Prognosis

The short-term mortality rate in patients with hypernatraemia has been reported to be 32% to 70%.[10][12]​​​​[17][20][41][47]​​​​​​ Patients with hypernatraemia tend to do worse than patients with other electrolyte abnormalities such as hyponatraemia.[15][104][105]​​​ Studies have shown that older adults in hospital who have hypernatraemia have higher mortality rates.[71]​ Disorders of sodium balance (whether hospital- or community-acquired) are independent risk factors for in-hospital mortality.[1][10][106][107]​​​​​​​

Severity of hypernatremia

The relative contribution that hypernatraemia makes to a poor prognosis in patients with serious underlying diseases is unclear. Some authors believe that, at least with severe hypernatraemia, the hypernatraemia itself contributes to a poor prognosis.[108] One study found that hypernatraemia directly contributed to mortality in 16% of patients.[12]​ Another study found that only severe hypernatremia (defined as >160 mmol/L in the study) was independently associated with mortality in a neurological intensive care unit.[109] Hypernatraemia has also been shown to be an independent risk factor for mortality in other intensive care units.[18][110][111] Interestingly, it is the severity of the hypernatraemia, not the duration, that was associated with mortality, especially with community-acquired hypernatraemia.[20][112]

Chronic, mild hypernatraemia and normal serum sodium concentrations that are at the higher end of the normal range have been associated with a significantly increased risk of cardiovascular events and mortality in older men.[113] Pre-operative hypernatraemia has also been found to be an independent predictor of peri-operative morbidity and mortality.[114][115] Hypernatraemia has been associated with longer hospital stays.[116]

Recurrence

Recurrence depends on whether the inciting factors continue to be present. In patients with dementia who do not have access to water or who have lost their sense of thirst, the risk of developing hypernatraemia is always high.

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