Extracellular fluid (ECF)

(see also [Fluid compartments])

Functional ECF

• Water in bone and dense connective tissues, and water in transcellular compartment move more slowly and not considered in acute fluid shifts.
• Functional ECF = the rest of ECF (plasma + ISF)

Thus,

• ICF to Functional ECF = 55:27.5 = 2:1 (approx)

Typical electrolyte concentration in some transcellular fluids (mmol/L)

• Saliva
  * Na+ = 20-80
  * K+ = 10-20
  * Cl- = 20-40
  * HCO3- = 20-60
• Gastric juice
  * Na+ = 20-100
  * K+ = 5-10
  * Cl- = 120-160
  * HCO3- = 0
• Pancreatic juice
  * Na+ = 120
  * K+ = 5-10
  * Cl- = 10-60
  * HCO3- = 80-120
• Bile
  * Na+ = 150
  * K+ = 5-10
  * Cl- = 40-80
  * HCO3- = 20-40
• Ileal fluid
  * Na+ = 140
  * K+ = 5
  * Cl- = 105
  * HCO3- = 40
• Colonic fluid
  * Na+ = 140
  * K+ = 5
  * Cl- = 85
  * HCO3- = 60
• Sweat
  * Na+ = 65
  * K+ = 8
  * Cl- = 39
  * HCO3- = 16
• CSF
  * Na+ = 147
  * K+ = 3
  * Cl- = 113
  * HCO3- = 25