Bronchiolitis is the most common reason for hospitalization in infants in the first year of life. 1 There are no proven therapies to treat this common condition, with the mainstay of therapy being supportive care with intravenous fluid (IVF) and supplemental oxygen when needed. Hyponatremia is often encountered in children with bronchiolitis and has been associated with more severe disease and worse outcomes, and neurologic complications have been reported. 2-6 Explicit recommendations for IVF therapy in children with bronchiolitis are lacking in both consensus guidelines and authoritative reviews. [7][8][9] The historical approach to providing maintenance fluids in children has been to administer hypotonic IVF with a sodium concentration similar to that found in breast and cow milk (30 mEq/L). 10 In 2003, we began recommending 0.9% saline in 5% dextrose for the prevention of hospital-acquired hyponatremia, based on numerous reports of iatrogenic deaths related to hypotonic fluids and the incidence of syndrome of inappropriate secretion of antidiuretic hormone (SIADH)-like states in acutely ill children. 11 A 0.9% saline solution has a sodium concentration (154 mEq/L), which is isotonic to the aqueous phase of plasma water. 12 Since our initial recommendation, there have been .15 randomized, prospective trials involving .2000 children confirming that hypotonic maintenance fluids result in hospital-acquired hyponatremia and that isotonic fluids decrease the incidence of hyponatremia without associated complications. 13-16 It would be reasonable to conclude that hypotonic fluids should be avoided in infants with bronchiolitis in favor of 0.9% saline, because bronchiolitis is associated with SIADH. 2,17-20 However, surprisingly few studies have examined IVF prescribing practices in bronchiolitis or the impact of the sodium composition on the development of hyponatremia and how these fluids may affect outcome. 21In this issue of Hospital Pediatrics, Shein et al evaluated how the sodium composition of IVF may affect the development of hyponatremia and outcome in children with bronchiolitis. 22 They evaluated a large retrospective cohort of .1500 children, comparing those who received maintenance IVF with a sodium concentration ,70 mEq/L with those .70 mEq/L. They found that children with hyponatremia had an increased length of stay and higher need for mechanical ventilation. Those who received a more hypotonic fluid, ,70 mEq/L, had both an increased length of stay and a significantly increased incidence of hyponatremia. These data demonstrated the deleterious effects that both hyponatremia and the administration of hypotonic IVF have on children with bronchiolitis. One area of this study that we would like to draw particular attention to is the ongoing pervasive practice of administering hypotonic maintenance IVF, even to the sickest children who are in the ICU on mechanical ventilation.