What is the rapid-infusion dose for hypertonic crystalloids in horses?

• A. 2 ml/kg
• B. 4 ml/kg
• C. 6 ml/kg
• D. 8 ml/kg

Answer: (B)

Hypertonic crystalloids work by creating an osmotic gradient that pulls fluid from the interstitial space into the blood vessels, giving rapid plasma-volume expansion with a relatively small fluid volume. In horses, the standard rapid-infusion dose is 4 ml/kg of a hypertonic solution (typically around 7.5% NaCl) given over a short period. This small-volume bolus can quickly improve perfusion in shock, and is usually followed by isotonic crystalloids to sustain the volume. Doses much lower than this may not achieve the desired rapid effect, while higher doses increase the risk of complications such as hypernatremia, osmotic shifts, and cardiovascular or neurologic side effects.