DENVER -- Autopsy results for the president and face of Kacey Fine Furniture showed that her death was not the result of an overdose or an allergic reaction to the injections she was receiving, according to the chief medical examiner.

Leslie Fishbein, the well-known businesswoman featured in ads for her family business, died from a serious reaction to an injection for chronic back pain, according to autopsy results released Thursday.

Denver Chief Medical Examiner Amy Martin stated in the report that Fishbein died due to the lack of oxygen to the brain (hypoxic encephalopathy) after her heart stopped beating.

Fishbein was receiving the injections for pain associated with a horseback riding injury several years ago.

Her death has been ruled an accident, but her family questions that conclusion.

Sam Fishbein, Leslie's widower, has hired medical malpractice attorney Jim Leventhal.

Leventhal told 7NEWS, "Even if the initial placement of the needle was an accident, there still remains a serious question about why the doctor was unable to resuscitate Leslie. Was his response appropriate? Did he have the proper equipment to resuscitate? If not, why not?"

"To conclude this is an accident and absolve the doctor of fault is premature," added Leventhal.

Fishbein was the face of the company. The 55-year-old appeared in ads for her family business for 20 years, up until her death in March.

Autopsy results show Fishbein died from a lack of oxygen to the brain. That was caused by cardiopulmonary arrest (her heart essentially stopped beating), according to the report. The medical examiner said the cardiac arrest occurred during pain trigger point injections in the back.

The drug used for those injections was Marcaine (bupivacaine) and Depo-Medrol. The autopsy does not indicate a massive overdose of bupivacaine, and shows no evidence of an allergic reaction. Martin stated that adverse reactions at low levels are uncommon, but have happened.

Fishbein also appeared to have had a somewhat low level of potassium in her blood when she first arrived at the hospital, which may have contributed to her development of cardiopulmonary arrest, the autopsy said. The cause of the low potassium was never determined but low levels of potassium can affect the heart, Martin said.

Fishbein was admitted to Presbyterian/St. Luke's Hospital March 4 after she had the bad reaction to the injection at a private doctor's office. She was later placed on life-support. She died at the hospital March 19.

What remains unanswered is how the drug was administered, and whether something went wrong during that process.

The Food and Drug Administration warns that bupivacaine should only be employed by clinicians well versed in dose-related toxicity. The FDA also stated that a delay in proper management of toxic reactions could result in death.

In autopsy report, the chief medical examiner concludes that Fishbein was in relatively good health as a middle-aged woman.

Leventhal said it is still unclear whether the family will file a medical malpractice lawsuit, but he said he wouldn't be involved if that weren't a possibility.

Bupivacaine is a local and regional anesthetic but severe effects with high doses can result in seizures, coma, arrhythmias, respiratory arrest, and cardiovascular collapse, according to medical journals.