I guess it should be noted that you are talking about patients, not normal people at home. The daily amount of salt is recommended by organizations such as the WHO
(which has already made a few mistakes), but there is supposed to be a maximum, to avoid health problems such as hypertension.
Anyway, when a person is injected with a bag of saline solution, it is supposed to regulate hydration, electrolyte quantity, because it is understood that he/she
has had a deficit in this sense, due to an accident, fasting before an operation or a test... etc.