Abstract
To evaluate the effects of levobupivacaine on neuromuscular transmission and neuromuscular blockade produced by pancuronium in vitro. Thirty rats were distributed into groups (n = 5) according to the drug used alone or in combination: Group I - levobupivacaine (5 µg.mL-1); Group II - pancuronium (2 µg.mL-1); Group III - pancuronium (2 µg.mL-1) + levobupivacaine (5µg.mL-1). The following parameters were evaluated: 1) amplitude of diaphragmatic response to indirect stimulation, before and 60 minutes after the addition of levobupivacaine and pancuronium alone, and after the addition of levobupivacaine combined with pancuronium; 2) membrane potentials (MP) and miniature endplate potentials (MEPP). Levobupivacaine alone did not alter the amplitude of muscle response and MP. In preparations previoulsy exposed to levobupivacaine, the block with pancuronium was significantly denser (90.2 ± 15.2%), showing a significant difference (p=0.031) in comparison to the block produced by pancuronium alone (48.9% ± 9.8%). There was a decrease in the frequency and amplitude of MEPPs. Levobupivacaine potentiated the neuromuscular blockade produced by pancuronium, confirming a presynaptic action by a decrease in miniature endplate potentials.
Highlights
To explain the interaction between local anesthetics and neuromuscular blocking agents, several mechanisms have been described, including a presynaptic action by inhibition of acetylcholine release, a postsynaptic action due to stabilization of the postjunctional membrane, and interference with the phenomenon of excitation-contraction coupling of the muscle fiber[1,2,3,4]
Student’s t test was used for the comparative evaluation of the degree of motor blockade produced by the combination of levobupivacaine and pancuronium in relation to the block produced by pancuronium alone
In preparations that had been previously exposed to levobupivacaine, the block produced by pancuronium was 90.2 ± 15.2%, with a significant difference (p=0.031), compared to the block produced by pancuronium alone (48.9% ± 9.8%)
Summary
To explain the interaction between local anesthetics and neuromuscular blocking agents, several mechanisms have been described, including a presynaptic action by inhibition of acetylcholine release, a postsynaptic action due to stabilization of the postjunctional membrane, and interference with the phenomenon of excitation-contraction coupling of the muscle fiber[1,2,3,4]. Only high concentrations of local anesthetics can produce neuromuscular blockade, the interaction between these drugs and nondepolarizing neuromuscular blocking agents in particular is relevant in clinical practice, when both groups of drugs are used simultaneously and careful patient monitoring is required. Pancuronium is a longacting aminosteroid, nondepolarizing neuromuscular blocking agent, used in prolonged surgeries and in intensive care units[1]. It is fundamental to identify the interaction between these drugs, since the duration of their effects may be prolonged. The aim of this study was to evaluate the effect of levobupivacaine on neuromuscular transmission in an experimental model and its influence on the neuromuscular block produced by pancuronium
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