Studying up for an exam and have hit a problem: What in the crap are milliequvalents? In a biological sense? I’ve tried a bunch of websites that explained it in chemistry terms, to no avail.
I get that it has to do with how much of the functional compound is dissolved in the solution. And I know that if, for example, I had a liter of subcutaneous fluids with 4 mEq of potassium, and I wanted to give 6mEq, I would add 2 mEq of potassium to the bag. But what does that translate to in milligrams per liter? Or mL per L, or basically any measure that is more familiar? If a professor is warning me that Potassium pennicilin G contains 1.7mEq of potassium per million unitsa, and therefore has to be watched for possible potassium toxicity at large doses, exactly how much potassium am I putting into my patient?
A milliequivalent is a millimole of charge. For ions with a single positive charge, 1 millequivalent=1 millimole. On medical labs, ions are often reported as mEq/L–with potassium for example blood levels are often reported as mEq/L, which is the same as 1 mM since the valence of K+ is 1.
If you are dealing with ions with a valence of more than 1 (eg Ca[sup]2+[/sup]), the millimolar concentration varies from the mEq concentration. For example, a 1 mM solution of Mg[sup]2+[/sup] is a 2 mEq solution of magnesium ions.
Oh, so it has more to do with molecular weight, and not necessarily charge, when converting equivalents to grams? If the molecular weight of iron is 55g, then 1 mEq of iron = 55mg iron?
Does it only apply for charged iron molecules? If there was a 1 liter bag of subcutaneous fluids with 1mEq of iron, did the manufacturer really add more iron, knowing that only a certain proportion would be in the charged state at any given time, or did they literally put 55mg of iron in the bag?
Hirundo, I get what your saying about unit of charge when dissolved in a fluid. I guess I’m not understanding how they actually make these things with a specific number of charged particles. Do they just rely on the dissociation constants of whatever salt they are adding to the bag of fluids?