Definition and Clinical Features of Hypernatraemia

In this article, we will discuss the Definition and Clinical Features of Hypernatraemia. So, let’s get started.


Hypernatraemia is defined as plasma sodium concentration greater than 145 mEq/L. Hypernatraemia infactis hyperosmolarstate because Na+ is a major effective ECF osmole and a major detertminant of osmolality.
Hypematraemia may be due to primary Na+ gain or water deficit. Thus hypematremic patients are usually hypovolaemic, while hypervolemia is frequently seen as iatrogenic complication in hospitalised patients with impaired access to free water. The two physiological responses to hypernatraemia are increased water intake stimulated by thirst and excretion of concentrated urine reflecting ADH secretion in response to an increased osmolality.

Clinical Features

The clinical manifestations are as a result of hypertonicity which shifts water out of the cells leading to contraction of ICF (intracellular fluid) volume. A decreased brain cell volume results in CNS features and increases the chances of brain haemorrhage. The symptoms
and signs are:

1. CNS involvement
• Altered mental status, restlessness,
lethargy, weakness
• Neuromuscular irritability, e.g.
muscular twitchings, hyperreflexia, tremulousness, ataxia.
• Focal neurological deficits
• Occasionally seizures and coma.
• Polyuria and excessive thirst.

2. Volume depletion
• Severe thirst.
• Dryness of tongue, loss of skin turgor.
• Tachycardia, hypotension (low BP)
• Oliguria, concentrated urine, raised urea and Na+

3. Vascular consequences: There are
increased chances of intracerebral and subarachnoid haemorrhage leading to irreversible neurological sequalae.

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