PICU Fluid Therapy in Hyponatremia and Hypernatremia

Fluid Therapy in Hyponatremia and Hypernatremia Hyponatremia, defined as a serum sodium concentration below ۱۳۵ mmol/L, and hypernatremia, defined as levels above ۱۴۵ mmol/L, represent two critical disorders of water and electrolyte balance in pediatrics. Their management requires a careful balance between correcting sodium abnormalities and preventing iatrogenic complications, particularly neurologic injury. In hyponatremia, the underlying volume status (hypovolemic, euvolemic, or hypervolemic) guides therapeutic decisions. Mild, asymptomatic cases are often managed with fluid restriction and correction of underlying causes. In symptomatic or severe cases—such as seizures or altered mental status-hypertonic saline (۳ %) is administered cautiously. The correction rate must not exceed ۸-۱۰ mmol/L per ۲۴ hours to prevent osmotic demyelination syndrome, a devastating complication of overly rapid sodium correction. Hypernatremia, in contrast, usually arises from water deficit due to gastrointestinal losses, renal concentrating defects, or inadequate fluid intake. The therapeutic priority is to restore intravascular volume with isotonic saline if hypovolemia is present, followed by gradual replacement of the free-water deficit using hypotonic solutions such as ۵% dextrose in water (D۵W). The decline in serum sodium should not exceed ۰.۵ mmol/L per hour, or approximately ۱۰-۱۲ mmol/L per day, to minimize the risk of cerebral edema due to rapid osmotic shifts. Both disorders demand vigilant monitoring of serum electrolytes, neurologic status, and hemodynamic parameters. Importantly, treatment should address the underlying etiology—such as syndrome of inappropriate antidiuretic hormone secretion (SIADH) in hyponatremia or diabetes insipidus in hypernatremia while individualizing fluid therapy to patient age, weight, and clinical condition. Fluid management of sodium disorders requires a precise, gradual, and closely supervised approach. Safe correction strategies balance the urgency of symptom relief with the imperative to avoid neurologic injury, reflecting the central principle of pediatric electrolyte therapy