EFFECTIVE replacement of water and electrolyte in patients with diarrhea should
be based on exact knowledge of changes in composition of body fluids. Measurements
of the concentrations of water and electrolyte in serum can only reveal the concentrations
in serum and extracellular fluids, but cannot define the changes in volume of
extracellular fluids nor the changes in volume or composition of the fluid within the
cells. A first approximation of the changes in composition of extracellular and intracellular
fluids may be obtained by estimating the balances of water, nitrogen, chloride,
sodium, potassium, phosphorus and calcium occurring from the onset of treatment until
apparent recovery. The balances which are obtained by subtracting the losses in urine and
stools from the intake must be corrected for the loss of water and electrolyte from the
lungs and skin. The loss of water from the lungs and skin can be measured quite closely
and although the losses of electrolyte from the skin offer more difficulties of estimation, a
reasonable approximation can be achieved. If the composition of the body is normal at
the time of apparent recovery, the balance of water and electrolyte represents quite accurately
the deficits of water and electrolyte which were present at the onset of the balance
study. Knowledge of the relation of tissue nitrogen to cellular potassium and phosphorus
and the relation of bone calcium to bone phosphorus permits the differentiation
of the changes accompanying starvation from the loss due to dehydration per se.
The present study presents data and concepts derived from metabolic balances on seven