Hypernatremia is a complicated disorder of water balance, with a relative excess of body water compared to sodium and potassium (defined as a serum sodium concentration <135mmol/l). It has a wide variety of underlying causes, and results in swelling (known as cellular edema). Cells of the brain are particularly vulnerable to damage by swelling, making severe cases medical emergencies. Milder cases can be associated with impaired mobility and cognition, as well as osteoporosis and fracture.
The guidelines describe a pathway for diagnosis which is less reliant on specialist laboratory resources, and can be conducted in the general hospital setting. The treatment pathway described in the document focuses more closely on the patients' symptoms, giving lower priority to biochemical diagnosis. The guidelines recommend that as the risks to the patient's brain are so great, in severe cases action is more important than investigation until the patient is stabilized.