Differential Diagnosis

Excessive parenteral sodium administration in an unconscious patient whose thirst mechanism is absent.

Excessive use of diuretics or other drugs leading to water loss in the patient who cannot compensate by intake of water.

Diabetes insipidus may be central (neurogenic), acquired nephrogenic, or congenital nephrogenic.

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Mineralocorticoid or glucocorticoid excess from primary hyperaldosteronism and Cushing syndrome with or without ectopic adrenocorticotropic hormone (ACTH) production.

Insensible water loss through the skin in the patient unable to obtain water or swallow.

Dangerous Situations

Clinical findings progress from somnolence to confusion, coma, and respiratory paralysis as the hypernatremia worsens.

Commonly Encountered Situations

Hypernatremia most frequently occurs in an ICU when excess intravenous (IV) sodium is given to an unconscious patient.

Suggested Additional Lab Testing

Urinary electrolytes to assess for diabetes insipidus.

Serum aldosterone to identify primary hyperaldosteronism 24-hour urine free cortisol to identify Cushing syndrome, with or without ectopic ACTH production.