What Is Epinepherine?

A quick inside tip on field instructors; we all have our favorite questions to ask new riders. Those questions that help us get a more firm understanding of where our students knowledge base rests. What kind of practical knowledge are they carrying out into the field? Some of them are fair questions. Some of them aren’t. That’s life.

One of my favorite questions to ask that new rider early in the ride along is, “So what is epinephrine anyway?” (For the record, this is an extremely fair question.) I’ve found this to be a telling conversation because the scope of the question gives the student a lot of rope. This is a question where the student can choose to be shockingly simple or impressively complex. The choice is theirs.

I ask this question regardless of the students experience or training. I’ve had brand new EMT students knock the question out of the park and I’ve had experienced paramedics strike out miserably. All baseball metaphors aside, it’s a telling question. It speaks to a care givers understanding of the drugs we are able to administer. (Yes, all of us.) It’s revealing about ones understanding of the autonomic nervous system and it exposes an individuals understanding of basic pathophysiology.

When I ask the question, the answer I’m looking for is something like this:

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Rapid Diagnosis: Pinpoint Pupils

Abnormally constricted or “pinpoint” pupils are a great finding for our rapid diagnosis series. There are many things that can cause the pupil to abnormally dilate. Very few things will make the pupil abnormally constrict. Constricted pupils are a doorway to a very short list of ailments and with a bit of background you should be able to hang your hat on one fairly quick.

How do we assess for “pinpoint” pupils?

Recall that the pupil should be mid-range and reactive under normal lighting conditions. When subjected to bright light, the pupil will constricted to reduce the volume of light entering the iris. In darkness the pupil will dilate to allow as much ambient light in as possible. Pupils smaller than 2mm in diameter under normal lighting conditions can be considered “pinpoint”. Any pupil that responds to changes in lighting conditions with 1mm of movement or less can be considered minimally reactive or nonreactive.

To assess for pinpoint pupils we need to subject the pupil to darkness by asking the patient to close their eyes or covering the patients eye. When we return the light source to the pupil we expect the pupil to be larger and rapidly return to its original size. If the pupils remain <2mm in diameter through the changing light conditions we have a “pinpoint pupils” finding. The fancy medical term for this phenomenon is abnormal miosis.

If the patient has bilateral pinpoint pupils consider the following possible etiologies:

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