Hydrochlorothiazide and spironolactone are diuretics that are commonly in preterm infants with bronchopulmonary dysplasia (BPD). Hyponatremia (low blood salt) is a common side effect. It is uncertain whether the best way to treat the hyponatremia is by oral salt supplementation or restricting fluid intake. Our hypothesis is that fluid restricted infants will be better able to preserve the beneficial effects of diuretics on the lungs. The study will include very low birth weight infants (VLBW) 400-1500g from Hermann Memorial Children's Hospital NICU or LBJ General Hospital NICU with BPD. They will be enrolled and randomly assigned to either the salt supplementation group or the fluid restriction group once they become hyponatremic (defined as serum Na <130). The study intervention will take place for four weeks. The primary outcome will be assessed by comparing the patient's initial oxygen and breathing machine requirements with those at the end of the four-week study period.