Serum sodium correction rate and the outcome in severe hyponatremia

Abstract

Study objective

We investigated the serum sodium correction rate on length of hospitalization and survival rate, in severe chronic hyponatremic patients at the Emergency Department (ED).

Design

An observational study using clinical chart review.

Setting

The ED of the University Hospital of Marcianise, Caserta, Italy with approximately 30,000 patients visits a year.

Type of participants

We reviewed sixty-seven patients with severe hyponatremia subdivided in 2 subgroups: group A consisting of 35 patients with serum sodium correction rate < 0.3 mmol/h and group B consisting of 32 patients with serum sodium correction rate between < 0.5 and ≥ 0.3 mmol/h.

Intervention

Emergency patients were evaluated for serum sodium correction rate for hyponatremia by clinical chart review.

Measurements and main results

Severe hyponatremia was defined as a serum sodium level < 120 mmol/l. Mean serum sodium correction rate of hyponatremia was of 0.17 ± 0.09% in group A and 0.41 ± 0.05% in group B (p < 0.001 vs group A). The length of hospital stay was 10.7 ± 3.7 days for group A, and it was significantly decreased to 3.8 ± 0.4 days for group B (p < 0.005 vs group A). In addition we observed that correction rate of hyponatremia in group A was associated with a significantly lower survival rate (25%) in comparison to group B (60%) (p < 0.001 vs group A).

Conclusion: We observed that serum sodium correction rate ≥ 0.3 and < 0.5 mmol/h was associated with a shorter length of hospital stay and a major survival rate.

Introduction

Hyponatremia is the most common electrolyte disorder in the Emergency Department (ED) and it represents a serious medical condition that is associated with higher risk of morbidity and mortality [1].

The prevalence of hyponatremia is about 3–10% in the ED [2], [3] and it is more frequent in hot seasons [4].

The serum sodium correction rate in hyponatremia is crucial for the outcome of emergency patients. Excessively fast correction of hyponatremia has been recognized as a major risk factor for the development of the osmotic demyelination syndrome (ODS). In fact, to reduce neurological complications, it has been recommended to avoid overcorrection of hyponatremia > 12 mmol/l in a 24 h period (0.5 mmol/h) [3], [5], [6], [7], [8].

Similarly, Spasovski et al., recommended to avoid an increase in serum sodium concentration rate > 10 meq during the first 24 h (0.4 mmol/h) [9]. Moreover, Verbalis et al., recommended [10] that the minimum goal of serum sodium correction is 4–8 mmol/l day with a maximum limit of 10–12 meq/l (0.4–0.5 mmol/h) in the first 24 h. In particular, Gross et al., [11] observed that, in chronic severe hyponatremia, problems might arise when it is corrected faster than 0.5 mmol/h. In fact, in patients with severe chronic hyponatremia, a maximum increase of 10–12 mmol/l/day (0.5 mmol/h), has been proposed the first day [6], [12].

However, very limited data are reported about the effects of too slow sodium correction rate on the outcome of severe hyponatremic patients in ED.

Thus, in the present study among severe hyponatremic patients at the ED, we report the length of stay and the survival rate of patients with a mean correction rate < 0.3 mmol/h (group A) and with a mean correction rate ≥ 0.3 and < 0.5 mmol/h (group B).