A patient was administered trimethaphan during surgery. This drug will cause which of the following responses?
Correct Answer: Tachycardia
Description: Trimethaphan is a ganglionic blocker that is sometimes administered during surgery to maintain controlled hypotension and to minimize blood loss. The trick to determining the effect of a ganglionic blocker is to first know the predominant tone of the end organ in question. The blocker will produce the opposite effect of the predominant tone. The vessels, aerioles and veins, are predominantly under sympathetic tone. Most everything else is under parasympathetic tone. The hea is under predominantly parasympathetic control. Parasympathetic stimulation of the hea causes bradycardia. Removal of this tone with trimethaphan would result in tachycardia. The eye is predominantly under parasympathetic control. Parasympathetic stimulation causes the eye to accommodate (focus for near vision). Removal of this tone with trimethaphan would produce focusing for far vision. Aerioles are predominantly under sympathetic control. Sympathetic stimulation produces vasoconstriction and possibly hypeension. Removal of this tone with trimethaphan would produce vasodilatation and hypotension. The gut is predominantly under parasympathetic control, which increases gut motility. Removal of parasympathetic tone with trimethaphan would diminish gut motility. Ref: Pappano A.J. (2012). Chapter 8. Cholinoceptor-Blocking Drugs. In B.G. Katzung, S.B. Masters, A.J. Trevor (Eds), Basic & Clinical Pharmacology, 12e
Category:
Pharmacology
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