Estimate fluid requirements for a patient with mild to moderate dehydration by calculating the fluid deficit, which is typically 50 ml/kg for children, and add maintenance fluids as per guidelines NICE CG84.
Administer 50 ml/kg for fluid deficit replacement over 4 hours, along with ongoing maintenance fluids, and monitor the patient's clinical response regularly NICE CG84.
Use oral rehydration solution (ORS) with low osmolarity (240–250 mOsm/l) for rehydration, giving it frequently and in small amounts, and consider nasogastric administration if oral intake is insufficient NICE CG84.
In cases requiring intravenous therapy, use isotonic solutions such as 0.9% sodium chloride, and add 50 ml/kg for fluid deficit if no shock is present, monitoring electrolytes and clinical status NICE NG29,NICE CG84.