Articles: anesthetics.
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Disordering, fluidizing and dilating effects of anesthetics upon cell membranes are well recognized. The fluidization can be precisely measured with phospholipid membranes. When phospholipids are dispersed in water, they form globules of bilayer structure. ⋯ The normalized values of the fluidizing action of these drugs at physiologic conditions correlated well with their nerve-blocking potencies. The present results indicate that the uncharged molecules fluidize the lecithin membrane by unsaturable nonspecific binding. The possible effect of the charged molecules upon the fluidity of natural membranes remains to be established.
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The cardiocirculatory responses to equianaesthetic concentrations (MAC 0.5 and MAC 1.0 plus 67% N2O) of halothane, methoxyflurane, enflurane and isoflurane were studied in a total of 35 closed-chest dogs during ventilation controlled to produce normocapnia. Each anaesthetic produced a dose-related decrease in mean arterial pressure and in values reflecting cardiac function. These included cardiac output, stroke volume, left ventricular max dp/dt and ejection fraction. ⋯ Parallel with the depression in cardiac performance and blood pressure as two of the main predictors of energy demand, myocardial oxygen consumption was found to be significantly reduced by each of the anaesthetics. The ratio of the external work of the left ventricle to its oxygen consumption indicated that myocardial efficiency deterioated. The clinical implications are discussed.
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Anaphylactic reactions to drugs used in general anesthesia have a complex mechanism: true anaphylaxis by antigen antibody reaction (IgG our IgE) histamine liberation by certain substances with a special chemical structure, activation of the alternative route of complement. The authors recall the immunological stages in each case and give examples.
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Acta Anaesthesiol Scand · Jan 1977
Comparative StudyHypoxia-induced vasoconstriction in isolated perfused lungs exposed to injectable or inhalation anesthetics.
Investigations during the last two decades have revealed a tendency to inpaired pulmonary gas exchange in patients during general anesthesia. In the awake state, arterial hypoxemia is counteracted by a mechanism which tends to normalize the ventilation/perfusion ratio of the lungs by way of a hypoxia-induced vasoconstriction in poorly ventilated areas. This results in a redistribution of perfusion to more adequately ventilated lung regions. ⋯ The experiments showed that the response was unaffected by N2O and injectable anesthetics, while a reversible, dose-dependent damping effect was demonstrated for the volatile inhalation anesthetics, ether, halothane and methoxyflurance. The effect could be demonstrated at blood concentrations comparable to those used in clinical anesthesia, and it was not due to a general paralysis of the vascular smooth muscle. The findings might, at least in part, explain the occurrence of arterial hypoxemia during general inhalation anesthesia.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparative anaesthetic properties of various local anaesthetic agents in extradural block for labour.
Various concentrations of lignocaine, etidocaine and bupivacaine in 10-ml doses of plain solutions were studied in a double-blind manner as agents for extradural analgesia to relieve the pain of labour. In 67 patients in established labour the onset time and duration of analgesia were assessed by the abolition and recurrence of the pain of uterine contractions, motor block on a 0-2 scale, dermatomal spread by pinprick testing, and arterial pressure by standard sphygmomanometry. Increasing the drug concentration reduced the onset times and increased both the duration of analgesia and the degree of motor block, but had little effect on dermatomal spread or on the frequency of hypotension. Based on the results the agents have been classified with regard to onset and duration of analgesia and degree of motor blockade.