Influence of local anesthetics on the neuromuscular blockade produced by rocuronium: effects of lidocaine and 50% enantiomeric excess bupivacaine on the neuromuscular junction.
OBJECTIVE
The effects of local anesthetics (LA) on neuromuscular transmission and their influence on the neuromuscular blockade produced by competitive neuromuscular blockers have not been fully investigated. The objective of this study was to evaluate, in vitro, the effects of lidocaine and 50% enantiomeric excess bupivacaine (S75-R25) on the neuromuscular blockade produced by rocuronium.


METHODS
The rats were divided in five groups (n = 5) according to the drug used: isolated lidocaine, bupivacaine (S75-R25), or rocuronium (groups I, II, and II); and rocuronium in preparations previously exposed to LAs (groups IV and V). The concentrations used were as follows: 20 microg x mL(-1), 5 microg x mL(-1), and 4 microg x mL(-1) of lidocaine, bupivacaine (S75-R25), and rocuronium, respectively. The following parameters were evaluated: 1) the strength of muscular contraction of the diaphragm to indirect electrical stimulations, before and 60 minutes after the isolated addition of the LAs and rocuronium, and the association AL-rocuronium; and 2) the effects of LAs on membrane potential (MP) and miniature end-plate potentials (MEPP). The effect of LAs on muscle contraction in response to acetylcholine was evaluated in chick biventer cervicis preparations.


RESULTS
Isolated lidocaine and bupivacaine (S75-R25) did not change the muscular response and the levels of MPs. In preparations exposed to LAs, rocuroniuminduced blockade was significantly greater than that produced by rocuronium alone. In chick biventer cervicis preparations, lidocaine and bupivacaine (S75R25) decreased contraction in response to acetylcholine. Lidocaine increased the frequency of MEPPs, which was followed by the blockade; bupivacaine (S75R25) caused a reduction in MEPPs followed by blockade.


CONCLUSIONS
Local anesthetics caused a potentiation of the neuromuscular blockade produced by rocuronium. The results showed pre- and post-synaptic effects.
Braga
Angélica de Fátima de Assunção
Ade F
Departamento de Anestesiologia da FCM/UNICAMP, Campinas, SP. franklinbraga@terra.com.br
Carvalho
Vanessa Henriques
VH
Braga
Franklin Sarmento da Silva
FS
Rodrigues-Simioni
Léa
L
Loyola
Yolanda Christina S
YC
Potério
Glória Braga
GB
D000732:Androstanols / Q000008:administration & dosage; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000494:pharmacology*; D000818:Animals; D002045:Bupivacaine / Q000008:administration & dosage* / Q000494:pharmacology; D066298:In Vitro Techniques; D008012:Lidocaine / Q000008:administration & dosage* / Q000494:pharmacology; D008297:Male; D019148:Neuromuscular Blockade; D009469:Neuromuscular Junction / Q000187:drug effects*; D003473:Neuromuscular Nondepolarizing Agents / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar; D000077123:Rocuronium
D000732:Androstanols; D000779:Anesthetics, Local; D003473:Neuromuscular Nondepolarizing Agents; D008012:Lidocaine; D000077123:Rocuronium; D002045:Bupivacaine