A man had brain surgery in Vietnam on Monday while completely conscious, the first time this type of surgery had been done in the country.

Nguyen Trung K, a 36-year-old businessman from Hanoi, underwent the surgery at the Vietnam-Germany Friendship Hospital on January 28, Viet Nam News reported. Nguyen’s surgery lasted six hours and he was fully conscious for two hours.

He reportedly sang during the time he was awake, although there were no reports on what song he sang.

The patient started having random headaches at the beginning of last year, which he shrugged off until he started having seizures. The Vietnam-Germany Hospital diagnosed him with glioma, a common form of a brain tumor.

Nguyen went through a conventional surgery to have his tumor removed in April last year, but it was unsuccessful as the tumor was too large and too close to the brain’s functional areas.

At the same time, the hospital had plans to carry out an awake surgery and had sent doctors to study the technique abroad. Two doctors from Japan were invited to the hospital in June for a review that determined if the hospital was ready for the awake surgery.

On Monday, the two Japanese doctors carried out the surgery on Nguyen as a live demonstration for Vietnamese surgeons. The purpose of the awake surgery was to allow doctors to stop the surgery if something went wrong, as the doctors cannot gauge whether the surgery altered the speaking and motor skills of the patient in a completely anesthetic surgery.