To develop hyponatremia (plasma sodium concentration (PNa) < 136 mM), there must be a source of electrolyte free water (EFW) and actions of antidiuretic hormone (ADH) to prevent its excretion. A low PNa is the most common electrolyte disorder in hospitalized children and it makes them more prone to neurological damage.
To establish the incidence of and to identify risk factors for the development of hospital-acquired hyponatremia in a tertiary care hospital.
We included all children (n = 432) who had two or more PNa-measurements in the Emergency Department in a 3-month period and in hospital over the first 48 hours.
The incidence of hyponatremia was 22.5% of whom 14.4% were hyponatremic on presentation and 9.3% developed hyponatremia in hospital (five patients fell in both groups). ADH was likely elevated due to disease (7.9%; e.g. bronchiolitis), symptoms (47%; e.g. nausea) and treatment (45.1%; e.g. surgery). Eighty-three percent of the EFW responsible for the falls in PNa was administered as either hypotonic intravenous (66%) or oral fluids (34%) and was excessive in 53% of the cases. Those who did not seem to receive excessive EFW had an occult source of water, hyperglycemia (16%), mannitol (8%) and/or excreted hypertonic urine (62%).
The most important factor for hospital-acquired hyponatremia is the administration of hypotonic fluids. Hospital-acquired hyponatremia is iatrogenic and therefore preventable. It unnecessarily puts children at risk of neurological damage. The practice of IV-fluid therapy should be re-evaluated.