The primary objective of this study is to compare the mean serum sodium at 48 hours following the initiation of therapy with either 0.45% NaCl/dextrose 5% or 0.9% NaCl/dextrose 5%, in children requiring maintenance IV fluid administration.

Hyponatremia, has become increasingly recognized as a cause of morbidity and mortality in hospitalized children. The main etiology of hyponatremia in these children has been attributed to the use of hypotonic maintenance IV fluids. The practice of providing IV solutions containing 20-30 mmol/L of Na is based on "physiological needs" proposed by Holliday and Segarin 1957, derived from studies of 61 adults and children. The presence of non-physiologic ADH secretion in the great majority of hospitalized children due to nausea, stress, pain, and surgical interventions, has confirmed that Holliday and Segar's recommendations are frequently inappropriately applied. To avoid the development of hyponatremia, it has been suggested that isotonic 0.9% NaCl/dextrose 5% should be the standard maintenance IV solution.

The routine use of an isotonic maintenance fluid solution has not yet been studied, and concerns exist regarding the potential for hypernatremia and salt and water overload. If isotonic solutions are to be recommended routinely, their overall safety, and specifically the occurrence of dysnatremias and volume overload, should be evaluated in a controlled prospective trial.

Inclusion Criteria:

• Aged 1 month to 18 years
• Anticipated hospitalization >48 hours
• Initial plasma Na between 135-145 mmol/L, with a management plan(determined by the responsible physician) to include IV fluids at > 80% of maintenance
• For children who have had an IV saline bolus, it must have been completed three or more hours prior to having baseline bloods
• Baseline bloods must be drawn within 3 hours of initial patient contact.

Exclusion Criteria:

• Diagnosed with, or clinically suspected to have, any of the following: dehydration/gastroenteritis, heart or liver failure, portal hypertension with ascites, metabolic disease, SIADH, diabetes insipidus or mellitus, hypertension, adrenal insufficiency, renal failure [creatinine>100 μmol/L (<3 years); >150 μmol/L (> 3 years)], nephritic or nephrotic syndrome, Kawasaki disease, Sickle cell disease if requiring hyperhydration.
• Clinically edematous
• On diuretic medications
• Plasma glucose is >15 mmol/L
• Require CCU admission
• Any patients requiring IV maintenance therapy having conditions/diseases not listed as excluded are eligible to be in this study