Hyponatremia Associated With Cancer
Hyponatremia is the most common electrolyte disorder encountered in patients with malignancies. Studies have reported a prevalence that ranges from approximately 4% to as high as 47%.
1,2 Approximately 14% of hyponatremia encountered in medical inpatients is due to an underlying malignancy-related condition.
3 It is important to note that nearly half of these cases represented hospital-acquired hyponatremia, suggesting that management of these patients (most likely with intravenous fluids) significantly contributes to the development of hyponatremia.
Hyponatremia is clearly associated with significant morbidity and mortality when it occurs in the patient with cancer. For instance, hospital length of stay is nearly doubled in patients with moderate to severe hyponatremia.
1 The hazard ratio for death within 90 days after the diagnosis of hyponatremia was 4.74 in those patients with moderate hyponatremia and 3.46 in patients with more severe hyponatremia.
1 Other studies have also demonstrated a marked association with hyponatremia and mortality in patients with non-Hodgkin’s lymphoma, renal cell carcinoma, gastric cancer, and small-cell lung cancer.
4-6 Hyponatremia may affect patient response to therapy, as shown in non-Hodgkin’s lymphoma, in which patients with serum sodium less than 137 mEq/L had a lower rate and shorter duration of remission after chemotherapy as compared with patients with higher sodium levels.
4 Likewise, hyponatremia may limit the use of chemotherapeutic options that require extensive hydration. Symptoms attributable to hyponatremia, such as confusion, lethargy, and headache, may also further compromise quality of life in this population.
It is debatable whether hyponatremia independently contributes to these poor outcomes or is simply a marker of disease severity, progression, and overall debility. A recent study would argue that the latter is the case, although correction of hyponatremia before hospital discharge does seem to improve outcomes whereas persistent hyponatremia was associated with worse outcomes.
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