10b - Inotropic + Chronotropic Drugs Flashcards
(22 cards)
What is the formula for delivery of O2?
DO2 = CO X CaO2
- DO2 = Delivery of Oxygen
- CO = Cardiac Output (HR X SV)
- CaO2 = Arterial O2 Content
What are 4 reasons for Heart Failure
- Pump against too much resistance
- Overload w/ too much fluid
- Give too little fuel
- Stress it too much over time
Inotropes
What are inotropes?
Drugs that affect the strength of cardiac muscle tension
Inotropes
What are 2 categories of inotropes?
- Positive Inotropes
- Negative Inotropes
(+): Increase muscle strength
(-): Decrease muscle strength
Inotropes
What are they often used for?
Increasing CO + Increasing MAP
Inotropes
What are the main categories?
- Catecholamines
- Phosphodiesterase Inhibitors
- Cardiac Glycosides
Drug: Dobutrex (Dobutamine)
What receptors does it target?
- B1 = Strong affinity (HR increases)
- B2 = Weak affinity (vasodilation)
Drug: Dobutrex (Dobutamine)
What is the outcome of using this drug?
- Increased contractility (B1)
- Mildly increase HR (B1)
- Mildly decreased SVR (B2>A1)
Drug: Primacor (Milrinone)
What is it?
A Phosphodiesterase inhibitor that results in increased cAMP in cardiac and vascular smooth muscle.
Drug: Primacor (Milrinone)
What does it result in?
- Increased myocardial contractility
- Vasodilation + ↓SVR
Both Dobutamine + Milrinone are labelled as inodilators. What is a inodilator?
Inodilator –> Inotropic Effects + Vasodilation Effects
Drug: Lanoxin (Digoxin)
What is it and what does it do?
- Cardiac glycoside derived from digitalis plants
- Increase myocardial contractility
Lanoxin (Digoxin)
How does it increase myocardial contractility?
- Inhibiting Na/K ATPase pump in heart
- Remove built up Na+ by increasing active exchange of Na+ for Ca2+
- Lead to increased intracellular Ca2+.
Chronotropes
What are they?
Drugs that affect the rate of cardiac muscle contraction.
(+) = Increase HR
(-) = Decrease HR
Chronotropes?
What are 2 types of chronotropic drugs?
- Atropine
- Isoproterenol
Atropine
Describe Characteristics of this drug
- Anti-muscarinic given to increase HR
- Direct acting competitive antagonist
Atropine
When is it best to use it?
In cases of excessive vagal nerve parasympathetic stimulation
Atropine
What are potential side effects?
- Drying Secretions
- Blurred Vision
- Nausea
Isoproterenol
What does this drug act on?
- B1 receptors (Chronotropic effects + some inotropic)
- B2 receptors (Some vascular smooth muscle relaxation)
Isoproterenol
Why is this drug usually a secondary option?
- Other chronotropes preferred (atropine)
- Other inotropes more specific (dobutamine)
Myocardial O2 Consumption
Why does increasing HR and/or SV come at a cost?
Makes heart work faster, more O2 required
What is most likely used in heart related causes of lower BP?
Inotropes
