The physiological saline is made from 0.9% NaCl solution. That means the ionic composition of the solution would be Na and Cl with 308 mOsmol/L. The osmolality of the solution is near blood osmolality so it can be called isotonic. The isotonic solution will not induce osmosis so they will not hurt the cells. Saline ion also easily removed so it will be safe to administer a high amount of the solution, unlike solution with dangerous ion like potassium. That is why the physiological saline is used when fluid resuscitation.
