Asymptomatic hyponatremia: is it time to abandon this entity?

Introduction Hyponatremia is the most common electrolyte abnormality seen in clinical practice. It occurs in wide variety of clinical conditions. Studies have shown that presence of hyponatremia is a risk factor for morbidity and mortality. Despite hyponatremia being a commonly encountered condition, there is no consensus in its management. Recently published guidelines have made an attempt to bring uniformity in management of hyponatremia. There is a consensus that all symptomatic hyponatremia must be treated. The purpose of this paper is to question the existence of ‘asymptomatic hyponatremia.’ Analogy is similar to hypokalemia wherein even milder degree of hypokalemia is treated because of risk of cardiac arrhythmia. But most of the clinicians are ready to accept mild degree of hyponatremia as harmless. Hyponatremia is defined as serum sodium of less than 135 mEq/l. It is the most common abnormality of fluid and electrolytes encountered in clinical practice. It occurs in up to 30% of hospitalized patients and can lead to a wide spectrum of clinical symptoms, from subtle to severe or even life threatening (1). It can be classified on basis of duration, severity and symptoms (Box 1). Traditional teaching is to classify hyponatremia as symptomatic and asymptomatic based on symptoms. Based on recent studies the very existence of ‘asymptomatic hyponatremia’ needs to question. Does asymptomatic hyponatremia really exist? Symptoms of hyponatremia can vary from mild, nonspecific to severe and life-threatening. Severe symptoms are because of cerebral edema and increased intracranial pressure. Severe signs of acute hyponatremia are well established and can be easily recognized by the clinicians. It is of utmost importance to understand the fact that even patients with chronic hyponatremia and no apparent symptoms can have subtle clinical abnormalities (Box 2). The subtle effects may be go undetected on a casual clinical examination.