Cardiac Glycosides Chapt 42
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Cardiac Glycosides naturally occur in plants like Digitalis. What is the action of Cardiac Glycosides?
Inhibit the Na+/K+ pump, resulting in an ^in intracellular Na+. This ^ leads to an influx of calcium, causing the cardiac muscle fibers to contract more efficiently.
Digitalis preparations have 3 effects on the heart muscle, what are they?
- +inotropic action
- -chronotropic action
- -dromotropic action
Explain what a +inotropic action is.
+inotropic action ^myocardial contraction stroke volume.
Explain what -chronotropic action is.
-chronotropic action <HR
Explain what -dromotropic action is.
-dromotropic action <conduction of the heart cells.
How do the 3 effects of Digitalis effect not only the heart, but the rest of the body too? (+inotropic, -chronotropic, -dromotropic)
The ^in myocardial contractility of the +inotropic effect strengthens cardiac, peripheral, & kidney fxn by enhancing cardiac output, <preload, improving blood flow to the periphery & kidneys, <edema, & promoting fluid excretion. as a result fluid in the lung & extremities is <.
What do +Inotropic drugs do & what are they used to treat?
- ^the force of myocardial contraction
- Tx heart muscle failure
- *cardiac glycosides: digoxin
- *Phosphodiesterase inhibitors
Explain what Heart Failure is.
The heart is unable to pump blood in sufficient amounts from the ventricles to meet the body's metabolic needs.
With Heart Failure the symptoms vary depending on the affected cardiac area. What types of s/s are noted with Left ventricular & Right ventricular failure?
- Left ventricular failure: pulmonary s/s
- Right ventricular failure: systemic s/s
What are the possible causes of Heart Failure?
- Cardiac defect: Myocardial infarction or valve deficiency.
- Defect outside of heart: coronary artery disease, pulmonary HTN, & diabetes
- Supraventricular dysrhythmias: Atrial fib, Atrial flutter
How many stages of Heart Failure are there?
- 4 stages
- 1-4, 4th stage being the worst.
Cardiac Glycosides (digitalis) were originally obtained from what plant? & what drug is the prototype of Digitalis?
- Digitalis is originally from the Foxglove plant.
- **Digoxin is the prototype
What is the mechanism of action for the Cardiac Glycoside, Digoxin (Lanoxin)?
- ^myocardial contractility
- change electrical conduction properties of the heart.
- result: <HR & improve cardiac efficiency -> "slows & strengthens the heart"
What are the A/E of Digoxin?
- Cardiovascular: Dysrhythmias, bradycardia or tachy.
- CNS: HA, fatigue, malaise, confusion, convulsions.
- Eyes: Colored vision (green, yellow, purple), halo vision, flickering lights.
- GI: Anorexia, N/V/D
- ***if vomit, NEVER give Dig after!! CALL MD.
- **dig level NEEDED
The cardiac glycoside, Digoxin (lanoxin) has a VERY narrow therapeutic window. What things can effect this window?
- <K+ levels ^Dig toxicity
- Predisposing conditions: Hypokalemia, Hypercalcemia, dysrhythmias, advanced age.
What drug is used for life threatening Bradycardia, Advanced heart block or Dysrhythmias caused by Digoxin toxicity?
Digibind (digoxin immune fab therapy)
What are the critical nursing assessments for Cardiac Glycosides like Digoxin?
- Apical pulse 1 whole minute
- Check Dig levels
- if AP <60 or >120b/min HOLD & call MD
What are the nursing implications for Cardiac Glycosides like Digoxin?
- Hold dose & call MD if pt has s/s of toxicity
- Pts should report ASAP Wt gain of 2lbs or more in 1day or 5lbs or more in 1week
- Infants & children need BID dosing
- *NEEDS to be given 12hrs apart.
Name some Inotropic drugs used to treat Acute Heart Failure.
- Cardiac Glycosides: Digoxin
- Phosphodiesterase Inhibitors: Inocor & Primacor
How does the Inotropic drug class, Phosphodiesterase Inhibitors work?
by inhibiting the enzyme phosphodiesterase, promoting a positive inotropic response & vasodilation.
The Inotropic drugs Inocor & Primacor (phosphodiesterase Inhibitors) work by doing what?
^stroke volume & cardiac output & promote vasodilation.
What are the A/E related to the phosophodiesterase inhibitor, Inocor & Primacor?
- Inocor: Thrombocytopenia
- ^liver enzymes w/long-term use
- Primacor: Dysrhythmia
What are the nursing considerations with the Phosphodiesterase inhibitors, Inocor & Primacor?
- *short-term managment of HF
- *Given when pt has NOT responded to Tx w/Digoxin, diuretics &/or vasodilators.
- *Given IV for NO longer than 48-72hrs
- *Monitor EKG & cardiac status
What are the nursing Implications with Inotropic drugs?
- Monitor for therapeutic effects
- Are s/s of HF resolving???-^urinary output
- -<edema, SOB, dyspnea, crackles, fatigue
- -resolving of paroxysmal nocturnal dyspnea
- -improved PP, skin color, temp
- Monitor for A/E
Name some of the other agents used to Tx HF beside the +inotropic drugs.
- Vasodilators: <venous return to heart
- Angiotensin-converting enzyme (ACE) Inhibitors: dilate venules & arterioles, improving renal blood flow & <blood fluid volume.
- Angiotensin II receptor blockers (ARBs)
- Diuretics: thiazides, lasix & spirolactone: reduce fluid & blood volume.
- Certain beta-blockers: carvedilol & metoprolol
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