Which type of fluid should not be administered subcutaneously?

Hypertonic fluids should not be administered subcutaneously because they can draw water out of the surrounding tissues and into the bloodstream, leading to potential cellular dehydration and local tissue irritation. Hypertonic solutions have a higher osmolarity than the body’s cells, which can cause an osmotic gradient that is harmful when given in subcutaneous spaces. This type of fluid is typically used intravenously to quickly expand plasma volume in cases of hypovolemia, but their use in subcutaneous administration is contraindicated due to the adverse effects on tissue hydration and integrity.

In contrast, isotonic fluids are compatible for subcutaneous administration because their osmolarity is similar to that of body fluids, leading to less risk of irritating the tissue. Hypotonic fluids are also administered carefully, but they can be used subcutaneously; however, they are less common because they can cause cell swelling. Balanced fluids are designed to maintain electrolyte balance and can typically be administered subcutaneously without the risks associated with hypertonic solutions.