[Effects of Serum Sodium Concentrations on Nausea and Vomiting after Moderately Emetogenic Chemotherapy]

Chemotherapy-induced nausea and vomiting (CINV) is the most unbearable adverse effect of chemotherapy. The antiemesis guidelines of the National Comprehensive Cancer Network indicate that hyponatremia is a risk factor for CINV, although the relationship between the incidence of CINV and hyponatremia has not been sufficiently studied. This two-center prospective observational study evaluated whether low serum sodium concentrations were a risk factor for CINV. The study included 34 patients who were scheduled to receive first-line carboplatin- or oxaliplatin-based chemotherapy for gynecological or colorectal cancers. Patient diaries were used to record the daily incidences of CINV events during a 5-day period. The patients were divided based on the median serum sodium concentration into a low Na⁺ group (<141 mEq/L) and a high Na⁺ group (≥141 mEq/L). The incidences of delayed nausea were 27.8% in the high Na⁺ group and 62.5% in the low Na⁺ group (p=0.042), with complete control rates (no vomiting, rescue medication, or grade 2 nausea) of 77.8% and 43.8%, respectively (p=0.042). The time to complete control failure in each group was analyzed using the Kaplan-Meier method, which revealed a significantly shorter time in the low Na⁺ group (p=0.03). Therefore, these results indicate that low serum sodium concentrations may increase the risk of CINV.