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
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
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.
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
Mechanism of Hyperkalemia-Induced Metabolic Acidosis
Here is a reference jasn.asnjournals.org
Mechanism of Hyperkalemia-Induced Metabolic Acidosis
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