What was expected to be a routine dental visit ended in heartbreaking tragedy for 9-year-old Silvanna Moreno, who died on March 18, 2025, just hours after undergoing a dental procedure at Dreamtime Dentistry in Vista, California.

More than two months after her passing, the San Diego County Medical Examiner’s Office officially ruled her death an accident. The cause was identified as “methemoglobinemia in the setting of recent nitrous oxide administration.”

Methemoglobinemia (often abbreviated as MetHb) is a rare but serious blood disorder in which hemoglobin—the protein in red blood cells responsible for carrying oxygen—cannot effectively release oxygen to body tissues. According to the Cleveland Clinic, certain medications and anesthetic agents, including nitrous oxide, can trigger the condition in susceptible individuals. When this occurs, oxygen delivery throughout the body decreases, potentially leading to hypoxia, a dangerous state of oxygen deprivation.

Although uncommon, methemoglobinemia can present with visible symptoms such as blue or purple discoloration of the lips, skin, or nails. In other cases, symptoms may be subtle or initially go unnoticed, making early detection difficult.

According to People magazine, Silvanna had experienced a fever the day before the procedure and had been given children’s Tylenol. The dental office later stated that she was a new patient referred for treatment of a decayed molar requiring a root canal. During the approximately three-hour procedure, multiple baby teeth were extracted along with one permanent tooth affected by decay.

NBC News reported that Dr. Ryan Watkins, the office’s anesthesiologist, issued a statement describing Silvanna as “a healthy 9-year-old with a history of regular medical checkups.” He stated that she underwent a standard preoperative evaluation and was considered “an appropriate candidate for outpatient general anesthesia.”

According to the Medical Examiner’s summary report, Silvanna was moved to a recovery room following the procedure. Her mother later told investigators that her daughter appeared disoriented—“out of it”—while intermittently opening her eyes and mumbling incomprehensibly. On the drive home, Silvanna remained asleep, and she continued sleeping after arriving home.

Approximately 30 minutes later, her breathing reportedly began to slow. When her family was unable to wake her, they immediately called 911. Emergency responders transported Silvanna to a nearby hospital, where she was pronounced dead.

In a public statement, Dr. Watkins said, “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.”

The case has also drawn attention to Dr. Watkins’ professional history. In 2016, he was investigated in connection with an incident involving a 54-year-old patient who nearly died while under general anesthesia. The Dental Board of California determined that one of the medications administered to that patient should not have been given, as it contributed to cardiac arrest. As a result of that investigation, Watkins was placed on probation from 2020 to 2023 under a decision order issued by the board.

Silvanna’s death has prompted renewed discussion about pediatric anesthesia safety, particularly in outpatient dental settings. While general anesthesia and nitrous oxide are widely used and considered safe when properly administered, experts note that rare but severe complications can still occur. The tragedy has left a grieving family searching for answers and raised broader concerns about monitoring protocols, risk assessment, and emergency preparedness in dental practices.

As investigations and reviews continue, Silvanna’s case serves as a painful reminder of how even routine medical procedures can carry unforeseen risks.