List the properties of an ideal inotrope (50% of marks). How does adrenaline compare
to these ideal properties (50% of marks)?
Many candidates scored very highly on this core topic. It was expected information be included
on pharmaceutics, cost, availability and compatibilities. Relevant pharmacokinetics
(onset/offset, titratability) and pharmacodynamics (including relevant receptors, nuances of
haemodynamic effects e.g. effect on diastolic pressure and regional perfusion) should have
been detailed. Adverse effects and safety profile (e.g. use in pregnancy, therapeutic index)
should also have been included.
Good answers were structured and highlighted differences with specific facts and data
|Cheap and widely available||A box of 25 ampoules retails for $399.96|
|Long shelf life||Shelf life of glass ampoules is 2 years, provided they are stored out of direct sunlight|
|Compatible with other infusions||No, usually needs to run in its own lumen|
|Administered by a range of routes||IV, IM, subcutaneous, nebulised, topical, as eye drops and directly into the ETT during an arrest.|
|Rapid onset and offset||Onset of action within one circulation time; half life ~ 2-3 minutes; easily titratable|
|Cleared in a non-organ-dependent manner||Adrenaline is rapidly metabolised by COMT and MAO|
|Inactive and inert metabolites||Metabolic byproducts of adrenaline have no activity|
|Directly acting||Adrenaline directly acts on adrenergic receptors|
|Lacks tolerance or tachyphylaxis||No tolerance|
|Does not cause tachycardia||Causes plenty of tachycardia|
|Demonstrates lusitropy||Adrenaline is lusitropic, but this is often concealed by the tachycardia|
|Energy-neutral||Significantly increases myocardial oxygen consumption|
|Safe in pregnancy||Category C|
|Wide therapeutic index||Significant complications occur with high doses, but these are 50-100 times larger than the low doses.|
Elliott, Peter. "Characteristics of an ideal inotrope." Anaesthesia & Intensive Care Medicine 9.7 (2006): 326-330.