Classify the commonly used inotropic agents and describe their mechanism of action.
This question required a classification based on chemical structure and class action.
Sympathomimetics, phosphodiesterase inhibitors, calcium sensitizers and cardiac
glycosides should have been mentioned. Additional detail was expected,
subdividing Sympathomimetics into catecholamines (naturally occurring and
synthetic), and non-catecholamines (direct and indirect acting). Further classification
based on peripheral vasomotor action demonstrated greater understanding
Better answers included diagrams illustrating the mechanism and point of action on
the cardiac myocyte. Discussion of receptors, second messengers, and the role of
calcium was essential.
The question was aimed at “commonly used” agents, although some marks were
awarded for discussion of calcium, glucagon and other rarely used drugs.
Insufficient detail regarding mechanisms of action was a common observation.
Syllabus: C2d 2
References: Pharmacology and Physiology in Anaesthetic Practice, Stoelting 4th Ed
p293-320. Basic and Clinical Pharmacology Katzung 10th Ed p121-198.
Pharmacology Rang & Dale 6th Ed p168-187, 290-291