A rare complication tied to nitrous oxide caused the death of a nine-year-old California girl following a dental procedure, according to an autopsy report.
Silvanna Moreno, a third-grader from Vista, Calif., died March 18 after undergoing surgery at Dreamtime Dentistry. An autopsy obtained by PEOPLE from the San Diego County Medical Examiner’s Office listed her cause of death as methemoglobinemia, a rare blood disorder that can prevent oxygen from reaching body tissues.
Nitrous oxide, also known as laughing gas, was among the anaesthetics administered during the procedure. In rare cases, it can alter hemoglobin in the blood, reducing its ability to carry and release oxygen. A 2017 study noted the risk may be underestimated, even at low concentrations.
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The autopsy report said Moreno had surgery for tooth pain, and that she’d had a mild fever the day before, which resolved with children’s Tylenol. She was reportedly alert during prep and stable during recovery.
But on the way home, she appeared groggy and later began snoring heavily. After returning home, her breathing slowed and she became unresponsive. She was rushed to hospital, where she was pronounced dead just before 6 p.m.
Dr. Ryan Watkins of Dreamtime Dentistry said Moreno showed no warning signs during the procedure and maintained normal oxygen levels. He called the condition “extremely rare” and said the clinic followed standard protocols and is now conducting an internal review.