Cardiovascular: Adrenergic Blockers and Diuretics pharm unit3 (2)

Combined Alpha and Beta-Adrenergic Blockers

• Mechanism of Action: These medications block both alpha and beta receptors simultaneously.     - Alpha-1 receptors: Located in the arteries. Blocking them results in vasodilation.     - Beta receptors: Referred to as "Beats." Blocking them slows the heart rate and affects contractility.     - The combination affects both the heart (beats) and the vessels (arteries).

• Pharmacological Effects:     - Decreases heart rate ($HR$).     - Decreases blood pressure ($BP$).     - Promotes vasodilation.

• Naming Conventions and Examples:     - Carvedilol: Note carefully that it ends in $-ilol$ (specifically $I-L-O-L$), not $-olol$. It is a combination blocker, not just a standard beta blocker.     - Labetalol: Ends in $-alol$ ($A-L-O-L$).

• Therapeutic Uses:     - Hypertension.     - Heart failure.     - Pregnancy: Labetalol is considered safe and is used specifically for managing gestational hypertension.

• Adverse Effects:     - Hypotension and bradycardia.     - Fatigue, dizziness, and weakness.     - Drowsiness and insomnia.     - Chest pain and dyspnea (shortness of breath).     - Gastrointestinal issues: Diarrhea.

• Contraindications:     - Severe bradycardia.     - Decompensated heart failure.     - Asthma: This is a critical contraindication. Mnemonic: "Beta Asthma." Because of the beta-blocking component, it can trigger bronchospasms.

• Precautions:     - Controlled heart failure.     - Chronic bronchitis.     - Hepatic (liver) or cardiac impairment.     - Diabetes.     - Pregnancy and lactation (with the specific exception of Labetalol for hypertension in pregnancy).

• Drug Interactions:     - Digoxin (Dig): Increases the risk of Digoxin toxicity.     - Antidepressants: Use with alpha-beta blockers can cause tremors.     - Clonidine: Increases the effect of the blocker, potentially leading to severe hypotension and severe bradycardia.

• Nursing Considerations and Patient Teaching:     - Monitor Blood Pressure and Heart Rate.     - Respiratory Status: Watch closely for worsening heart failure or respiratory distress.     - Adherence: Teaching patients that medication adherence is critical; they must take it exactly as prescribed.     - Safety: Patients should rise slowly from a sitting or lying position to prevent falls. They must report shortness of breath, chest pain, or extreme fatigue.

Antiadrenergic Agents: Centrally and Peripherally Acting

• Peripherally Acting Antiadrenergics:     - Mechanism: These decrease the release of norepinephrine at the nerve endings in the periphery.     - Examples:         - Minipress.         - Reserpine: Note that although it ends in $-pine$, it is not a calcium channel blocker; it is a peripheral antiadrenergic.

• Centrally Acting Antiadrenergics:     - Mechanism: These act within the Central Nervous System ($CNS$) to decrease sympathetic activity.     - Example: Clonidine.

• General Uses:     - Hypertension, arrhythmias, and Benign Prostatic Hyperplasia ($BPH$).

• Adverse Effects:     - Peripheral Agents: Hypotension, weakness, lightheadedness, bradycardia, and specifically depression with the use of Reserpine.     - Central Agents: Dry mouth, sedation, drowsiness, anorexia, rash, and weakness.

• Contraindications:     - Reserpine: Contraindicated in patients with Peptic Ulcer Disease ($PUD$), ulcerative colitis, or a history of depression (due to the risk of worsening the condition).     - Centrally Acting: Contraindicated in active liver disease or concurrent $MAOI$ therapy.

• Drug Interactions:     - Beta Blockers: Ironically, taking these with centrally acting agents can put the patient at risk for paradoxical hypertension.     - Lithium: Increases the risk of lithium toxicity.     - Haloperidol (Haldol): May increase psychotic behavior.

• Clonidine Patch Application:     - Must be applied to a hairless area. If the patch does not adhere well due to hair, the medication delivery is inconsistent, risking stroke or heart attack.     - The patch should be changed every $7$ days.     - Rotation of sites is mandatory; do not apply at the same site every time.

• Patient Teaching:     - Do not stop abruptly: Sudden discontinuation causes rebound hypertension, which can lead to a heart attack, stroke, or arrhythmias.     - Timing: Take the medication at the same time every single day.     - Safety: Avoid alcohol and use caution when driving due to sedation risks. Report severe sedation or mood changes immediately.

General Nursing Considerations for Adrenergic Blockers

• Vital Sign Monitoring:     - Always monitor Heart Rate and Blood Pressure.     - Hold Parameters: Generally, hold the medication if the Heart Rate is less than $60$ beats per minute ($bpm$) (especially for beta blockers).     - Blood Pressure Parameters: Use nursing judgment if the systolic blood pressure is less than $90\,mmHg$. While you can technically give it at $92\,mmHg$ depending on patient trends, you must be mindful of how the patient reacts.

• Safety and Postural Changes:     - Watch for orthostatic hypotension and dizziness.     - Environmental Factors: Avoid hot showers or baths, as heat causes further vasodilation and lowers blood pressure even more.     - The "Dangling" Technique: In the morning, patients should sit up in bed first, wait for their head to stop spinning, and then stand up slowly (or call for help in the hospital).

• Patient Monitoring at Home:     - Keep a log of heart rate and blood pressure values.     - Hypertension is often asymptomatic; patients must continue medication even if they feel fine.

• Red Flags to Report Immediately:     - Chest pain (indicative of a heart attack).     - Shortness of breath or weight gain (signs of heart failure).     - Fainting or severe dizziness.     - Palpitations (may indicate an arrhythmia).

