Background: Although hyponatremia with concomitant renal dysfunction has been described anecdotally, little is known about how these two conditions are related, which type of renal dysfunction usually occurs, and which patients are at risk.
Methods: From 3029 measured serum sodium (S(Na)) concentrations in 3 months, patients with at least one S(Na) < or =125 mmol/l were selected, and divided in patients with at least 1 S(Creat) > or =125 micromol/l (study group, n=20), and patients whose S(Creat) remained normal (control group, n=50).
Results: During the first 5 days of hospitalization, S(Creat) almost doubled in the study group from 125 +/- 40 micromol/l to 207 +/- 72 micromol/l, while S(Na) decreased concurrently from 130 +/- 2 mmol/l to 122 +/- 3 mmol/l. The peak S(Creat) and S(Na) values coincided, and the average courses were highly correlated (r = 0.88, p < 0.001). The study group more often had heart failure (10/20 vs. 1/50, p < 0.001) and liver failure (7/20 vs. 4/50, p = 0.009), and received more often loop diuretics (13/20 vs. 12/50, p = 0.002), spironolactone (11/20 vs. 7/50, p = 0.001), and/or angiotensin-converting enzyme inhibitors (5/20 vs. 2/50, p = 0.02). Four patients were admitted to the intensive care (10 in control group, p = 1.0), and 5 patients died (10 in control group, p = 0.7).
Conclusions: Renal dysfunction is common in severe hyponatremia and usually develops in an acute-on-chronic fashion with concomitant deterioration of both conditions. This concourse is associated with heart failure, liver failure, and/or a renal drug regimen. Given the recent results of clinical trials, this patient group may be especially suitable for treatment with vasopressin antagonists.