Effect of atracurium, vecuronium, pancuronium and tubocurarine on renal sympathetic nerve activity in baroreceptor denervated dogs.

The mechanism of arterial hypotension induced by non-depolarizing neuromuscular blocking agents may be multifactorial and differ between drugs. The purpose of this study was to evaluate the effect of high-dose atracurium and equivalent doses of other non-depolarizing neuromuscular blocking agents on haemodynamic state and sympathetic nervous activity. In studies on 24 mongrel dogs anaesthetized with alpha-chloralose, the left kidney was exposed retroperitoneally and renal sympathetic nerve activity was recorded continuously after bilateral sino-aortic denervation and cervical vagi section. The dogs were allocated to four groups; atracurium 1.5 mg kg-1, tubocurarine 0.3 mg kg-1, pancuronium 0.3 mg kg-1 or vecuronium 0.3 mg kg-1 was administered to six dogs in each group. Histamine 1 micrograms kg-1 was given to two dogs in each group, 1 h before administration of neuromuscular blocking agents. We observed that atracurium and tubocurarine significantly decreased arterial pressure, heart rate and renal sympathetic nerve activity (P < 0.05), but pancuronium and vecuronium did not Histamine-induced arterial hypotension but did not affect heart rate or renal sympathetic nerve activity. As both arterial and cardiopulmonary baroreflex pathways were inactivated in these animals, we conclude that atracurium decreased arterial pressure by suppressing efferent sympathetic nerve activity in a manner similar to that of tubocurarine.