Articles: anesthetics.
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Brachial plexus block (axillary approach) has been compared with ulnar nerve block for the evaluation of local anaesthetic drugs. Duration of analgesia is the same in both techniques with the same drugs. Following axillary nerve block the median, ulnar and radial nerves are blocked for a different time. ⋯ Larger amounts of local anaesthetic solutions are necessary for plexus blockade and this may cause toxic effects. The volunteer's comfort is less after plexus block because of more widespread paralysis. Therefore, ulnar nerve block and extradural block are in many respects the most suitable techniques for evaluation of new local anaesthetic agents.
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Comparative Study
Evaluation of clinical tolerance of local anaesthetic agents.
The clinical tolerance to local anaesthetic drugs can be assessed from a knowledge of their pharmacokinetic behaviour, their absorption properties and the effects produced by controlled i.v. infusions. Pharmacokinetic behavior can be calculated from the plasma concentrations of the drugs injected i.v. in non-toxic doses. Absorption properties can likewise be determined from plasma concentrations following injection at various sites. ⋯ Such dosage is considerably affected by the rate of injection. The venous plasma concentrations at the height of toxicity are unreliable guides to toxicity. Experiences using the new local anaesthetic etidocaine are reported.
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Information derived from measurements of blood concentrations of local anaesthetics can be extended by the application of pharmacokinetic anaylsis. A better understanding of quantitative aspects of the disposition and absorption of these drugs should assist the anaesthetist in deciding the optimal agent and dosage for regional block techniques.