Hesi 8

Renal System Drugs

Candice Overholser, MSN, RN

Overview of the Renal System

  • Kidney Functions:

    • The primary functional unit of the kidneys is the nephron which performs several essential tasks:

    • Glomerular filtration:

      • Filters blood while retaining blood cells, proteins, and lipids.

      • What is removed from the blood is called filtrate (99% returned to circulation; rest constitutes urine).

      • Damage to glomeruli can lead to blood cells, proteins, and lipids leaking into filtrate (observed in urinalysis).

    • Fluid Volume Regulation:

      • Adjusts urine concentration to maintain fluid balance.

    • Electrolyte Regulation:

      • Sodium (Na) regulation via Loop of Henle.

      • Chloride (Cl) regulation.

      • Potassium (K) regulation.

    • Blood Pressure Control (BP):

      • Modulates blood pressure through the Renin-Angiotensin-Aldosterone System (RAAS).

    • Red Blood Cell Production:

      • Secretes Erythropoietin to stimulate RBC production.

Nephron Structure

  • Key anatomical structures include:

    • Afferent Arteriole: Brings blood to the glomerulus.

    • Efferent Arteriole: Carries blood away from the glomerulus.

    • Glomerulus: Network of capillaries that filters blood.

    • Bowman's Capsule: Encases the glomerulus.

    • Proximal Convoluted Tubule:

    • Loop of Henle: Has ascending and descending limbs.

    • Distal Convoluted Tubule:

    • Collecting Duct: Final urine concentration site.

    • Peritubular Capillaries: Surround nephron aiding in tubular reabsorption and secretion.

    • Calyx: Receives urine from the collecting ducts.

Diuretics

  • Definition: Medications that increase sodium and water excretion through urination.

  • Use Cases:

    • Commonly used to treat:

    • Edema related to heart failure.

    • Pulmonary edema.

    • Liver disease (cirrhosis).

    • Renal disease.

    • Hypertension (HTN).

    • Glaucoma.

  • Classes of Diuretics:

    • Thiazide and Thiazide-like:

    • Loop Diuretics:

    • Carbonic Anhydrase Inhibitors:

    • Potassium-Sparing Diuretics:

    • Osmotic Diuretics:

Adverse Effects of Diuretics

  • Common Side Effects:

    • Gastrointestinal upset.

    • Fluid and electrolyte imbalances.

    • Hypotension (low blood pressure).

    • Fluid Rebound: Return of edema after diuretic use, especially when water intake is decreased.

Site of Action for Diuretics

  • Glomerulus: Functions in the initial filtrate formation.

  • Proximal Convoluted Tubule: Major site for sodium, bicarbonate, and water reabsorption.

  • Loop of Henle:

    • Descending Limb: Permeable to water; impermeable to electrolytes.

    • Ascending Limb: Permeable to salts; impermeable to water.

  • Distal Convoluted Tubule:

  • Collecting Duct: Final adjustment of urine concentration occurs here.

Thiazide and Thiazide-like Diuretics

  • Examples:

    • Hydrochlorothiazide.

    • Chlorothiazide (Diuril).

  • Mechanism of Action:

    • Blocks the chloride pump, preventing sodium from reabsorbing back into circulation.

    • Notable for being less efficacious in producing large urine volumes but have significant vasodilatory effects to help lower blood pressure.

  • Contraindications:

    • Allergy to sulfonamides (sulfa drugs).

    • Severe renal disease and fluid/electrolyte imbalances.

  • Adverse Effects:

    • Hypokalemia, increased blood calcium levels, increased uric acid levels leading to gout, and mild metabolic alkalosis.

Loop Diuretics

  • Example: Furosemide (Lasix).

  • Characteristics:

    • Known as high-ceiling diuretics producing larger urine outputs than other types.

    • Blocks chloride pumps in both the ascending and descending loops of Henle, enhancing fluid loss significantly.

    • Can cause rapid diuresis essential for acute heart failure or severe edema.

  • Administration Routes: IV, IM, PO.

  • Contraindications:

    • Anuria, hepatic coma, and severe renal disease.

  • Adverse Effects:

    • In addition to diuretic side effects: ototoxicity, metabolic alkalosis, hypocalcemia, and potential for sudden drops in blood pressure.

Carbonic Anhydrase Inhibitors

  • Example: Acetazolamide (Diamox).

  • Usage: Primarily for glaucoma, adjunctive use with other diuretics.

  • Mechanism of Action:

    • Blocks carbonic anhydrase, leads to increased bicarbonate and sodium loss in urine.

  • Adverse Effects:

    • Metabolic acidosis, hypokalemia, paresthesia, confusion, drowsiness.

Potassium-Sparing Diuretics

  • Example: Spironolactone (Aldactone).

  • Mechanism of Action:

    • Aldosterone antagonist acting in the distal tubule, retaining potassium while excreting sodium.

  • Uses:

    • Counteracting hypokalemia due to other diuretics and managing conditions of hyperaldosteronism.

  • Adverse Effects:

    • Hyperkalemia, lethargy, confusion, muscle cramps, and arrhythmias.

Osmotic Diuretics

  • Example: Mannitol (Osmitrol).

  • Characteristics:

    • Large sugar molecule that creates osmotic pressure pulling water into the renal tubules without significant sodium loss.

  • Indications:

    • Management of intraocular pressure, intracranial pressure, and prevention of acute renal failure due to shock or trauma.

  • Administration: IV only.

  • Contraindications:

    • Renal disease, dehydration, pulmonary congestion.

  • Adverse Effects:

    • Sudden drops in fluid levels, hypotension, nausea, headache, light-headedness.

Patient Education and Nursing Considerations for All Diuretics

  • Take with food or milk if orally administered to mitigate GI upset.

  • Administer IV diuretics slowly.

  • Monitor urinary output and adjust to oral formulations as soon as feasible.

  • Administer mainly in the morning to avoid nocturia.

  • Assess fluid volume status, daily weights, and electrolyte levels.

  • Ensure potassium-rich or potassium-restricted diets based on the specific diuretic utilized.

  • Educate patients to report weight gain of 3+ pounds in one day, monitor for signs of electrolyte imbalances, and maintain fluid intake to prevent fluid rebound.

Urinary Tract and Bladder Drugs

Key Concepts:

  • Anti-infectives:

    • Ciprofloxacin (Cipro) and Cotrimoxazole (Bactrim) are commonly used for UTIs.

    • Cranberry juice may prevent E.coli adherence but does not cure UTIs.

    • Importance of hydration: 6-8 glasses of water daily, along with potential consumption of cranberry juice (monitor sugar intake).

  • Urinary Antispasmodics:

    • Oxybutynin (Ditropan XL) has anticholinergic effects and blocks urinary tract muscle spasms.

  • Urinary Analgesics:

    • Phenazopyridine (Pyridium) provides symptomatic relief from UTI pain, but may discolor urine.

  • Bladder Protectant:

    • Pentosan polysulfate sodium (Elmiron) protects the bladder wall in chronic interstitial cystitis; however, it has bleeding risks due to its heparin-like properties.

Treating Benign Prostatic Hyperplasia (BPH)

  • Drug Types for BPH Management:

    • Alpha-adrenergic blockers (e.g., Doxazosin, Tamsulosin) help dilate blood vessels and relax urinary tract effects.

    • Testosterone Inhibitors (e.g., Finasteride) inhibit the conversion of testosterone to dihydrotestosterone (DHT), leading to potential reduction in prostate size.

  • Cautions:

    • Monitoring for prostate cancer risks associated with testosterone inhibitors.

    • Avoiding conflicting medications and monitoring fluid intake to manage BPH symptoms effectively.