[The prevalence and causes of hyponatremia in hospitalized patients].

The study was aimed to investigate the prevalence and causes of hyponatremia in hospitalized patients, and to analyze the relationship between hyponatremia and mortality. A retrospective analysis was carried out in 525 patients with hyponatremia, who were older than 14 years old and hospitalized in the Zhoushan Hospital from Jan. 2014 to Apr. 2014. Based on the severity of the hyponatremia the patients were divided into three groups: the mild, moderate and severe hyponatremia groups. The underlying causes of hyponatremia were analyzed, and the association between hyponatremia and mortality was explored using logistic regression analyses. (1) The prevalence of hyponatremia was 5.26% in whole hospitalized patients (9 989) during the study period. It was 6.1% in the elderly population (≥60 years old). (2) Malignant tumors and infectious diseases were the main primary diseases of hyponatremia in all three groups. Among them, lung cancer was the most common malignant tumor, and pneumonia was the most common infectious disease associated with hyponatremia. Cerebral hemorrhage was common in patients with moderate and severe hyponatremia, in which subarachnoid hemorrhage was the major primary disease associated with moderate to severe hyponatremia. In the subgroup of elderly patients, malignant tumor and infectious diseases were the major basic diseases. (3) Among the 525 cases, 13.7% and 3.8% of them were diagnosed with syndrome of inappropriate antidiuretic hormone secretion (SIADH) and cerebral salt-wasting syndrome (CSWS), respectively. The proportions of SIADH and CSWS increased to 17.4% and 4.2%, respectively, in the elderly hyponatremic patients (264). (4) More patients were prescribed with sodium-excretion drugs in the moderate and severe hyponatremia groups than those in the mild one(42.2% vs.21.4%, 43.2% vs.21.4%, all 0.05). (5) Patients with moderate or severe hyponatremia had a higher mortality compared to those with mild hyponatremia (moderate vs. mild group: 6.92, 95 2.53-18.92, 0.001; severe vs. mild group: 4.54, 95 1.05-19.58, 0.043). Hyponatremia was common in hospitalized patients. The major primary diseases were malignant tumor (lung cancer), infectious diseases (pneumonia) and cerebral hemorrhage complicated with SIADH and CSWS. Use of sodium-excretion drugs increased the risk of moderate to severe hyponatremia. Patients with moderate to severe hyponatremia had a higher risk of death in hospitals.