What are the management strategies for hypernatremia (elevated sodium levels) and hyponatremia (low sodium levels)?

Management of Sodium Level 146 mmol/L (Mild Hypernatremia)

Initial Assessment

A sodium level of 146 mmol/L represents mild hypernatremia that requires evaluation of the underlying cause and correction strategy. 1

• Assess volume status by examining for signs of dehydration: confusion, non-fluent speech, extremity weakness, dry mucous membranes, dry tongue, furrowed tongue, sunken eyes, decreased venous filling, low blood pressure, and postural pulse changes 1
• Determine the mechanism: inadequate water intake (impaired thirst, lack of access to water), excessive water loss (diarrhea, vomiting, burns), or renal concentrating defects (diabetes insipidus) 1, 2
• Check for high-risk populations: elderly patients with impaired thirst mechanism are the typical presentation 3

Treatment Strategy

For Mild Hypernatremia (146 mmol/L)

Oral rehydration is preferred if the patient can tolerate it; otherwise, use hypotonic intravenous fluids. 2

• Fluid selection for correction:

  • 0.45% NaCl (half-normal saline) containing 77 mEq/L sodium with osmolarity ~154 mOsm/L is appropriate for moderate hypernatremia 1
  • 5% dextrose (D5W) delivers no renal osmotic load and allows controlled decrease in plasma osmolality 1
  • 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, risking worsening hypernatremia 1

• Correction rate: Maximum 0.4 mmol/L/hour or 10 mmol/L per 24 hours to prevent cerebral edema 1

• Initial fluid administration rate: 25-30 mL/kg/24 hours for adults 1

Special Considerations

• For nephrogenic diabetes insipidus: Ongoing hypotonic fluid administration is required to match excessive free water losses; isotonic fluids will worsen hypernatremia 1, 2
• For ongoing losses (diarrhea, vomiting): Replace with hypotonic fluids matching the composition of losses while providing adequate free water 1
• Correction timeline: Aim for correction over 24-48 hours for stable patients 4

Monitoring

• Track serum sodium levels every 4-6 hours initially during active correction 1
• Monitor for neurologic symptoms: Changes in mental status, seizures, or altered consciousness indicate need for more aggressive management 2
• Assess fluid balance: Daily weights and intake/output to guide ongoing therapy 1

Common Pitfalls to Avoid

• Never use isotonic saline in patients with renal concentrating defects as this exacerbates hypernatremia 1
• Avoid overly rapid correction (>10 mmol/L per 24 hours) which risks cerebral edema 1, 4
• Do not delay treatment while pursuing extensive diagnostic workup in symptomatic patients 2