Articles: histamine.
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The authors studied 20 surgical patients to determine the effect of large doses of vecuronium on plasma histamine concentrations. Patients were unpremedicated and anaesthetized with nitrous oxide and halothane via a mask. Tracheal intubation was performed without the use of muscle relaxants. ⋯ However, these decreases in MAP were not clinically important. Changes in plasma histamine concentrations did not correlate with corresponding changes in MAP. Heart rate did not change significantly in any patient during the study.(ABSTRACT TRUNCATED AT 250 WORDS)
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Histamine is released during allergic reactions, and is known to produce cardiac dysrhythmias. The authors compared the cardiac effects of histamine and epinephrine during exposure to halothane in the isolated perfused guinea pig heart. Responses studied were spontaneous sinus rate, intra-atrial conduction time, atrial-septal conduction time (ASCT), intraventricular conduction time (IVCT), and left ventricular pressure (LVP). ⋯ Halothane antagonizes the inotropic and chronotropic effects of epinephrine, but increases the incidence of ventricular tachycardia from 6% to 28%, and the incidence of premature ventricular excitations from 0% to 40%, compared with epinephrine alone. The authors' in vitro findings show that histamine and halothane, like epinephrine and halothane, can cause dysrhythmias, but that the genesis and type of dysrhythmias induced by these agents are dissimilar. Consequently, the release of histamine with an anaphylactoid reaction during halothane anesthesia, and the treatment of the reaction with epinephrine, could result in dangerous ventricular tachydysrhythmias.
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The radio enzyme assay for histamine based on the transmethylation with purified histamine-N-methyltransferase and utilizing [3H-methyl]-S-adenosylmethionine as the methyl donor has been optimized to measure low histamine concentrations, for example in plasma. The pH-optimum for the assay is pH 8.3 in Tris-glycine buffer at 20 degrees C. ⋯ EDTA and dithiothreitol were included in the assay to keep the histamine-N-methyltransferase active as agents that oxidize -SH groups were found to be inhibitory to the reaction. The present assay is sensitive to about 0.5 nmol/l of histamine in a sample volume of 50 microliter (about 3 pg/sample).
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Persistent pruritus is one of the most common symptoms in hemodialysis patients. The cause of pruritus is not known, and conventional treatment for pruritus is rarely helpful. Some authors thought that release of histamine from increased mast cells in uremic patients was the cause of pruritus. ⋯ Oral zinc sulfate, 445 mg daily for two months, relieved pruritus subjectively in 53% of the patients. After treatment, serum histamine levels decreased significantly, as well as serum zinc levels increased significantly. These findings suggest that zinc deficiency participates in increased histamine levels in dialysis patients, and subsequently in the development of uremic pruritus.
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Comparative Study
Diminished flare response in neuropathic diabetic patients. Comparison of effects of substance P, histamine, and capsaicin.
The flare response in skin largely depends on an intact primary sensory fiber, the C-fiber. We measured the flare response to the intradermal injection of substance P, histamine, and capsaicin in control subjects and in diabetic patients with and without clinically obvious polyneuropathy. ⋯ Alternatively, dysfunction of the mast cell or vascular reactivity may contribute to the diminished flare. Because C-fibers participate in nociception in addition to the flare response, the findings of this study, by a method that permits a quantifiable measurement of the function of peripheral sensory neurons in diabetic subjects, has potential usefulness in evaluating sensory neuropathy in diabetic patients.