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62 Cards in this Set
- Front
- Back
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What classes of drugs do you use to reduced preload on the heart?
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a diuretic, or venodilator
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what class of drug do you use to reduce afterload on the heart?
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arteriodilator
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what class of drug do you use to increase the contractility of the heart?
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inotropic drugs
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what class of drug to you use to lower the heart rate, and reduce energy expenditure of the heart?
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B-adrenergic antagonists
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What are the main effects of digoxin on the heart?
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contractility is increased
Heart rate is slowed CO is increased only in failing hearts |
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How does Digoxin increased myocardial contractility and thus stroke volume?
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This inhibits the Na+, K+, ATPase
this increases Na and Ca inside the cell, and lowers K inside the cell. Due to high Ca+ - actin-myosin interaction is increased. |
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How do potassium and digoxin interact?
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K+ and digoxin compete for a binding site on the Na/K ATPase receptor. (so excess K blocks digoxin)- and reduces abnormal cardiac automaticity due to digoxin toxicity
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How does calcium affect digoxin toxicity?
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this increases the toxic effects
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What do you treat digoxin toxicity with?
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potassium, as it blocks digoxins binding to the Na/K ATPase
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how does digoxin slow the heart in normal people?
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the decreases the HR due to vagal stimulation.
(by sensitizing arterial baroreceptors, stimulating central vagal nuceli, and increasing SA node sensitivity to ACh) |
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How does digoxin slow the HR in failing hearts?
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digoxin will increase myocardial contractility, and this will reduce the sympathetic tone acting on the heart
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how does digoxin affect CO in failing hearts?
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this will increase CO in failing hearts- due direct action of the myocardium and in direct action by the PNS
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How is digitialis used in conjunction with Class IA antiarrhythmic drugs?
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pretreatment with digitalis will prevent paradoxical ventricular tachycardia
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What are the vascular effects of digoxin in CHF pts?
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increase contractility, and increased CO- results in less baroreceptor activation, and thus a decrease in sympathetic tone on the vasculature. so vasodilation
(it was vasoconstricted in an attempt to bring BP of the failing system up) |
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When would you expect diuresis to occur in a pt treated with digoxin?
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only if they have edema. the improved CO will pump more blood to the kidneys, allowing them to filter more fluid out
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How does Digoxin affect the GI system?
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Anorexia and diarrhea
Vomiting due to chemoreceptor stimulation abdominal pain |
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What is the lipid solubility of digoxin?
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medium
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what is the oral availability of digoxin?
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75%
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what is the half-life in hours for digoxin?
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40 hours
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what is the plasma protein binding for digoxin?
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20-40% bound
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what is the renal elimination percentage for digoxin?
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greater than 80%
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what is the volume of distribution in L/Kg for digoxin?
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6.3 L/Kg
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How long (in days) will it take digoxin to reach steady state at constant dosing?
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1 week (7 days)
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What is the dosing regimine for rapid digitalization?
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3 doses given over 24-36 hours followed by regular maintenance doses
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What is the margin of safety like for digoxin?
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these have narrow margins of safety- so toxic effects can occur even with therapeutic doses
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What are the early signs of digoxin toxicity?
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GI symptoms, anorexia, nausea, vomiting, diarrhea, salivation
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What kind of cardiac arrhythmias can digoxin produce?
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Bradycardia
Ectopic ventricular beats AV block Bigeminy Ventricular Fib |
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What is the most common cause of death in pts taking digoxin?
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Ventricular fibrillation
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Why is digoxin toxicity declining?
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use of serum level monitoring
noting drug interactions |
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What are the CNS effects of digoxin?
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headache, fatigue, malaise, drowsiness, disorientation, hallucinations
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What does digoxin do to the skin?
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causes rashes, eosinophilia, gynecomastia
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What is the treatment of for digitalis toxicity?
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stop digitalis administration
or potassium (NEVER Ca2+) Lidocaine, phenytoin, propranolol Digitalis Immune Fab (immunotherapy) |
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How does Quinidine affect digoxin?
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this displaces it from its binding sites in plasma proteins, while decreasing its renal clearance. this increases its toxicity greatly.
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What types of actions increase digoxin toxicity?
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decreasing its renal clearance, or decreasing its volume of distribution
Increasing its absorption |
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How do diuretics that dont spare K affect digoxin?
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thiazies and loop diuretics will decrease the volume of distribution, as well as dump K+ from the body
this increases digoxin toxicity |
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How does dosing of Digoxin different for kids and old people?
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old people are very sensitive to digoxin toxicity (due to hypochlorhydria, or reduced GFR)
Kids require MORE digoxin per Kg than adults |
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What is the ending both phosphodiesterase inhibitors share?
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-rinone
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What do phosphodiesterase inhibitors do?
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these inhibit cAMP phophodiesterase isozyme....which increases diastolic function and mycardial contractility
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What is Inamrinone
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this is phosphodiesterase inhibitor (bipyridine, or indolator)
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what is milrinone?
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this is phosphodiesterase inhibitor (bipyridine, or indolator)
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who should be given bipyridines?
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pts who can be closely monitored, and are not responding to digoxin, diuretics, or vasodilators
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are bipyridines safe for long term?
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no they are not, they increase mortality and hospitalization risks
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What is low dose dopamine used for?
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this increases Cardiac output, and improves renal blood flow in low doses
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What disease is Dopamine use indicated for?
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used in severe refractory congestive heart failure
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What does Dobutamine do?
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this is a B-1 selective agonist, used for its positive inotropic effect on the heart
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What do calcium sensitizers do?
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these inhibit phosphodiesterase III and sensitize troponin-C to Ca2+ levels
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What are calcium sensitizers used for?
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Survive and Revive situations
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How do loop diuretics like furosemide treat CHF?
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these are used for intensive diuresis, to remove large volumes of edema
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how do thiazides treat CHF?
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these are used for maintenance therapy
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What kinds of problems come with using triamterene and amiloride in CHF?
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these can cause hyperkalemia when combined with ACE inhibitors, or angiotensin II receptor antagonists
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What is Nesiritide?
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this is recombinant human B-type Natriuretic peptide (hBNP)
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What does Nesiritide do?
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this treats CHF,
reduces global symptoms, including dyspnea, fatigue |
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How does Nesiritide compare to nitroglycerin?
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Nesiritide doesnt have the tolerance issues like nitro does
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How does the renin-angiotensin system affect afterload?
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this increases afterload due to angiotensin induced vasoconstriction
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how does the renin-angiotensin system affect stroke volume?
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the high afterload impedes ejection, and thus decreases stroke volume
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how does the renin-angiotensin system affect preload?
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this increases preload by expanding the fluid volume of the body- via aldosterone (from angiotensin)- uptake of Na+ in the collecting duct
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How does the renin-angiotensin system affect cardiac tissue?
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this promotes remodeling of cardiac tissue
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How do ACE inhibitors help with CHF?
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these decrease afterload (that angiotensin induced)
and decrease preload (that was induced by aldosterone) |
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How are beta blockers used in CHF?
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these are dangerous in severe CHF, but are used in pts with diastolic dysfunction or cardiomyopathies
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What does Sodium Nitroprusside do?
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this is a vasodilator, used to reduce preload and afterload in CHF
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What does Nitroglycerine and Isosorbide dinitrate do?
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this lowers preload (VEINS)
more than arteries (afterload) |
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what does Hydralazine do?
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this is a peripheral vasodilator,
causes relaxation of Arteries Heart responds to BP drop via autonomics increasing HR, CO, and ejection fraction |
