Isotonic, Hypotonic, and Hypertonic Solutions

Key Concepts

• Understand cell behavior under different solution conditions.
• Identify types of fluids used in medical settings for these conditions.
• Key concepts for exams and NCLEX.

Resources

• Visit registernurseRN.com for a quiz and additional resources.

Cell Basics and Osmosis

• Intracellular: Inside the cell (organelles, electrolytes).
• Extracellular: Outside the cell (fluid, electrolytes).
• Osmosis: Movement of water from less concentrated to more concentrated area through a semi-permeable membrane.
• Sodium & Water: Water follows sodium; used as a mnemonic for fluid shifts.

Isotonic Solutions

• Definition: Equal concentration inside and outside the cell.
• Purpose: Increase extracellular fluid volume without causing cell swelling or shrinking.
• Common Isotonic Fluids:
  • 0.9% Saline
  • Dextrose 5% in Water (D5W) - Isotonic before administration, becomes hypotonic after.
  • Lactated Ringers (LR)
  • 5% Dextrose in 0.225% Saline
• Usage:
  • Blood loss
  • Dehydration from vomiting, diarrhea, or surgery

Hypotonic Solutions

• Definition: Lower concentration outside the cell than inside.
• Effect: Fluid moves into cells, causing them to swell and potentially lyse.
• Risks: Depletes circulatory fluid, causing hypovolemia.
• Common Hypotonic Fluids:
  • 0.45% Saline (half normal saline)
  • 0.225% Saline (1/4 saline)
  • 0.33% Saline (1/3 saline)
  • D5W after metabolism
• Usage: Dehydrated cells such as in diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemia.
• Contraindications:
  • Increased intracranial pressure
  • Burns or trauma (risk of hypovolemia)

Hypertonic Solutions

• Definition: Higher concentration outside the cell than inside.
• Effect: Fluid moves out of cells, causing them to shrink.
• Common Hypertonic Fluids:
  • 3% Saline
  • 5% Saline
  • 10% Dextrose in Water
  • 5% Dextrose in 0.9% Saline
  • 5% Dextrose in 0.45% Saline
  • 5% Dextrose in LR
• Usage:
  • Intensive care settings, via central line due to vein irritation.
  • Conditions such as cerebral edema, hyponatremia.
• Risks:
  • Fluid overload and pulmonary edema

Study Tips

• Pay attention to fluid concentrations and their corresponding uses.
• Remember the number of types for each solution type: hypotonic (3), isotonic (4), hypertonic (6).
• Review related videos and quizzes on fluid and electrolytes.