According to published hyponatremia guidelines, profound
hyponatremia, defined as a serum sodium value
of less than 125 mmol/L, is common and occurs in 2% to
3% of hospitalized individuals.1–4 Symptoms of profound
hyponatremia are largely related to dysfunction of the
central nervous system, vary from mild (nausea, headache,
confusion) to severe (seizures, coma), and depend mostly
on the degree, time, and speed of onset of the hyponatremia.5
Individuals with acute hyponatremia develop brain
edema. A shift of water from the extracellular compartment
to the intracellular compartment of the brain with
consecutive swelling of all brain cells results mostly in neurological
symptoms.6,7 Adaptation of increased brain cell
volume occurs within a few hours, and normalization of
brain cell volume is completed within 48 hours because of
cellular electrolyte loss.8 Consequently, individuals with
stable, chronic hyponatremia are mostly asymptomatic.
Nevertheless, recent retrospective data show that individuals
with hyponatremia considered to be clinically asymptomatic
have a higher incidence of falls as a result of gait
disorder and attention impairments.9 Prospective studies to
assess symptoms and characteristics in individuals with
profound hyponatremia are lacking, so a prospective study
was conducted to assess participant characteristics,
symptoms, and etiological causes and the management of
individuals admitted to two tertiary care centers in
Switzerland with profound hyponatremia.