Hypernatraemia

From Ganfyd

Introduction

A plasma [Na] > 150 mmol/l

Types

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
  • Diabetes insipidus (whole body sodium is normal)
  • High volume diarrhoea such as cholera (likely to be also sodium depleted)

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.

Hypervolaemic hypernatraemia

• 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!