What is the treatment for a patient with hyponatremia (low sodium levels) at a level of 128 mmol/L?

Treatment of Hyponatremia at 128 mmol/L

For a patient with hyponatremia at 128 mmol/L, treatment depends critically on symptom severity and volume status: if severely symptomatic (seizures, altered mental status), administer 3% hypertonic saline immediately targeting 6 mmol/L correction over 6 hours; if asymptomatic or mildly symptomatic, determine volume status and treat accordingly—hypovolemic patients receive isotonic saline, euvolemic patients (SIADH) require fluid restriction to 1 L/day, and hypervolemic patients need fluid restriction to 1-1.5 L/day. 1

Initial Assessment

Before initiating treatment, rapidly assess three critical parameters:

• Symptom severity: Look for severe neurological symptoms including seizures, coma, confusion, altered mental status, or cardiorespiratory distress versus mild symptoms (nausea, headache, weakness) versus asymptomatic 1, 2
• Volume status: Examine for orthostatic hypotension, dry mucous membranes, poor skin turgor (hypovolemic); normal volume status without edema (euvolemic); or jugular venous distention, peripheral edema, ascites (hypervolemic) 1
• Acuity: Determine if onset is acute (<48 hours) or chronic (>48 hours), as this affects correction rate safety 1

Obtain serum and urine osmolality, urine sodium concentration, and assess for underlying causes including medications (diuretics, SSRIs), heart failure, cirrhosis, or SIADH 1, 3

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

If the patient has seizures, coma, severe confusion, or cardiorespiratory distress:

• Administer 3% hypertonic saline immediately as 100-150 mL IV bolus over 10 minutes 1, 4
• Target correction of 6 mmol/L over 6 hours or until severe symptoms resolve 1, 5
• Can repeat the bolus up to three times at 10-minute intervals if symptoms persist 1
• Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome 1, 6
• Monitor serum sodium every 2 hours during initial correction 1
• Consider ICU admission for close monitoring 1

Asymptomatic or Mildly Symptomatic Hyponatremia

At 128 mmol/L without severe symptoms, treatment is determined by volume status:

Treatment Based on Volume Status

Hypovolemic Hyponatremia

If the patient shows signs of volume depletion (orthostatic hypotension, dry mucous membranes, decreased skin turgor):

• Administer isotonic (0.9%) saline for volume repletion 1, 3
• Discontinue diuretics if contributing to hyponatremia 1
• A urine sodium <30 mmol/L predicts good response to saline infusion (71-100% positive predictive value) 1
• Continue isotonic fluids until euvolemia is achieved 1
• Correction rate should not exceed 8 mmol/L in 24 hours 1

Euvolemic Hyponatremia (SIADH)

If the patient appears euvolemic (no edema, normal blood pressure, normal skin turgor):

• Fluid restriction to 1 L/day is first-line treatment 1, 3
• If no response to fluid restriction after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1, 5
• Consider high protein diet to augment solute intake 5
• For resistant cases, consider urea or vasopressin receptor antagonists (tolvaptan 15 mg daily, titrate as needed) 1, 4
• Monitor sodium levels every 4-6 hours initially 5

Common pitfall: Using fluid restriction in cerebral salt wasting (CSW) worsens outcomes—in neurosurgical patients, distinguish SIADH from CSW as CSW requires volume and sodium replacement, not restriction 1, 7

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

If the patient has volume overload (peripheral edema, ascites, jugular venous distention):

• Implement fluid restriction to 1-1.5 L/day 1, 3
• Discontinue diuretics temporarily if sodium continues to drop 1
• For cirrhotic patients, consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens edema and ascites 1
• Treat underlying condition (optimize heart failure management, manage cirrhosis) 3
• For persistent severe hyponatremia despite fluid restriction, consider vasopressin antagonists short-term 1

Important note: In cirrhosis, it is sodium restriction (not fluid restriction) that produces weight loss, as fluid passively follows sodium 1

Critical Correction Rate Guidelines

The single most important safety principle is limiting correction speed:

• Maximum 8 mmol/L correction in 24 hours for all patients 1, 6, 2
• For high-risk patients (advanced liver disease, alcoholism, malnutrition, severe hyponatremia), use even more cautious rates of 4-6 mmol/L per day 1, 4
• For chronic hyponatremia, avoid correction faster than 1 mmol/L/hour 1
• The FDA label for tolvaptan warns that correction >12 mEq/L/24 hours can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, seizures, coma, and death 6

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours:

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse the rapid rise 1, 4
• Target relowering to bring total 24-hour correction to no more than 8 mmol/L from starting point 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Monitoring Requirements

• During active correction: Check sodium every 2 hours for severe symptoms, every 4 hours for moderate symptoms 1
• After symptom resolution: Check sodium every 4-6 hours 1, 5
• Calculate sodium deficit using: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1, 5
• Monitor for signs of volume overload or depletion during treatment 1

Common Pitfalls to Avoid

• Ignoring mild hyponatremia as clinically insignificant—even at 128 mmol/L, hyponatremia increases fall risk (21% vs 5% in normonatremic patients) and mortality 1, 2
• Using fluid restriction in cerebral salt wasting instead of volume replacement 1
• Administering hypertonic saline to hypervolemic patients without life-threatening symptoms 1
• Inadequate monitoring during active correction leading to overcorrection 1
• Failing to identify and treat the underlying cause 1
• Continuing diuretics when sodium drops below 125 mmol/L 1