• Vanessa Henriques Carvalho, Angélica de Fátima de Assunção Braga, Franklin Sarmento da Silva Braga, Yolanda Christina S Loyola, Daniele Ribeiro de Araújo, and Mario Mantovani.
• Department of Pharmacology, Faculty of Medical Sciences, UNICAMP, Sao Paulo, Brazil.
• Acta Cir Bras. 2009 May 1;24(3):211-5.

PurposeTo evaluate in vitro lidocaine and racemic bupivacaine effects in neuromuscular transmission and in neuromuscular blockade produced by rocuronium.MethodsRats were distributed in 5 groups (n = 5) in agreement with the studied drugs: lidocaine, racemic bupivacaine, rocuronium, separately (Groups I, II, III); rocuronium in preparations exposed to local anesthetics (Groups IV, V). The concentrations used were: 20 microg/mL, 5 microg/mL and 4 microg/mL, for lidocaine, bupivacaine and rocuronium, respectively. It was evaluated: 1) amplitude of diaphragm muscle response to indirect stimulation, before and 60 minutes after separately addition of lidocaine, racemic bupivacaine and rocuronium and the association of local anesthetics - rocuronium; 2) membrane potentials (MP) and miniature end-plate potentials (MEPP).ResultsLidocaine and bupivacaine separately didn't alter the amplitude of muscle response and MP. In preparations previously exposed to lidocaine and racemic bupivacaine, the rocuronium blockade was significantly larger (90.10 +/- 9.15% and 100%, respectively), in relation to the produced by rocuronium separately (73.12 +/- 9.89%). Lidocaine caused an increase in the frequency of MEPP, being followed by blockade; racemic bupivacaine produced decrease being followed by blockade.ConclusionsLocal anesthetics potentiated the blockade caused by rocuronium. The alterations of MEPP identify presynaptic action.

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