Polite Dissent

Fallen Angel #21
Peter David, writer
J.K. Woodward, artist

The Scene (spoiler warning): A scorned wife sneaks up behind her husband while he in flagrante delicto and injects him in the neck with a syringe. She explains to him that she injected air into his veins which will “cause a thrombosis. This will go to your heart and kill you.” Right on cue, he grabs his chest and collapses, dead.

While it is possible to kill someone by injecting air in their veins, it is nowhere near as easy nor as convenient as suggested by this issue of Fallen Angel (and before that, Manhunter #11, and popular fiction in general).

First, let’s get the terminology out of the way. Air in the blood vessels causes an embolus, not a thrombus. An embolus is a mass that circulates through the blood system and eventually lodges in and obstructs a blood vessel. Emboli can be from many different sources including blood clots, bacterial clumps, tissue fragments, or air bubbles. A thrombus, on the other hand, is a clot that forms in and obstructs a blood vessel (thrombosis is a related word which refers to a blood clot in a blood vessel).

Now, let’s look at the medicine. When air enters the venous system, it is pushed to the heart and then into the lungs where it becomes trapped. Small amounts of air don’t cause symptoms because they are broken up and absorbed by the lungs. Air emboli of around 50ml are enough to cause symptoms such as pulmonary edema, pulmonary hypertension, systemic hypotension, arrythmias, and in extreme cases, cardiac failure or arrest. A very large embolus can block the entire right atrium and ventricle leading to sudden cardiac arrest and death. This requires around 300ml of air.

If the victim happens to have an open foramen ovale (a small hole between the right and left atria, it occurs in about 20% of the population) and the blood pressure builds up enough in the lungs to cause a right to left shunt, the air bubble may get into the arterial circulation and end up blocking some smaller artery somewhere in the body. Usually, this will result in ischemic damage to some tissue or organ, which may or may not cause symptoms. However, if the embolus happens to block a coronary artery then it would cause a heart attack; similarly, a blockage of the cerebral arteries would cause a stroke. This isn’t instantaneous though, as after injection the embolus has to go to the lungs first, cause an increased pressure, and then move into the arterial circulation — that’s if the victim even has an open foramen ovale — and even then it isn’t likely to be fatal unless the air bubble ends up in a key artery¹.

Next, let’s look at the scene itself. The killer plunges the syringe in the victim’s neck while he is…otherwise engaged. It’s hard enough hitting a vein in a blind stick on an immobile patient; it’s much harder to hit a moving target. Plus you not only have to hit the vein, but you have to hit it in such a way to inject the air bubble into the vein and not the surrounding tissue. That’s impressive aim². Finally, you’ll notice she seems to be holding a 3cc syringe — which is only 1/100th of the amount actually required to reliably kill someone³.

NOTES:
¹ But on the other hand, it doesn’t take as large of an air embolus in the arterial system to cause severe damage, just 0.5ml was enough to block a main coronary artery in one study.
² If she had managed to hit the carotid artery, that might have been even worse. Air injected directly into the carotid can cause an impressive stroke.
³ I guess the victim might have had a patent foramen ovale, and being his wife, the killer might have known that fact, and even counted on it. If that were the case, the small amount of air she injected could have caused a heart problem, if it ended up in the correct artery, which is pretty much a crap shoot. And even then it would take significantly longer to have an effect than the 30 seconds or so it seems to take here.