Anesthesiology
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Comparative Study
Mucociliary flow in the trachea during anesthesia with enflurane, ether, nitrous oxide, and morphine.
Tracheal mucociliary flow rates in dogs were measured with a radioactive droplet technique during thiopental anesthesia, and subsequently during enflurane, either, and nitrous oxide-morphine anesthesia on different occasions. Enflurane, at 0.6, 1.2, 1.8 MAC, produced a dose-dependent, reversible depression of mucociliary flow equal to that previously reported for halothane. Nitrous oxide-halothane and nitrous oxide-morphine depressed mucociliary flow to the same extent as halothane at equivalent MAC levels. Ether did not depress mucociliary flow significantly from the thiopental control at any MAC level.
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To determine the effects of variations in temperature on the neuromuscular blockade produced by pancuronium, the drug was infused intravenously into 18 cats anesthetized with chloralose and urethane at a constant continuous rate to produce and maintain 90 per cent depression of twitch tension of the anterior tibial muscle following supramaximal stimulation of the peroneal nerve. The mean (+/-SE) infusion rates of pancuronium needed were 0.44 +/- 0.05, 0.99 +/- 0.11, and 1.05 +/- 0.09 microng/kg/min (r = 0.73) at 29, 37, and 41 C, respectively. ⋯ The durations of neostigmine action were longer at 29 and 37 than at 41 C. It is concluded that hypothermia augments neuromuscular blockade produced by pancuronium and prolongs the time to peak effect, and possibly the duration of action, but not the dose of neostigmine needed to antagonize the blockade.
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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.