How do you treat hyponatremia (low sodium levels) in a patient?

Treatment of Hyponatremia

Hyponatremia treatment depends critically on symptom severity and volume status, with severe symptomatic cases requiring immediate 3% hypertonic saline to correct 6 mmol/L over 6 hours, while never exceeding 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment

Before initiating treatment, rapidly assess three critical factors that determine your approach 1:

• Symptom severity: Severe symptoms (seizures, coma, altered mental status) require emergency hypertonic saline, while mild symptoms (nausea, headache) allow more conservative management 1, 2
• Volume status: Determine if the patient is hypovolemic (orthostatic hypotension, dry mucous membranes), euvolemic (normal exam), or hypervolemic (edema, ascites, jugular venous distention) 1
• Acuity: Acute hyponatremia (<48 hours) can be corrected more rapidly than chronic (>48 hours), which carries higher risk of osmotic demyelination 1

Obtain serum and urine osmolality, urine sodium, and urine electrolytes to determine the underlying cause, but do not delay treatment while pursuing diagnosis 1, 3

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

Administer 3% hypertonic saline immediately for patients with seizures, coma, confusion, or altered consciousness 1, 4:

• Target: Correct 6 mmol/L over first 6 hours or until severe symptoms resolve 1
• Dosing: 100 mL bolus of 3% saline over 10 minutes, can repeat up to 3 times at 10-minute intervals 1
• Maximum correction: Never exceed 8 mmol/L in 24 hours 1, 3
• Monitoring: Check serum sodium every 2 hours during initial correction 1
• ICU admission: Required for close monitoring during treatment 1

Mild to Moderate Symptomatic or Asymptomatic Hyponatremia

Treatment is determined by volume status 1, 3:

Treatment Based on Volume Status

Hypovolemic Hyponatremia

Discontinue diuretics immediately and administer isotonic saline (0.9% NaCl) for volume repletion 1, 3:

• Initial rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on response 1
• Indicator of hypovolemia: Urine sodium <30 mmol/L predicts 71-100% response to saline 1
• Continue until euvolemic, then reassess 1

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of treatment 1, 3:

• First-line: Restrict fluids to <1 L/day 1
• If no response: Add oral sodium chloride 100 mEq three times daily 1
• Pharmacological options: Vasopressin receptor antagonists (tolvaptan 15 mg once daily, titrate to 30-60 mg) for resistant cases 1, 5
• Alternative agents: Urea, demeclocycline, or lithium may be considered 1

Critical distinction in neurosurgical patients: Cerebral salt wasting (CSW) mimics SIADH but requires opposite treatment—volume and sodium replacement, NOT fluid restriction 1. CSW is characterized by true hypovolemia with CVP <6 cm H₂O and high urine sodium despite volume depletion 1.

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1, 3:

• Discontinue diuretics temporarily if sodium <125 mmol/L 1
• For cirrhosis: Consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens edema and ascites 1
• Sodium restriction (not fluid restriction) results in weight loss as fluid follows sodium 1
• Vaptans: May be considered for persistent severe hyponatremia despite fluid restriction and maximization of guideline-directed therapy 1, 5

Critical Correction Rate Guidelines

The single most important safety principle is never exceeding 8 mmol/L correction in 24 hours 1, 3, 4:

• Standard rate: 4-8 mmol/L per day, maximum 10-12 mmol/L in 24 hours 1
• High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy): Limit to 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours 1
• Severe symptoms: Correct 6 mmol/L over first 6 hours, then only 2 mmol/L additional in next 18 hours 1

Monitoring During Correction

• Severe symptoms: Check sodium every 2 hours initially 1
• Mild symptoms: Check every 4 hours after symptom resolution 1
• After acute phase: Daily monitoring until stable 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours, immediately intervene 1:

• Discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider desmopressin to slow or reverse the rapid rise 1
• Target: Relower sodium to bring total 24-hour correction to ≤8 mmol/L from starting point 1
• Watch for osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Special Population Considerations

Neurosurgical Patients

• Distinguish SIADH from CSW: CSW requires volume and sodium replacement with isotonic or hypertonic saline, plus fludrocortisone 0.1-0.2 mg daily for severe symptoms 1
• Subarachnoid hemorrhage patients at risk of vasospasm: Never use fluid restriction; consider fludrocortisone or hydrocortisone 1
• Never use fluid restriction in CSW—this worsens outcomes 1

Cirrhotic Patients

• More cautious correction required: 4-6 mmol/L per day maximum 1
• Higher risk of complications: Sodium ≤130 mmol/L increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
• Tolvaptan caution: Higher risk of gastrointestinal bleeding (10% vs 2% placebo) 1, 5

Patients with Renal Failure

• Avoid salt tablets in severe renal failure (GFR <10) as kidneys cannot handle sodium load 1
• Consider renal replacement therapy: Continuous venovenous hemofiltration with low-sodium replacement fluid for controlled correction 1

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours causes osmotic demyelination syndrome 1, 4
• Using fluid restriction in CSW worsens outcomes—requires volume replacement 1
• Inadequate monitoring during active correction 1
• Failing to recognize underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—increases fall risk (21% vs 5%) and mortality (60-fold increase for sodium <130 mmol/L) 1, 2, 4
• Stopping diuretics prematurely in volume-overloaded heart failure patients due to mild hyponatremia 1

Calculating Sodium Deficit

Use this formula to determine sodium supplementation needs 1:

Sodium deficit (mEq) = Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg)

This helps guide the amount of hypertonic saline or sodium supplementation required 1.