Inotropic Agents Flashcards
Why is pimobendan termed an “inodilator”?
Has both calcium sensitizing and phosphodiesterase inhibitory properties
Has positive inotrophic effects and peripheral vasodilatory effects
What are the therapeutic uses of dobutamine?
Acute management of heart failure, particularly in profound forward pump failure or hypotension
What is the mechanism of action of calcium sensitizing agents? How is this different than other inotrophic agents?
Instead of increasing Ca influx, calcium sensitizing agents sensitize the contractile elements to the level of Ca already present
What is the mechanism of action of beta adrengeric agonists?
Stimulation of beta adrengeric receptors -> ATP to cAMP ->activation of protein kinases -> Ca influx
What is the mechanism of action of cardiac glycosides such as digitoxin and digoxin?
Inhibits the Na-K ATPase- Na cannot be transported out of the cell, intracellular Na rises, Na-Ca exchanger corrects imbalance, intracellular Ca rises
Direct parasympathetic stimulation- inhibits AV node
How should the dosage of digoxin be determined?
Should be determined based on lean body weight without any ascitic fluid
Digoxin is not distributed to fat or ascitic fluid
What are the signs of digoxin toxicity?
Gastrointestinal- inappetance, nausea, vomiting, diarrhea
Cardiac arrhythmias
Neurologic- malaise, dizziness, fatigue, headaches, visual disturbances
What are the therapeutic uses of digoxin?
Systolic myocardial failure as a result of severe valvular heart disease or dialated cardiomyopathy
True or false:
Dobutamine stimulates both beta adrenergic and dopaminergic receptors.
False. It predominantly stimulates beta 1 receptors, has some beta 2 and alpha receptor activity, and no dopaminergic receptor activity
When should serum digoxin levels be tested after starting therapy?
How long after the dose is given should serum be collected?
1 week after starting therapy
6-8 hours after administration
What two conditions can predispose a patient to developing digoxin toxicity?
Hypokalemia and azotemia
Dose should be decreased in patients with hypokalemia
What are the pharmacological actions of beta adrengeric agonists?
Positive inotrophic and chronotrophic effects
Increased arrhythmogenicity
How is dobutamine administered to patients?
As a CRI. It requires close monitoring.
Define inotropy
Contractility of the heart muscle
What are the pharmacologcial actions of digoxin?
(give all five, pg 248 of SCAVMA notes)
Positive inotropy
Negative chronotophy (slows heart rate)
Natriuresis
Vasomodulation (mild vasoconstriction, vasodilation in patients with heart failure)
Baroreceptor modulation (decreases responsiveness)
