Sodium Bicarbonate

Normal ECF [Na] = 140mmol/L (x19L) = 2660mmol Na

Normal ECF [HCO3] = 24mmol/L (x19) = 456mmol HCO3

Therefore will have

• volume effects
• osmotic effects
• change [Na]
• change [HCO3

Increases [HCO3]

Normal ECF [HCO3] = 24mmol/L (x19) = 456mmol HCO3

Adding 100mmol HCO3 = 556mmol HCO3 = 29mmol/L

Extra HCO3 will be converted into CO2 and expired in approximately 30 seconds!

Increases [Na] ECF

Na will remain in ECF

Adding 100mmol Na = 2760mmol Na in 19.4L = 142mmol/L

→ Accounts for the volume & osmotic shifts

→ You have also just added 100mmol Na without any Chloride

→ If you are a Stewardite, you have just increased your SID

→ therefore altering the state of dissociation of Plasma H2O such that less plasma H2O is dissociated

→ because of that your pH goes up, you have alkalanised the plasma

 Osmotic effects & Volume Effects

Normal osmolality = 290 mOsm/L

∴ ECF osmolality = 290/L x19 = 5510 mOsm/L ECF

∴ ICF osmolality 290/L x 23 = 6670 mOsm/L ICF

adding 200mOsm to ECF = 5710 mOsm/L

New total osmolality = 5710 + 6670 = 12341 mOsm in 42L = 294mOsm/L

ECF 5710 osmoles/294 = 19.4L

∴ ECF expansion with 400ml water from increased osmolality

Osmolarity increases 1.3% \ stimulates osmoreceptors → ­ADH secretion from PPG