Fractional Urate Excretion in Nonedematous Hyponatremia
Status:
Withdrawn
Trial end date:
2014-12-01
Target enrollment:
Participant gender:
Summary
Hyponatremia, defined as a serum sodium < 135 mmol/l, in patients without edema has undergone
significant changes where it is now evident that even mild hyponatremia should be treated
because of its association with symptoms, especially a fourfold increase in falls over the
age of 65 years. There is an unresolved controversy over the relative prevalence of the
syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and cerebral/renal salt
wasting (C/RSW). Resolution of this diagnostic dilemma becomes urgent because of divergent
therapeutic goals, to water-restrict in SIADH or to give salt and water supplementation in
C/RSW. The dilemma is compounded by recent reports of C/RSW occurring in patients without
cerebral disease, thus adding further confusion in defining the relative prevalence of both
syndromes. Because of overlapping laboratory and clinical findings in both syndromes, only
differences in the state of extracellular volume differentiates one syndrome from the other,
being high normal to increased in SIADH and decreased in C/RSW. The investigators have used
fractional excretion (FE) of urate to categorize patients with hyponatremia. The increased
FEurate that is observed in hyponatremic patients with SIADH and C/RSW can be used to
differentiate both syndromes by correcting the hyponatremia and determining whether FEurate
normalizes as in SIADH or remains increased in C/RSW. The present studies have been designed
to determine total body water by deuterium and extracellular water by sodium bromide in
patients with nonedematous hyponatremia with normal and increased FEurate to differentiate
more conclusively whether the patient has normal or decreased water volumes. The
investigators will also correct serum sodium rapidly with judicious administration of
hypertonic saline over approximately three days and determine whether FEurate normalizes as
in SIADH or remains increased as in C/RSW. In another group of patients, The investigators
have data to suggest that those with normal sodium and increased FEurate is consistent with
C/RSW. The investigators intend to do the same water volume studies to determine whether an
increased FEurate with normonatremia would have decreased total and extracellular water that
these patients have C/RSW without the need to correct a prior hyponatremia.