Thread by @medrants

1/ #UncleBob recently presented a patient who had a hyperkalemia, normal gap acidosis (type 4 RTA) to @DxRxEdu & @rabihmgeha

But why does hyperkalemia cause a normal gap acidosis?

@tony_breu

2/ Some basic physiology - we metabolize around 1 mEq of H+ daily from our diet. We buffer that acid using titratable (phosphate) and non-titratable (NH4+) acids.
The phosphate pathway does not vary much, but our kidneys can normally control the ammonium pathway

3/ Where does the ammonia come from? Glutamine -> glutamate under the enzyme glutaminase produces NH3

Here is the interesting part. Increased K inhibits this enzyme, thus we produce insufficient NH3 to buffer our dietary intake.

4/ (interesting that low K stimulates the enzyme) which may contribute to hepatic encephalopathy - probably explains with low K is a risk factor for hepatic encephalopathy.

5/ Thus, if we can return the K to normal, the normal gap acidosis will resolve.

Here is a reference jasn.asnjournals.org/content/29/5/1…
Mechanism of Hyperkalemia-Induced Metabolic Acidosis