What can I do for a patient with hypernatremia (elevated serum sodium level of 156 mmol/L)?

Management of Hypernatremia (Serum Sodium 156 mmol/L)

For a patient with hypernatremia (serum sodium 156 mmol/L), you should correct the sodium slowly with hypotonic fluids, aiming for a reduction of no more than 8-10 mmol/L per 24 hours to prevent cerebral edema, while simultaneously identifying and treating the underlying cause. 1, 2

Initial Assessment

Determine the acuity and underlying cause:

• Assess volume status by examining for signs of dehydration (dry mucous membranes, poor skin turgor, orthostatic hypotension) versus volume overload 1, 3
• Check urine osmolality to differentiate between renal and extrarenal water losses - concentrated urine (>600 mOsm/kg) suggests extrarenal losses, while dilute urine (<300 mOsm/kg) suggests diabetes insipidus 3
• Evaluate thirst mechanism - impaired thirst or lack of access to water is the most common cause of mild hypernatremia 1
• Review medications and medical history for potential causes including diuretics, osmotic agents, or diabetes insipidus 3

Correction Strategy Based on Chronicity

For Chronic Hypernatremia (>48 hours or unknown duration)

The correction rate is critical to prevent cerebral edema:

• Limit sodium reduction to 8-10 mmol/L per 24 hours (approximately 0.5 mmol/L per hour maximum) 2, 1
• Use hypotonic fluids such as 0.45% saline or 5% dextrose in water (D5W) 1, 2
• Monitor serum sodium every 2-4 hours initially during active correction to ensure you don't exceed the safe correction rate 2

The rationale: Chronic hypernatremia allows the brain to generate idiogenic osmoles to protect against cellular dehydration. Rapid correction causes water to shift into brain cells faster than these osmoles can dissipate, leading to cerebral edema 2, 4.

For Acute Hypernatremia (<24 hours)

• More rapid correction is safer in truly acute cases, though this is rare in clinical practice 2
• Hemodialysis can be considered for rapid normalization if the hypernatremia developed acutely 2

Specific Treatment Approaches

If Hypovolemic (Most Common)

• Replace free water deficit using hypotonic fluids (0.45% saline or D5W) 1
• Calculate water deficit: Water deficit (L) = 0.6 × body weight (kg) × [(current Na/140) - 1] 1
• Replace deficit over 48-72 hours to avoid exceeding 8-10 mmol/L per day correction 2

If Diabetes Insipidus is Suspected

• Administer desmopressin (DDAVP) if central diabetes insipidus is confirmed 2
• Note: Desmopressin should be used with caution as it can predispose to hyponatremia if free water intake is excessive 5
• For nephrogenic diabetes insipidus, address the underlying cause and provide adequate hypotonic fluid replacement 2

If Euvolemic with Intact Thirst

• Encourage oral water intake as the primary intervention 1
• Supplement with hypotonic IV fluids if oral intake is inadequate 1

Critical Monitoring Parameters

• Check serum sodium every 2-4 hours during initial correction phase 2
• Watch for signs of cerebral edema including headache, confusion, seizures, or altered consciousness - these indicate overly rapid correction 4
• Adjust fluid rate if sodium is dropping too quickly (>0.5 mmol/L per hour) 2
• Monitor urine output and osmolality to assess response to treatment 3

Common Pitfalls to Avoid

• Correcting too rapidly (>10 mmol/L per 24 hours) risks cerebral edema, which carries high morbidity and mortality 2, 4
• Using isotonic saline in hypernatremia will not correct the sodium and may worsen the condition 1
• Failing to identify the underlying cause - hypernatremia will recur if the etiology isn't addressed 3
• Starting renal replacement therapy without considering the correction rate - dialysis can drop sodium too rapidly in chronic hypernatremia 2

Special Considerations

In critically ill patients with severe hypernatremia (>155 mmol/L):

• Recent evidence suggests that rapid correction (>0.5 mmol/L per hour) was not associated with increased mortality or neurologic complications in ICU patients 6
• However, this contradicts traditional teaching and should be applied cautiously - the safest approach remains gradual correction at 8-10 mmol/L per 24 hours unless hypernatremia is definitively acute 2

For patients with liver disease or cirrhosis:

• A sodium level of 150 mmol/L or higher may indicate worsening hemodynamic status and requires particularly careful management 7