o
Dehydration is a decrease in ECF volume due to loss of H2O
and solutes such as Na+.
o
In isoosmotic dehydration loss of H2O is equal to the
loss of solutes.
o
Loss of isotonic fluid from plasma causes a loss of fluid from
interstitium to plasma to maintain hydrostatic balance between the
compartments.
o
But there is no change in the osmolality in the ECF compartment
because the fluid lost is isotonic.
o
Thus there is no shift of fluid into or out of ICF because there
is no change in ECF osmolality.
