Neuromuscular Blocking and Autonomic Effects of Vecuronium and Atracurium in the Anaesthetized Cat

Abstract

The effects of vecuronium and atracurium on neuromuscular transmission, on the responses of the heart rate to vagal stimulation and on the responses to preganglionic stimulation of the nictitating membrane were compared in the chloralose-anaesthetized cat. Vecuronium was four times more potent than atracurium as a neuromuscular blocking agent, whereas the two compounds had similar potencies in blocking the effects of stimulation of the cardiac vagus. The vagal/neuromuscular ratios measured at 50% inhibition were 96 for vecuronium and 25 for atracurium. Vecuronium possessed a slightly shorter recovery time than atracurium and shorter duration of action on the soleus muscle. The onset times of the two compounds were not significantly different. Both compounds had longer time-courses of action than suxamethonium. Very large doses of vecuronium decreased the responses of the preganglionic stimulation of the nictitating membrane, suggesting that at high doses the compound possesses ganglion blocking activity. Large doses of atracurium also decrease the nictitating membrane responses and, in some cats, contractions of the nictitating membrane associated with increases in heart rate and arterial pressure were observed.

Effects of a New Neuromuscular Blocking Agent (Org 9426) in Anaesthetized Cats and Pigs and in Isolated Nerve-Muscle Preparations

“…The vagal: neuromuscular block ratio found for Org 9426 was much lower than that for vecuronium, the latter value confirming results from previous studies [14][15][16] which show that vecuronium has a high vagal ratio. Compounds with lower vagal ratios (in the region of [14][15][16][17][18][19][20][21][22][23][24][25], such as dimethyltubocurarine [13,17] and atracurium [14,18], have been shown in man to be free of cardiovascular side effects associated with vagal block [19][20][21]. Thus our use of vecuronium represents an especially stringent standard for neuromuscular/vagal block selectivity.…”

“…In terms of neuromuscular blocking potency, Org 9426 falls within the acceptable range, being much greater than 10% of the potency of vecuronium in both the species tested. The neuromuscular blocking potency of Org 9426 is similar to that of atracurium [13,14]. The vagal: neuromuscular block ratio found for Org 9426 was much lower than that for vecuronium, the latter value confirming results from previous studies [14][15][16] which show that vecuronium has a high vagal ratio.…”

High-dose vecuronium neuromuscular block: a comparison of arrhythmias and onset of block during sufentanil anaesthesia

“…,s Sutherland et al supported this conclusion in a separate cat study. 19 Booij administered three times EDg0 in dogs and found no change in heart rate, blood pressure or cardiac output. 20 They concluded that vecuronium has no effect on heart rate; however, its lack of vagolytie activity may allow bradyarrhythmias to occur more easily during surgery, whether drug or reflex induced.…”

Effect of intraurethral administration of atracurium besylate in male cats with urethral plugs

“…Atracurium besylate (AB) is a curare derivate employed in humans and tested in cats (Coker and others , Sutherland and others ) to obtain optimal muscle relaxation during surgery. AB acts as a neuromuscular blocking agent by antagonising acetylcholine at the nicotinic receptors in the neuromuscular junction and, therefore, induces paralysis of striated muscle (Coker and others , Sutherland and others ). The metabolism of AB does not depend on renal or liver function, but AB is quickly inactivated by plasma esterases or by spontaneous degradation (Neill and Chapple ).…”