Coulthard proposes that 0.18% saline should be the maintenance fluid of choice in children and that an intravenous fluid with a sodium composition of 0.45% saline or higher will lead to more cases of hypernatraemia.1 His arguments are based primarily on two false premises: (i) that the syndrome of inappropriate antidiuretic hormone secretion (SIADH) is extremely rare and (ii) that renal concentrating defects are common. In 2003, we proposed the use of 0.9% saline as a maintenance parenteral fluid for the prevention of hospital-acquired hyponatraemia, as hypotonic fluids were associated with numerous cases of death and neurological injury from hyponatraemic encephalopathy …