Hypernatremia

• Definition: serum sodium > 145 mEq/L
• Most patients have impaired thirst or no access to water (elders, infants, mental impairment, intubated/paralyzed patients).

Clinical features

• Nausea & vomiting
• Weakness
• Polyuria & polydipsia
• Signs of hypovolemia: hypotension, tachycardia, orthostatic hypotension, poor skin turgor, dry mucous membranes
• Edema in hypervolemic hypernatremia
• Altered mental status, seizures

Evaluation

Treatment

General approach

1. Volume replacement
   • Hemodynamically unstable: normal saline (0.9%)
   • Hemodynamically stable: half-normal saline (0.45%) at ~100 mL/hour (adjust to clinical response)
2. Etiology-specific therapy: antipyretics for fever, antiemetics for vomiting, desmopressin for central DI, dialysis for impaired renal function. Life-threatening acute salt ingestion: 5% (dextrose in water) D5W and/or hemodialysis.
3. Replace total body water: 5% D5W or oral free water when appropriate.

Correction rates

Onset	Correction rate
Acute hypernatremia (within 48 h)	~1 mEq/L/hour
Chronic hypernatremia	No more than 0.5 mEq/L/hour or 10–12 mEq/24 hours (slower to avoid cerebral edema)

• If correction occurs too rapidly, or if the patient begins to show symptoms of cerebral edema or hyponatremia, stop treatment of hypernatremia, and treat the patient with fluid restriction or addition of electrolytes/saline to the fluid infusion.