Normal saline is a solution of sodium chloride (NaCl) in water, and typically contains 0.9% NaCl by weight. A hypertonic solution is one that has a higher concentration of solutes (such as NaCl) than the cells that are surrounded by it. By comparison, a hypotonic solution has a lower concentration of solutes than the cells.

In the case of normal saline with 20 percent kcl, the concentration of kcl is much higher than the concentration of kcl in the cells, so the solution is hypertonic. This means that the cells will lose water to the solution by osmosis, causing them to shrink.