Hypernatremia

Learning objectives

Mild symptoms	Severe symptoms
Anorexia Muscle weakness Restlessness Headache Confusion Nausea	Vomiting Seizures Coma Brain shrinkage, resulting in vascular rupture and intracranial bleeding

Primary hypodipsia	Lack of thirst Usually caused by destruction of the hypothalamic thirst center Due to primary or metastatic tumors, granulomatous disease, vascular disease or trauma
Diabetes insipidus	Caused by a defect in the secretion of ADH in the hypothalamus or by a defective response to ADH in the renal tubules Resulting in production of large amounts of urine (polyuria), thereby raisings the Na+
Pure hypertonic saline gain	Relatively rare cause of hypernatremia caused by the ingestion of hypertonic solutions
Combination of inadequate fluid intake + increased free water loss	The most common cause of hypernatremia in the elderly Pathophysiology: the thirst mechanism weakens and renal function declines with increasing age Frail elderly people, particularly those living alone may also have difficulties obtaining adequate fluid volumes
Hyperglycemia
Hyperaldosteronism

Estimate volume status and total body water deficit with this formula: WD1 = 0.6 × bodymass × [1 − (140 ÷ Na+)]
Treat the underlying cause and correct the water deficit
- First choice of fluid: oral free water
- IV: use hypotonic solutions
- Do NOT rapidly correct or overcorrect, this increases the risk for cerebral edema
A correction rate of 1 mmol/L per hour is considered a safe rate of correction
- NOTE: This rate is NOT recommended in chronic hypernatremia!
In patients where hypernatremia is present for a longer period, the sodium level should be corrected at a rate of 0.5 mmol/L per hour, max 8 – 10 mmol/L per 24 hours
In patients with acute hypernatremia, quick correction of sodium can be perfomed safely with isotonic saline or water without the risk of cerebral edema

Hypernatremia, hypovolemic, euvolemic, hypervolemic, urinary osmolality, sodium, hypodypsia, diiabetes insipidus