chemistry lesson

Sam, my medical student, got to have a "learning experience" with me the other night. One of the nurses asked him to grab 10mg of morphine, and all we had was the 50mg/ml uuber concentrated vials. Normally I dilute it to 1mg/ml, but none was made up. When it became clear that there was some confusion with the concept of mg vs. ml - more specifically, with the distinction "volume vs. weight" - I saw a great teaching opportunity.

Since the patient was in acute pain, we took care of the dose, then I sat Sam down for a chemistry lesson. "If I have a pound of feathers, and a pound of lead, which weighs more?" was my first question. Then I remembered, I'm in Haiti - metric system - so rephrased the question with kilogram in place of pound. And, just like all of us, he answered "the kilogram of lead. Metal weighs more than feathers."

A kilogram weighs a kilogram, no matter what the material, but the kilo of feathers takes up more space than the kilo of lead. That "space" is the volume. We discussed it theoretically, but the concept didn't seem to be sticking. So I grabbed a bottle of pills off the shelf, and used each one to represent a milligram of morphine, and a tray as the milliliter. Some of us are more visual learners. Once the idea had sunk in, and he did the math, I let him do the dilution for the 1mg/ml morphine stock solution (under supervision, of course).

Back when I was doing my undergrad, I student taught chemistry, and Jim (Professor Schnieder) would have been proud of me. And I'm so proud of Sam - not only did he master a new concept in chemistry at 3am, he did it in his second language. Because, as I like to remind him, his English is WAY better than my creole.

~PJ