Fluid and Drug Therapy Notes week 5

Fluid and Drug Therapy for Fluid Volume Excess

Key Terms

  • Anasarca: Generalized massive edema, swelling everywhere.
  • Anuria: Absence of urine production.
  • Ascites: Accumulation of fluid in the abdominal cavity.
  • Edema: Excessive accumulation of fluid in body tissue, generally localized.
  • Dependent Edema: Edema localized in the feet and ankles, or other dependent areas like elbows for those with limited movement.

Kidney Function and Diuretics

  • Diuretics work directly on kidney function.
  • Diuretics act by creating a blockade of sodium and chloride reabsorption in the nephron.
  • This increases osmotic pressure in the nephron, which prevents passive water reabsorption.
  • Increased urine flow is directly related to the amount of sodium and chloride reabsorption blocked.

Hypokalemia: Signs and Symptoms

  • Potassium levels are significantly affected by diuretics and have a major impact on bodily functions.
  • Mnemonic: SICK WALT
    • Alkalosis
    • Shallow respirations
    • Irritability
    • Confusion and drowsiness
    • Weakness and fatigue
    • Arrhythmias
    • Lethargy
    • Thready pulse
  • Other signs and symptoms include intestinal motility issues.

Loop Diuretics

  • Prototype: Furosemide (Lasix)
  • Furosemide works in the thick ascending limb of Henle's loop.
    • Blocks reabsorption of Na+Na^+ and Cl−Cl^-. More sodium in the filtrate draws more water into the urine, reducing blood volume and blood pressure.
  • Mechanism of Action: Blocks reabsorption of sodium in the loop of Henle, proximal convoluted tubule, and distal convoluted tubule.
  • Lasix was rumored to be named because it lasts six hours, but most diuretics last about six hours.
  • Administer before 2 PM to avoid nocturia.
  • Adverse Effects: Fluid and electrolyte imbalance.
  • Loop diuretics have the most significant effect compared to thiazide and potassium-sparing diuretics.
  • Knowing the difference between loop, thiazide, and potassium-sparing diuretics is crucial.
  • Patients should monitor fluid volume by weighing themselves daily on the same scale.
  • Drug-Drug Interactions:
    • Ototoxicity is a concern, especially with high doses and renal impairment.
    • Monitor for vertigo, tinnitus, and hearing loss.
    • Increased risk with other ototoxic drugs (e.g., aminoglycosides).
    • May cause a minor increase in blood sugar.
    • Monitor carefully for electrolyte imbalances, especially when prescribing more than one diuretic.
    • May cause dizziness due to lowered blood pressure.

Thiazide Diuretics

  • Prototype: Hydrochlorothiazide (HCTZ)
  • Works in the early distal convoluted tubule.
  • Mechanism of Action: Decreases reabsorption of sodium, water, chloride, and bicarbonate.
  • Uses: Hypertension, edema, heart failure, nephrotic syndrome.
  • Contraindications: Allergy to sulfa drugs, anuria, pregnancy.
  • Have a ceiling threshold; increasing the dose beyond a certain point will not produce a greater effect.
  • Cause ototoxicity, especially with high serum drug levels, renal impairment, and concurrent use of other ototoxic drugs like aminoglycoside antibiotics.

Potassium-Sparing Diuretics

  • Work in the late distal convoluted tubule and the collecting duct (distal nephron).
  • Two categories:
    • Aldosterone antagonists (e.g., spironolactone/Aldactone)
    • Non-aldosterone antagonists (e.g., triamterene)
Spironolactone (Aldactone)
  • Aldosterone antagonist.
  • Used for acne in females because it blocks androgen hormones.
  • Can cause hormone imbalance.
  • Should not be used in the first trimester of pregnancy due to potential risk to a male fetus.
  • Aldosterone, androgens, and estrogen are all produced in the adrenal cortex
Triamterene
  • Non-aldosterone antagonist.
  • Directly inhibits the exchange of potassium and sodium in the distal nephron.
  • Does not cause significant diuresis.
  • Uses: Hypertension and edema; counteract potassium loss.
  • Adverse Effects: Hyperkalemia, leg cramps, and dizziness.

Hyperkalemia: Signs and Symptoms

  • Nausea
  • Slow, weak, irregular pulse
  • Sudden collapse
  • Irritability
  • Numbness
  • Muscle weakness
  • Diarrhea or abdominal cramping

Combination Diuretics

  • Example: Dyazide (Triamterene + Hydrochlorothiazide).
  • Combining diuretics can decrease the likelihood of hypokalemia.

Osmotic Diuretics

  • Prototype: Mannitol (Osmitrol).
  • Works in the proximal convoluted tubule.
  • Given IV.
  • Mechanism of Action: Creates an osmotic force within the lumen of the nephron, inhibiting passive reabsorption of water.
  • Uses: Renal failure, intracranial pressure, intraocular pressure.
  • Adverse Effects: Edema, may precipitate congestive heart failure and pulmonary edema in patients with heart disease, coma, hypotension.
  • Contraindications: Anuria, low blood volume, pulmonary edema, active intracranial bleed.
  • Filtered at the glomerulus and not reabsorbed.
  • Isosorbide is another osmotic diuretic.