Fluid and electrolyte balance in children

Fluid management in the perioperative period is divided into replacing the preoperative fluid deficit, ongoing maintenance requirements and replacement of intraoperative losses, continuing into the postoperative period. For elective patients the deficit before surgery should be minimal because oral fluids may be safely given until 2 hours before surgery. For the emergency patient, the degree of dehydration must be assessed and corrected, along with any electrolyte disturbance. During surgery we need to give maintenance fluid to replace insensible and obligatory losses, along with replacing blood loss and loss of fluid into the third space due to the trauma of surgery. The maintenance fluid we use needs to have an appropriate dextrose and electrolyte content to maintain homeostasis. During surgery, the stress response will maintain normoglycaemia in all ages of child, and dextrose free or low concentration dextrose solutions should be used to avoid hyperglycaemia. The commonest electrolyte disturbance in the postoperative period is hyponatraemia, usually as a result of inappropriate antidiuretic hormone secretion, often in combination with the use of hypotonic solutions with a low sodium concentration. Diagnosis and correction of various electrolyte disturbances are discussed.