The influence of lidocaine and racemic bupivacaine on neuromuscular blockade produced by rocuronium. A study in rat phrenic nerve-diaphragm preparation.
OBJECTIVE
To evaluate in vitro lidocaine and racemic bupivacaine effects in neuromuscular transmission and in neuromuscular blockade produced by rocuronium.


METHODS
Rats 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).


RESULTS
Lidocaine 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.


CONCLUSIONS
Local anesthetics potentiated the blockade caused by rocuronium. The alterations of MEPP identify presynaptic action.
Carvalho
Vanessa Henriques
VH
Department of Pharmacology, Faculty of Medical Sciences, UNICAMP, Sao Paulo, Brazil.
Braga
Angélica de Fátima de Assunção
Ade F
Braga
Franklin Sarmento da Silva
FS
Loyola
Yolanda Christina S
YC
de Araújo
Daniele Ribeiro
DR
Mantovani
Mario
M
D000732:Androstanols / Q000494:pharmacology*; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D002045:Bupivacaine / Q000494:pharmacology; D003964:Diaphragm / Q000294:innervation; D004353:Drug Evaluation, Preclinical; D004558:Electric Stimulation; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D009045:Motor Endplate / Q000187:drug effects; D019148:Neuromuscular Blockade / Q000379:methods*; D009469:Neuromuscular Junction / Q000187:drug effects*; D003473:Neuromuscular Nondepolarizing Agents / Q000494:pharmacology*; D010791:Phrenic Nerve / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D000077123:Rocuronium; D018709:Statistics, Nonparametric
D000732:Androstanols; D000779:Anesthetics, Local; D003473:Neuromuscular Nondepolarizing Agents; D008012:Lidocaine; D000077123:Rocuronium; D002045:Bupivacaine