Body Fluid Compartments - Muster

Question 1

What are the primary solutes of the plasma?

Answer 1

• Na⁺
• Cl^-
• HCO₃^-
• Urea
• Weak organic acids ^-
• Glucose
• K⁺
• Ca²⁺
• Mg⁺
• H₂PO₄^-
• Albumin

Question 2

What are the primary solutes of the Intracellular Compartment?

Answer 2

• K⁺
• PO₄^-
• Cl^-
• Protein^-
• Na⁺
• Mg⁺
• SO₄^-

Question 3

What is the total amount of water in the body (estimate)?

Answer 3

Total Body Water ~60%

70 kg person → 42 L

_{(Men ~60%, Women ~50%)}

Question 4

What is the total extracellular fluid volume (estimate)?

Answer 4

~1/3 of Total Body Water

70 kg person → 42 L Total → 14 L Extracellular Fluid

Question 5

What is the total interstitial fluid volume (estimate)?

Answer 5

~3/4 of Extracellular Fluid

70 kg person → 42 L Total → 14 L Extracellular →

10.5 L Interstitial

Question 6

What is the total intracellular fluid volume based on gender?

Answer 6

• Female
  
  • 50% of weight = total body fluid
  • extracellular fluid ~1/3 of total body fluid
  • interstitial is ~3/4 of extracellular fluid
• Male
  
  • 60% of weight = total body fluid
  • extracellular fluid ~1/3 of total body fluid
  • interstitial is ~3/4 of extracelluar fluid

Question 7

What is the Gibbs Donnan Effect across both capillary wall?

Answer 7

• Capillary wall = semi-permeable membrane
  
  • freely permeable to small ions
  • not permeable to large anionic proteins
  • b/t plasma space and capillary

Question 8

What happens to the movement of solute and water between the intracellular and extracellular compartments based on INCREASES in extracellular osmolality?

Answer 8

• Increased extracellular osmolality:
  
  • Increase serum [Na⁺] →
  • H₂O enters extracellular space to compensate for increased extracellular osmolality
    
    • intracellular space shrinks
    • extracellular space expands

Question 9

What happens to the movement of solute and water between the intracellular and extracellular compartments based on DECREASES in extracellular osmolality?

Answer 9

• Decreased extracellular osmolality:
  
  • Decreased serum [Na⁺] →
  • H₂O leaves extracellular space to compensate for decreased osmolality
    
    • extracellular space shrinks
    • intracellular space expands

Question 10

How does normal saline distribute throughout the fluid compartments of the body?

Answer 10

• Normal Saline = isosmotic (308) and isotonic (won’t change volume)
  
  • no change in intravascular/plasma [Na⁺]
  • no change in [H₂O]
  • will distribute between intravascular and interstitial spaces only
    
    • Na⁺/K⁺ ATPase pumps Na⁺ out of intracellular space, thus preventing distribution of NS in intracellular space
    • H₂O follows Na⁺

Question 11

How does 1/2 normal saline distribute throughout the fluid compartments of the body?

Answer 11

• 1/2 Normal Saline = hypotonic, hypoosmotic (145)
  
  • 1/2 will distribute proportionately to all compartments according to the volume of the compartments (like H20)
  • 1/2 will distribute proportionately to interstitial and intervascular (like NS)

Question 12

How does D5W distribute throughout the fluid compartments of the body?

Answer 12

• D5W = (5% Dextrose = 5 grams/100 ml water): isosmotic
  
  • increased [H₂O] in plasma → moves through aquaporins
  • increased [H₂O] in interstitial → moves through aquaporins
  • increased [H₂O] in ICF
  • [H₂O] will distribute proportionately according to the volume of the compartments.
  • Glucose gets metabolized (removed)

Question 13

What is the difference between volume depletion and dehydration?

Answer 13

• Depletion:
  
  • Extracellular volume loss from any cause (most often loss of salt and water)
  • Extracellular loss of NaCl and H₂O
• Dehydration:
  
  • Presence of hypernatremia due to pure water loss

Question 14

What situations require NS?

Answer 14

• Diabetic ketoacidosis
• Sepsis
• Secretory diarrhea

Question 15

What situations require 1/2 NS?

Answer 15

• Sweat loss
  
  • athletes
• Hospitalization
  
  • febrile states

Question 16

What situations require D5W?

Answer 16

• Diabetic insipidus
  
  • nephrogenic or central
• Severe hypoglycemia