Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
11 Cards in this Set
- Front
- Back
|
What is meant by the term preload? |
Pressure exerted on the heart by the filling of blood. Increased preload means the heart must pump harder to remove it. |
|
|
What is meant by the term afterload? |
Pressure heart must overcome in order to pump against arterial pressure. Increased afterload means the heart must pump harder in order to pump blood. |
|
|
What is the issue with the body's natural response to congestive heart failure? |
Simply makes the heart work harder which is beneficial in the short-term but will lead to accelerated decline of heart function. |
|
|
What are the main positive inotropes? |
Digoxin Pimobendan (vet only) |
|
|
What is digoxin and what is its MOA? |
Binds and inactivates Na+K+ATPase pump causing accumulation of Na+ in cell. Body reverses Ca2+N+ pump to counteract build-up of Na+ causing increased Ca2+ intracellularly. Increased Ca2+ cause increased contraction. |
|
|
What are the other effects of digoxin other than its postive inotrope effect? (one much less significant) |
Neuroendocrine effect: Causes increased sensitivity of heart baroreceptors to PSNS stimulation causing slower heart rate Decreases serum RAAS levels: reduces harmful compensatory effects of RAAS |
|
|
What aspects of digoxin's pharmacokinetics that affect how it must be administered? |
Has high volume of distribution - meaning leads large loading dose because it rapidly leaves the circulation. Has narrow therapeutic window - meaning large doses can be risky. results in having to give multiple loading doses with close monitoring. |
|
|
What is pimobendan and what is its MOA? |
Inodilator (+ve inotrope and vasodilator) - Inotrope MOA = Makes contractile proteins more sensitive to existing Ca2+ levels. - Vasodilator MOA = Inhibits phosphodiesterase III (normally causes vasoconstriction) |
|
|
What is dobutamine and what is its MOA? |
+ve inotrope Increases heart contractility by stimulating B receptors. |
|
|
Why can't dobutamine be used long term? |
Because if used long term (72hrs+) the body begins to down-regulate the the number of B receptors on the heart |
|
|
How do the effects of positive inotropes differ from the body's natural response to heart failure? |
Natural response to heart failure is to make heart beat harder against increased resistance thus maintaining blood pressure. +ve inotropes make the heart contract more efficiently thus conserving oxygen and reducing ischemia and arrhythmias. |
