Treatment of euvolemic hyponatremia in the intensive care unit by urea

Abstract

Introduction: Hyponatremia in the intensive care unit (ICU) is most commonly related to inappropriate secretion of antidiuretic hormone (SIADH). Fluid restriction is difficult to apply in these patients. We wanted to report the treatment of hyponatremia with urea in these patients.

Methods: Two groups of patients are reported. The first one is represented by a retrospective study of 50 consecutive patients with mild hyponatremia treated with urea. The second group is presented by a series of 35 consecutive patients with severe hyponatremia acquired outside the hospital (≤ 115 mEq/L) who where treated by isotonic saline and urea (0.5 to 1 g/kg/day), administered usually by gastric tube.

Results: In the first group with mild hyponatremia (128 ± 4 mEq/L) the serum sodium (SNa) increased to a mean value of 135 ± 4 mEq/L (P < 0.001) after two days of urea therapy (46 ± 25 g/day), despite a large fluid intake (> 2 L/day). The mean duration of urea therapy was six days (from 2 to 42 days). Six patients developed hyponatremia again once the urea was stopped, which necessitated its reintroduction. Six patients developed hypernatremia (maximum value 155 mEq/L). In the second group, SNa increased from 111 ± 3 mEq/L to 122 ± 4 mEq/L in one day (P < 0.001). All the patients with neurological symptoms made a rapid recovery. No side effects were observed.

Conclusions: These data show that urea is a simple and inexpensive therapy to treat euvolemic hyponatremia in the ICU.

Figure 1

Evolution of SNa and blood urea in 50 patients before and after urea therapy.

Figure 2

Evolution of SNa in 35 patients with severe hyponatremia treated by urea and isotonic saline. (a) Daily evolution of SNa (mean ± SD) in 35 patients with severe hyponatremia (≤ 115 mEq/L) treated with isotonic saline and urea (*P < 0.001 compared to Day 0). (b) Daily evolution of SNa (mean ± SD) in 12 patients with severe hyponatremia (≤ 115 mEq/L) who received the first day only isotonic saline (1 or 2 L). The addition of urea increased significantly SNa (*P < 0.01 compared to Day 0). (c) Evolution of SNa (mean ± SD) each four hours in 10 patients with severe hyponatremia treated with 1 L isotonic saline over 12 hr and urea (0.5 g/kg) (P < 0.01 compared to time 0).