7. Volume and Osmolarity in Abnormal states

• What factors can cause changes in extracellular and intracellular volumes?

  Water ingestion, dehydration, fluid loss
• Why do osmolarities of intracellular and extracellular fluids remain equal?

  Water moves rapidly across cell membranes
• What happens to osmolarity when isotonic saline is added to extracellular fluid?

  Osmolarity remains unchanged
• What is the effect of adding a hypertonic solution to extracellular fluid?

  Increases extracellular osmolarity and decreases intracellular volume
• What occurs when a hypotonic solution is added to extracellular fluid?

  Extracellular osmolarity decreases, water moves into cells
• How do you calculate the total milliosmoles added from a 3.0% sodium chloride solution?

  1.0256 mole of sodium chloride is added
• What is the concentration of sodium chloride in a 3.0% solution?

  30 grams per liter
• How many osmoles are in 1 mole of sodium chloride?

  Approximately 2 osmoles
• What is the total milliosmoles in the body after osmotic equilibrium?

  13,811 milliosmoles
• How do you calculate the intracellular fluid volume after osmotic equilibrium?

  Divide total milliosmoles by concentration
• What is the volume of intracellular fluid after osmotic equilibrium?

  24.98 liters
• What is the volume of extracellular fluid after osmotic equilibrium?

  19.02 liters
• Why is a 5% glucose solution used for dehydration treatment?

  It is nearly isosmotic and prevents cell swelling
• What is the effect of adding 2 liters of hypertonic sodium chloride solution?

  Increases extracellular fluid volume by over 5 liters
• What are the basic principles for calculating fluid shifts and osmolarities?

  • Water moves rapidly across cell membranes
  • Cell membranes are impermeable to many solutes
• How can one calculate changes in fluid volumes and osmolarities in clinical problems?

  • Use principles of osmotic equilibrium
  • Apply calculations to fluid volume regulation