A case report of hyperammonemic encephalopathy induced by high-dose continuous infusion of 5-fluorouracil in a patient with rectal cancer.

Background: Hyperammonemic encephalopathy caused by high-dose infusion of 5-fluorouracil (5-FU) is a rare adverse reaction in rectal cancer patients with an incidence rate of 5.7%. Although the patient could be restored to normal after supportive treatments, the occurrence of this side effect was still inevitable. Therefore, we analyzed the data of patients during chemotherapy and combined with relevant literature to provide reference for the prevention and treatment of hyperammonia-induced encephalopathy.

Case description: The patient experienced severe consciousness disorders, unresponsive to stimuli, and stiff limbs during two cycles of 5-FU chemotherapy (after 40 hours of infusion), meanwhile the levels of blood ammonia were 117.0 and 349.0 µmol/L, lactate were 9.1 and 7.6 mmol/L respectively. The patient recovered consciousness and all of those laboratory indicators and vital signs turned to be normal through interrupting use of 5-FU and corresponding treatments after approximately 12 hours.

Conclusions: Hyperammoniac encephalopathy was hard to prevent, we still recommended to conduct a comprehensive evaluation of the patient's physical condition including nutritional status, liver and kidney function, dihydropyrimidine dehydrogenase (DPD) level before chemotherapy in cases of muscle loss, infection or dehydration. In additional, therapeutic drug monitoring (TDM) can be considered to monitor blood drug concentration and guide the 5-FU dosage if possible. The early consciousness changes of patients during chemotherapy can remind us of prompt detection and treatment to avoid coma or even death.