Code blue!

It’s like Code Red, but at Michigan.

What I actually want to talk about is something that is not at all an emergency: the phenomenon of conditioned response. Let’s face it: we are all part Pavlovian dog (bells, food, saliva…you know how it goes). This is medically relevant in numerous contexts.

Response to decaffeinated coffee

You have all heard of the placebo effect and can easily imagine how it would work with coffee (i.e. give someone decaf, tell them it’s the real black gold, and then ask about their energy levels). The more exciting part is that these measurements of increased energy go beyond simply a person’s biased report. People who regularly drink regular coffee have a conditioned response to the taste of coffee. That is, when you give them decaf, you can measure a higher heart rate and respiration rate! Bodies physically respond if your brain simply thinks it got caffeine.

Response to fake sugar

We all sometimes crave sugar and the associated feelings of happiness and energy. Some people even report increased energy before it is possible for the consumed sugar to have entered their bloodstream. Things start to go haywire when you try to fool your body with sugar substitutes. When animals taste something sweet, they are trained to anticipate calories (with the corresponding changes in insulin levels, etc.). Products like saccharin-containing diet soda disrupt the sweetness and calorie link. People who eat normal sugar continue to exhibit the expected increase in core body temperature at mealtime, while people who use substitutes for too long are unknowingly conditioning their bodies not to rev up the metabolic engine.

Response to culprit food

If you get food poising from a particular item, you might never be able to dissociate the sight or smell of that food from the feeling of nausea. For some people, the association is so strong that they involuntarily vomit when they see that food, every time they see it for the rest of their lives. Obviously your body does not actually get food poisoning again, but it can’t control the cycle once triggered.

Response to ridiculously tiny needles that are not even painful

This whole Pavlov thing helps explain a certain type of fainting that has nothing to do with fear. Take, for instance, a hypothetical girl who once fainted when she gave blood since she had low blood pressure to begin with. She is not squeamish about blood, needles, dead animals, you name it, but for some reason she continues to embarrass herself during simple procedures like having dye injected before getting a hip MRI or having a PPD skin prick given to check for tuberculosis. It is odd that the fainting occurs much later that the trigger, or the “conditioned stimulus.” This reinforces the fact that it is not anticipatory fear, but a genuine, uncontrollable, physical response. She can watch enormous needles being stuck into her and continue the conversation with the nurse about how she loves swimming in very salty water. It won’t be until ten minutes later – while rescheduling a follow-up appointment – that she calmly tells the receptionist, “I am going to pass out now.” At least this person never faints or vomits after intense exercise, heat…or other activities.

The technical term might be “vasovagal syncope,” where some sort of trigger causes a sudden drop in heart rate and blood pressure, reducing blood flow to the brain. A person in decent condition who already has a low heart rate and low blood pressure might be predisposed. The autonomic (involuntary) part of the nervous system includes the vagus nerve, which releases hormones that slow the heart and widen the blood vessels. Since the vagus nerve also controls digestive tract function, you can easily see why fainting and nausea often go together.

The upside of passing out, for some people, is that they have incredibly intense dreams even if they are unconscious for only 15 seconds. We’re talking about entire novels playing out in their head, complete with intricate plots and vivid scenery. Not that I would know. That sounds like crazy talk to me.