NCLEX Review Guide: Positive Inotropic and Cardiotonic Medications

Definition and Purpose

• Positive inotropic agents increase the force of cardiac muscle contraction, improving cardiac output in patients with heart failure or reduced ejection fraction.
• Cardiotonic medications strengthen heart muscle contractions while potentially affecting heart rate and conduction, primarily used in acute and chronic heart failure management.

Cardiac Glycosides

• Digoxin (Lanoxin) - Most commonly used cardiac glycoside that inhibits sodium-potassium ATPase pump, increasing intracellular calcium and contractility.
• Therapeutic range: 0.5-2.0 ng/mL - levels above 2.0 indicate toxicity risk.

Phosphodiesterase Inhibitors

• Milrinone (Primacor) - IV medication that increases contractility and causes vasodilation, used in acute heart failure.
• Inamrinone - Similar mechanism but less commonly used due to side effect profile.

Sympathomimetics

• Dobutamine - Beta-1 agonist that increases contractility with minimal effect on heart rate, used for short-term cardiac support.
• Dopamine - Dose-dependent effects: low doses affect kidneys, moderate doses increase contractility, high doses cause vasoconstriction.

Critical Assessment Parameters

1. Check apical pulse for 1 full minute before administration
2. Monitor blood pressure and cardiac rhythm continuously
3. Assess for signs of fluid overload or improvement
4. Monitor electrolyte levels, especially potassium and magnesium
5. Evaluate kidney function through creatinine and BUN levels