In: Anatomy and Physiology
0.9% saline( normal saline) is isotonic, meaning has the same concentration of sodium and other solutes as your body fluids.
Water is hypotonic , meaning concentration of dissolved solutes is less than that of your body fluid and cells.
Since water moves from an area of higher concentration ,an infusion of normal saline will not result in changes in fluids movement into or out of your blood stream and cells
Normal saline(0.9% saline) has an osmolality close to that of
plasma. Any solution that has less salt will be hypo-osmolar. Rapid
infusion of a hypo-osomolar solution can cause osmotically induced
water shift into the cells, and this can lead to detrimental
effects such as hemolysis. Addition of 5% dextrose ensures that the
infused solution will have an osmolality equal to or higher than
plasma regardless of the salt concentration.
A 5% dextrose solution provides at least some calories to a person
who might have no other nutritional intake and will reduce
catabolism.
The patient is with dehydration absolutely will have no energy so it is better to provide with 5% saline for both calories and dehydration