Fluid therapy preserves the normal volume and composition of body fluids and, if needed, corrects any existing abnormalities. In children, the most common clinical abnormality requiring fluid therapy is hypovolemia, primarily due to vomiting and diarrhea from gastroenteritis.
Thus, it is clinically useful to divide fluid therapy into two potential components: provision of volume for homeostatic needs (maintenance therapy), and provision of fluid for deficit requirements (repletion therapy).
●Maintenance therapy replaces the ongoing losses of water and electrolytes occurring via normal physiologic processes.
●Repletion therapy replaces the water and electrolyte deficits that have accrued via some perturbation in normal processes. Repletion returns the patient to a normal volume and electrolyte status. Thus, in a patient who is hypovolemic, fluid therapy will include both repletion and maintenance therapy.
Maintenance fluid therapy, including alterations in maintenance requirements, will be reviewed here. Assessment of hypovolemia and treatment of dehydration are discussed elsewhere. (See "Clinical assessment and diagnosis of hypovolemia (dehydration) in children" and "Treatment of hypovolemia (dehydration) in children".)