This randomized controlled trial compared isotonic and hypotonic intravenous fluids in children ages 29 days to 18 years admitted to pediatric intensive care. The study aimed to determine if isotonic fluids prevent hyponatremia and reduce adverse events. Patients receiving isotonic fluids had a lower rate of hyponatremia at 24 hours (5.1%) compared to those receiving hypotonic fluids (20.6%). No other adverse events differed between groups. The study demonstrates that isotonic fluids may prevent iatrogenic hyponatremia without increasing side effects.