a couple questions

Intrested in hearing someone smarter then me answer your questions!

1. i have been seeing a lot of negative ua's - completely wnl, and then the culture will come back posititve. can anyone explain how this may happen. contamination at some point?

2. since regular insulin lowers serum potassium by driving it into the cell, does anyone see chronic hypokalemia in insulin dependent diabetics, because i have never. and is it only regular insulin that does this?

I don't know anything about the first question.

My understanding of the relationship between insulin and lowered potassium though is that it's more about the pathophysiology of metabolic acidosis.

My understanding is that if the patient is acidotic due to a lack of insulin (ie DKA) the body tries to hide the acid (H+ ions) in the cell, once that happens, in order to maintain equilibrium, potassium in the cell (K+) comes out when the H+ goes in. This is why when DKA is in the early stages, serum potassium is actually high, it continues to get lower as the potassium is excreted in the urine (and as the DKA patient is polyuric, that can happens quickly).

So, potassium decreasing as insulin is given is because the potassium (K+) can go back into the cell. As much of the K+ that was in the bloodstream has been excreted out, this leaves a low serum potassium and is why with DKA, once blood glucose gets to a certain level, potassium is given as well.

But I don't think insulin lowers K+ if there isn't an acidotic condition being reversed......but I could be wrong

insulin pushes K+ out of the blood. Some K+ will go to cells and the rest will be excreted (assuming kidneys work). ANY insulin will do this, including endogenous, but the more insulin at one time the greater the K+ push. So ANYONE can have hypokalemia due to insulin bolus, even if from own pancreas. Could be a clue to malfunctioning pancreas. If your patient is on insulin drip the K+ level is something to watch.

Thank You