What is the recommended approach for correcting hyponatremia in a patient?

Hyponatremia Correction: Evidence-Based Approach

Immediate Assessment: Symptom Severity Determines Urgency

For severe symptomatic hyponatremia (seizures, coma, altered mental status, respiratory distress), immediately administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeatable up to 3 times, targeting a 6 mmol/L increase over 6 hours or until symptoms resolve. 1, 2, 3

• Severe symptoms constitute a medical emergency requiring prompt intervention with hypertonic saline, not fluid restriction 1, 4
• The goal is rapid initial correction to reverse life-threatening cerebral edema, then slower maintenance correction 4, 3
• Monitor serum sodium every 2 hours during this acute phase 1

For mild-to-moderate symptoms (nausea, headache, confusion, weakness) or asymptomatic patients, treatment is based on volume status and underlying cause rather than emergency hypertonic saline 1, 3

Critical Safety Limit: The 8 mmol/L Rule

Never exceed 8 mmol/L sodium correction in any 24-hour period for chronic hyponatremia to prevent osmotic demyelination syndrome. 1, 5, 2

• This translates to approximately 0.33 mmol/L per hour maximum 5
• High-risk patients (cirrhosis, alcoholism, malnutrition, severe hyponatremia <120 mmol/L) require even slower correction at 4-6 mmol/L per day 1, 5
• Overcorrection causes osmotic demyelination syndrome—a devastating neurological complication with parkinsonism, quadriparesis, or death 1, 2
• If overcorrection occurs, immediately stop all sodium-containing fluids, switch to D5W, and administer desmopressin to reverse the correction 1, 5, 4

Treatment Algorithm Based on Volume Status

Hypovolemic Hyponatremia (Dehydration, Diuretic Overuse)

Administer isotonic saline (0.9% NaCl) for volume repletion, starting 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
• Discontinue diuretics immediately if sodium <125 mmol/L 1
• Once euvolemic, reassess—if sodium remains low, the patient likely has euvolemic hyponatremia (SIADH) requiring different management 1

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of treatment for SIADH. 1, 2, 6

• If no response to fluid restriction after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1
• Second-line options include urea (effective and safe) or vaptans (tolvaptan 15 mg daily, titrate to 30-60 mg) 1, 2, 6
• Urea is considered very effective with better tolerability than vaptans in many cases 6
• Nearly half of SIADH patients do not respond to fluid restriction alone, requiring pharmacological intervention 6

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L, combined with treatment of the underlying condition. 1, 3, 6

• In cirrhosis, consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms present—it worsens edema and ascites 1
• Temporarily discontinue diuretics if sodium <125 mmol/L 1
• Vaptans may be considered for persistent hyponatremia despite fluid restriction, but use cautiously in cirrhosis due to increased bleeding risk (10% vs 2% placebo) 1

Special Population: Neurosurgical Patients

Distinguish cerebral salt wasting (CSW) from SIADH—they require opposite treatments. 1

• CSW requires volume and sodium replacement with normal saline or hypertonic saline, NEVER fluid restriction 1
• CSW is characterized by true hypovolemia (CVP <6 cm H₂O), high urine sodium despite volume depletion, and clinical dehydration signs 1
• Consider fludrocortisone 0.1-0.2 mg daily for severe CSW or subarachnoid hemorrhage patients 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm—this worsens outcomes 1

Monitoring Requirements

Frequency of sodium checks depends on symptom severity and treatment phase. 1, 5

• Severe symptoms: every 2 hours during initial correction 1
• Mild symptoms or asymptomatic: every 4-6 hours during active correction 5
• Once stable: every 24-48 hours 1
• Watch for osmotic demyelination syndrome signs 2-7 days post-correction: dysarthria, dysphagia, oculomotor dysfunction, quadriparesis 1

Common Pitfalls to Avoid

• Never ignore mild hyponatremia (130-135 mmol/L) as "clinically insignificant"—it increases fall risk 4-fold (21% vs 5%) and mortality 60-fold when <130 mmol/L 1, 7
• Never use fluid restriction for hypovolemic hyponatremia or CSW—this worsens outcomes 1
• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours—even if symptoms improve, the brain adaptation takes time to reverse 1, 5, 2
• Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms—it exacerbates fluid overload 1
• Never fail to distinguish acute (<48 hours) from chronic (>48 hours) hyponatremia—acute can be corrected more rapidly without osmotic demyelination risk 1, 7

Acute vs. Chronic Hyponatremia

The rapidity of onset fundamentally changes correction safety. 7, 4

• Acute hyponatremia (<48 hours): can be corrected more rapidly as brain adaptation is incomplete 1
• Chronic hyponatremia (>48 hours): requires strict adherence to 8 mmol/L per 24-hour limit due to completed brain adaptation 1, 5
• When duration is unknown, assume chronic and use conservative correction rates 1