AVP and Hyponatremia: There is a prevalent view that the administration of hypotonic fluid therapy is associated with the occurrence of hyponatremia in patients with high circulating plasma levels of antidiuretic hormone arginine-vasopressin (AVP).4 Consequently, the prescription of hypotonic fluid therapy to most hospitalized children is discouraged, particularly in the post-operative and medical acute care setting.1 As such, the choice and volume of optimal fluid therapy required for adequate fluid and electrolyte balance continues to challenge physicians.5,6