5th April 2024

Hypernatraemia

High plasma sodium > 145 mmol/L is usually the result of water depletion but can be caused by excess salt intake, diabetes insipidus and administration of hypertonic sodium. Low serum protein may result in falsely raised sodium levels. The cause can be determined by the timeline of events with accompanying serum and urine sodium testing. Hypernatraemia can be classified according to the patient’s fluid status:

• Hypovolemic hypernatraemia from excessive sweating and dehydration; vomiting, diarrhoea, diuretic use and kidney disease. 
• Euvolemic hypernatraemia due to fever, diabetes insipidus and drugs including lithium.
• Hypervoleamic hypernatraemia causes include hyperaldosteronism, excess administration of hypertonic saline or sodium bicarbonate and rarely, from excess salt intake 
• Low serum protein may result in falsely raised sodium

Clinical manifestations 

Early symptoms include polydipsia, anorexia, nausea and weakness. Severe symptoms include confusion, myoclonic jerks and seizures.