Epidemiology

The prevalence of hypernatraemia in hospitalised patients varies, depending on the definition used. Severe hypernatraemia (defined as serum sodium concentration of >155 mmol/L) occurred in 0.4% of the entire inpatient population of one US hospital.[10]

Hospital-acquired hypernatraemia is the most common form of hypernatraemia, and it is iatrogenic in some cases.[11][12]​​[13][14]​ In a study of hospitalised cancer patients, 90% of patients with hypernatraemia acquired it during their stay.[15]

Hypernatraemia is more common in intensive care units, especially trauma and burns units. Prevalence has variously been reported as: 2.5% in one surgical intensive care unit; 9.9% in one burns intensive care unit; 7.9% in one medical intensive care unit.[16][17]​​​[18] A study in a paediatric intensive care unit found that 18% of patients had severe hypernatraemia (defined as a serum sodium concentration of 151-160 mmol/L).[19] Another study of more than 200,000 patients in intensive care units found that 4.3% of patients developed hypernatraemia.[20] The highest prevalence has been found in patients with severe traumatic brain injury (16% to 40% of patients).[21]

Hypernatraemia that is present on admission to hospital is less common. It usually occurs in older people and is often associated with fever, infection or sepsis.[2][12][22][23][24][25]​​ Hypernatraemia on admission to hospital is more common in people who live in residential care homes, compared with those who live in their own homes.​[26] In one academic medical centre, 0.2% of patients had a serum sodium concentration >150 mmol/L on admission, while 1% of patients developed hypernatraemia after admission.[12]​​ Those who developed hypernatraemia after admission​ were 20 years younger on average than the patients presenting to hospital with hypernatraemia.

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