What is the appropriate management for hyponatremia?

How to Increase Low Sodium

The treatment of hyponatremia depends critically on symptom severity and volume status—severely symptomatic patients require immediate hypertonic saline (3% NaCl) to correct 6 mmol/L over 6 hours, while most chronic cases are managed by treating the underlying cause with fluid restriction for SIADH or volume/sodium replacement for cerebral salt wasting. 1

Initial Diagnostic Workup

When sodium drops below 131 mmol/L, immediately obtain:

• Serum and urine osmolality
• Urine sodium and electrolytes
• Serum uric acid
• Clinical volume status assessment (physical exam findings, vital signs, invasive monitoring if available)

Do not waste time measuring ADH or natriuretic peptide levels—these are not supported by evidence. 1

Volume status determines your treatment pathway:

• Hypovolemic: extrarenal losses, cerebral salt wasting (CSW), diuretics, adrenal insufficiency
• Euvolemic: SIADH (after ruling out thyroid disease, hypocortisolism, polydipsia)
• Hypervolemic: cirrhosis, heart failure, renal failure 1

Treatment Based on Symptom Severity

Severe Symptoms (Seizures, Coma, Mental Status Changes)

This is a medical emergency requiring ICU admission. 1

Immediate action:

• Give 3% hypertonic saline to correct 6 mmol/L over 6 hours OR until severe symptoms resolve
• Critical safety limit: Do not exceed 8 mmol/L correction in 24 hours total 1
• If you correct 6 mmol/L in the first 6 hours, you can only increase sodium by 2 mmol/L more in the remaining 18 hours
• Monitor sodium every 2 hours
• Calculate sodium deficit: Desired increase (mmol/L) × 0.5 × ideal body weight (kg) 1

Why this matters: Slower correction in severely hyponatremic patients (Na <115 mmol/L) increases mortality—survivors had sodium of 127.1 mmol/L at 48 hours versus 118.8 mmol/L in those who died (P=0.0016). 1

Mild Symptoms (Nausea, Vomiting, Aches) or Na <120 mmol/L

• Transfer to intermediate care unit
• Monitor sodium every 4 hours
• Fluid restriction to 1 L/day
• Daily sodium checks 1

Asymptomatic or Mild Chronic Hyponatremia

Never rapidly correct chronic hyponatremia—this causes osmotic demyelination syndrome and central pontine myelinolysis. 1 Reserve rapid correction (>1 mmol/L/hour) only for acute hyponatremia (<48 hours) with severe symptoms. 1

Treatment by Underlying Cause

SIADH (Euvolemic)

Fluid restriction is the cornerstone unless severely symptomatic. 1

Treatment algorithm:

1. First-line: Fluid restriction to 1 L/day 1
2. If no response: Add oral sodium chloride 100 mEq three times daily 1
3. Additional measures: High protein diet 1
4. Severe/refractory cases:
   • Hypertonic saline (3% NaCl) for severe symptoms 1
   • Vasopressin receptor antagonists (vaptans) 2, 3
   • Urea 40g in 100-150 mL normal saline every 8 hours 1

Stop hypertonic saline when severe symptoms resolve and transition to less aggressive protocol. 1

Cerebral Salt Wasting (Hypovolemic)

CSW requires the opposite approach—volume and sodium replacement, NOT fluid restriction. 1

Critical warning: Fluid restriction in CSW causes cerebral infarction. In one study, 21 of 26 fluid-restricted patients with subarachnoid hemorrhage developed cerebral infarction. 1

Treatment protocol:

• Severe symptoms: ICU admission with 3% hypertonic saline PLUS fludrocortisone for 7 days 1
• Correction rate: Same as above (6 mmol/L over 6 hours, max 8 mmol/L per 24 hours) 1
• Maintenance: Normal saline IV fluids, monitor ins/outs, daily weights 1
• Alternative: Hydrocortisone 1200 mg/day reduces sodium and water loss 1

Special case—Subarachnoid hemorrhage patients: Treat even when sodium is 131-135 mmol/L due to vasospasm risk. 1

Cirrhosis with Hypervolemic Hyponatremia

Management depends on severity: 4, 5

Sodium 126-135 mmol/L, normal creatinine:

• Continue diuretics
• Monitor electrolytes closely
• Do NOT water restrict 4

Sodium 121-125 mmol/L, normal creatinine:

• Stop diuretics (controversial—some experts continue, but safer to stop) 4
• Observe patient

Sodium 121-125 mmol/L with elevated creatinine (>150 mmol/L):

• Stop diuretics immediately
• Give volume expansion with colloid (gelofusine, haemaccel, voluven) or saline 4

Sodium <120 mmol/L:

• Stop diuretics
• Volume expansion with colloid or saline
• Avoid increasing sodium >12 mmol/L per 24 hours 4

Outpatient management (asymptomatic):

• Sodium restriction (90 mmol/day)
• Water restriction (1-1.5 L/day)
• Modify diuretics and laxatives 5

Inpatient management (severe/symptomatic):

• Sodium and water restriction
• Discontinue diuretics and laxatives
• IV albumin based on volume assessment
• Consider oral vasoconstrictor therapy 5

Common Pitfalls to Avoid

1. Never use fluid restriction for cerebral salt wasting—this causes cerebral infarction 1

2. Never correct chronic hyponatremia rapidly—maximum 10 mmol/L per day to prevent osmotic demyelination 1

3. Never assume SIADH without ruling out volume depletion—many neurosurgical patients are actually volume depleted and respond to fluid/sodium replacement 1

4. Never water restrict patients with cirrhosis and sodium >125 mmol/L—this worsens effective hypovolemia and ADH secretion 4

5. For large volume paracentesis (>5L): Give 20-25% IV albumin 6-8g per liter removed 5

Monitoring Requirements

• Severe symptoms: Check sodium every 2 hours 1
• Mild symptoms: Check sodium every 4 hours 1
• Stable patients: Daily sodium checks 1
• Monitor daily weights, ins/outs, urine output 1