Fluid therapy is aimed to compensate for fasting which is required for surgery, to meet the ongoing fluid losses and to maintain electrolyte balance during surgery. Fluid deficit of a healthy child who is not fed parenterally may be estimated by multiplying hourly maintenance requirement for fluid by number of hours since the child's last oral intake (50% of deficit + maintenance in first hour, 25% of deficit + maintenance in second hour). Maintenance fluid therapy represents the volume of fluids and amount of electrolytes and glucose needed to replace anticipated physiological losses from breath, sweat and urine and to prevent hypoglycaemia. This maintains homeostasis while an individual is unable to control his/her own fluid intake while being operated. Replacement fluid represents the volume of fluid given to replace the volume lost during the surgical procedure. For 50 years, this therapy was based on Holliday and Segar's formula.