefore would not reach the medullary centers; b. the development of opioids with specific affinity to kappa- and for delta- and little or no affinity to mu-receptors, primarily responsible for side effects; and c. combining lower doses of opioid agonists with alpha 2-adrenergic agonists (e.g. clonidine) or with somatostatin. It is conceivable that in the not-too-distant future, it will be possible to achieve through these measures, selective spinal analgesia without side effects.
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PMID:Pain control with intrathecally and peridurally administered opioids and other drugs. 168 73

In regional anesthesia the onset of analgesia is usually determined by stimulating the skin with sharp or cold objects: when sensations of sharp pain or cold are lost, all nociceptive afferents are regarded as blocked. Sharp pain and cold are mediated by thin, myelinated axons whereas the majority of nociceptor axons are unmyelinated. In peripheral nerve blocks unmyelinated fibers are blocked first, followed by those mediating sharp pain and cold. In spinal and epidural blocks the levels of anesthesia to sharp pain and cold correspond within 1-2 segments. Although pinprick seems to be a simple test for analgesia, it involves the risk of infection and is disliked by the patient. As the stimulus is spatially discontinuous, coarse testing may simulate analgesia. An ideal stimulus for testing analgesia should be noninvasive, give distinct sensations, not frighten the patient, and allow spatially continuous examination of larger skin areas. A stimulus that meets these conditions is cold applied to the skin by a metal roller (Fig. 1). If the roller is kept at room temperature (20 degrees-24 degrees C), it gives a strong cold sensation when it is slowly rolled (5-10 cm/s) over the warm skin (usually 30 degrees-35 degrees C on the trunk). With this noninvasive device, the levels of anesthesia to cold can be determined rapidly, with high precision, and without frightening the patient.
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PMID:[A simple technique for estimating the level of analgesia in regional anesthesia]. 178 Apr 86

Brachial neuritis is an unusual syndrome of unknown etiology that can be confused with other causes of pain or weakness, or both, of the shoulder and arm. It is important to distinguish this disorder because of its dramatic symptoms and relatively good prognosis. Sharp pain, usually in the elbow or shoulder, marks the onset of brachial neuritis, but is relatively short-lived. Weakness generally occurs as the pain is subsiding and most frequently involves the deltoid, spinati, serratus anterior, biceps, and triceps. Paresthesias, atrophy, and sensory loss are inconstant features. Electromyographic findings of fibrillation potentials and positive waves characteristically are found in a pattern indicating combined nerve-root and peripheral nerve involvement. Electromyography more frequently than clinical examination shows that the lesion is bilateral, and also is of both diagnostic and prognostic value. Other laboratory studies serve only to exclude other causes of shoulder pain. The clinical course is variable, but in 90 per cent of patients complete recovery occurs within three years. Recurrences are uncommon.
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PMID:Brachial neuritis. 401 36