Effect of phototherapy on neonatal fluid and electrolyte status

Three groups of "healthy' fullterm infants with hyperbilirubinaemia exposed to continuous phototherapy of different intensities, increased their oral intake of milk formula by 33%, 48% and 52% and 24, 48 and 72 h, respectively, irrespective of the intensity of exposure; this was significantly more than in the controls, who were swaddled. Serum osmolality and electrolyte values demonstrated no significant change from pre-phototherapy values, and were similar to those of the control group except for significantly raised potassium levels at 72 h in 2 of the 3 phototherapy groups. These raised values were, however, not dangerously high, and rapidly reverted to normal with cessation of phototherapy. The osmolality of the milk formula feeds was 272.4 +/- 8.2 (mean +/- SE) mmol/kg, potassium 27.8 +/- 1.4 mmol/l and sodium 16.0 +/- 0.8 mmol/l. Phototherapy even for 72 h does not significantly affect the fluid and electrolyte status of hyperbilirubinaemic infants fed with fairly high solute load milk formulas.