Tuesday, March 19, 2013

Killing a Patient Using an Air Embolism

My villain approaches a patient in the hospital and injects a syringeful of air, killing the patient. How would this be done, and how much air would it take?

An air embolism is a quantity of air traveling as a single mass within the vascular system.
There are several factors at work when writing your scenario.

The first is whether it’s a venous air embolism, an arterial air embolism, or a paradoxical air embolism:

Venous air embolism: An IV (intravenous) line in a peripheral vein—like an arm vein—is unlikely to accommodate enough air in a rapid enough fashion to cause much trouble. Air bubbles that go in through such an IV are filtered out by the lungs, and generally cause no problems.

You’d need a very large syringe—fifty cc’s—and need to blow in several boluses of air in quick succession. The air takes up space in the right side of the heart, and restricts blood flow to the lungs.

If the patient has a large IV line in the internal jugular vein (called a central venous line), it’d be fairly easy to blow in a lot of air quickly and within a few centimeters of the heart. This is your best bet for this scenario. Patients with central lines aren’t necessarily confined to ICU. Temporary dialysis catheters are placed in the internal jugular, for instance.

Arterial air embolism: Access to an artery would be necessary. An artery is under pressure, and the air injected will meet more resistance than on the venous side. A few cc’s of air in the carotid artery can cause a stroke. The drawback is as soon as the killer pulls the needle out of the carotid artery, it’ll bleed profusely as the blood is under pressure. The killer’s method would be obvious right away if he left the bedside. Air to the brain isn’t uniformly fatal.

Paradoxical embolism: Air injected into the right sided venous circulation travels to the arterial left side of the heart without going through the lungs. This occurs via a hole between the right (venous) and left (arterial) sides of the heart, usually between the top two chambers (the atria), but can be between the bottom two chambers (the ventricles).
For a paradoxical embolism to work, the killer would need knowledge beforehand that the patient had such a hole, or he’d have to be very lucky to have selected a victim with an undiagnosed defect.

Since the arteries that supply blood to the heart originate where the arterial blood leaves the heart, air can travel down these coronary arteries and cause a heart attack and/or cardiac arrest.

The air can travel straight up into the carotid arteries (that supply the blood to the brain) and cause a stroke.

Hope this helps!
Cheers, Kelly

Diagram: Dr. R. Singer, heartlungdoc.com
Kelly has worked in the medical field for over twenty years, mainly at large medical centers. With experience in a variety of settings, chances are Kelly may have seen it.

Sometimes truth seems stranger than fiction in medicine, but accurate medicine in fiction is fabulous.
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  1. I remember seeing something like this in a movie I saw awhile back. I wish I could remember the name of the movie. A syringe full of air was injected into the IV line and then you could slowly watch the air going through the line until it entered the patient's arm. Scary stuff!

    1. It IS scary. Makes for a scary premise for a movie scene!
      Cheers, Kelly

  2. So interesting, as always, Kelly. I never knew one could kill with air.

    1. Thanks, Madeleine. Glad you liked it!
      Cheers, Kelly

  3. Hi Kelly
    I just came across your blog while doing a search on air embolisms and wondered if it wasn't too late to ask you a question. I write romantic suspense, and would love some help with a scene I'm writing. My killer is about to kill his victim via air embolism.
    Given the victim's heart will be racing, is it fair to assume death would be reasonably quick if the air is injected into the carotid artery? Would 50cc be enough? Could death occur in a matter of minutes? What symptoms would the killer observe? Could that include shortness of breath and body stiffening, as if they have chest pain?
    Thank you so much in advance.
    Michelle Somers

  4. Hello, Michelle. Sorry to be late seeing your request.
    Yes, death will be fast, within minutes using that much air; 50 cc should be plenty.
    The patient will show stroke-like symptoms: weakness/paralysis on one side, progressing to brain damage within a few minutes. If the victim is found at this point, resuscitation might be tried. The more brain damage the worse it will be. It's not uncommon for a patient to have bleeding into the damaged area of the brain after 24-48 hours.
    Hope this helps!