Changes in Serum Creatinine Levels Can Help Distinguish Hypovolemic From Euvolemic Hyponatremia

This study evaluates the usefulness of the changes in serum creatinine in differentiating between euvolemia and hypovolemia in hyponatremic patients. Changes in serum creatinine were retrospectively analyzed . The latter was calculated subtracting the serum creatinine value of eunatremia from that of hyponatremia, and was categorized as an increase when it was "positive", or "decrease/no change" when it was negative or equal to zero. The percentual change in serum creatinine was also calculated.

Two groups of patients were selected for the current study. First group was conformed by patients with hypovolemic hyponatremia, and second group by patients with euvolemic hyponatremia. Data from eunatremia as well as the hyponatremic episode were collected. Both groups were matched in Receiver operating characteristic curve analyzes where both arithmetical and percentual changes in serum creatinine were assessed and cut-off points were selected for an additional Odd Ratio analysis.

Inclusion criteria

• Patients with hypovolemic hyponatremia secondary to any cause
• Patients with euvolemic hyponatremia caused by Syndrome of inappropriate antidiuresis
• Complete clinical volemia assessment during hyponatremia.
• Presence of serum creatinine measured in eunatremia as well as in hyponatremic episodes.

Exclusion criteria

• Pregnants.
• Patients with a prior history of diabetes, advanced chronic kidney disease (glomerular filtrate rate below 30 ml/min), cirrhosis, or heart failure were excluded.
• Patients with hypervolemic hyponatremia.