Longer Hospital Stays and Higher Mortality for Cancer Patients with Hyponatremia, Study Shows

Hyponatremia is associated with longer hospital stays and higher mortality among cancer patients who exhibit the condition, according to the results of a large study that combined a retrospective analysis and with prospectively collected data.

The study, published in February in the American Journal of Kidney Diseases, looked at data from 4,702 admissions of 3,357 patients with cancer. Of those patients, 1,596 (47%) presented with hyponatremia, defined as serum sodium < 135 mEq/L, with cases of hyponatremia being classified as either mild (134-130 mEq/L; n=1,235, 36%), moderate (129-120 mEq/L; n=342, 10%), or severe (< 120 mEq/L; n=19, 1%). Hyponatremia was hospital-acquired in 24% of cases.

The study used length of hospital stays and 90-day mortality as primary outcomes. Patients with hyponatremia had significantly higher hospital stays (10.2 days ± 10.2 days) compared to patients with eunatremia, or normal sodium levels (5.6 days ± 5.0 days, P < .01). When analyzed by severity, patients had significantly longer stays if they had mild hyponatremia (9.9 days ± 9.2 days) or moderate hyponatremia (13.0 days ± 14.1 days). The severe hyponatremia group had few patients and therefore did not have a statistically significant difference in hospital stay that could be evaluated as part of this study.

Among the 3,357 patients in the study, 283 (8.4%) patients died during the 90-day follow-up period. After the study’s authors adjusted for age, type of malignancy, chemotherapy, antibiotic use, and levels of serum creatinine, calcium, potassium, hematocrit, and blood glucose, the hazard ratios (HRs) for 90-day mortality were higher in the mild (HR, 2.04; 95% CI, 1.41-2.91; P < .01), moderate (HR, 4.74; 95% CI, 3.21-7.01; P < .01) and severe (HR, 3.46; 95% CI, 1.05-11.44; P = .04) hyponatremia groups relative to patients with eunatremia (HR, 1.00; reference).

While the study does not account for the causes of hyponatremia among these patients, the data was collected from large academic medical centers, therefore encompassing a wide variety of tumor types, and the authors were able to account for corrections to hyponatremia as the data was collected. The authors suggested that further studies should investigate long-term correction of hyponatremia to observe its effects on patient mortality and length of hospital stay.