acidosis and hyperkalemia

[MudPhud20XX]

The way Kaplan physio explains this is that developing an acidosis forces H+ to go inside cells and K+ to leave the cells causing hyperkalemia. So acidosis causes hyperkalemia. So I get that concept, but won't acidosis (too much proton outside cell, thus too much positive charge outside of cell) prevent potassium leaving from inside of cells if you think in terms of the electric balance between inside and outside of cells?

What am I missing here? Many thanks in advance.

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[Handinhand]

I believe in an attempt to buffer the acidosis, most cells take in excess H+ from the extracellular environment. The second part of your question is true -- and in an attempt to maintain electroneutrality, potassium is then excreted.

 

[Nephronlearner]

The H/K transporter can work in both directions. So it goes in 'favoured' direction: acidosis -> more H+ outside cells -> it will go inside in exchange for K+ -> hyperkalaemia.

As for electrical neutrality -> yes, that's why you can only have co-transport of ions with opposite charge or exchange of ions with the same charge (here, K+ is exchanged for H+). And, the reason excess H+ doesn't prevent it is probably related to the fact that H+ is used in the process (so it goes down) and also the excess H+ is what pushes the process forward in the first place.

 

[Handinhand]

There is an added complexity to this as well when your acidosis is the result of DKA. During the acute acidosis you're still going to get a "hyperkalemia" while in reality you're going to lose the excess potassium in your urine and eventually will become HYPOkalemic.

Now, in DKA, at least in a type 1 diabetic you can have further problems with potassium. When you start to give insulin to correct blood glucose levels, that's going to force K+ inside of the cells. This is a problem when you've been shifting K+ outside of your cells and then urinating out the excess. In this case, you need to supplement with K+ to prevent profound hypokalemia.