The prevalence of dysnatremia in the elderly patients without CKD

Dysnatremia is one of the most commonly encountered electrolyte disorders in the emergency department (ED). Few studies have reported the prevalence of dysnatremia in elderly patients without chronic kidney disease (CKD). We investigated the prevalence of dysnatremia in elderly patients without CKD in an emergency department in Japan.

We reviewed 10,558 patients presenting to the ED between July 2015 and December 2017. The adult group consisted of 4562 patients aged between 18 and 64 years old, and the elderly group consisted of 5996 patients aged over 65 years. Information collected included age, gender, serum sodium and serum creatinine. Hyponatremia was defined as serum sodium level < 135 mEq/L, and severe hyponatremia was defined as a serum sodium level < 125 mEq/L. Hypernatremia was defined as a serum sodium level > 145 mEq/L, and moderate to severe hypernatremia was defined as a serum sodium level ≧ 150 mEq/L.

In the adult group, the prevalence of hyponatremia was 2.8% in patients without CKD and 10.3% in patients with CKD (P < 0.001). On the other hand, in the elderly group, the prevalence of hyponatremia was 14.8% in patients without CKD and 12.9% in patients with CKD (P = 0.034). In the adult group, the prevalence of hypernatremia was 0.7% in patients without CKD and 2.0% in patients with CKD (P = 0.003). Similarly, in the elderly group, the prevalence of hypernatremia was 1.5% in patients without CKD and 3.5% in patients with CKD (P < 0.001).

In elderly patients, the prevalence of hyponatremia was higher in patients without CKD than in patients with CKD. Special attention should be paid to elderly patients without CKD in order to prevent severe hyponatremia.