Class 6 Deck 1 Flashcards
What are the 2 types of positive inotropes?
- cAMP Dependent
- cAmp Independent
What are the 3 cAMP dependent positive inotropes?
- Beta agonists
- Dopaminergic agonists
- Phosphodisterase inhibitors
What are the 2 cAMP independent (direct acting) positive inotropes? and what do they do?
- Cardiac glycosides (digoxin) = Inhibits Na-K ATPase
- Calcium = ↑Ca gradient
How do cAMP dependent phosphodisterase inhibitors work?
- Inhibit metabolism of cAMP
- Increase Ca sensitivity of contractile proteins
- Increase Ca influx
- Antagonize adenosine
What are the pure Beta 1 agonists?
- Dobutamine
- Isoproterenol
What are the hemodynamic effects of pure Beta-1 agonists?
- Increased HR
- Increased A-V conduction
- Decreased SVR and PVR (Beta 2 effect)
What are the mixed alpha/beta agonists?
-NorEpi, Epi, Dopamine
What are the hemodynamic effects of mixed alpha/beta agonists?
- Increased vascular resistance
- Increase myocardial O2 consumption
- increased HR
When are the effects of inotropes more pronounced?
-Failing heart
when are direct acting positive inotropes used?
-To increase SV in low flow states when myocardial contractility is depressed
What 3 direct acting inotropes drugs can worsen tachyarrhythmias?
- Isoproterenol
- Dopamine
- Dobutamine
What 2 inotrope drugs will may decrease tissue perfusion and lead to renal failure in low CO states?
-NorEpi and Epi
Digoxin should be used cautiously in what 3 patient types for fear of digoxin toxicity?
- Hypokalemia
- Renal failure
- Preop digoxin administration
From lowest to greatest, list the positive inotropes arrhythmogenic potential.
-Dobutamine<Isoproterenol
What is the prototypical catecholamine? and what receptors does it stimulate?
- Epinipherine
- Alpha 1, Beta 1 & 2
What is the most potent activator of Alpha 1 receptors?
-Epinepherine
What is the low dose of EPI and what does it do?
- 1-2 mcg/min (BETA 2)
- Essentially a vasodilator
- Decrease SVR
- Increased blood to skeletal muscle
What is the intermediate dose of EPI and what does it do?
- 4 mcg/min (BETA 1)
- Increases in HR, Contractility, CO and automaticity
- Inotrope
What is the high dose of EPI and what does it do?
- > 10 mcg/min (ALPHA 1)
- Vasoconstrictor
- Most potent activator of Alpha 1 receptors
- Maintain myocardial and cerebral perfusion
- Possible reflex brady
Continuous epinepherine IV infusion is used to treat what?
-Decreased myocardial contractility
NorEpi is also known as what? and is primarily a what?
- Levophed
- Alpha 1 agonist
NorEpi (Levophed) is used to treat what?
-Refractory hypotension (titrate to flow not BP)
What doe NorEpi (levophed) do to CO?
- Increase at low doses (2mcg/min) Beta stimulation
- Decrease at higher doses (>3mcg/min) Alpha 1 = peripheral vasoconstriction
What drug is a better inotrope, Epi or NorEpi? and Why?
- Epi
- Produces greater CO
