Effect of phototherapy on nitrogen and electrolyte levels and water balance in jaundiced preterm infants.

Twenty-four-hour metabolic balance studies were performed in ten jaundiced preterm infants, five light-treated (phototherapy) and five controls. Each of the light-treated infants was studied twice, once during phototherapy (period I) and once 48 hours after phototherapy (period II). Control infants were similarly studied during the corresponding days. Compared to period II and control infants, during period I the light-treated infants had less weight gain. Intestinal transit time was decreased by 50%. Fecal excretion of nitrogen, sodium, and potassium was increased. Stool water loss was increased twofold to threefold with a decrease in water balance. Unmeasured water loss was increased. These studies underscore the need for careful attention to fluid and caloric supplementation during phototherapy.