Cardiac Drugs: Diuretics & Nitrates

Diuretics Overview

  • Promote water excretion, often used for fluid overload
  • First-line drug for heart failure
  • Can be administered orally (PO) or intravenously (IV)

Types of Diuretics

  • Thiazide Diuretics (Pages 494 & 635)
  • Loop Diuretics (Page 631)
  • Potassium-Sparing Diuretics (Page 637)

Thiazide Diuretics

  • Example: Hydrochlorothiazide (HCTZ)
    • Drug of choice for hypertension
    • Given via PO or IV
Mechanism of Action
  • Inhibits the reabsorption of sodium and chloride
  • Increases secretion of sodium and water
  • Decreases plasma volume
  • Lowers preload and workload of the heart
  • Results in decreased blood pressure
Uses
  • Blood pressure management
  • Fluid retention (edema) associated with heart failure
Adverse Effects
  • Hypotension, especially when sodium and potassium are low
  • Electrolyte imbalances (higher risk with pre-existing kidney issues)
  • Ototoxicity when taken with
    • Alcohol
    • Barbiturates
    • MAOIs
    • Beta blockers
    • Corticosteroids
  • Potential interactions with NSAIDs
Nursing Implications
  • Monitor blood pressure and electrolytes (especially potassium and sodium)
  • Watch for dehydration and signs of hypotension
  • Caution in patients with sulfa allergies or pregnancy

Loop Diuretics

Mechanism of Action
  • Inhibits sodium and chloride reabsorption in Henle's loop
  • Produces significant diuresis
Example
  • Furosemide (Lasix): Rapid effect, preferred when fast diuresis is needed; must confirm urine output to ensure effectiveness
  • Available in PO and IV
Uses
  • Heart failure, pulmonary edema, hepatic and renal disease, hypertension
Adverse Effects
  • Electrolyte imbalances (Na+ & K+)
  • Dehydration, hypotension, ototoxicity
Nursing Implications
  • Pre-administration check of
    • Blood pressure
    • Laboratory results (sodium, potassium, BUN/creatinine)
  • Post-administration monitoring of BP, I/O, signs of fluid reduction, and side effects
  • Potential drug interactions: Ibuprofen may decrease effect; corticosteroids and digoxin may require careful monitoring

Potassium-Sparing Diuretics

Example
  • Spironolactone (Aldactone): Preserves potassium while promoting sodium and water excretion.
Mechanism of Action
  • Blocks aldosterone
  • Promotes sodium and water excretion with potassium retention
Uses
  • Heart failure, ascites, hypertension, hypokalemia, hyperaldosteronism
Adverse Effects
  • Dizziness, headache, abdominal cramping, diarrhea, increased serum potassium levels
  • Black box warning for tumor growth and contraindications in abnormal kidney function or during 1st trimester of pregnancy
Nursing Implications
  • Administer same time daily (preferably morning)
  • May take with food to minimize GI irritation
  • Monitor for dehydration and electrolyte imbalances.
  • Assess for interactions with lithium and digoxin, which may become toxic; ginger and licorice can enhance effects

Organic Nitrates Overview

Mechanism of Action
  • Cause vasodilation, improve coronary perfusion, and decrease workload of the heart
Uses
  • Treating angina; usual administration is PRN, also can be given ongoing
  • Fast-acting via multiple routes (IV, sublingual, PO, topical)
Adverse Effects
  • Common: Severe headache, hypotension, bradycardia, dizziness, syncope
Contraindications
  • Patients on erectile dysfunction medications
  • Hypotension, severe anemia, hypovolemia, head injuries, cerebral hemorrhage, abnormal kidney function
Nursing Implications
  • Check BP and heart rate prior to administration (hold if systolic < 90 or HR > 100)
  • Reassess pain and monitor for adverse effects post-administration
  • Sublingual forms must be kept in brown bottles due to light sensitivity, and replaced every 6 months.

Clinical Scenario Considerations

Diuretic Administration
  • If a client is on spironolactone and has a BP of 94/42, the nurse should hold the medication due to hypotension.
Nitroglycerin for Chest Pain
  • Prior to administering sublingual nitroglycerin, the nurse should assess blood pressure, heart rate, current pain level, medication history, and allergies.