Onset Time for Alcuronium and Pancuronium after Cremophor‐Containing Anaesthetics

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Abstract
Cremophor is a nonionic, surface‐acting agent, previously shown to bind to proteins and biological membranes. The compound is used as a solvent for certain anaesthetics. The effects of this surfactant on the onset times for alcuronium and pancuronium were investigated. Both artery‐to‐muscle (A‐M) and vein‐to‐muscle (V‐M) onset times were determined after cremophor‐ and non‐cremophor‐containing induction agents. Circulatory effects of the surfactant were investigated by measuring the blood velocity of the brachial artery using pulsed Doppler ultrasound. A significant reduction in both A‐M and V‐M onset times was found for pancuronium after cremophor‐containing anaesthetics. However, no difference was found for the onset times for alcuronium in the two induction groups. In contrast to alcuronium, there was no significant difference between A‐M and V‐M onset times for pancuronium. Arterial blood velocity was found to be practically the same after cremophor and non‐cremophor induction agents. The possibility of a stronger affinity of pancuronium than alcuronium to intravascular binding sites is suggested. Cremophor might, due to its protein and membrane effects, interfere with pancuronium association to these sites.