Methemoglobinemia, or MetHb, occurs when nitrous oxide affects hemoglobin, reducing oxygen delivery to the body’s tissues and causing hypoxia. According to the Cleveland Clinic, the condition is rare and can appear with blue or purple lips, skin, or nails—or sometimes show no symptoms at all.

Health Background Before the Procedure

The day before her three-hour procedure, Silvanna had a fever and took children’s Tylenol, according to People. She was a new patient at the clinic, referred for a root canal on a molar.

During the procedure, the dentist extracted several baby teeth along with one decayed permanent tooth. Dr. Ryan Watkins, the clinic’s anesthesiologist, described Silvanna as a healthy child with a history of regular checkups. He stated she had passed the office’s standard preoperative evaluation and was an appropriate candidate