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Key Concepts of Fluids and Electrolytes

Apr 25, 2025

Lecture Notes on Fluids and Electrolytes

Homeostasis and Body Fluid Compartments

  • Homeostasis: Balance and normal limits within body systems.
  • Intracellular Fluid (ICF): Inside cells, essential for cell function/metabolism; contains solutes like potassium and glucose.
  • Extracellular Fluid (ECF): Outside cells, carries water, electrolytes (sodium, chloride), and oxygen to cells, removes waste.
    • Interstitial Fluid: Space between cells, excess fluid here causes edema.
    • Intravascular Fluid: Plasma within blood, transports blood cells.
    • Transcellular Fluid: Specialized fluids (e.g., cerebrospinal fluid).
  • Third Spacing: Fluid trapped in non-functional areas (e.g., pericardial effusion).

Types of Solutions

  • Isotonic Solutions: Used for volume expansion, does not move fluid in/out of cells.
  • Hypertonic Solutions: Pull fluids from cells, causing cells to shrink.
  • Hypotonic Solutions: Move fluids into cells, causing cells to swell.

Fluid Intake and Output

  • Intake: 2700-3700 mL/day, includes fluids that enter the body.
  • Output: Urine (1400-1500 mL/day), sensible loss through skin and lungs, feces.

Major Electrolytes

  • Sodium (Na+): Regulates fluid volume, muscle contraction, nerve impulses.
  • Potassium (K+): Key in cellular metabolism, cardiac rhythm regulation.
  • Calcium (Ca2+): Bone health, neuromuscular and cardiac function.
  • Magnesium (Mg2+): Biochemical reactions, nerve muscle activity.
  • Chloride (Cl-): Works with sodium for fluid balance.
  • Phosphate: Bone health, inverse relationship with calcium.

Electrolyte Relationships

  • Inverse and direct relationships between electrolytes (e.g., sodium and potassium).

pH Balance

  • Acceptable pH Range: 7.35-7.45, crucial for body function.

Laboratory Studies

  • CBC: Complete Blood Count.
  • Serum Electrolytes: Monitoring of key electrolytes.
  • Urinalysis: Assesses kidney function, fluid balance.
  • Increases/decreases in laboratory values indicate fluid balance issues.

Diuretics

  • Loop Diuretics: Increase urine output, used for edema.
  • Thiazide Diuretics: Treat high blood pressure, increase calcium levels.
  • Potassium-Sparing Diuretics: Preserve potassium while promoting diuresis.

Fluid Imbalances

  • Fluid Volume Deficit (Dehydration): Loss of fluid, causing dry skin, decreased urine output.
  • Fluid Volume Excess (Overhydration): Excess fluid, causing elevated BP, edema.

Management of Electrolyte Imbalances

  • Hyponatremia: Low sodium, treat with sodium intake.
  • Hypernatremia: High sodium, manage with water intake.
  • Hypokalemia: Low potassium, supplement potassium intake.
  • Hyperkalemia: High potassium, avoid potassium-rich foods.

Dietary Recommendations

  • Limit sodium intake, increase potassium and calcium.
  • Encourage reading food labels, especially for sodium content.

Parenteral Replacement

  • IV Therapy: Used when oral intake isn't sufficient.

General Interventions

  • Monitor vital signs, intake/output, daily weights.
  • Educate patients on dietary changes and medication implications.

Clinical Prioritization

  • Recognize which lab values need immediate attention based on normal ranges (e.g., elevated potassium levels).

Problem-Solving Scenarios

  • Example scenarios involve adjusting medications based on fluid/electrolyte balance.

These notes should provide a comprehensive overview of the key concepts discussed during the lecture on fluids and electrolytes. The information covers fluid compartments, types of solutions, major electrolytes, imbalances, diuretics, and management strategies. Make sure to review and understand the relationships between different electrolytes and the implications of their imbalances.

Full transcript