Wk 10 Diuretics & Nitrates revised

Cardiac Drugs: Diuretics & Nitrates

Overview

  • Diuretics: Promote water excretion, primarily for fluid overload.

  • Commonly used in combination with other blood pressure medications to effectively control arterial pressure.

  • Can be administered orally (PO) or intravenously (IV).

Diuretic Categories

  • Thiazide Diuretics: Referenced on pages 494 and 635.

  • Loop Diuretics: Referenced on page 631.

  • Potassium-Sparing Diuretics: Referenced on page 637.

Thiazide Diuretics

Hydrochlorothiazide (HCTZ)

  • Drug of Choice: For hypertension.

  • Routes of Administration: Oral or intravenous (IV).

  • NOC Coding: 16729-183-17, Hydrochlorothiazide, Tablets USP 25 mg.

Mechanism of Action

  • Inhibits the reabsorption of sodium and chloride in the distal convoluted tubule of the nephron.

  • Increases the secretion of sodium and water into the urine, reducing plasma volume.

  • Leads to decreased preload and workload of the heart, ultimately lowering blood pressure.

Uses

  • Primary Uses:

    • Management of blood pressure.

    • Treatment of fluid retention (edema), especially in heart failure.

Adverse Effects

  • Hypotension: Especially in cases of low potassium and sodium levels.

  • Electrolyte Imbalances: More prevalent with existing renal issues or concurrent use of ototoxic drugs.

  • Ototoxicity: Potential when combined with alcohol, barbiturates, MAOIs, beta blockers, corticosteroids.

    • Medications that may increase the effects include NSAIDS.

    • Medications that may decrease effects include other antihypertensives.

Nursing Implications

  • Monitoring:

    • Regular checks on blood pressure and electrolytes, particularly potassium and sodium.

    • Watch for signs of dehydration and hypotension.

  • Cautions:

    • Consider allergy to sulfa medications.

    • Caution advised during pregnancy.

Loop Diuretics

Mechanism of Action

  • Inhibit Na+ and Cl- reabsorption specifically in the loop of Henle, producing significant diuresis.

Furosemide (Lasix)

  • Rapidity: Diuretic of choice for instances requiring rapid diuresis.

  • Use in Renal Impairment: Recommended when kidney function is compromised, provided the patient can produce urine.

  • Dosing: Can be titrated to achieve maximum effect; effective via both oral and IV routes.

Uses

  • Indications for Loop Diuretics:

    • Management of pulmonary edema.

    • Treatment of hepatic and renal diseases.

    • Control of hypertension.

Adverse Effects

  • Commonly affects Na+ and K+ levels; may necessitate supplementation.

  • Risks of electrolyte imbalances and dehydration.

  • Ototoxicity noted as a significant risk.

  • Hypotension is a contraindication if urine output is insufficient.

Nursing Implications

  • Monitoring: Check blood pressure, laboratory values (Na, K, BUN/Creat), and glucose levels in diabetic patients.

  • After administration, continue to monitor blood pressure, input/output, and signs of fluid reduction (e.g., decreased edema).

  • Potential Drug Interactions:

    • Decreased effectiveness with ibuprofen and phenytoin.

    • Increased effects when combined with corticosteroids and digoxin.

Potassium-Sparing Diuretics

Spironolactone (Aldactone)

  • Combination Therapy: Effective when combined with loop diuretics to reduce potassium loss, necessitating lower doses of loops.

  • Route: Administered orally; maximum effect may take up to 6 weeks.

Mechanism of Action

  • Promotes sodium excretion while blocking aldosterone, consequently retaining potassium.

Uses

  • Primary Applications:

    • Heart failure management.

    • Treatment of ascites and hypokalemia.

    • Control of hypertension and hyperaldosteronism.

Adverse Effects

  • Commonly reported side effects include dizziness, headaches, abdominal cramping, diarrhea, and elevated serum potassium levels.

Black Box Warning

  • Warning for potential tumor growth; unnecessary use is discouraged in cases of abnormal kidney function or during the first trimester of pregnancy due to contraindications.

Nursing Implications

  • Administer at the same time each day, preferably in the morning; can be taken with food to minimize gastrointestinal distress.

  • Advise patients to continue the medication even if they feel asymptomatic.

  • Similar monitoring practices as loop diuretics, including blood pressure, electrolytes, and BUN/creatinine levels.

  • Be vigilant for dehydration and electrolyte imbalances.

  • Drug Interactions: Assess for lithium and digoxin, as they can reach toxic levels; ginger and licorice may amplify effects.

    • Increasing Effects: ACE inhibitors, ARBs, potassium-containing drugs, and beta blockers.

    • Decreasing Effects: Alcohol, vasodilators, and salicylates.

Organic Nitrates

Overview of Nitrates

  • Involved in vasoconstriction and vasodilation processes.

Angina

  • Defined as a lack of perfusion and oxygenation to the heart, typically resulting in pain and potentially other symptoms.

Drugs for Angina Treatment

  • Categories include organic nitrates, calcium channel blockers, and beta-blockers.

Mechanism of Action of Organic Nitrates

  • Effects: Cause vasodilation, open coronary arteries, and improve myocardial perfusion.

  • Additionally decrease heart workload by affecting both preload and afterload.

Administration and Usage

  • Typically PRN for angina relief; can also be used for ongoing treatment.

  • Various routes: IV, sublingual, oral, topical (transdermal and disc).

Common Organic Nitrates

  • Examples: Nitroglycerin, isosorbide mononitrate, isosorbide dinitrate.

  • Dosage Information:

    • Nitroglycerin: 50 mg per 250 mL; dispensed in compliance with patient package insert.

    • Isosorbide mononitrate: 20 mg tablets, requires storage in tight containers avoiding light exposure.

Adverse Effects

  • Severe headaches are common; can be managed with acetaminophen.

  • Other side effects include hypotension, orthostatic hypotension, bradycardia, dizziness, and potential syncope.

Contraindications

  • Use caution with erectile dysfunction medications and existing hypotension; potential issues with severe anemia, hypovolemia, head injuries, and cerebral hemorrhages.

  • Abnormal kidney function is a further concern, along with beta blockers that may exacerbate side effects.

Nursing Implications

  • Pre-Administration Checks:

    • Blood pressure (hold if systolic <90 mm Hg or 30 mm Hg below patient's normal).

    • Heart rate (hold if HR > 100).

    • Assess chest pain level, and ascertain last time the patient used ED medications, particularly in acute pain situations, where EKG may be warranted.

  • Post-Administration Monitoring:

    • Continuously reassess pain and blood pressure, observing any potential adverse effects closely.

  • Sublingual Nitrates:

    • Maintain in a brown bottle, avoid light exposure, keep in a cool, dry area, and replace every six months.

    • Should tingle under the tongue; absence of tingling indicates ineffectiveness.

  • Oral Nitrates:

    • Administering them in the morning post-nitrate-free night; take 1-2 hours before meals.

    • Sustained-release forms should not be crushed, broken, or chewed.

  • Ointment: Requires measurement with application papers; primarily for administrative use in ICU or step-down units.

Case Study: Practical Application

Scenario 1: Spironolactone Administration

  • When preparing to administer spironolactone for a heart failure patient, the nurse encounters a blood pressure of 94/42. This low BP should trigger the nurse to:

    • Considerations: Hold the medication based on low blood pressure readings.

Scenario 2: Nitroglycerin Administration

  • In managing a patient with chest pain requiring sublingual nitroglycerin, the nurse must assess:

    • Essential Checks: Blood pressure, heart rate, pain level, medication history, and allergies must be accounted for before administration.