How should I correct a serum sodium of 120 mmol/L?

Management of Serum Sodium 120 mmol/L

For a serum sodium of 120 mmol/L, your immediate priority is determining symptom severity and volume status, as these dictate whether you use hypertonic saline emergently or implement fluid restriction—opposite treatments that can be catastrophic if reversed.

Immediate Assessment (First 30 Minutes)

Assess for severe symptoms requiring emergent hypertonic saline:

• Seizures, coma, altered mental status, somnolence, obtundation, or cardiorespiratory distress indicate severely symptomatic hyponatremia requiring immediate 3% hypertonic saline 1, 2
• Moderate symptoms (confusion, nausea, vomiting, headache, weakness) suggest slower correction is safer 1, 2
• Asymptomatic patients require the most cautious approach to avoid osmotic demyelination syndrome 1, 3

Determine chronicity:

• Acute (<48 hours): typically postoperative, post-marathon, or polydipsia—can be corrected more rapidly without demyelination risk 3
• Chronic (>48 hours): most common presentation—requires strict adherence to 8 mmol/L/24-hour limit 1, 3

Assess volume status through physical examination:

• Hypovolemic signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Euvolemic: normal volume status, no edema, no orthostasis 1
• Hypervolemic: peripheral edema, ascites, jugular venous distention, pulmonary congestion 1

Emergency Management for Severely Symptomatic Patients

If seizures, coma, or severe neurological symptoms are present:

• Administer 150 mL of 3% hypertonic saline as a bolus over 10 minutes 2, 4
• This bolus can be repeated up to 3 times at 10-minute intervals until symptoms improve 2
• Target correction: 4-6 mmol/L increase over the first 1-2 hours to reverse cerebral edema 1, 2
• Absolute maximum: 8 mmol/L increase in any 24-hour period to prevent osmotic demyelination syndrome 1, 2, 3

Critical monitoring during acute correction:

• Check serum sodium every 2 hours during initial correction phase 1
• Once severe symptoms resolve, switch to checking every 4-6 hours 1
• If correction exceeds 6 mmol/L in 6 hours, immediately stop hypertonic saline and reassess 1

Management Based on Volume Status (Non-Emergency)

Hypovolemic Hyponatremia (True Volume Depletion)

This is the ONLY scenario where normal saline is appropriate:

• Discontinue all diuretics immediately 1, 5
• Administer isotonic saline (0.9% NaCl) for volume repletion at 15-20 mL/kg/hour initially, then 4-14 mL/kg/hour based on response 1, 5
• Urine sodium <30 mmol/L predicts good response to saline (positive predictive value 71-100%) 1
• Still respect the 8 mmol/L/24-hour correction limit even with volume repletion 1, 3

Euvolemic Hyponatremia (SIADH)

Fluid restriction is the cornerstone of treatment:

• Implement strict fluid restriction to 1 L/day (or <800 mL/day for refractory cases) 1, 5, 6
• If no response after 24-48 hours, add oral sodium chloride 100 mEq (approximately 6 grams) three times daily 1, 5
• Alternative pharmacological options for resistant SIADH: urea (15-30 grams twice daily), loop diuretics, demeclocycline, or tolvaptan 15 mg once daily 1, 6, 2
• Avoid hypertonic saline unless severely symptomatic 1, 2

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Fluid restriction with cautious diuretic management:

• Implement fluid restriction to 1-1.5 L/day 1, 5
• Temporarily discontinue diuretics if sodium <125 mmol/L 1, 5
• For cirrhotic patients, consider albumin infusion (8 grams per liter of ascites removed) alongside fluid restriction 1, 5
• Hypertonic saline is contraindicated unless life-threatening symptoms are present, as it worsens fluid overload 1
• Sodium restriction (2-2.5 g/day) is more effective than aggressive fluid restriction for weight loss in cirrhosis 1

Critical Correction Rate Guidelines

Standard-risk patients (no liver disease, alcoholism, or malnutrition):

• Target: 4-8 mmol/L per day 1, 3
• Absolute maximum: 8 mmol/L in any 24-hour period 1, 2, 3
• Never exceed 10-12 mmol/L in 24 hours under any circumstances 1

High-risk patients (cirrhosis, alcoholism, malnutrition, prior encephalopathy):

• Maximum correction: 4-6 mmol/L per day 1, 5
• Absolute ceiling: 8 mmol/L in 24 hours 1
• These patients have 0.5-1.5% risk of osmotic demyelination even with careful correction 1

Management of Overcorrection

If sodium rises >8 mmol/L in 24 hours:

• Immediately stop all hypertonic saline or sodium-containing fluids 1, 3
• Administer 5% dextrose in water (D5W) or desmopressin to lower sodium back down 1, 3
• Goal: bring total 24-hour correction back to ≤8 mmol/L from baseline 1
• Osmotic demyelination syndrome typically manifests 2-7 days after overcorrection with dysarthria, dysphagia, oculomotor dysfunction, and quadriparesis 1

Special Populations

Neurosurgical patients (subarachnoid hemorrhage, brain injury):

• Distinguish cerebral salt wasting (CSW) from SIADH—they require opposite treatments 1
• CSW: true hypovolemia requiring aggressive volume and sodium replacement with normal saline 50-100 mL/kg/day, never fluid restriction 1
• Consider fludrocortisone 0.1-0.2 mg daily for CSW 1
• Never use fluid restriction in SAH patients at risk of vasospasm 1

Cirrhotic patients:

• 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
• Use the most conservative correction rates (4-6 mmol/L/day maximum) 1, 5
• Tolvaptan carries 10% risk of GI bleeding vs 2% with placebo in cirrhosis 1, 7

Common Pitfalls to Avoid

• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours—this causes osmotic demyelination syndrome 1, 3
• Never use fluid restriction for hypovolemic hyponatremia—this worsens outcomes and delays correction 1
• Never use hypertonic saline for hypervolemic hyponatremia unless life-threatening symptoms are present 1
• Never ignore mild hyponatremia (130-135 mmol/L)—it increases fall risk (21% vs 5%) and mortality (60-fold increase with sodium <130 mmol/L) 1
• Never use normal saline for SIADH—it can paradoxically worsen hyponatremia 1, 5
• Never stop monitoring after initial correction—overcorrection can occur hours later, especially with spontaneous water diuresis 1, 4