Which intravenous fluids should be administered to raise serum sodium in a patient with hyponatremia?

What Fluids to Give to Increase Sodium Level

For symptomatic or severe hyponatremia, hypertonic saline (3%) is the fluid of choice to rapidly raise serum sodium, while for hypovolemic hyponatremia, normal saline (0.9% NaCl) is preferred. 1, 2

Clinical Approach Based on Presentation

Severe/Symptomatic Hyponatremia (Emergency)

When patients present with severe symptoms (seizures, coma, altered mental status, cardiorespiratory distress):

• Administer 3% hypertonic saline as 100-150 mL IV bolus 3, 2, 4
• Target: Increase serum sodium by 4-6 mEq/L within first 1-2 hours to reverse cerebral edema 2, 5
• Critical correction limits: Do NOT exceed 8-10 mEq/L in first 24 hours 1, 2
• Monitor serum sodium every 2 hours initially 3

Key pitfall: Overcorrection causes osmotic demyelination syndrome (ODS), which can result in permanent neurological damage including quadriparesis, dysarthria, and death 1. If overcorrection occurs, immediately administer desmopressin and/or hypotonic fluids to re-lower sodium 1.

Hypovolemic Hyponatremia

When volume depletion is the cause (evidenced by orthostatic hypotension, low urine sodium <30 mEq/L, elevated BUN/creatinine ratio):

• Use normal saline (0.9% NaCl) or lactated Ringer's solution 1, 6
• Discontinue diuretics 1
• Alternative: 5% albumin in cirrhotic patients 1

This addresses both the sodium deficit and volume depletion simultaneously. The body will naturally correct sodium as volume is restored 3.

Hypervolemic Hyponatremia (Cirrhosis, Heart Failure)

For patients with fluid overload and hyponatremia:

Severity-based approach 1:

• Mild (Na 126-135 mEq/L): Water restriction only, no specific fluids needed
• Moderate (Na 120-125 mEq/L): Water restriction to 1000 mL/day + stop diuretics
• Severe (Na <120 mEq/L): More severe water restriction + albumin infusion (NOT saline, which worsens volume overload) 1

Hypertonic saline is reserved ONLY for:

• Severely symptomatic patients 1
• Patients with imminent liver transplant 1

Euvolemic Hyponatremia (SIADH)

For syndrome of inappropriate antidiuretic hormone:

• Primary treatment: Fluid restriction (500-1000 mL/day), NOT IV fluids 3, 4
• If symptomatic: 3% hypertonic saline as above 3
• Second-line options: Vasopressin receptor antagonists (vaptans) or oral urea 1, 4

Critical distinction: In neurosurgical patients, cerebral salt wasting (CSW) mimics SIADH but requires OPPOSITE treatment—aggressive fluid and sodium replacement with normal saline, NOT restriction 3. Fluid restriction in CSW causes cerebral infarction 3.

Correction Rate Guidelines

For chronic hyponatremia (>48 hours duration) 1, 2:

• Standard risk patients: 4-8 mEq/L per 24 hours, maximum 10-12 mEq/L
• High-risk patients (cirrhosis, alcoholism, malnutrition, hypokalemia): 4-6 mEq/L per 24 hours, maximum 8 mEq/L

For acute hyponatremia (<48 hours): Can correct more rapidly without ODS risk 1

Monitoring Requirements

• Check serum sodium every 2-4 hours during active correction 3
• Monitor urine output closely—high diuresis correlates with overcorrection risk 7
• Measure serum sodium within 6 hours of any hypertonic saline bolus 8
• Do not re-administer hypertonic saline until sodium <155 mEq/L 8

Fluids to AVOID

• Do NOT use hypotonic fluids (D5W, 0.45% saline) to raise sodium—these worsen hyponatremia 9, 10
• Avoid normal saline in hypervolemic hyponatremia—worsens ascites and edema 10
• Never use hypertonic saline for asymptomatic chronic hyponatremia—risk exceeds benefit 1