Pseudomyxoma peritonei (PMP) is a mucinous tumor and rare disease. Surgical removal is basic treatment and peritoneal lavage with dextrose in water conducts for removing remnant. A 61-year-old woman was diagnosed PMP and underwent surgery. Despite initial serum glucose was 103 mg/dl, hyperglycemia (serum glucose 359 mg/dl) was detected after intraperitoneal irrigation with dextrose in water. She recovered breath, but mental state was unconscious. She was transferred to post-anesthesia care unit, in state of keeping of intubation. Insulin was infused, and serum glucose was 275 mg/dl. It took more than three hours to recover consciousness. Postoperatively, newly appeared QT interval prolongation and pleural effusion developed. Two weeks later, she was discharged without any sequelae. In conclusion, intraperitoneal dextrose irrigation might be related to intraoperative hyperglycemia, therefore the serum glucose monitoring and proper treatment during and after the intraperitoneal irrigation with dextrose are needed.