Intravenous maintenance fluid therapy (IV-MFT) is routinely used for hospitalized children with reduced oral intake in various clinical conditions to preserve extracellular volume [1]. Hypotonic fluids containing 30 to 50 mmol/L of sodium have been traditionally used for IV-MFT, which was based on daily requirements of water and electrolytes described by Holliday and Segar [2]. However, a number of literatures have described case series of deaths secondary to hyponatremia associated with the use of hypotonic fluids [3,4,5]. Because the Holliday–Segar formula was developed based on weight, energy expenditure, and physiologic losses in healthy children [2], it is obvious that the formula does not apply to all hospitalized children. Acutely ill children often have clinical symptoms such as fever, nausea, vomiting, seizure, and respiratory distress, all of which can cause non-osmotic anti-diuretic hormone (ADH) secretion, resulting in water retention and dilutional hyponatremia [6]. When children in these conditions receive electrolyte-free water such as hypotonic saline, they can develop hospital-acquired hyponatremia.

Many randomized controlled trials (RCTs) have been conducted to compare isotonic fluids and hypotonic fluids in IV-MFT, and most studies have described that hypotonic fluids have a higher risk of hospital-acquired hyponatremia [7,8,9]. Several systematic reviews and meta-analyses have been conducted, concluding that isotonic fluid would be a safer choice for IV-MFT [10,11,

An important issue remains the electrolyte concentration in the maintenance fluid solutions for newborns and infants in the first months of life. Well-designed studies are needed in this field.

Eventually, IV-MFT should be treated like any other drug and used with careful attention to all potential risks, including iatrogenic hyponatremia and volume overload.