BUPIVACAINE DOES NOT SUPPRESS CARDIAC SYMPATHETIC-NERVE ACTIVITY DURING HALOTHANE ANESTHESIA IN THE CAT

Background: The finding that IV lidocaine suppresses cardiac sympathet ic nerve activity during 1 MAC halothane, but not during 2 MAC or 3 MA C halothane, suggests that the neurally mediated circulatory effects o f IV local anesthetics may vary with background autonomic activity. Th is study aimed to compare the effects of IV lidocaine and bupivacaine on cardiac sympathetic nerve activity (CSNA) during normal and high le vels of CSNA. Methods: Cats were anesthetized with halothane and alloc ated to three groups. In groups I-L and I-B, sympathetic hyperactivity was induced by electrical stimulation of the posterior hypothalamus. CSNA, heart rate and mean arterial pressure were then measured before and after administration of lidocaine 2 mg.kg BW-1 IV (Group I-L, n=7) or bupivacaine 0.5 mg.kg BW-1 IV (Group I-B, n=7) during 1% halothane anesthesia. In Group II (n=7), following administration of bupivacain e 0.5 mg.kg BW-1 IV, CSNA, sinus cycle length (SCL), and subintervals of atrioventricular conduction time (A-H, H-V, and H-S) at pacing were measured during 0.8%, 1.6% and 2.4% halothane anesthesia without symp athetic hyperactivity. Results: Lidocaine suppressed CSNA hyperactivit y and tachycardia significantly in Group I-L, but bupivacaine did not do so in Group I-B. In Group II, bupivacaine did not affect CSNA at an y concentrations of halothane, but lengthened SCL, A-H, HV and H-S int er als significantly at each concentration of halothane. Conclusions: We conclude that IV bupivacaine, unlike IV lidocaine, does not suppres s CSNA during either normal or high CSNA under halothane anesthesia al though IV bupivacaine has stronger depressive effects on cardiac condu ction than does IV lidocaine during deep halothane anesthesia. (C) Act a Anaesthesiologica Scandinavica 41 (1997).