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Hyponatremia and SIADH Frequency in Clinically Euvolemic Patients Receiving Chemotherapy: Prospective Study in Unselected Patients Cohort

Abstract

Dada Reyad, Jamal Zekri, Kamel Farag and Mohamed Bayoumy

Purpose: Biochemical hyponatremia is a common electrolyte abnormality in patients with cancer. In this prospective single center trial we aim to study the frequency of hyponatremia in patients receiving chemotherapy with special emphasis on syndrome of inappropriate secretion of anti-diuretic hormone (SIADH).
Patients and Methods: This is a prospective study of consecutive patients receiving different types of outpatient chemotherapy between January 2013 and June 2014. Serum Sodium was measured as part of routine assessment for all patients receiving chemotherapy. Euvolemic patients with hyponatremia (Na <135 mmol/L) were also tested for Serum and urine osmolality and urinary Na excretion. Criteria of SIADH are: serum Osmolality <275 mOsmol/ kg, urine Osmolality >100 mOsmol/kg and urinary Sodium >30 mmol/L.
Results: 1254 patients received different chemotherapy regimens were screened and 1150 fulfilled the inclusion criteria. Median age was 55 year (19-75). Biochemical hyponatremia developed in 105 (9.1%) of all patients and in 42/298 (14%), 25/357 (7%) and 38/495 (7.7%) of patients who received cisplatin, carboplatin/oxaliplatin and non-platinum chemotherapy regimens respectively. 68/105 (65%) fulfilled biochemical criteria of SIADH of which 26/42 (62%), 13/25 (52%) and 29/38 (76%) of hyponatremic patients received cisplatin, carboplatin/oxaliplatin and non-platinum regimens respectively. Cisplatin based regimens were significantly associated with SIADH compared to non-cisplatin regimens (OR: 1.521, 95% CI: 1.105-2.093; p=0.022).
Conclusion: 9.1% of euvolemic patients receiving out-patient chemotherapy manifest a degree of biochemical hyponatremia with highest risk associated with cisplatin based regimens. Hyponatremia can be attributed to SIADH in two thirds of cases.