How to correct mild hyponatremia (sodium level of 131 mmol/L)?

Management of Mild Hyponatremia (Sodium 131 mmol/L)

For a sodium level of 131 mmol/L, implement fluid restriction to 1-1.5 L/day if the patient is euvolemic or hypervolemic, identify and treat the underlying cause, and monitor sodium levels every 24-48 hours initially. 1

Initial Assessment

• Determine volume status by examining for orthostatic hypotension, dry mucous membranes, decreased skin turgor (hypovolemic), peripheral edema, ascites, jugular venous distention (hypervolemic), or absence of these findings (euvolemic) 1
• Obtain urine sodium and osmolality to differentiate between SIADH (urine sodium >20-40 mmol/L, urine osmolality >300 mOsm/kg) and other causes 1, 2
• Check serum osmolality to exclude pseudohyponatremia and confirm hypotonic hyponatremia 2
• Review medications for diuretics, SSRIs, antidepressants, or other drugs that can cause hyponatremia 1, 3

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Discontinue diuretics immediately if contributing to hyponatremia 1
• Administer isotonic saline (0.9% NaCl) for volume repletion at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response 1, 3
• Urine sodium <30 mmol/L predicts good response to saline with 71-100% positive predictive value 1

Euvolemic Hyponatremia (SIADH)

• Implement fluid restriction to 1 L/day as first-line treatment 1, 4
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction alone 1, 5
• Consider high protein diet to augment solute intake 5
• Alternative pharmacological options include urea, demeclocycline, or lithium for resistant cases, though these have significant side effects 1, 6

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1, 3
• Temporarily discontinue diuretics if sodium continues to drop 1
• Consider albumin infusion in cirrhotic patients alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms develop, as it worsens edema and ascites 1
• Sodium restriction (2-2.5 g/day) is more important than fluid restriction for weight loss in cirrhosis, as fluid follows sodium 1

Correction Rate Guidelines

• Maximum correction of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 4
• Target correction rate of 4-6 mmol/L per day for high-risk patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy 1, 5
• Monitor sodium levels every 24 hours initially, then adjust frequency based on response 1

Special Considerations

Neurosurgical Patients

• Distinguish between SIADH and cerebral salt wasting (CSW) as treatments are opposite 1
• CSW requires volume and sodium replacement, not fluid restriction, and is characterized by true hypovolemia with CVP <6 cm H₂O 1
• Consider fludrocortisone 0.1-0.2 mg daily for CSW in subarachnoid hemorrhage patients at risk of vasospasm 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1

Clinical Significance of Mild Hyponatremia

• Even mild hyponatremia (130-135 mmol/L) increases fall risk (21% vs 5% in normonatremic patients) and mortality (60-fold increase with sodium <130 mmol/L) 1, 4
• Associated with cognitive impairment, gait disturbances, and increased fracture rates over long-term follow-up 4
• Should not be ignored as clinically insignificant despite being asymptomatic 1

Common Pitfalls to Avoid

• Ignoring mild hyponatremia as clinically insignificant when it requires investigation and treatment 1
• Using fluid restriction in CSW worsens outcomes in neurosurgical patients 1
• Administering normal saline to euvolemic or hypervolemic patients can worsen hyponatremia 1
• Failing to identify and treat the underlying cause leads to persistent hyponatremia 1
• Inadequate monitoring during correction risks overcorrection and osmotic demyelination syndrome 1