ImportantCar Flashcards
(39 cards)
cardiac output
the quantity of blood pumped into the systemic circulation by the ventricle each minute
- dependent upon the heart rate and stroke volume
Stroke volume
the amount of blood ejected by the left ventricle with each heart beat or contraction
Preload
time for the heart to fill with blood + enough volume of blood entering the right side of the heart; necessary for adequate stroke volume
Afterload
describes the force needed to push blood out of the ventricles or arterial pressure against which the ventricle must pump
what factors influence cardiac output?
high blood pressure and/or constriction of the vasculature
in response to hypotension the sympathetic nervous system releases ?
Renin-Angiotensin-Aldosterone system + norepinephrine to increase heart rate and cause vasoconstriction of small arteries as a short term solution to raise blood pressure
What does the Renin-Angiotensin-Aldosterone system do in response to hypotension?
activated when the kidney detects hypotension and the juxtaglomerular cells release renin and angiotensinogen
How are Angiotensinogen and ACE related/work together?
Angiotensinogen converts angiotensin1 to angiotensin2 which is a potent vasoconstrictor, and supports blood pressure. The enzyme that enables conversion of angiotensin1 to angiotensin2 is called angiotensin converting enzyme also known as “ACE”
How does the RAA system influence blood pressure?
causes the release of the mineralcorticoid hormone aldosterone from the adrenal gland –> the kidney conserves sodium and water –> blood pressure maintenance
Clinical signs of advanced heart disease are caused by?
response to decreased cardiac function, low cardiac output and poor venous return, thus the body tissues no longer receive sufficient blood and oxygenation
RAA cascade as a short term vs long term solution
short term - good solution to low blood pressure and cardiac output
long term - increase in sodium and water retention as well as vasoconstriction eventually makes it more difficult for the heart to work against the systemic pressure and weakens the heart muscle
What are important treatments of CHF /focus of cardiac drug therapy
inhibinting the RAA system and/or vasodialation by other mechanisms of action, diuresis to remove excess fluid, and strengthenign the force of heart muscle contration
What are the (important) sympathetic adrenergic receptors involved with cardiac function?
Alpha-1 (peripheral vessel constriction, increase BP)
Beta-1 (increase HR, force of constriction and blood glucose)
Beta-2 (bronchodilation)
compare the functions of the different sympathetic adrenergic receptors involoved with cardiac function
Alpha-1 (peripheral vessel constriction, increase BP)
Beta-1 (increase HR, force of constriction and blood glucose)
Beta-2 (bronchodilation)
What compensatory mechanisms will the heart take on to decrease workload on the heart and increase cardac output in response to a failing heart?
the heart will enlarge in an attempt to pump out more blood (dilated cariomyopathy and hypertrophic cardiomyopathy)
compare dilated cardiomyopathy and hypertrophic cardiomyopathy
DC- heart chamber dilation
HC- thickened myocardium
Postitive Inotropes
- Drugs that increase the heart’s stroke volume by increased force of heart muscle contraction
- are used if the heart muscle is too weak to adequately pump
- Drugs in this category include the cardiac glycosides, and sympathomimetic drugs which mimic the action of adrenergic sympatheticstimulation.
What am I?
- cardiac glycoside
- derivative of purple foxglove plant (Digitalis purpurea)
- treat CHF and arrhytmias (atrial fibrillation and supraventricular tachycardia)
- narrow margin of safety
- interact with many other drugs
- must be dosed based on lean body mass and monitored through periodic blood testing (due to adverse effects and toxicity)
- fallen out of favor with the development of less toxic drugs
digoxin (Cardoxin) and Digitoxin (Crystodigin)
What am I?
- sympathomimetic
- directly stimulates the heart
- used in cases of shock, severe allergic reactions and cardiac asystole emergencies
- affects both alpha and beta adrenergic receptors –> increased heart rate and contractility, increased blood pressure, increased blood glucose, bronchodilation, constriction of peripheral vessels and antagonizes the effects of histamine
- immediate onset when administered intracardiac, IV or intratracheal in emergency situations
Epinephrine (Adrenalin)
What is a contraindication of Epinephrine?
use cautiously due to caridac side effect of causing arrhythmias (ventricular fibrillation and hypertension)
Why would Epi be added to a local anesthetic?
The solution (Epi) is available in various strengths and is an ingredient found in local anesthetics such as lidocaine for its ability to constrict local vessels allowing the lidocaine to remain in the area.
Pay attention! Theres a cardiovascular emergency, why should you pause before administering Epi (solutions)?
Lidocaine is also used to correct ventricular arrhythmias such as PVCs and ventricular tachycardia, therefore DO NOT USE lidocaine intended for local anesthesia in these cases since it contains epinephrine as it will cause tachycardia and worsen arrythmias!!
Compare/contrast Dopamine and Dobutamine
Both :Dopamine and dobutamine are sympathomimetics used in critical care settings to increase cardiac output and have the effects of increasing heart rate, heart contractility and blood pressure.
- Due to their shortduration of action these drugs are given as a constant rate of infusion.
Dopamine is able to increase organ perfusion, especially blood flow to the kidney but is more likely to have tachycardia as a side effect.
Dobutamine is less likely to cause tachycardia as a side effect but does not have as much ability to increase blood flow to the viscera and kidney.
Vasodilator
drugs used in cardiac therapy to bring about the vasodilation of arteries and/or veins to allow for improved cardiac output
