Execution by lethal injection may cause death by asphyxiation, and prisoners being executed may be conscious and may experience pain, claim the authors of a new study published this week in PLoS Medicine. Leonidas Koniaris and colleagues from the University of Miami assessed data from two US states that release information on executions together with previously published work on the drugs used in the protocols for lethal injections. They conclude that these protocols may not reliably effect death through the mechanisms intended.
Lethal injection is used for execution in a number of countries, most notably the US and China. The current regimens for lethal injection in the US are based on one drawn up by legislators in Oklahoma, which in turn to appear to have been based on personal opinion rather than independent research. The drugs used are a barbiturate, thiopental (which acts as an anesthetic, but does not have any analgesic effect), a neuromuscular blocker, pancuronium bromide (which causes muscle paralysis); and an electrolyte, potassium chloride (which stops the heart from beating).
Each of these drugs on its own was apparently intended by those who derived the protocols to be sufficient to cause death; the combination was intended to produce anesthesia then death due to respiratory and cardiac arrest. Following a number of executions in the US, however, it has recently become apparent that the regimen as currently administered does not work as intended. Some prisoners take many minutes to die, and others become very distressed.
The authors concluded that in the current regimen thiopental might not be fatal and might even be insufficient to induce surgical anesthesia for the duration of the execution, and that the doses of potassium chloride used did not reliably induce cardiac arrest. Hence, potentially aware inmates are likely to die through asphyxiation induced by the muscle paralysis caused by pancuronium. The authors conclude that even if lethal injection is administered without technical error, those executed may suffocate, and therefore ''the conventional view of lethal injection as an invariably peaceful and painless death is questionable.''
Citation: Zimmers TA, Sheldon JP, Lubarsky DA, López-Muñoz F, Waterman L, et al. (2007) Lethal injection for execution: Chemical asphyxiation? PLoS Med 4(4): e156. (http://dx.doi.org/10.1371/journal.pmed.0040156)
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