Hyponatremia at admission is associated with in-hospital death in patients with hip fracture

Hyponatremia in hospitalized patients has been reported to be associated with in-hospital mortality. We studied patients treated at our hospital for hip fracture regarding the factors related to hyponatremia at admission. Among 580 patients aged 60 years or above who were admitted to our hospital since January 1997 for treatment of hip fracture, 512 patients (110 males, 402 females) from whom serum sodium level at admission was available were studied. In 512 patients, the age at injury ranged from 60 to 103 (mean 82.6) years. Fracture types were femoral neck fracture in 191 patients, and trochanteric fracture in 321. These patients were divided into two groups by the blood sodium level at admission: a hyponatremia group with sodium levels lower than 135 mEq/L, and a normonatremia group with sodium levels within normal range. The age, gender, fracture type, residence before injury, pre-injury walking capability, anemia at admission, liver function, kidney function, inflammatory status, urinary glucose status, lung disease, ECG abnormality, systemic chronic disease, status of dementia, treatment modality, hospital stay (days), and in-hospital death were investigated. First a univariate study was conducted to identify the factors that differ significantly between the two groups. Then multivariate analysis was conducted using the parameters with significant difference as independent variables Hyponatremia was found in 49 of 512 (9.6 %) patients. In univariate analyses, six factors (age; residence before injury; anemia; dementia; treatment modality; in-hospital death) were significantly different between the hyponatremia group and normonatremia group. Multivariate analysis identified in-hospital death [odds ratio (OR) = 3.64, p = 0.035] and age (OR = 1.05, p = 0.029) as independently associated with hypernatremia. Hyponatremia at admission is prevalent in old aged patients with fracture, and is related to in-hospital death.