Sodium chloride in water dissociates to provide sodium (Na+) and chloride (Cl‾) ions. These ions are normal constituents of the body fluids (principally extracellular) and are essential for maintaining electrolyte balance.
The distribution and excretion of sodium (Na+) and chloride (Cl‾) are largely under the control of the kidney which maintains a balance between intake and output.
The small volume of fluid and amount of sodium chloride provided by 0.9% Sodium Chloride Injection, USP when used only as an isotonic vehicle for parenteral injection of drugs, is unlikely to exert a significant effect on fluid and electrolyte balance except possibly in neonates and very small infants.
Water is an essential constituent of all body tissues and accounts for approximately 70% of total body weight. Average normal adult daily requirement ranges from two to three liters (1.0 to 1.5 liters each for insensible water loss by perspiration and urine production).
Water balance is maintained by various regulatory mechanisms. Water distribution depends primarily on the concentration of electrolytes in the body compartments and sodium (Na+) plays a major role in maintaining physiologic equilibrium.