Adjuncts (Tramadol and Magnesium) Potentiate Impulse Inhibition by a Local Anaesthetic in Isolated Frog Siatic Nerves?


Abstract: Aim: In clinical use, the addition of adjuncts (magnesium or tramadol) to local anesthetic agents is used for different reasons. However, reports about the effect of magnesium plus bupivacaine and of tramadol plus bupivacaine on in vitro preparations are scarce. The aim of this study was to examine the ability of local anesthetics to reduce the amplitude of compound nerve action potentials of the isolated frog sciatic nerve in the absence and presence of adjuncts (magnesium and tramadol). Materials and Methods: The experiments were done on frog sciatic nerves, using an extracellular recording technique. Isolated frog sciatic nerves were bathed in each test solution for 10 min. In each nerve, action potentials were recorded before exposure to the test solution, which served as the control data. The extracellular action potentials were recorded after 10 min of exposure to the test solution by using a BIOPAC MP 100 Acquisition System Version 3.5.7 (Santa Barbara, USA). Results: Inhibition of the compound nerve action potentials induced by bupivacaine was markedly enhanced by magnesium but was not changed by tramadol. The amplitude of compound nerve action potentials increased from 15.10% with bupivacaine alone to 35.43% with bupivacaine plus magnesium. Conclusions: These results suggest a potentially important interaction between magnesium and bupivacaine for nerve block, but there was no interaction between tramadol and bupivacaine.

Keywords: Bupivacaine, magnesium, tramadol, compound nerve action potential, frog sciatic nerve

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