Incidence and mortality due to hyponatremia in patients with cancer

Abstract

Introduction: Hyponatremia is the most common electrolytic disorder in the clinical practice and it is associated with an increase in mortality in cancer and other illnesses. Objectives: a) To determine the incidence and type of hyponatremia (defined as plasmatic sodium ≤130 mEq/L) at admission in lung, breast and gastrointestinal cancer patients hospitalized due to clinical complications. b) To determine if the hyponatremia at admission is associated with hospital-mortality in lung, breast and gastrointestinal cancer patients. Methods: A prospective observational study was conducted between January and December 2009; all patients with lung, breast and gastrointestinal cancer (locally advanced or metastatic) admitted in Alexander Fleming Institute due to non-scheduled consults were included. Hyponatremia was classified as hypotonic (hypovolemic, euvolemic and hypervolemic) or isotonic according to plasmatic osmolality and clinical data. Type of discharge was registered. Results: Three hundred and fifty seven admissions were included; 221 (61.9%) were females. Median age (range) was 60 (27-85) years. One hundred and nineteen (33.3%) were in lung cancer patients, 118 (33.1%) in breast cancer and 120 (33.6%) in gastrointestinal cancer patients. The median natremia (range) was 135 (114-146) mEq/L. The incidence of hyponatremia was 15.9% (57 cases). Plasma osmolality was measured in 53 cases of hyponatremia (92.9%). The median plasma osmolality (range) was 266 (216-291) mOsm/kg H2O. Forty three of the 53 cases of hyponatremia (83%) were hypotonic. The median urinary osmolality (range) was 371 (153-829) mOsm/kg H2O. Ten cases were isotonic. Of the 43 hypotonic hyponatremia, 18 (42%) were hypovolemic, 5 (11.5%) were isovolemic (inappropriate antidiuresis) and 20 (46.5%) were hypervolemic. Global mortality was 19.6% (70 /357). In the cases with hyponatremia the mortality was 47.3% (27/57) vs.14.3% (43/300) in the cases without hyponatremia (p< 0.0001). The odds ratio for mortality in cases with hyponatremia was 5.38 (IC 95% 2.92-9.92) Eighteen of the 43 cases (41.8%) of hypotonic hyponatremia died (9 hypovolemic, 8 hypervolemic and 1 isovolemic). No statistical differences (p: 0.4699) in mortality between the groups of hypotonic hyponatremia were found. Six of the 10 cases of isotonic hyponatremia died. No statistical differences (p: 0.4823) in mortality between the hypotonic and isotonic hyponatremia were found. Conclusions: The incidence of hyponatremia in patients with lung, breast and gastrointestinal cancer was 15.9%. The most common type of hyponatremia was the hypotonic and within them, the hypervolemic. Hyponatremia at admission was associated with an increase in hospital-mortality.