The heartbreaking cause of death for a 9-year-old San Diego girl who passed away just hours after a routine dental procedure has been confirmed.
On March 18, third grader Silvanna Moreno underwent a three-hour operation at Dreamtime Dentistry in Vista, California. Later that same day, she was pronounced dead at Rady Children’s Hospital, per the Daily Mail.
According to the San Diego County Medical Examiner’s Office, Silvanna died from methemoglobinemia — a rare but dangerous blood disorder that reduces the ability of red blood cells to carry oxygen.
The condition was triggered in her case by nitrous oxide, or “laughing gas,” which had been administered during her dental treatment.
The report ruled her death accidental. Still, the new details have raised questions about the events leading up to her final hours and the procedures followed by the dental team.
What is Methemoglobinemia?
The Cleveland Clinic explains that methemoglobinemia can be inherited, but is most often acquired through exposure to certain medications, chemicals, or recreational drugs.
Symptoms may include bluish skin, lips, or fingernails — and in severe cases, it can be fatal.
Dr. Ryan Watkins, the anesthesiologist and dentist who treated Silvanna, confirmed the condition can be brought on by nitrous oxide.
A routine dental visit turns tragic
Silvanna had been referred to Dreamtime Dentistry because of her age and what Watkins described as “acute situational anxiety.”
Her treatment plan included a root canal on a molar, crowns on permanent teeth, and the extraction of several decayed baby and permanent teeth.
The night before the procedure, her mother reported Silvanna had a 101-degree fever and was given Children’s Tylenol, according to NBC News. By the morning, her symptoms had resolved.
Though the child mentioned a headache before her appointment, the medical examiner’s report said she did not appear distressed.
Dreamtime Dentistry later claimed the staff “were not aware of a fever nor any illness,” adding that her mother had marked “NO” on a pre-operative form asking if Silvanna was sick.
“All medications were administered according to manufacturer guidelines based on Silvanna's age and weight,” Watkins said in a statement obtained by PEOPLE. “She never exhibited warning signs of methemoglobinemia.”
He also noted that oxygen monitoring showed no abnormalities throughout the procedure.
Watkins said Silvanna was awake and “stable” while being monitored in recovery. She was cleared for discharge after being evaluated for oxygenation, consciousness, pain, nausea, vomiting, and mobility.
Though she was able to stand, she needed help getting into her family’s car. On the ride home, she fell asleep and began snoring loudly.
Back at home, she continued to sleep for an hour and a half. Her snoring grew quieter and eventually slowed, according to the autopsy report. Alarmed, her family checked on her and found her unresponsive.
They called 911 at 4:46PM and attempted CPR while waiting for help.
Emergency responders rushed Silvanna to Rady Children’s Hospital, where doctors continued lifesaving measures including oxygen, intubation, and medication. Despite efforts, there was no cardiac activity.
She was pronounced dead at 5:44PM.
Medications and contributing factors
Alongside nitrous oxide, the medical examiner listed additional drugs used in the anesthesia process, including dexamethasone, glycopyrrolate, hydromorphone, isoflurane, ketorolac, midazolam, ondansetron, propofol, and sevoflurane.
Dreamtime Dentistry insisted the problem wasn’t with dosage. “Any interactions or negative side effects were not due to dosage but instead due to her rare but undiagnosed/undetected medical condition,” the office said.
Watkins also emphasized: if there had been any visible signs of methemoglobinemia — such as refractory hypoxemia — the procedure would have been stopped immediately and emergency care provided.
Previous concerns
This is not the first time Watkins’ anesthesia practices have come under scrutiny.
In 2016, a 54-year-old patient suffered cardiac arrest under his care due to a drug interaction.
Investigators later determined that one of the drugs used should never have been administered. Watkins was placed on probation from 2020 to 2023 and later settled a lawsuit filed by the patient.
Dentistry responds
In the wake of Silvanna’s death, Dreamtime Dentistry said it has launched a “thorough internal review” and is consulting with national experts to improve safety protocols.
“We are profoundly saddened by the tragic loss of Silvanna Moreno, and our hearts continue to go out to her family during this incredibly difficult time,” Watkins said in a statement.
He added: “We extend our deepest condolences to Silvanna's family and ask for continued respect for their privacy during this time of grief.”