Prehydration

Prehydration is the practice of administering intravenous or oral fluids before a planned medical procedure or event to optimize hydration status and hemodynamic stability.

In surgical and anesthesia care, prehydration often involves isotonic crystalloids such as normal saline or lactated Ringer's solution given before or at the start of anesthesia to prevent intraoperative hypotension, maintain renal perfusion, and reduce postoperative complications. Fluids may be given as a preload or coload strategy, and in some protocols oral or carbohydrate drinks are allowed to ensure hydration and reduce thirst.

Prehydration is also used before imaging studies with iodinated contrast to lower the risk of contrast-induced nephropathy by preserving renal perfusion. In obstetric anesthesia, preloading with isotonic fluids before spinal anesthesia can reduce the incidence of maternal hypotension.

In sports medicine and athletics, prehydration refers to consuming fluids and electrolytes before exercise, especially in hot or prolonged events, to improve baseline hydration and performance.

Benefits and evidence vary by context; some studies show reduced hypotension, better urine output, and fewer complications, while others show limited or no effect. Decisions depend on patient risk factors and procedure type. Risks include fluid overload, edema, electrolyte disturbances, and complications in patients with heart, lung, or kidney disease. Crystalloids are generally preferred over hypotonic or dextrose-containing solutions in perioperative settings.