By Kerry Breen

Tennessee authorities are investigating after a drug mix-up at a Nashville hospital caused patients to experience dire complications during what should have been routine surgeries.

The error occurred at Ascension Saint Thomas Midtown on Friday, Aug. 14. It ws reported that four patients had received doses of potassium instead of standard pain drugs while undergoing joint replacement operations. All of the operations were supposed to be outpatient procedures.

The families of the patients said that two patients were left paralyzed, and one is in the intensive care unit.

One of the victims is 72-year-old Glenda Dorton. Her attorney Mark Walwyn said that she underwent a knee replacement surgery. The operation itself went well, Walwyn said, but due to the mix-up, she is currently paralyzed. He described her prognosis as unclear but dire.

In a statement on behalf of the Dorton family, Walwyn said she remains under medical care and is "facing a long and uncertain recovery."

The hospital acknowledged that a mix-up in the pharmacy led to four patients being injected not with mepivacaine, a standard anesthetic, but potassium phosphate, which if not diluted properly can cause catastrophic complications.

And while the two drugs can come in different types of packaging, photos of two vials of these medicines, which we do not know if these are the types of vials that were confused, do at least show how similar the two medications can appear.

Ascension Saint Thomas Midtown now says it has taken steps to prevent another drug mix-up in its pharmacy. But there are questions now about why these measures were not already in place.

Ascension Saint Thomas also said in its statement announcing the changes that all spinal medicine must now be double checked by a second trained pharmacist.

And the hospital said that it brought in independent, third-party experts to review and validate these new safety measures.

Dr. Shubhada Jagasia, the hospital president and CEO, said in a statement that the facility became aware of the "event" the day it occurred. Jagasia said the hospital self-reported to state regulators and launched an investigation.

"We identified the cause and have implemented corrective safeguards," Jagasia said.

Jagasia said hospital staff have met with the families of the impacted patients. Jagasia said the hospital would not share "specific clinical details" about the affected patients.

Potassium has a number of uses in hospitals. Potassium itself is an essential mineral and electrolyte that the body needs to maintain a certain level of to function. Potassium citrate can be used to treat kidney stones. Potassium chloride can support heart and nerve function. However, too much potassium can be dangerous: It can cause cardiac arrest if too much is given too quickly, and high doses of potassium chloride are used in executions.

Medical malpractice attorney Clint Kelly said the case is one of the worst he's ever heard of. Kelly is not representing any of the patients affected.

"Just think of like, battery acid, going into the most tender nerves in your body," he said, describing the effects of receiving too much potassium. "It's the worst type of injury you can imagine."