Explain anaphalactic shock

[Johnny L.A.]

I was watching an anime, and one of the characters was given a "vitamin shot" by her guardian. It was really eggs. Later they go out to dinner and the victim eats eggs, which causes her to go into anaphalactic shock.

Wouldn't injecting raw eggs into the bloodstream be a Bad Thing to begin with? If that wasn't fatal, why would eating eggs later be fatal? I know that anaphalactic shock has something to do with proteins, but how does it work? What would cause, say, a bee sting to cause anaphalactic shock? How would the person become "sensitized" (another word I've heard in association with it) in the first place?

[Duck Duck Goose]

Sidestepping the issue of whether it's a good idea to inject raw eggs into your bloodstream, because I have no clue, but it's probably not something you'd want to try at home, especially considering the lamentable propensity of raw eggs to harbor salmonella. (But hey, then you'd save yourself all those agonizing hours of wondering whether your vomiting and diarrhea was salmonella or just the flu--you could go straight to the hospital and tell the ER triage person with confidence, "Yes, I'm quite certain it's salmonella, and the reason I know that is...")

Anyway.

http://www.medisearch.co.uk/scripts/anaphylaxis.asp

What is Anaphylaxis?
During the first exposure to an allergen, the immune system becomes sensitised. This means immune cells are familiarized with the allergen and produce antibodies and B cells (lymphocytes) specific to it.

When the immune system is exposed to the allergen on a subsequent occasion, the immune system is able to quickly recognise it. This causes cells to release vasoactive amines e.g. histamine which results in:

Bronchospasm
Vasoconstriction
Laryngeal oedema
Urticarial rash
Shock

Anaphylaxis occurs immediately or at most within two hours of exposure to the allergen.

Unfortunately, nobody knows why some people get sensitised to some allergens and some people don't.

I suppose it's possible that injecting egg protein directly into the bloodstream might have the effect of sensitising someone to eggs if that person were already predisposed to become sensitised. But for all the Wicked Guardian knew, she might not have become sensitised, and his whole evil scheme might have fallen through. She might have sat there calmly eating her eggs, with nothing happening, while he got more and more frustrated, and the cartoon would have ended with him running her over with the car out in the parking lot instead.

[Whack-a-Mole]

I would assume that injecting raw egg into your blood would be a bad thing but IANADoctor so my answers are suspect.

However, my brother was on a flight to Europe, ate an almond and went into shock. My brother-in-law, a doctor, was on the plane and he promptly adminitered a shot of Epenephrine(sp?) and all was good (the plane carried a medical kit with that inside). They didn't have to divert the plane or anything and continued on their merry way.

Because of this incident I asked my brother-in-law about how this whole thing works so here is my layman's answer as best as I can remember it.

My brother had eaten almonds in the past with no effect. However, just because you don't see an effect doesn't mean that something isn't going on inside. For whatever reason your body decides it doesn't like almonds (in my story...but it could be lots of different things). On the first go around you don't notice a reaction but your body created antibodies to fight the almonds (not precisely correct but go with it...I suppose the real answer is the particular protein found in almonds or whatever it is you have a reaction to). Your body also creates memory cells that 'remember' what to do with almond proteins if it ever sees them again.

Move forward a few weeks and nibble a few more almonds. This time your body recognizes the proteins it doesn't like much quicker and reacts violently to the 'invasion' of these proteins. *POOF* Anaphalactic shock sets in. Your body produces tons of histamine that contracts muscle cells making it hard to breathe and may cause vomiting or a bevy of other nasty side effects. When asking my brother-in-law why people just don't pop an anti-histamine pill (such as is found in most allergy medications) he said it doesn't work fast enough to counteract the effects of the histamine. Epenepherine, however, relaxes muscle cells quickly so it is the medication of choice when this happens.

So your movie seems to have gotten the whole thing right (with the egg injection being questionable in my mind unless it was just some egg proteins and not an egg cracked into a syringe).

[douglips]

The key is that the first time you are exposed to a protein to which you are allergic, nothing happens. It's like a vaccination, except that instead of a healthy immune response being generated for next time, an unhealthy immune response is generated the next time.

IANAD - this info is from an immunology course I took ten years ago.

Injecting raw eggs is not smart, but injecting some preparation of egg protein is OK. In fact, that's what a flu shot is.

[honkytonkwillie]

The part that's missing is an explanation of shock. Shock is inadequate perfusion of blood in the tissues. Most commonly due to losing sufficient volumes of blood.

The bleeding doesn't have to be all over the floor, as internal bleeding can be of such quantity that not enough blood remains in the (now open) circulatory system to bring oxygen to body tissues.

With anaphalactic shock, the weird thing is that bleeding doesn't occur and blood isn't lost. Instead, as part of the allregic/immune response, capillaries become a lot more "leaky" and a lot of the fluid component of blood is lost to the surrounding tissues. This is what causes the swelling.

The result of all this is that there's not enough volume of (albiet thicker) blood remaining in the circulatory system to get pushed around throughout the body.

It's been a few years since my last formal schoolin' on the topic, so I welcome any corrections and contributions.

[Gaspode]

[quote]Originally posted by honkytonkwillie
With anaphalactic shock, the weird thing is that bleeding doesn't occur and blood isn't lost. Instead, as part of the allregic/immune response, capillaries become a lot more "leaky" and a lot of the fluid component of blood is lost to the surrounding tissues. This is what causes the swelling.
QUOTE]
While you're quite right about the increased fluid loss from the cappilaries this isn't the main reason for the loss of BP due to shock reactions. Rather the blood vessels themselves become dilated, losing most of their normal muscular tone. This essentially means the diameter of the pipes of the circulatory system is greater, giving a greater overall volume to be filled. There just isn't enough blood to fill this volume of plumbing and still maintain pressure. Hey presto insant drop in blood pressure, rather than the slow drop that would be caused by fluid leak.

[D18]

Originally posted by Whack-a-Mole
However, my brother was on a flight to Europe, ate an almond and went into shock. My brother-in-law, a doctor, was on the plane and he promptly adminitered a shot of Epenephrine(sp?) and all was good (the plane carried a medical kit with that inside). They didn't have to divert the plane or anything and continued on their merry way.

Fortunately, your brother was in the care of a physician during this flight, so he was able to make the call about whether further therapy was necessary or not!

But in the absense of a physician . . .

IANAD, but my doctor did make it clear to me that if I ever had to use my Epipen(r) that I was still to get myself to an ER ASAP.

The Epipen is only designed to buy you time. From the 2001 CPS:

[Epipens] are designed as emergency supportive therapy only and not as a replacement or substitute for subsequent medical or hospital care, nor are they intended to supplant insect venom hyposensitization.

And regarding Ana-Kit(r):

Ana-Kit is not intended to be a substitute for medical attention or hospital care. The kit is designed . . . to provide emergency treatment when medical care is no immediately available.

There was a tragic case reported in the paper about a year ago of a girl who died of analphylactic shock despite getting epinephrine from something like an Ana-Kit or Epipen. I forget whether the family did not know that they needed to still take her to the ER, or whether they were so far away from a hospital that they didn't make it in time.

[/public service hijack]