What is the best approach to correct hyponatremia in an adult patient?

Hyponatremia Correction in Adults

Immediate Assessment: Symptom Severity Determines Treatment Urgency

For severe symptomatic hyponatremia (seizures, coma, altered mental status, cardiorespiratory distress), immediately administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeatable up to 3 times at 10-minute intervals, with a target correction of 6 mmol/L over 6 hours or until symptoms resolve. 1, 2

• Severe symptoms require emergency intervention—this is not a situation for fluid restriction or observation 1
• Check serum sodium every 2 hours during initial correction for severe symptoms 1, 2
• Never exceed 8 mmol/L total correction in 24 hours to prevent osmotic demyelination syndrome, regardless of symptom severity 1, 2, 3

For asymptomatic or mildly symptomatic patients (nausea, headache, weakness), treatment is based on volume status and underlying cause, with correction rates of 4-8 mmol/L per 24 hours 1, 4

Critical Safety Principle: Correction Rate Limits

The single most important principle is never exceeding 8 mmol/L correction in 24 hours—this causes osmotic demyelination syndrome, which can result in dysarthria, dysphagia, quadriparesis, coma, or death. 1, 2, 3

• For high-risk patients (advanced liver disease, alcoholism, malnutrition, severe hyponatremia <120 mmol/L), limit correction to 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours 1, 2
• The FDA warns that correction >12 mEq/L/24 hours significantly increases osmotic demyelination risk, particularly in susceptible patients 3
• Monitor for osmotic demyelination signs 2-7 days after correction: dysarthria, dysphagia, oculomotor dysfunction, quadriparesis 1

Treatment Algorithm Based on Volume Status

Hypovolemic Hyponatremia (Dehydration, Diuretic Overuse)

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

• Urine sodium <30 mmol/L predicts 71-100% response to saline infusion 1
• Discontinue diuretics immediately if sodium <125 mmol/L 1
• Once euvolemic, switch to maintenance isotonic fluids at 30 mL/kg/day 1
• Avoid hypotonic fluids (lactated Ringer's, 0.45% saline, D5W) as they worsen hyponatremia 1, 4

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of SIADH treatment. 1, 5

• If no response to fluid restriction after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1
• For persistent hyponatremia despite fluid restriction, consider tolvaptan 15 mg once daily, titrating to 30-60 mg as needed 1, 3
• Tolvaptan must be initiated in hospital with close sodium monitoring due to risk of overly rapid correction 3
• Alternative pharmacological options include urea, demeclocycline, or loop diuretics for resistant cases 1, 5

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L, and avoid hypertonic saline unless life-threatening symptoms are present. 1, 4

• Temporarily discontinue diuretics if sodium <125 mmol/L 1
• For cirrhotic patients, consider albumin infusion alongside fluid restriction 1
• Hypertonic saline worsens ascites and edema in hypervolemic states without life-threatening symptoms 1
• Tolvaptan may be considered for persistent severe hyponatremia despite fluid restriction and maximization of guideline-directed medical therapy 1, 3

Special Considerations for Neurosurgical Patients

In neurosurgical patients, distinguish between SIADH and cerebral salt wasting (CSW)—they require opposite treatments. 1

• SIADH: euvolemic state, treat with fluid restriction 1
• CSW: true hypovolemia (CVP <6 cm H₂O), treat with volume and sodium replacement using isotonic or hypertonic saline 1
• Never use fluid restriction in CSW or subarachnoid hemorrhage patients at risk of vasospasm—this worsens outcomes 1
• Consider fludrocortisone 0.1-0.2 mg daily for CSW or subarachnoid hemorrhage patients 1

Monitoring Requirements

During active correction, check serum sodium every 2 hours for severe symptoms, every 4-6 hours for mild symptoms or asymptomatic patients. 1, 2

• Once severe symptoms resolve, continue monitoring every 4 hours 1
• After initial correction phase, monitor daily until stable 1
• Track daily weight, fluid balance, and volume status 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours, immediately discontinue all sodium-containing fluids and switch to D5W (5% dextrose in water). 1, 2

• Administer desmopressin to slow or reverse the rapid rise in serum sodium 1, 2
• Target relowering to bring total 24-hour correction to no more than 8 mmol/L from starting point 1
• High-risk patients require even more aggressive intervention if correction exceeds 6 mmol/L in 24 hours 1

Common Pitfalls to Avoid

• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours—this is the most common cause of osmotic demyelination syndrome 1, 2, 5
• Never use fluid restriction as initial treatment for severe symptomatic hyponatremia—this is a medical emergency requiring hypertonic saline 1, 4
• Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms—it worsens fluid overload 1
• Never ignore mild hyponatremia (130-135 mmol/L) as clinically insignificant—it increases fall risk (21% vs 5%) and mortality (60-fold increase with sodium <130 mmol/L) 1, 5
• Inadequate monitoring during active correction leads to overcorrection and osmotic demyelination 1

Acute vs. Chronic Hyponatremia

• Acute hyponatremia (<48 hours onset) can be corrected more rapidly without osmotic demyelination risk 1
• Chronic hyponatremia (>48 hours) requires strict adherence to 8 mmol/L per 24-hour limit due to completed brain adaptation 1, 2
• When duration is unknown, assume chronic and use conservative correction rates 1, 4