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Questions and Answers
What percentage of total body water (TBW) does the intracellular fluid (ICF) constitute in adults?
What percentage of total body water (TBW) does the intracellular fluid (ICF) constitute in adults?
- 40% (correct)
- 50%
- 60%
- 20%
What is the approximate total water loss per day from the respiratory tract?
What is the approximate total water loss per day from the respiratory tract?
- 100 ml
- 1400 ml
- 2100 ml
- 700 ml (correct)
Which of the following is NOT a source of water input in the body?
Which of the following is NOT a source of water input in the body?
- Metabolic processes
- Urine (correct)
- Food water
- Drinking
What is the approximate percentage of total body water (TBW) in female adults?
What is the approximate percentage of total body water (TBW) in female adults?
Which of the following is a characteristic of the intracellular fluid (ICF)?
Which of the following is a characteristic of the intracellular fluid (ICF)?
Which type of solution has the same osmotic concentration as plasma?
Which type of solution has the same osmotic concentration as plasma?
What happens to blood cells when a hypertonic solution is administered?
What happens to blood cells when a hypertonic solution is administered?
What would be the effect of administering a hypotonic solution?
What would be the effect of administering a hypotonic solution?
How do isotonic solutions affect blood cell volume?
How do isotonic solutions affect blood cell volume?
What is the purpose of using clinically used solutions that are isotonic?
What is the purpose of using clinically used solutions that are isotonic?
Which solution is used in cases of salt and water depletion such as vomiting or diarrhea?
Which solution is used in cases of salt and water depletion such as vomiting or diarrhea?
Which indicator is commonly used for measuring plasma?
Which indicator is commonly used for measuring plasma?
What does 'Osmolality' refer to in the context of body fluids?
What does 'Osmolality' refer to in the context of body fluids?
What is the unit for expressing concentration in millimolar?
What is the unit for expressing concentration in millimolar?
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Study Notes
Osmosis and Osmotic Pressure
- Osmosis: diffusion of water or solvents through a semipermeable membrane from a solution with lower solute concentration to a solution with higher solute concentration.
- Osmotic pressure: minimum pressure that prevents osmosis when applied to the side with higher solute concentration.
Types of Solutions
- Isotonic solution: same osmotic concentration as plasma, administration doesn't affect blood cell volume.
- Hypertonic solution: higher osmotic concentration than plasma, administration increases concentration and shrinks blood cells.
- Hypotonic solution: lower osmotic concentration than plasma, administration decreases concentration and swells blood cells.
Clinically Used Solutions
- Examples: NaCl 0.9% (Saline) used for salt and water depletion, e.g., vomiting, diarrhea, mild bleeding, or hypotension.
Body Fluids and Water
- Total body water (TBW): approximately 75% of body mass in infants, 60% in adults, and 50-55% in females.
- Water balance: water input = water output.
- Water input: drinking, food water, and metabolic processes.
- Water loss: urine, feces, insensible water loss, and sensible water loss.
Fluid Compartments
- Intracellular fluid (ICF): 40% of TBW, stable and important for maintaining osmolality.
- Extracellular fluid (ECF): 20% of TBW, subdivided into plasma and interstitial space.
Measurement of Fluid Compartments
- Indicator-dilution technique (Fick's principle) used to measure fluid compartments.
- Volume of distribution (Vd) calculated using the indicator-dilution technique.
- Examples of indicators: deuterated water for TBW measurement, Evans blue dye for plasma measurement.
Characteristics of Indicators
- Can distribute only to the compartment being measured.
- Not toxic.
- Not allergic.
- Easy to measure.
- Does not affect body water distribution.
Parameters for Expressing Fluid Composition
- Gram molecular weight (GMW): number of grams/mole of a substance.
- Molality: moles of solute per kilogram of solvent.
- Molarity (M): moles of solute per liter of solvent.
- Osmoles: MW in grams/number of freely moving particles in solution.
- Osmolality: number of osmoles per kilogram of solvent.
- Osmolarity: number of osmoles per liter of solvent.
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