In children with cardiac disease receiving loop diuretics, enteral sodium chloride supplementation does not result in a measurable increase in body weight despite an increase in fluid balance, indicating that body weight is an insensitive marker of fluid retention in this population.

When extra salt is given to children with heart disease on diuretics, their blood sodium levels rise, which tells the kidneys to stop holding onto so much salt and water. This makes the diuretic medicine work better, so more fluid leaves the body through urine. But because the child is also taking in more salt and water from food, the extra fluid coming out is exactly matched by the extra fluid going in. The total fluid in the body goes up, but since the body isn't storing extra water as swelling or in tissues, the weight stays the same.