RESUMEN
The present study was designed to evaluate the effects of pretreatment with d-tubocurarine and tracrium on succinylcholine induced increases in plasma catecholamines concentration, plasma K+ level, mean blood pressure, heart rate and fasciculation in patients anesthetized with halothane. Eighteen patients were randomly divided into three groups: Saline, d-tubocurarine and tracrium groups. The mean plasma catecholamines concentration, mean plasma K+ level, mean blood pressure and mean heart rate were significantly increase in the saline group after 4 and 10 minutes from i.v. succinylcholine injection. Also, the fasciculation was peaked. In d-tubocurarine group, there were no significant changes in the above measurements. In tracrium group, there were significant increases in catecholamines and K+ levels. D-tubocurarine attenuated the cardiovascular effects and the induced increases in plasma catecholamines and K+ levels following succinylcholine injection. Tracrium attenuated the cardiovascular effects, but to a lesser extent and did not attenuate the increases in plasma catecholamines following succinylcholine injection. The results obtained in the present study showed that the nicotinic receptors on the sympathetic ganglia are not the only sites of interaction, suggest the possibility that the presynaptic nicotinic receptors on the postganglionic sympathetic terminals might be involved in the interaction between these drugs