Articles: anesthetics.
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The interactions of four anaesthetic drugs (ketamine, propanidid, Althesin and methohexitone) with two neuromuscular blocking agents (suxamethonium and pancuronium) have been investigated. On the isolated rat phrenic nerve-diaphragm preparation, all the anaesthetic drugs examined potentiated suxamethonium more than they potentiated pancuronium. ⋯ With the exception of Althesin, all the anaesthetics decreased the sensitivity of the frog rectus preparation to acetylcholine. The possible sites and mechanisms of these interactions are discussed.
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Operating-room personnel exposed over a long period to trace concentrations of anesthetic gases may acquire both organic disturbances and impairment of cerebral function, though this has not been proven. However, the dangers of miscalculations due to disturbances of cerebral function and the fact that all working personnel should be breathing unpolluted air are sufficient indications to make scavenging of anesthetic gases mandatory. Scavenging has been carried out in many hospitals. At Vancouver General Hospital venting of the gases has decreased the nitrous oxide pollution to what is considered an acceptable level.
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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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Plasma concentrations of local anaesthetic agents have been measured after 40 interscalene brachial plexus blocks in 39 patients, using lignocaine, prilocaine, bupivacaine and etidocaine. Lignocaine produced greater concentrations than prilocaine, and bupivacaine greater concentrations than etidocaine. The addition of adrenaline resulted in much lower concentrations in the case of all four agents.