Hypernatremia Estimation and Treatment Strategies

Learn about hypernatremia: its definition, clinical signs, water deficit estimation, and tailored management.

Definition and clinical manifestations

Hypernatremia is defined as a serum sodium level > 145 mEq/L. Clinical symptoms range from lethargy, irritability, restlessness, muscle spasticity, hyperreflexia, seizures, coma, and death (in severe cases).

NPS-adv

Estimation of free water deficit

Use the Adrogue-Madias equation for a rough estimate:

0.6 × wt (kg) × [serum sodium / 140 – 1]
For women, use 0.5 × wt (kg) instead of 0.6.
Note: This equation often underestimates total body water deficit.

Management of Hypernatremia

Acute Hypernatremia (≤ 48 hours): Rare

Goal: Decrease serum sodium by 1–2 mEq/L per hour, with a maximum of 10 mEq/L reduction in 24 hours.

Therapy: Administer 5% dextrose (D5W) IV at 3–6 mL/kg/h until serum sodium is 145 mEq/L.

Monitor serum sodium q2–3hr.
Once at 145 mEq/L, reduce D5W to 1 mL/kg/hr until serum sodium reaches 140 mEq/L.

Special cases (e.g., Central Diabetes Insipidus): Add desmopressin

Intranasal: 5–10 mcg qhs
Oral: 0.1–0.2 mg qhs
Subcutaneous: 1 mcg q12hr (if intranasal/oral not feasible)
IV: 2 mcg q12hr (if inadequate response to subcutaneous)

Chronic Hypernatremia (> 48 hours): Common

Goal: Reduce serum sodium by a maximum of 10 mEq/L per 24 hours.

Therapy: D5W IV 1.35 mL/hr × weight (kg).

Concurrent hypovolemia: Use 0.225% NaCl at 1.8 mL/kg/hr.
Concurrent hypovolemia + hypokalemia: Use 0.225% NaCl with KCl 40 mEq/L at 2.7 mL/kg/hr.

Monitor serum sodium q4–6hr until goal achieved, then q12–24hr.

Hypernatremia secondary to severe hyperglycemia (e.g., DKA, HHS): Use 0.45% NaCl at 6–12 mL/kg/hr.

NPS-adv

Practical tips

Hypernatremia requires careful and gradual correction to avoid complications like cerebral edema.
Always adjust treatment based on the underlying cause (e.g., dehydration, central diabetes insipidus, hyperglycemia).
Educate patients or caregivers on recognizing signs of worsening symptoms and the importance of timely follow-ups.

References

Muhsin SA, Mount DB. Diagnosis and treatment of hypernatremia. Best Pract Res Clin Endocrinol Metab. 2016;30(2):189-203.
Rushlow D, Miller N, Stacey S. Diagnosis and Management of Sodium Disorders: Hyponatremia and Hypernatremia. American Family Physician. 2023;108(5):476-486.