What to know about lethal injections after botched attempts in Tennessee

The execution of Christa Pike appears to have been botched, after she survived two doses of lethal injection before being transported to a local hospital in Tennessee where she is in critical condition, according to her attorneys.

The planned execution of Tony Carruthers earlier this year, also in Tennessee, was allegedly botched and had to be halted after authorities were unable to find a suitable vein to place an IV to administer the injection after trying for over an hour, his attorneys said at the time.

Here is what you need to know about lethal injections and how they may go wrong.

What is lethal injection?

Lethal injection is the most common method of execution in the United States.

Medications used in lethal injections usually act in three steps -- first sedating the individual, then paralyzing them, before ending important bodily functions necessary for life.

Protocols for lethal injection vary by state, ranging from one to three medications.

Tennessee utilizes a single medication protocol with the medication pentobarbital. The same protocol is authorized in 14 other states.

This change came in 2024, in response to a 2022 review of the state’s oversight in lethal injection medication preparation.

Pentobarbital is a sedating medication that can quickly render an individual unconscious. It then shut down areas of the brain that control breathing and heartbeat, ultimately resulting in death.

In recent years, drug shortages and actions by pharmaceutical companies have made it more challenging to secure the needed medications.

How can lethal injection go wrong?

Lethal injections have been responsible for over 7% of botched executions, the highest among all methods and more than double the average rate of all executions, according to the Death Penalty Information Center.

Medical professions do not participate in lethal injections, as professional bodies, including the American Medical Association, consider it unethical and have banned the practice for their members. The medical procedures to carry out the injections are therefore relegated to untrained staff, according to editorial in PLoS Medicine.

IV access failures are frequent due to misplaced needles, leading to blood vessels being damaged, and medications being delivered under the skin or into muscles instead of the blood, according to an article in the BMJ. Delays and chemical burns have been reported as a result, which can cause pain and discomfort to the individual.

Studies have also suggested that medication doses used in lethal injections may come short of being fatal, or may not sedate adequately to prevent individuals from experiencing suffocation or the burning sensation associated with heart-stopping medication.

Individuals with long-term use of sedating drugs or prior drug use history may also require higher doses of medications used in lethal injection to achieve intended outcomes, or have difficulty accessing veins.

What 1 expert retained by Pike's attorneys says may have happened

Surviving lethal injection after medications were given has not been reported prior to the case of Pike, according to the Death Penalty Information Center.

Pike's attorneys told reporters on Thursday that Pike is alive but in "critical condition receiving life-saving medical care." But they said, "We don't have a sense of her prognosis or much update on her health at the moment."

In an interview with ABC News Live anchor Kyra Phillips, Dr. Joel Zivot, an Emory University professor of anesthesiology and medical expert retained by Pike’s legal team, provided his opinion on her botched lethal injection.

Zivot, who did not witness Pike's attempted execution, pointed to remarks that witnesses and Pike's attorneys said Pike made in the execution chamber about her arm "burning" after the injection was administered.

"That all sounded to me like the intravenous was no longer in the vein if it ever really was. And instead the chemical was then being infiltrated into the skin and tissues of her arm," rather than her bloodstream, he said.

If that is what happened, "only a small quantity of that maybe made it into her and she did not die," Zivot said. "And so the protocol then required a second attempt. Now, whether that second intravenous was on the same arm or the opposite arm, I don't know, but a second attempt seemed to result in the same thing."

Dr. Allen Chang is a Geriatric Medicine subspecialist at Dalhousie University and a member of the ABC News Medical Unit.