Severe Solute Depletion in Patients with Hyponatremia Due to Diuretics Despite Biochemical Pictures Similar Than Those Observed in the Syndrome of Inappropriate Secretion of Antidiuretic Hormone.

Background/aims: Hyponatremia secondary to distal diuretics intake could have a biochemical picture similar to the one observed in the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). In these patients, water retention is considered to be the main causal factor and solute depletion a secondary one.

Methods: We compared the level of cation (Na + K) depletion and water balance in patients with high or low uric acid levels (< 4 mg/dL or 238 µmol/L) or with high or low (< 30 mg/dL or 5 mmol/L) urea levels. Data were collected from 15 consecutive patients treated in a similar way by a daily infusion of 2 L isotonic saline with potassium chloride until SNa reached at least 132 mmol/L. The same procedure was performed in 6 patients with hyponatremia due to salt depletion not related to diuretic intake.

Results: Hyponatremia, associated with low or high uric acid level is mainly due to severe cation depletion (around 600 mmol) and not due to water retention, since body weight did not change significantly (SNa 122 ± 2.0 mEq/L). If patients were classified according to serum urea levels those with higher urea levels (≥30 mg/dL) presented with a mild increase in BW (0.84 ± 0.37 kg). In patients with salt depletion and hyponatremia not related to diuretic intake, we observe as expected an increase in BW (1.5 ± 0.3 kg) and similar cation retention with the treatment.

Conclusion: We therefore suggest that diuretic induced hyponatremia with an SIADH-like biochemical profile, should be treated mainly by solute -repletion.