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
NorEpi can be used as a Beta 1 agonist when combined with what alpha blocking drug?
-Phentolamine
What does dobutamine do?
- Beta 1 Receptor
- Dilates coronaries
- Increases CO/HR
- Decreases filling pressure
- Inotropic properties w/o dysrhythmias
Dopamine and dobutamine need to mixed what solution?
-D5W
Dobutamine can be combined with what drug to increase SVR and Urine output.
-Dopamine
Isoproterenol works on what 2 receptors?
-Beta 1 and 2
Isoproterenol increases what 4 things?
- HR
- Contractility
- systolic BP
- Automaticity
What is the net effect of Isoproterenol?
- Increased CO
- Decreased MAP
- Bronchodilator
What are 4 problems with Isoproterenol
- Tachycardia
- Diastolic hypotension
- ↑ MVO2
- ↑ dysrhythmias
What are the uses for Isoproterenol?
- Chemical pacemaker
- Decrease PVR in pulmonary HTN and RV failure
What clinical situations is dopamine used?
- Decreased CO
- Decreased systemic BP
- Increased LVEDP
What are the problems associated with dopamine?
- Vent response to hypoxemia
- Inhibit insulin (hyperglycemia)
- Extravisation causes vasoconstriction
What receptors does dopexamine work on?
- Beta 2 and DA1
- Inhibits presynaptic uptake of NE
How does Dopaximine compare to Dopamine?
-As effective at increasing CO, but tachycardia is more common
When is dopaximine used?
-CHF with high SVR
Fenoldopam works on what receptor?
- Selective D1 agonist
- Moderate affinity for Alpha 2
What does fenoldopam do?
-Decrease SVR and renal resistance = decreased BP and increased LVEF and RBF
How does fenoldopam compare with SNP?
- As effective in controlling BP with benefit of increased renal blood flow
- Slower on/off than SNP
8 Advantages of fenoldopam?
- Rapid on/off
- No fall in BP
- No coronary steal
- No negative ino/chronotropic
- No invasive monitoring
- No interactions
- Easy titrate
- Preserve renal function
What are the 6 disadvantages of fenoldopam?
- Reflex tach
- ECG changes
- Tolerance
- Hypokalemia
- Increase in IOP
- Cost
