Influencia dos anestesicos locais no bloqueio neuromuscular produzido por diferentes bloqueadores neuromusculares : estudo experimental / The influence of local anesthetics on neuromuscular blockade produced by differents neuromusculars blockades : experimental study

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Local anesthetics commonly used in clinical practice can interact with neuromuscular blockers and potentiate their effects. Many authors studied this interaction, but the mechanism involved in the potentiation of neuromuscular blockers and the action of local anesthetics in the pre and postjunctional sites were not completely elucidated- In this study, in specific experiments in the neuromuscular junction the following parameters were studied: the effects of the local anesthetics procaine and lidocaine in the neuromuscular transmission; its influence on the neuromuscular blockade produced by d-tubocurarine and by rocuronium; the efficacy of neostigmine and of 4-aminopyhdine in the reversion of the blockade produced by the association of local anesthetics - neuromuscular blockers; the effects of local anesthetics on the membrane potentials and miniature end - plate potentials. It was also evaluated in chronically denervated rat diaphragm preparation and chick biventer cervicis preparation the effects of local anesthetics on acetylcholine contracture. The results were expressed in average and standard deviation and analyzed through the Wilcoxon and Mann-Witney tests, adopting a level of significance of 5% (p <0.05). In rat phrenic nerve diaphragm preparations under indirect electric stimulation, local anesthetics in the concentrations used did not change the amplitude of the muscle response but potentiated the effects of d-tubocurarine and of rocuronium. This blockade was partially and totally reverted by neostigmine and by 4-aminopyridine, respectively. Procaine and lidocaine caused no significant alteration in the membrane potentials, not demonstrating depolarizing action in the muscle fiber. Procaine caused a decrease in the amplitude and frequency of the miniature end - plate potentials {meps) and lidocaine, in contrast, promoted an initial increase in the frequency of meps followed by blockade. In chick biventer cervicis preparations and chronically denervated rat diaphragm, procaine and lidocaine promoted a significant decrease in the response to acetylcholine contracture evidencing a post-junctional effect. The results obtained demonstrate a synergism among the drugs mainly due to a postjunctional effect

ASSUNTO(S)

transmissão sinaptica novacaina tubocurarina tubocurarine bloqueadores neuromusculares anestesia local medicamentos - interações synaptic transmission rocuronium drug interactions rocuronio neuromuscular blockades procaing lidocaine local anesthetics lidocaina

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