A Case of 5-Fluorouracil-Induced Hyperammonemia and Lactic Acidosis Successfully Treated With Continuous Hemodiafiltration Dialysis

A 51-year-old male patient with stage IVc upper rectal cancer received treatment with aflibercept beta and folinic acid, fluorouracil, and irinotecan. Two days following treatment, he presented with an altered mental status. Head computed tomography showed no abnormalities, but blood tests revealed hyperammonemia and lactic acidosis. As these findings were thought to be side effects of 5-fluorouracil (5-FU), the patient underwent continuous hemodiafiltration. Subsequent to this intervention, the hyperammonemia, lactic acidosis, and impaired consciousness improved, and the patient was discharged on hospitalization day 10. In cases of impaired consciousness during 5-FU administration, in addition to the usual evaluation of the cause of impaired consciousness, ammonia and lactate levels should be measured, and branched-chain amino acids should be administered if impaired consciousness due to hyperammonemia is strongly suspected, and the patient's general condition is stable. If the disturbance of consciousness is prolonged or the patient's general condition becomes unstable, it is advisable to consider initiating blood purification. Additionally, patients with lactic acidosis or unstable general conditions should be considered for blood purification using continuous hemodiafiltration. Therapeutic interventions may lead to neurological improvement even in severe cases, highlighting the importance of prompt and targeted management approaches.