Final answer:
Hypotonic fluid should not be used with a brain injury due to worsening brain edema.
Step-by-step explanation:
When dealing with a brain injury and brain edema, there are certain fluids that should be avoided as they can worsen the condition. The fluid that should not be used is hypotonic fluid. Hypotonic fluids have lower concentrations of solutes compared to the fluids inside the body. When administered, hypotonic fluids can draw water molecules into brain cells, causing them to swell and exacerbating brain edema.