Question

When a patient comes to a hospital with severe dehydration, doctors will give

them an IV filled with a salt-water solution called saline, which is isotonic with
the body's blood cells.
Why is the patient not given pure water?

Answer 1

Dehydrated patients are given isotonic saline solutions instead of pure water to prevent cell swelling or lysis. Isotonic solutions have the same solute concentration as blood, maintaining osmotic pressure and preventing damage to the cells.

Step-by-step explanation:

Pure water is not given to a dehydrated patient because it is hypotonic with respect to the body's cells. Using a hypotonic solution could cause water to move into the cells, leading to swelling and potentially cell lysis. Instead, a physiological solution that is isotonic to blood, such as saline, is used.

An isotonic saline solution has the same concentration of solutes as the blood, which prevents the red blood cells from swelling or shrinking. An isotonic solution keeps the osmotic pressure across cell membranes stable, preventing damage to the cells. In cases where a saline solution is not suitable, other isotonic solutions like lactated Ringer's solution may be used.

If a patient is incorrectly given a solution that is not isotonic, there can be adverse effects including the destruction of red blood cells, as they may burst (hemolysis) if the solution is too hypotonic or shrink if it is too hypertonic. Therefore, it is vital that the correct isotonic solution is administered for the safe correction of dehydration.

Answer 2

The red blood cells could burst.

Step-by-step explanation:

If they are given pure water, the IV fluid will be hypotonic to the blood cells. That means water will end the red blood cells by osmosis, from a high concentration outside to a lower concentration inside.

This will result in the red blood cells becoming swollen and even potential bursting.