Highlights & Basics
- Hyponatremia is the most common electrolyte disorder encountered in clinical practice.
- Can occur in settings of volume depletion, volume overload, or euvolemia.
- History and physical exam can help establish volume status and are used to determine if the patient is hypovolemic, hypervolemic, or euvolemic. A thorough review of any underlying medical conditions and drugs should be undertaken. The cause of the hyponatremia is often apparent from the history and exam; however, some causes can only be identified with appropriate investigations.
- Cerebral edema is a medical emergency and occurs more frequently when hyponatremia develops over <48 hours. All patients with acute onset of hyponatremia and/or severe symptoms (e.g., nausea/vomiting, altered mental status, somnolence, seizures, coma) should be treated promptly with hypertonic 3% saline.
- Other treatment depends on the underlying cause and may include fluid restriction and stopping causative medications.
Quick Reference
History & Exam
Key Factors
Other Factors
Diagnostics Tests
Treatment Options
Definition
Epidemiology
Etiology
Pathophysiology
Images
Potential etiologies of hypotonic hyponatremia based on volume status of patient. CNS, central nervous system; SIADH, syndrome of inappropriate antidiuretic hormone
Etiologies of hypotonic hyponatremia (serum osmolality <275 mOsm/kg). SIADH, syndrome of inappropriate antidiuretic hormone
Brain magnetic resonance imaging of a patient with central pontine myelinolysis showing hypointensity within the basis pontis
Brain magnetic resonance imaging of a patient with central pontine myelinolysis showing: (a) trident-shaped hyperintensity within the pons; (b) hypointensity within the basis pontis; and (c) hyperintense focus in the central pons
Citations
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