A 3-year-old Kailua girl who stopped breathing and suffered cardiac arrest in the dentist’s chair died probably because of the drugs given to sedate her, the Honolulu medical examiner has concluded.

"This previously healthy 3-year-old with no history of chronic medical illness likely died as a result of the sedatives and local anesthesia given at the time of the dental procedure," Dr. Christopher Happy, chief medical examiner, concluded in his autopsy report.

Finley Puleo Boyle, a cheerful girl with aquamarine eyes, lapsed into a coma Dec. 3 in the office of Dr. Lilly Geyer at Island Dentistry for Children. The autopsy report said she had suffered cardiopulmonary arrest, and the lack of oxygen led to brain damage. She never regained full consciousness and died Jan. 3.

The child had no signs of underlying heart problems or an allergic reaction to the array of sedatives and anesthetic she received at the dentist, the examiner found.

"There was no evidence of cardiac pathology on gross or microscopic examination and no medical or clinical history of anaphylaxis," Happy wrote.

Boyle received five drugs in preparation for the filling of cavities and root canals, according to the autopsy report. They included demerol (31.03 mg), hydroxyzine (10.34 mg) and chlorohydrate (824 mg) as well as nitrous oxide, commonly known as laughing gas. She also had an injection of a local anesthetic, lidocaine with epinephrine.

"Immediately following the lidocaine injection, the decedent became unresponsive and went into cardiopulmonary arrest," the medical examiner said.

He described the cause of death as "infectious complications following cardiopulmonary arrest during dental procedure" and determined that the contributing cause of death was the administration of the five drugs. He classified the death as an accident.

Ashley Boyle, Finley’s mother, said her daughter had complained of no pain before making her first visit to the dentist in November, and had no fear of the dentist. Nonetheless, Geyer recommended extensive dental work, including "baby root canals."

In his detailed description of Finley Boyle’s condition during the autopsy, the medical examiner noted that her teeth were in good shape, saying "the oral cavity has native dentition in good repair."

While their only child was in a coma, Ashley and Evan Boyle filed a lawsuit Dec. 30 in Circuit Court against Geyer, Island Dentistry for Children and unidentified staff members, alleging negligent and dangerous conduct in sedating their daughter, and failing to prepare for or respond appropriately to the medical emergency. Their attorney, Rick Fried, alleged that Finley Boyle received "an egregious overdose of three central nervous system suppressant drugs."

After Boyle died, Fried intended to replace the initial complaint with a lawsuit for wrongful death, after completion of the autopsy. That suit has not yet been filed. Fried would not comment on the autopsy report.

Geyer’s attorney, John Nishimoto, has said it would be inappropriate for him or his client to comment on "unproven allegations," given the pending lawsuit. He did not respond to a call and an email Thursday regarding the autopsy report.

Island Dentistry for Children closed after the tragedy. Geyer has been licensed to practice general dentistry in Hawaii since July 2005.

The autopsy was performed Jan. 6, and the report was dated March 10. It can take more than two months to get toxicology reports from the mainland, according to the Medical Examiner’s Office.

On Jan. 27 new state rules took effect tightening oversight of dental sedation in Hawaii. They require dentists to complete comprehensive postgraduate training and obtain permits before administering moderate conscious sedation. Dentists are also mandated to have proper facilities and staff to handle problems and emergencies.

Previously, dentists in Hawaii had to get advanced training and written authorization only to administer general anesthesia and intravenous-conscious sedation. The regulations were silent on sedatives given orally, such as those given to Boyle to swallow.

The new rules had been in the works long before her death.