Untitled Flashcard Set

Class: Thiazide Diuretics

  • Drugs in Class: Hydrochlorothiazide (HydroDIURIL) is the prototype. Other drugs include chlorothiazide (Diuril), bendroflumethiazide (Naturetin), hydroflumethiazide, and polythiazide.

  • Indications: Used to treat hypertension (HTN), congestive heart failure (CHF), and edema.

  • Mechanism of Action (MOA): Works by inhibiting the pump that reabsorbs sodium (Na) and chloride (Cl), leading to increased excretion of Na and Cl. This results in a modest diuresis, and some potassium (K), magnesium (Mg), and Na are also excreted.

  • Pharmacokinetics: Administered orally (PO) and is rapidly absorbed. Its action begins within 1-2 hours. It is metabolized in the liver and excreted unchanged in the urine.

  • Adverse Effects: Orthostatic hypotension, dizziness, drowsiness, electrolyte imbalance, elevated glucose, headache, and dehydration. It also causes hyperuricemia (by blocking uric acid excretion) and hyperlipidemia (by increasing serum cholesterol and triglycerides).

  • Precautions & Contraindications: May predispose the patient to gout and may lead to hypercalcemia. Women tend to experience a greater decrease in serum potassium than men. It is contraindicated in patients with severe renal impairment (Creatinine clearance < 30ml/min) and is not effective when urine flow is scant, unlike loop diuretics. Use cautiously in diabetic patients and those with hyperlipidemia. Do not give if the patient has a sulfa allergy.

  • Drug Interactions: Has many drug interactions; notably, a diet high in sodium foods will decrease the effectiveness of the drug.

  • Specific Nursing Implications: Serum uric acid levels should be checked. Instruct patients to avoid high-sodium foods and increase potassium-rich foods. Routinely monitor electrolyte balances and blood glucose levels.

Class: Potassium-Sparing Diuretics

This class is divided into two distinct sub-categories: 1. Non-aldosterone Antagonists (Sodium Channel Blockers)

  • Drugs: Triamterene (Dyrenium) is the prototype, and amiloride (Midamor) is another drug in this subclass.

  • Mechanism of Action: Disrupts the sodium-potassium exchange in the distal tubules. This action is independent of aldosterone. It increases the loss of Na, Cl, water, calcium (Ca), and bicarbonate while retaining K and Mg. It works in 2-4 hours, produces scant diuresis, and inhibits uric acid excretion (which increases uric acid levels).

2. Aldosterone Antagonists

  • Drugs: Spironolactone (Aldactone) and eplerenone (Inspra).

  • Mechanism of Action: Blocks aldosterone directly in the distal tubule. This increases Na and water loss while retaining K. It takes 2 days to start working and produces scant diuresis.

  • Indications (For both subclasses): Hypertension, edema, and heart failure.

  • Adverse Effects (For both subclasses): Hyperkalemia, muscle cramping, arrhythmias, electrolyte imbalance, hypotension, nausea/vomiting, weakness, and fatigue.

  • Cautions & Drug Interactions: Use with caution in patients with renal insufficiency, liver disease, pre-existing hyperkalemia, or diabetes (as it can increase blood sugar). Special caution is needed for patients taking ACE inhibitors, NSAIDs, or potassium supplements, as these combinations can further increase potassium levels.

Class: Loop Diuretics

  • Drugs in Class: Furosemide (Lasix) is the prototype. Others include bumetanide (Bumex), torsemide (Demadex), and ethacrynic acid (Edecrin). Note: Ethacrynic acid is listed as IV only.

  • Therapeutic Uses: Usually reserved for volume excess, including pulmonary edema, heart failure, and other edematous states. It acts as a second-line treatment for hypertension and may be a better option for individuals with decreased renal function.

  • Mechanism of Action: Acts in the thick ascending limb of the loop of Henle by inhibiting the Na-K-Cl channel. This prevents the reabsorption of Na and Cl, and increases the excretion of K, Ca, and Mg. This class causes a much greater natriuresis than thiazide diuretics.

  • Pharmacokinetics: Can be administered PO, IV, or IM. It features a short onset, taking 60 minutes for oral administration and just 5 minutes for IV. It has variable absorption, a duration of action of 6-8 hours, and undergoes both renal and hepatic excretion.

  • Adverse Effects: Hypokalemia, orthostatic hypotension, dehydration, hypomagnesemia, hyponatremia, hypochloremia, ototoxicity, hyperuricemia, and hyperglycemia.

  • Cautions: Caution in patients with gout, impaired glucose tolerance, and renal disease (Creatinine clearance < 30ml/min).

