Low serum sodium levels at hospital admission: Outcomes among 2.3 million hospitalized patients

Fig 1. Flow chart of the sample selection process. aSerum sodium levels were corrected by adding 1.6 mEq/L for each 100 mg/dL above 100 mg/dL of the concomitantly measured serum glucose levels. bThis number was used to calculate the prevalence of hyponatremia (Na < 135 mEq/L) at hospital admission. cThe final cohort available for analysis.

Fig 2. Restricted cubic splines of the crude probability of in-hospital mortality, discharge to hospice, discharge to home, and discharge to nursing facility as a function of serum sodium levels at hospital admission. These estimated probabilities were derived from a multinomial logistic regression model. Serum sodium levels were corrected by adding 1.6 mEq/L for each 100 mg/dL above 100 mg/dL of the concomitantly measured serum glucose levels.

Fig 3. Forest plot of the relative risk ratios (95% CI) for in-hospital mortality, discharge to hospice, or discharge to nursing facility associated with different intervals of serum sodium levels (mEq/L) at hospital admission. The relative risk rations were derived from multinomial logistic regression models adjusted for age, gender, race, and the selected comorbidities and reasons for hospitalization. Discharge to home and serum sodium levels of (140 to <143 mEq/L) served as referent. Serum sodium levels were corrected by adding 1.6 mEq/L for each 100 mg/dL increase above 100 mg/dL of the concomitantly measured serum glucose levels. Error bars indicated 95% CI. CI = confidence interval.

Fig 4. Restricted cubic splines of the estimated probability of in-hospital mortality as a function of serum sodium levels for the different age groups. These estimated probabilities were derived from a multinomial logistic regression models stratified by age.

Fig 5. Forest plot of the relative risk ratios (95% CI) for in-hospital mortality associated with different intervals of serum sodium levels (mEq/L) at hospital admission for the different age groups. The relative risk ratios were derived from multinomial logistic regression models adjusted for age, gender, race, and the selected comorbidities and reasons for hospitalization. Serum sodium levels of (140 to <143 mEq/L) served as referent and each age group served as its own referent. Serum sodium levels were corrected by adding 1.6 mEq/L for each 100 mg/dL increase above 100 mg/dL of the concomitantly measured serum glucose levels. Error bars indicated 95% CI. CI = confidence interval. p<0.001 for all except for age 65 to <75 in the 135 to <138 mEq/L category (p = 0.43).