• Safety Concepts:     - First Dose Effect: Severe hypotension can occur with the very first dose, after a large dose increase, or when restarting therapy after a hiatus.     - Elderly Patients: At much higher risk for falls. They metabolize, distribute, and excrete medications differently, necessitating closer monitoring.

Introduction to Diuretics

• General Function: Diuretics are medications that act on the kidneys to increase urine production.
• Action: They remove excess fluid, sodium ($Na^+$), waste products, and potassium ($K^+$).
• Key Electrolyte: Potassium ($K^+$) is the most critical electrolyte to monitor during diuresis.
• Therapeutic Rationale: By decreasing blood volume, diuretics decrease blood pressure and significantly reduce cardiac workload (strain on the heart).
• Primary Classes:     - Loop Diuretics.     - Thiazide Diuretics.     - Potassium-Sparing Diuretics.

Loop Diuretics

• Mnemonic: "Loops lose lots of fluid."

• Examples:     - Furosemide (Lasix).     - Torsemide.     - Bumetanide.

• Mechanism of Action:     - Block sodium ($Na^+$) and chloride ($Cl^-$) reabsorption in the ascending loop of Henle.     - This area is responsible for reabsorbing significant amounts of sodium; blocking it causes massive fluid loss.     - Decreases preload, which is vital for heart failure management.

• Therapeutic Uses:     - Heart failure.     - Pulmonary edema.     - Hypertension.     - Renal disease.     - Ascities (fluid buildup related to liver issues).

• Adverse Effects:     - Electrolyte Imbalance: Low potassium (hypokalemia), low magnesium (hypomagnesemia), and low sodium (hyponatremia).     - Hypokalemia concerns: Can lead to life-threatening arrhythmias and muscle weakness that can affect breathing.     - Ototoxicity: Can cause hearing loss, especially if administered too quickly.     - Dehydration and orthostatic hypotension.     - Photosensitivity, nausea, and vomiting.

• Contraindications:     - Anuria: If the patient is producing no urine output, do not give a loop diuretic; the cause of the blockage/failure must be found first.     - Severe kidney or liver disease.

• Precautions:     - Diabetes and gout.     - Elderly patients (high risk for dehydration).     - Sulfa Sensitivity: Loop diuretics have a potential cross-sensitivity with sulfonamide antibiotics.

• Interactions:     - Digoxin: Hypokalemia increases the risk of Digoxin toxicity.     - Aminoglycosides: Increases the risk of ototoxicity.     - NSAIDs: These decrease the effectiveness of the diuretic.     - Lithium: Increases toxicity risk.

• Nursing Considerations:     - Monitor Intake and Output (I&O).     - Daily Weights: This is the best indicator of fluid loss ($1\,kg \approx 1\,L$ of fluid).     - IV Administration: Administer Lasix (Furosemide) slowly via IV push to prevent ototoxicity.     - Timing: Take the medication in the morning to prevent nocturia (getting up repeatedly at night to urinate).     - Diet: Encourage foods high in potassium such as bananas, oranges, and potatoes.

Thiazide Diuretics

• Example: Hydrochlorothiazide ($HCTZ$).

• Mechanism of Action: Inhibit sodium and chloride reabsorption in the distal tubule.

• Pharmacodynamics: These produce moderate diuresis (less than loop diuretics). They are considered first-line therapy for hypertension.

• Adverse Effects:     - Hypokalemia and hyponatremia.     - Hyperglycemia: Can increase blood sugar and potentially lead to Diabetic Ketoacidosis ($DKA$), a medical emergency.     - Gout (hyperuricemia) and photosensitivity.

• Contraindications and Cross-Sensitivity:     - Cross-sensitivity with Sulfonamides (if allergic to sulfa, likely allergic to thiazides).

• Drug Interactions:     - Antidiabetics: Thiazides decrease the effect of antidiabetic drugs, raising blood sugar further.     - Allopurinol: Increases the risk of hypersensitivity (allergic) reactions.     - Anesthetics: Using thiazides with anesthetics increases the effect/sedation of the anesthetic (e.g., patient may be slow to wake up).

• Teaching:     - Diabetics must monitor blood sugar closely at home.     - Report joint pain (sign of gout).     - Use sunscreen and protective clothing due to photosensitivity.

Potassium-Sparing Diuretics

• Examples:     - Spironolactone.     - Amiloride.     - Triamterene.

• Mechanism of Action:     - Block sodium reabsorption in the collecting tubule.     - Spironolactone specifically blocks aldosterone.     - Mnemonic: "K-sparing saves potassium."

• Pharmacodynamics: Retains potassium while excreting water and sodium. Used to prevent hypokalemia in patients with heart failure or cirrhosis.

• Adverse Effects:     - Hyperkalemia: This is the biggest danger; high potassium levels can cause cardiac arrest.     - Gynecomastia: Male breast enlargement (specific to Spironolactone).     - Drowsiness, diarrhea, and weakness.

• Contraindications:     - High potassium levels. The medication should be stopped if the potassium level reaches $5.3\,mEq/L$ or higher.

• Drug Interactions:     - ACE Inhibitors: Combining these with potassium-sparing diuretics significantly increases the risk of hyperkalemia.     - Potassium Supplements: Should be avoided entirely while on this class unless specifically prescribed.     - NSAIDs: Decrease the effectiveness of the diuretic.

• Nursing and Teaching:     - Avoid high-potassium foods and salt substitutes (which often contain potassium chloride).     - Monitor Blood Pressure and Potassium levels via regular lab work.     - Patients should be on telemetry or have regular $EKG$ monitoring to watch for arrhythmias if levels are unstable.