Validation of New Diagnostic Indices to Simplify Hyponatremia Therapy Assessment in Patients on Thiazide Diuretics

Validation of Diagnostic Indices to Simplify Hyponatremia Therapy Assessment - A Randomized, Controlled, Parallel-group Clinical Trial in Hospitalized Patients on Thiazide Diuretics (THAT Study)

This study is looking at two new parameters, aSID and ChU, to see if these can help physicians to distinguish between different causes of low sodium levels (hyponatremia) in Patients taking a medicament against high blood pressure (thiazide). Researchers also want to see if using these new parameters to decide on treatment works just as well, or better, than the current standard treatments.

Thiazide or thiazide-like diuretics associated hyponatremia (thiazide associated hyponatremia, TAH) has a high prevalence in hospitalized patients. Patients might present either with a hypovolemic hyponatremia due to volume loss as a diuretic effect of thiazide, or with a syndrome of inadequate antidiuresis (SIAD) like hyponatremia in need of fluid restriction. Canonical urine indices are not useful in differential diagnosis, being directly influenced by thiazide itself. Current guidelines suggest the use of a clinical volume status assessment, but this approach has a poor diagnostic performance, with less than 50% of patients being rightly diagnosed thru that. The investigators showed in a retrospective analysis the possible role of strong apparent ion difference (aSID) and of chloride and potassium levels in urine (ChU) in differential diagnosis of TAH. The goal of this study is to investigate prospectively whether implementation of aSID and, in case of inconclusive aSID, ChU, allows a correct differential diagnosis and treatment of TAH.

Inclusion Criteria:

• Hospitalized patients presenting at University Hospital Basel
• aged 18 years or older
• able to give informed consent as documented by signature
• with serum sodium level < 133 mmol/l and serum osmolality < 300 mOsm/kg
• with treatment with thiazide or thiazide-like diuretic

Exclusion Criteria:

• symptomatic hyponatremia in need of 3% hypertonic solution or intensive care treatment
• inability or contraindications to undergo the trial (i.e., any acute severe cardiovascular event requiring an immediate intervention)
• decompensated liver cirrhosis CHILD C
• decompensated heart failure NYHA III or higher
• severe valve impairment
• untreated adrenal insufficiency
• severe kidney disease in need of dialysis
• pregnancy or breastfeeding
• end of life care
• inability to follow the study procedures (i.e., language problem, dementia or critical illness).