A normal child with MILD dehydration should be rehydrated orally.
A child with MODERATE dehydration is at risk for IV fluids.
This is where the use of ONDANSETRON is advised, as it can reduce the risk of further episodes of vomiting, the patient needing IV fluids and the risk of immediate admission to the hospital.
SEVERE dehydration patients need immediate resuscitation with rapid administration of isotonic fluids. SEVERE patients should not have an oral fluid challenge. They are very sick and obtunded and should be managed accordingly.