What is the management for a patient with hypernatremia (elevated sodium level) of 167 mmol/L?

Management of Hypernatremia (Sodium 167 mmol/L)

For a patient with severe hypernatremia (sodium 167 mmol/L), immediately initiate hypotonic fluid replacement with 5% dextrose (D5W) or 0.45% NaCl, targeting a correction rate of no more than 0.4 mmol/L per hour or 10 mmol/L per 24 hours to prevent cerebral edema. 1, 2

Immediate Assessment

Determine the acuity and underlying cause:

• Assess volume status by examining for signs of hypovolemia (orthostatic hypotension, dry mucous membranes, decreased skin turgor, tachycardia) versus hypervolemia (edema, jugular venous distention) 1, 3
• Check urine osmolality and sodium to differentiate between renal and extrarenal losses 1, 4
• Obtain medication history focusing on lithium, diuretics, or recent hypertonic saline/sodium bicarbonate administration 1
• Evaluate for diabetes insipidus (central vs. nephrogenic) if urine osmolality is inappropriately low (<300 mOsm/kg) 1, 4

Fluid Replacement Strategy

Primary fluid choice is 5% dextrose (D5W) because it delivers no renal osmotic load and allows controlled decrease in plasma osmolality 5

Alternative: 0.45% NaCl (half-normal saline) containing 77 mEq/L sodium for moderate hypernatremia 5

Critical: Avoid isotonic saline (0.9% NaCl) as it delivers excessive osmotic load—requiring 3 liters of urine to excrete the osmotic load from just 1 liter of isotonic fluid, which risks worsening hypernatremia 5

Correction Rate Guidelines

For chronic hypernatremia (>48 hours duration):

• Maximum correction: 0.4 mmol/L per hour or 8-10 mmol/L per 24 hours 1, 2
• Slower correction prevents osmotic demyelination syndrome and cerebral edema 1, 2

For acute hypernatremia (<24-48 hours):

• Rapid correction improves prognosis by preventing cellular dehydration effects 1
• Consider hemodialysis for rapid normalization in acute cases 2

Initial fluid administration rates:

• Adults: 25-30 mL/kg per 24 hours 5
• Close laboratory monitoring every 2-4 hours during active correction 2, 6

Treatment Based on Underlying Cause

Hypovolemic hypernatremia (extrarenal losses):

• Replace ongoing losses from diarrhea, vomiting, or burns 5, 1
• Use hypotonic fluids to match free water deficit 3

Euvolemic hypernatremia (diabetes insipidus):

• Central diabetes insipidus: Administer desmopressin (Minirin) 2
• Nephrogenic diabetes insipidus: Requires ongoing hypotonic fluid administration to match excessive free water losses 5
• Correct underlying causes: discontinue lithium, correct hypokalemia 1

Hypervolemic hypernatremia:

• Consider diuretics to promote renal sodium excretion 6
• Evaluate for primary hyperaldosteronism in chronic cases 1

Critical Safety Considerations

Never exceed 10 mmol/L correction in 24 hours for chronic hypernatremia to avoid cerebral edema from rapid osmotic shifts 1, 2

Monitor closely when initiating renal replacement therapy in patients with chronic hypernatremia to avoid rapid sodium drops 2

High-risk populations (infants, malnourished patients) may benefit from smaller-volume frequent boluses (10 mL/kg) due to reduced cardiac output capacity 5

Clinical Monitoring

• Serum sodium every 2-4 hours during active correction 2, 6
• Neurological status: Watch for confusion, altered consciousness, seizures 1, 3
• Urine output and osmolality to assess response and guide ongoing therapy 1, 4
• Volume status reassessment to adjust fluid replacement strategy 3, 6