Post-hepatectomy tolvaptan-induced hypernatremia in a hepatocellular carcinoma patient with cirrhosis: a case report

BACKGROUND: Tolvaptan is used in Japan to reduce fluid retention caused by cirrhosis. However, hypernatremia is one of the most important side effects. This report is the first case report of a patient who developed hypernatremia after tolvaptan administration in the early stages following hepatectomy. CASE PRESENTATION: A female patient in her 60s, who was admitted to the psychiatric department of a different hospital for bipolar disorder, developed hepatocellular carcinoma with cirrhosis. She was transferred to our hospital, and hepatectomy was performed in October 2019, after which pleural effusion and severe edema due to fluid retention were evident. Thus, the patient was started on tolvaptan (7.5 mg/day) from postoperative day (POD) 1. The patient began to experience disturbance of consciousness after POD 4. On the fifth day, the serum sodium (Na) level increased to 174 mEq/L, and hypernatremia was diagnosed. The Na level gradually improved with fluid infusion therapy, dropping to preoperative levels on the ninth day; her consciousness also gradually improved. CONCLUSIONS: Tolvaptan administration must be performed under strictly controlled conditions, followed by careful observation during the early postoperative period, when the patient’s physical status is unstable.