1.The Effect of Adrenaline on the Blockade of Compound Action Potential by Local Anesthetics in Rat Sciatic Nerves.
Yoon CHOI ; Joog Woo LEEM ; Hyun Cheol YANG ; Jong Seok YANG ; Sung Min HAN ; Jae Young YU ; Seung Woon LIM ; Dong Myung LEE
Korean Journal of Anesthesiology 1999;37(4):675-684
BACKGROUND: Adrenaline has often been used to prolong the local anesthetic effect during surgical procedures. As a possible explanation for this, a local vasoconstriction caused by adrenaline has been proposed. However, in a recent study, clonidine, an alpha2 adrenergic receptor agonist, was reported to block the conduction of mammalian nerves in vitro. Thus, there is a possibility that adrenaline may block nerve conduction by acting on the adrenergic receptor. The present study is performed to see : (1) If adrenaline directly affects nerve conduction ; (2) If adrenaline affects conduction blockade caused by local anesthetic. METHODS: Recordings of compound action potentials (CAPs) of A- and C-components were obtained from isolated sciatic nerves of adult male Sprague-Dawley rats. Dose-response curves of lidocaine and adrenaline regarding depression of CAPs were determined. Effects of adrenaline on the lidocaine-induced nerve block was assessed by comparing the effect of lidocaine (3.5x 10 5) with a lidocaine-epinephrine mixture (Lido-Epi, 3.5 x10 5 lidocaine with 1:100,000 epinephrine). RESULTS: Adrenaline, near the clinical concentrations, had no effect on the size of either A- or C-component of CAPs. The ED50 of lidocaine was 3.5x 10 5. Lidocaine depressed A-CAP 45.9+/- 7.0 when compared with baseline value, and the Lido-Epi solution depressed A-CAP to 41.7+/- 5.0 (P > 0.05). Lidocaine depressed C-CAP 59.8 +/- 3.4 when compared with the baseline value, and the Lido-Epi solution depressed C-CAP to 60.5 8.1 (P > 0.05). Consequently, adrenaline did not augment lidocaine induced nerve blockade. CONCLUSION: This study confirmed that adrenaline applied to the peripheral nerve has no effect either on nerve conduction itself or on conduction block produced by lidocaine.
Action Potentials*
;
Adrenergic Agonists
;
Adult
;
Anesthetics
;
Anesthetics, Local*
;
Animals
;
Clonidine
;
Depression
;
Epinephrine*
;
Humans
;
Lidocaine
;
Male
;
Nerve Block
;
Neural Conduction
;
Peripheral Nerves
;
Rats*
;
Rats, Sprague-Dawley
;
Receptors, Adrenergic
;
Sciatic Nerve*
;
Vasoconstriction