Initial Management of Hyponatremia
Begin by assessing volume status (hypovolemic, euvolemic, or hypervolemic) and symptom severity, then obtain serum and urine osmolality, urine sodium, and uric acid to guide treatment—with correction rates never exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1
Immediate Assessment Steps
Volume Status Determination
- Hypovolemic signs: Orthostatic hypotension, dry mucous membranes, decreased skin turgor, tachycardia 1, 2
- Euvolemic signs: No edema, no orthostatic hypotension, normal skin turgor, moist mucous membranes 1
- Hypervolemic signs: Peripheral edema, ascites, jugular venous distention, pulmonary congestion 1, 3
Essential Laboratory Workup
- Serum osmolality and sodium to confirm true hyponatremia 1, 4
- Urine osmolality and urine sodium concentration (spot urine sodium <30 mmol/L suggests hypovolemia with 71-100% positive predictive value; >20 mmol/L with high urine osmolality suggests SIADH) 1, 2
- Serum uric acid (<4 mg/dL has 73-100% positive predictive value for SIADH) 1
- Thyroid-stimulating hormone and cortisol to exclude endocrine causes 1
Treatment Based on Symptom Severity
Severe Symptomatic Hyponatremia (Seizures, Coma, Altered Mental Status)
Administer 3% hypertonic saline immediately with a target correction of 6 mmol/L over 6 hours or until symptoms resolve, but never exceed 8 mmol/L total correction in 24 hours. 1, 2
- Dosing: 100 mL boluses of 3% saline over 10 minutes, repeatable up to three times at 10-minute intervals 1
- Monitor serum sodium every 2 hours during initial correction 1
- ICU admission required for close monitoring 1
Asymptomatic or Mildly Symptomatic Hyponatremia
Treatment depends entirely on volume status:
Hypovolemic Hyponatremia
- Discontinue diuretics immediately 1
- Administer isotonic (0.9%) saline for volume repletion 1, 4
- Urine sodium <30 mmol/L confirms this diagnosis 1
Euvolemic Hyponatremia (SIADH)
- Fluid restriction to 1 L/day is the cornerstone of treatment 1, 2
- If no response, add oral sodium chloride 100 mEq three times daily 1
- For resistant cases, consider vasopressin receptor antagonists (tolvaptan 15 mg once daily) 1, 5
Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)
- Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1, 4
- Discontinue diuretics temporarily if sodium <125 mmol/L 1
- Consider albumin infusion in cirrhotic patients 1
- Avoid hypertonic saline unless life-threatening symptoms present, as it worsens edema and ascites 1
Critical Correction Rate Guidelines
Standard Patients
High-Risk Patients (Advanced Liver Disease, Alcoholism, Malnutrition)
These patients require even slower correction at 4-6 mmol/L per day due to dramatically increased risk of osmotic demyelination syndrome. 1, 4
Special Considerations and Common Pitfalls
Neurosurgical Patients
- Distinguish cerebral salt wasting (CSW) from SIADH—this is critical as treatment approaches are opposite 1
- CSW requires volume and sodium replacement with isotonic or hypertonic saline, NOT fluid restriction 1
- Evidence of volume depletion (hypotension, tachycardia) indicates CSW 1
- Never use fluid restriction in subarachnoid hemorrhage patients at risk for vasospasm 1
- Consider fludrocortisone for CSW management 1
Cirrhotic Patients
- Hyponatremia increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
- Tolvaptan carries 10% risk of gastrointestinal bleeding vs. 2% with placebo—use with extreme caution 1, 5
- Albumin infusion should be tried before tolvaptan 1
Management of Overcorrection
If sodium rises >8 mmol/L in 24 hours:
- Immediately discontinue current fluids and switch to D5W 1
- Consider desmopressin to slow or reverse the rapid rise 1
- Watch for osmotic demyelination syndrome signs (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) appearing 2-7 days post-correction 1