A plasma [Na] > 150 mmol/l
Water depletion (Hypovolaemic hypernatraemia)
- Water deprivation
- Because hypernatraemia is a strong stimulus to thirst, reduced water intake is almost always involuntary (e.g. coma, dysphagia, extreme depression). Patients with water losses will become hypernatraemic more quickly:
- Loss of large volumes of hypotonic fluid
Treatment is by oral replacement of water in mild cases; 5% dextrose (i.v.) in moderate cases; and a combination of 5% dextrose and 0.9% (150mmol/l) saline (i.v.) if dehydration is severe, as volume expansion requires salt as well as water.
- Iatrogenic infusion of too much [Na]
This will usually be a strong driver to thirst in a conscious, capable patient. Treatment: stop giving them sodium!
This article is a work in progress. Please feel free to contribute to it.