RESUMO
Although hyponatremia is a common electrolyte disorder, its evaluation and management are not well defined. When diagnosed, hyponatremia should be categorized based on four criteria: volume status, urinary Na+, serum K+, and acid-base balance. This approach helps to determine what the cause of hyponatremia is and how it should be treated. Initially, hypovolemic hyponatremia, including cerebral salt wasting syndrome (CSWS), is treated by volume resuscitation and salt supplementation. Euvolemic hyponatremia, including the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), is treated by fluid restriction and salt supplementation, and hypervolemic hyponatremia is treated by fluid restriction and salt restriction. Hyponatremia can be managed well using these primary treatments and medications.