  • Drug Interactions: Interacts with other ototoxic drugs (like aminoglycosides), beta-blockers (can increase beta-blocker levels), and digoxin.

Other Common Classes of Antihypertensive Agents

While not detailed extensively, these classes are commonly used for hypertension:

  • Beta-adrenergic blockers: No longer considered a first-line treatment.

  • ACE inhibitors.

  • Angiotensin II receptor blockers (ARBs).

  • Calcium channel blockers.

  • Combination agents: Given in single or fixed-combined doses.

Universal Diuretic Class Principles & Nursing Education

  • Core Concepts: A diuretic promotes the excretion of urine, while a natriuretic specifically promotes the renal excretion of sodium. Most diuretics work by blocking the reabsorption of sodium and chloride, creating osmotic pressure that keeps fluid in the "pre-urine" rather than returning it to the circulating blood.

  • Rule of Efficacy: The more solute (Na, Cl) that is blocked from reabsorption, the greater the diuresis. Drugs that act at the beginning of the nephron (like the proximal tubule) block the greatest amount of solute and cause the most diuresis. Drugs acting in distal parts have little reabsorption left to block, causing less diuresis.

  • Universal Nursing Implications: Nurses must monitor for orthostatic hypotension, dehydration, electrolyte imbalances, kidney function, and acid-base balance. Patient response should be tracked through daily weights, vital signs, and intake/output (I&O). Diuretics should be given in the a.m. if possible (and early p.m. if ordered twice daily) to prevent nighttime urination. Nurses should round on the patient frequently and ensure that any IV push is administered slowly.

  • Universal Patient Education: Teach patients about foods high in potassium, specifying whether they need to eat more or restrict them based on their specific diuretic. Educate on the signs and symptoms of hypo/hyperkalemia and hyponatremia. Instruct patients to change positions slowly to prevent dizziness. Advise male patients that they may experience erectile dysfunction while on diuretics.

Foundational Hypertension (HTN) & Cardiovascular Concepts

  • Hypertension Definition: Termed "The Silent Killer," HTN occurs when systolic or diastolic blood pressure is elevated beyond normal ranges over time. If left untreated, it can lead to stroke, myocardial infarction (MI), kidney disease, CHF, or death.

  • Primary (Essential) HTN: Accounts for 90-95% of patients. It is idiopathic, chronic, and progressive. It most commonly affects older adults, African Americans, and postmenopausal women.

  • Secondary HTN: Affects less than 5% of patients. It has an identifiable primary cause, such as renal disease, Cushing's syndrome, pregnancy, or hyperthyroidism. Some individuals can be completely cured by treating the root cause.

  • Risk Factors & Non-Pharmacological Treatment: Risk factors include sodium intake, excess alcohol, genetics, obesity, and race. Non-pharmacological treatments include weight reduction, exercise, the DASH diet, sodium and alcohol restriction, smoking cessation, and relaxation therapy.

  • Determinants of Blood Pressure: BP is calculated as Cardiac Output (CO) multiplied by Systemic Vascular Resistance (SVR). CO is determined by Heart Rate and Stroke Volume (preload, afterload, contractility), while SVR is determined by vessel diameter and blood volume. BP is influenced by:

    • Sympathetic Nervous System: Alpha 1 receptors cause peripheral constriction (raising BP). Beta 1 receptors increase heart rate and force of contraction (raising CO and BP).

    • Baroreceptors: Nerve endings in large arteries that trigger vasoconstriction when BP drops, and vasodilation when BP rises acutely. These feedback reflexes may be blunted in the elderly.

    • Renal System (RAAS): Kidneys secrete Renin $\rightarrow$ Angiotensin I $\rightarrow$ Angiotensin II (a potent vasoconstrictor that raises BP). Angiotensin II stimulates the secretion of Aldosterone from the adrenal medulla, which increases Na and water retention, raising blood volume and BP.

    • Endocrine System: Involves aldosterone, antidiuretic hormone (ADH), and natriuretic peptides (ANP and BNP).

  • Kidney Function: The kidneys cleanse extracellular fluid (ECF), maintain ECF volume/composition, maintain acid-base balance, and excrete metabolic wastes. They use three processes:

    1. Filtration: Occurs in the glomerulus, filtering small molecules while large molecules remain in the blood.

    2. Reabsorption: 99% of water, electrolytes, and nutrients are reabsorbed back into the blood (most diuretics work here).

    3. Active Tubular Secretion: Occurs in the proximal convoluted tubule where pumps transport molecules from plasma back into the nephron for excretion.

  • Basic Cardiovascular Terminology: Action potential, automaticity, conduction velocity, dromotropic, rate, chronotropic, contractility, and inotropic.