Neville et al, conducted a prospective randomized study involving 124 children aged 6 months to 15 years admitted for surgery. They received isotonic or hypotonic fluid at 100% or 50% maintenance rate. Plasma electrolytes, osmolality and ADH at induction of anesthesia were compared with values at 8 hours (T8), and 24 hours (T24) after surgery.Blood glucose and ketones were measured every 4 hours. Electrolytes and osmolality were measured in urine samples. The study showed that plasma sodium concentrations fell in both N/2 groups at T8 (100%: -1.5mmol/L, 50%: -1.9 mmol/L; [P < 0.01]) with hyponatremia more common than in the NS groups at T8 (30% vs 10%;[P = 0.02]) but not T24. Median plasma antidiuretic hormone concentration increased 2 to 4 fold during surgery (P <0.001) and only reattained levels at induction of anesthesia by T24 in the N/2 100% group. Two children on 100% developed syndrome of inappropriate ADH secretion (SIADH) (1NS). Fourteen children (23%; 7NS) on 50% maintenance were assessed as dehydrated. Dextrose content was increased in 18 for hypoglycemia or ketosis.