Onset time for alcuronium and pancuronium after cremophor-containing anaesthetics

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 time 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 possible 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.