How does lethal injection work?

How does lethal injection work?
- asks Jim from Ohio

By Peter Sergo, posted November 12th, 2007.

The U.S. Supreme Court is now closely assessing the answer to this question as they consider the constitutionality of a method of execution that’s used in all but one of 38 death penalty states.

Execution by lethal injection has largely replaced other forms of capital punishment, such as electrocution and the cyanide gas chamber, because it is seen as a more humane way of ending a life. Constitutional law states that capital punishment is only acceptable if it doesn’t violate the Eighth Amendment’s ban on cruel and unusual punishment. A person shouldn’t be aware of or able to sense any pain during the procedure. Lethal injection is thought to adhere to this policy because an initial drug is used to induce a state of unconsciousness where pain can no longer be registered. For the person being executed, subsequent injections that rapidly stop their breathing and heartbeat should occur without their sensing it.

According to the Death Penalty Information Center in Washington D.C., the protocol for lethal injection in most states involves a sequence of three shots that are delivered via intravenous drips inserted in each arm.

The first of the three injections is an anesthetic, sodium thiopental, which is a fast-acting barbiturate that depresses the activity of the central nervous system. This initial shot doesn’t serve as an analgesic (pain killer) that numbs pain nerves, but instead rapidly puts a person into a state of unconsciousness that’s theoretically deep enough to make pain undetectable. The drug amplifies the effect of GABA, a neurotransmitter that depresses brain activity, while also blocking the actions of an excitatory brain receptor, AMPA, which acts in many parts of the brain. The state of unconsciousness can be reached in as little as 30 seconds. A single dose of this anesthetic is intended to last throughout the last two injections to prevent any pain during the moments leading up to death (pronounced after the heart stops beating for a certain amount of time).

After the initial injection, the intravenous line is quickly flushed with saline, a neutral substance commonly used to push a drug into the bloodstream more quickly. Subsequently, pancuronium bromide is administered. It acts as a neuromuscular blocker, preventing a nerve messenger, acetylcholine, from communicating with muscles. The result is a complete muscle paralysis, which causes respiratory arrest since the diaphragm—a muscle imperative to pulling air into the lungs—stops working.

Following another saline flush is the final injection, potassium chloride. This last dosage of chemical floods the heart with charged particles that interrupt its electrical signaling, stopping it from beating. According to a 2002 study in the Journal of Forensic Science, the average length of time from the first injection to death is 8.4 minutes.

The dosage of each drug administered in lethal injection is supposed to be redundant, which means that the amount of chemical contained in each shot is lethal. For example, during surgeries, patients are normally given 100 to 150 milligrams (mg) of sodium thiopental, the initial anesthetic used in capital punishment, over a period of 10 to 15 minutes – while up to 5,000 mg are provided during executions. For pancuronium bromide, 40 to 100 micrograms per kilogram of body weight is normally given pre-operatively (to aid intubation) while a thousand times that amount is used for execution. When all three injections are used in executions, the aim is to put the person into a state of total unconsciousness before they die from a mix of respiratory and cardiac arrest.

Not only that, to ensure that the first injection reliably maintains a sedated state during the entire execution, an effective amount must constantly be in the blood system to prevent any chance of regaining awareness and, in turn, suffering, according to a study published this year in Public Library of Science Medicine. This is especially important when a person being executed could potentially be in a state that incapacitates them from physically showing discomfort while still experiencing it nonetheless. (See an article concerning the controversy over one Florida case in the St. Petersburg Times.)

Improper delivery of the anesthetic, either because an insufficient amount is administered or the IV is misplaced in the arm, is one of many aspects of lethal injections that poses a challenge to its public acceptance.

Researchers also have debated lethal injection. According to a 2005 letter in The Lancet, which looked at post-mortem toxicology reports of executions carried out in Arizona, Georgia, North Carolina and South Carolina, the blood concentrations of thiopental were low enough that 21 out of 49 executions (43 percent) had concentrations that allowed for a regaining of awareness.

This finding was disputed in the same issue by Jonathan Groner, its also gets quickly absorbed into fat and muscle tissue—even after death. When considering this and the manner in which the anesthetic is delivered (a ‘bolus’ injection of a high quantity, all at once) post-mortem blood samples cannot be a reliable measure of the amount of sodium thiopental that was circulating in the blood.

Another controversial aspect of lethal drug administration is that health professionals are not present during the procedure. Currently, doctors and nurses in the United States are banned by their professional organizations from participating in executions.

The reliability of painless lethal injection procedures will come up when the Supreme Court hears the constitutional challenges specific to the three-chemical protocol. This case, which will be argued early next year and should be decided by early next summer, is in response to an appeal by two Kentucky death row inmates who challenged the execution process. Their argument is based on the belief that the injection of the three-chemical cocktail inflicts unnecessary pain and suffering that could be avoided.