What type of IV fluid is contraindicated in head injury patients?

Hypotonic solutions are contraindicated in head injury patients primarily because their administration can lead to cerebral edema. When hypotonic fluids are infused, they cause a fluid shift into the cells—this includes brain cells—resulting in increased intracellular volume. In patients with head injuries, the risk of cerebral edema is already elevated due to potential hemorrhage, inflammation, or other traumatic factors affecting the brain. The introduction of hypotonic fluids can exacerbate these conditions, potentially leading to increased intracranial pressure (ICP) and worsening the patient's neurological status.

In contrast, isotonic solutions typically maintain stable osmotic balance and are generally safe for use in head injury patients. Hypertonic solutions can be used judiciously in specific clinical scenarios to reduce ICP by drawing fluid out of cells; however, their administration must be carefully monitored. Colloid solutions can also be used to maintain intravascular volume, but they do not carry the same risks regarding cellular fluid shifts as hypotonic solutions do. Hence, the use of hypotonic solutions is considered inappropriate in this specific context.