Electrolyte Question - Medical type ppl help!?

Question

Even if you can only answer one or two would be great!

PS - if you dont know any of the below, PLEASE dont answer it saying you dont know or I shouldnt post the question etc, etc -cos most of the time someone does know! :)

1) Someone has low Na post op - what does this mean?

2) true/false- ppl require 60KCL per day for maintainence?

3) K is released from tissue post op - so an elevated K is expected - but how high is acceptable and for how long?

4) true/false - a high urea and creatinine indicate dehydration or kidney problems?

5) What happens to BIC post op?

6) Why does Mg follow K in U&Es?

Any help for any of the above would be appreciated, thanks in advance... If others have given an answer, pls feel free to give me your take, cos more answers = better. thanks :)

Answer 1

1) Many reasons, but commonly bad fluid management. However one physiological reason is that any kind of trauma to the body causes massive release of ADH (anti diuretic hormone), which causes retention of water. Basically the body knows it is injured and might not be able to go and find food and water, so it holds on to water as much as possible and this has a dilutional effect.

4) Hmm depends. The problem can be with the kidney or it can be pre-renal. E.g. there needs to be a certain amount of blood flowing through the kidney to be able to keep up with filtration. If there is a lot of blood loss and the person is fluid depleted, there is reduced blood flow to the kidney and creatinine and urea will rise regardless of how hard the kidneys are working. Eventually, the kidneys will suffer and acute renal failure will develop. Alternatively, there might be plenty of fluid and blood flow, but the kidneys just aren't working, causing urea and creatinine to rise. One major clue is how high the urea is - fluid depletion will cause a disproportionate rise in urea, i.e. a much higher percentage rise than the creatinine. This is because urea is partially re-absorbed from the renal tubules after it has been filtered. If someone is fluid-depleted, the flow through the tubules is slower and more urea gets re-absorbed, so blood levels get particularly high.

Urea can also be high due to things like GI bleeds (effectively mimics large amount of protein ingestion/digestion). Creatinine can be high because the person has a high muscle mass. It can also be misleadingly 'low' in someone with a low muscle mass, especially the elderly/frail.

6) Oh dear I should know this! I'm off to consult my books! :-) I do know that it has something to do with transport systems in the renal tubules - potassium and magnesium transport is linked somehow.