Water constitutes approximately how much of total body weight?
50-60%
Average young adult male: 60%
Average young adult female: 50% (higher adipose tissue)
Highest percentage of TBW (Total body water) is found in what group?
Newborns (80% TBW)
This decreases to approximately 65% by 1 year of age and thereafter remains fairly constant.
Total Body Water (TBW) is relatively constant for an individual. It is primarily a reflection of?
Body fat. Estimates of percentage for TBW should be adjusted downward by approximately 10-20% for obese individuals, and upward by 10% for malnourished individuals.
What are the functional fluid compartments of Total Body Water?
Extracellular Water: 20% of body weight (1/3 of TBW)
- 5% Plasma
- 15% Interstitial Fluid
Intracellular Water: 40% of body weight (2/3 of TBW)
- Largest proportion in skeletal muscle mass
Normal chemical composition of the ECF?
Na+ (Sodium): Principal Cation
Cl- (Chloride) and HCO3- (Bicarbonate): Principal Anions
Normal composition of the ICF?
K+ (Potassium) and Mg+2 (Magnesium): Principal Cations
PO4^3- (Phosphate) SO4^-3 (Sulfate): Principal Anions
Proteins
How are sodium-containing fluids distributed in the ECF?
The administration of sodium-containing fluids expands the interstitial space by approximately three times as much as the plasma.
(For 1L of PNSS, 250mL will go to the intravascular space; 750mL will go to the interstitial space.)
How do you calculate for serum osmolality?
Calculated serum osmolality = 2Na + (glucose/18) + (BUN/2.8)
Normal serum osmolality?
The osmolality of intracellular and extra cellular fluids is maintained between 290 and 310 mOsm in each compartment.
Highest percentage of TBW (Total body water) is found in what group?
Newborns (80% TBW)
This decreases to approximately 65% by 1 year of age and thereafter remains fairly constant.
Total Body Water (TBW) is relatively constant for an individual. It is primarily a reflection of?
Body fat. Estimates of percentage for TBW should be adjusted downward by approximately 10-20% for obese individuals, and upward by 10% for malnourished individuals.
What are the functional fluid compartments of Total Body Water?
Extracellular Water: 20% of body weight (1/3 of TBW)
- 5% Plasma
- 15% Interstitial Fluid
Intracellular Water: 40% of body weight (2/3 of TBW)
- Largest proportion in skeletal muscle mass
Normal chemical composition of the ECF?
Na+ (Sodium): Principal Cation
Cl- (Chloride) and HCO3- (Bicarbonate): Principal Anions
Normal composition of the ICF?
K+ (Potassium) and Mg+2 (Magnesium): Principal Cations
PO4^3- (Phosphate) SO4^-3 (Sulfate): Principal Anions
Proteins
How are sodium-containing fluids distributed in the ECF?
The administration of sodium-containing fluids expands the interstitial space by approximately three times as much as the plasma.
(For 1L of PNSS, 250mL will go to the intravascular space; 750mL will go to the interstitial space.)
How do you calculate for serum osmolality?
Calculated serum osmolality = 2Na + (glucose/18) + (BUN/2.8)
Normal serum osmolality?
The osmolality of intracellular and extra cellular fluids is maintained between 290 and 310 mOsm in each compartment.
