Valadaoa et al, conducted a randomized controlled trial involving 57 children aged 1 to 14 years with acute appendicitis and eligible for appendectomy. They were randomized to receive intravenous isotonic or hypotonic maintenance solutions. Samples were collected for measuring electrolytes, urea, creatinine at the start of the infusion, 24 hours and 48 hours after surgery and then analysed. The primary end point of the study was serum sodium levels during the intervention and at the end of 48 hours of the protocol. At admission, 49% patients had moderate hyponatremia (Na=130-135 meq/L) and 51% had normal sodium (Na >136 mEq/L). After 24 hours, 12 patients had hyponatremia of whom 7 had received hypotonic solution. After 48 hours, 17 children had hyponatremia of whom ten had received hypotonic solution. Between the initial Na and final Na levels, there was an increase of 0.9 mEq/L sodium in the isotonic group and of 0.4 mEq/L sodium in hypotonic group. In the group of eight patients with normal initial sodium (>136 mEq/L) and low final sodium (<135 mEq/L) three had received isotonic and five had received hypotonic saline solution with an initial variation of 136 to 140 mEq/L and of 132 to 135 meq/l at 48 h. In the group admitted with low sodium (130-135 mEq/L), nine children remained hyponatremic (132-135 mEq/L) at the end, of whom four had received isotonic solution and five hypotonic solution. Of the 15 patients who had initial hyponatremia (130-135 mEq/L) and normal Na at 48 h (136-140 meq/l) seven received isotonic solution and eight hypotonic solution.