• Simit M Doshi, Pankaj Shah, Xiudong Lei, Amit Lahoti, and Abdulla K Salahudeen.
• Division of Internal Medicine, University of Texas M.D. Anderson Cancer Center, Houston, 77030, USA.
• Am. J. Kidney Dis. 2012 Feb 1;59(2):222-8.

BackgroundHyponatremia is the most common electrolyte abnormality in clinical practice, yet little is known about its frequency in patients with cancer or its impact on their clinical outcomes.Study DesignRetrospective analysis of prospectively collected data.Setting & ParticipantsPatients with cancer admitted to the University of Texas M.D. Anderson Cancer Center in 2006 for 3 months.PredictorSerum sodium levels categorized as eunatremia (serum sodium, 135-147 mEq/L) and mild (134-130 mEq/L), moderate (129-120 mEq/L), and severe (<120 mEq/L) hyponatremia.Outcomes(1) Length of hospital stay and (2) 90-day mortality.ResultsIn 4,702 admissions in 3,357 patients with cancer, hyponatremia (serum sodium <135 mEq/L) was noted in 47% of admissions. It was mild in 36%, moderate in 10%, and severe in 1%. Hyponatremia was acquired during the hospital stay in 24%. Using the first admission data, mean length of stay was 5.6 ± 5.0 days for patients with eunatremia and 9.9 ± 9.2, 13.0 ± 14.1, and 11.5 ± 12.6 days for those with mild, moderate, and severe hyponatremia, respectively. The respective HRs in the multivariate Cox model for longer hospital stay, using patients with eunatremia as reference, were 1.92 (95% CI, 1.75-2.13; P < 0.01), 2.94 (95% CI, 2.56-3.45; P < 0.01), and 2.32 (95% CI, 1.32-4.00; P = 0.01). 283 (8.4%) deaths occurred during 90 days, and in the multivariate model, the respective HRs for 90-day mortality for mild, moderate, and severe hyponatremia were 2.04 (95% CI, 1.42-2.91; P < 0.01); 4.74 (95% CI, 3.21-7.01; P < 0.01), and 3.46 (95% CI, 1.05-11.44; P = 0.04). These findings were consistent when analyses were repeated with sodium levels in tertiles.LimitationsObservational study, retrospective, inability to adjust for all comorbid conditions.ConclusionHyponatremia in patients with cancer is associated with longer hospital stay and higher mortality. Whether long-term correction of hyponatremia would improve these outcomes remains to be determined.Copyright © 2012 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

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