9-year-old dies after routine dental visit in San Diego — rare reaction to anesthesia suspected
Silvanna Moreno’s death in San Diego was ruled accidental; rare condition linked to nitrous oxide cited as cause.

The San Diego County Medical Examiner's Office has ruled the death of Silvanna Moreno, 9, as an accident, two months after her death following a dental procedure. The updated report lists the official cause of death as methemoglobinemia—an uncommon blood disorder—after receiving nitrous oxide during the procedure.
It happened on March 18 at Dreamtime Dentistry in Vista, California. Dr. Ryan Watkins, the anesthesiologist at the procedure, stated that during and after the three-hour procedure, there were no visual signs of methemoglobinemia. According to the Cleveland Clinic, methemoglobinemia can interfere with oxygen delivery in the blood and can be life-threatening in some cases.
Rare condition linked to nitrous oxide use
The report references multiple contributing factors in which multiple anesthetic drugs were listed as contributors. Dr. Watkins reported that Silvanna had a routine preoperative assessment that had been completed, with monitoring throughout the procedure. She apparently met the criteria for stable at the end of the operative recovery room. It was reported that her quick review of vital signs allowed Dr. Watkins to feel comfortable with discharge and that Silvanna was discharged to her mother.
Silvanna reportedly fell asleep during the car ride home and was found unresponsive hours later. When the child was taken to the hospital, she was pronounced dead shortly thereafter. According to the autopsy report, the child had a fever the day before the surgery and had taken children's Tylenol, and was noted to have a mild headache the day of the appointment.
Dentist previously investigated over anesthesia incident
Dr. Watkins, who is now performing an internal review of the case, was previously placed on probation by the Dental Board of California. In an incident in 2016, a 54-year-old patient experienced disciplinary action due to the patient’s heart stopping as a result of an inappropriate drug combination. That patient later settled a lawsuit against Watkins.
Watkins stated: "We are deeply saddened by the tragic loss of Silvanna Moreno, and our hearts continue to go out to her family during this very difficult time."