Maintenance intravenous (IV) fluids are used in children who cannot be fed enterally. Along with maintenance fluids, children may require concurrent replacement fluids if they have excessive ongoing losses, such as may occur with diarrhea, vomiting, or drainage from an enteral feeding tube. In addition, if dehydration is present, the patient also needs to receive deficit replacement .
Maintenance fluids are composed of a solution of water,
glucose, sodium, potassium, and chloride. This solution replaces electrolyte losses from the urine and stool, as well as water losses from the urine, stool, skin, and lungs. The glucose in maintenance fluids provides approximately 20% of normal caloric needs. This is enough to prevent the development of starvation ketoacidosis and diminishes the protein degradation that would occur if the patient received no calories. Maintenance fluids do not provide adequate calories, protein, fat, minerals, or vitamins. Patients should not remain on maintenance therapy indefinitely; parenteral nutrition should be used for children who cannot be fed enterally for more than a few days. Daily water losses are measurable (urine and stool) and not
measurable (insensible losses from the skin and lungs). Failure to replace these losses leads to a thirsty child and, ultimately,a dehydrated child.
.After calculation of water needs and electrolyte needs, children typically
receive D5 in Normal Saline plus 20 mEq/L of KCl as a maintenance solution. This assumes that there is no disease process present that would require an adjustment in either the volume or the electrolyte composition of maintenance fluids. Children with renal insufficiency may be hyperkalemic or unable to excrete potassium and may not tolerate 20 mEq/L of KCl. In children with complicated pathophysiologic derangements, it may be necessary to adjust the electrolyte composition and rate of maintenance fluids empirically based on electrolyte measurements and assessment of fluid balance

Ref: Nelson Essentials of Pediatric 9th edition 2023