Three experienced board-certified endocrinologists
retrospectively adjudicated the final diagnosis of the underlying
cause of hyponatremia in a structured, standardized
fashion using data prospectively collected at admission and
throughout hospitalization, covering the entire inpatient
course, including response to all interventions. These three
experts were not involved in participant treatment and
care, but complete medical records, all comorbidities,
previous medication, and laboratory values (fractional
excretion of uric acid (FEUA), fractional excretion of urea
(FEurea), urine sodium, plasma and urine osmolality) were
available and used in the final decisions.
Each physician adjudicated the underlying cause of
hyponatremia independently; in cases of discordance, the
panel discussed the data in depth to reach consensus, and
if etiology was multifactorial, the predominant cause was
chosen as the final classification.
According to recently published guidelines,10 acute
hyponatremia was defined as hyponatremia documented to
exist for less than 48 hours. In cases without a previously
documented serum sodium level, hyponatremia was classi-
fied as being chronic. Treatment in the intensive care unit
and in-hospital death from any cause was recorded.