⁉️What is the difference between mineral and organic acidosis?
⁉️Why does one cause more hyperkalemia than the other?
Join me on this 🐇🕳️rabbit hole #tweetorial on metabolic acidosis and it's effect on potassium.
📊To start, which type of acidosis causes more hyperkalemia?
Metabolic acidosis is defined as a ⬇️low pH due to a ⬇️decrease in bicarbonate extracellularly
💎Mineral acids (aka inorganic acids) are “synthesized from earth minerals.”
🥬Organic acids are metabolized by the cell and occur naturally.
Both can have a 🩸high anion-gap...just depends on anion accumulated.
💎Mineral acids are often (not always) a hyperchloremic normal anion gap metabolic acidosis
Think of 🥬organic acidosis as high anion gap metabolic acidosis (though not always true)
📊What is the classic relationship between acidosis and potassium?
Hyperkalemia and acidosis go hand in hand, but type of acidosis does affect it
💎Mineral acidosis tends to cause ⬆️more hyperkalemia compared to 🥬organic acidosis due to 🌟cell shift.🌟
pubmed.ncbi.nlm.nih.gov/29495/
pubmed.ncbi.nlm.nih.gov/3884666/
There are a few ways acidosis can affect transcellular shift of potassium
📌low intracellular Na, low intracellular pH resulting in ⬇️reduced Na/K ATPase activity
📌Low extracellular bicarb leading to K efflux through Cl/HCO3 exchanger
pubmed.ncbi.nlm.nih.gov/21980112/
Skeletal muscle cells also have Cation/Cl exchanger and H/OrganicAnion (H/A) cotransport leading to 🌟differential effects on potassium🌟
pubmed.ncbi.nlm.nih.gov/27756725/
In 🥬organic acidosis → ⬆️ more H/A activity → ⬇️less K efflux
pubmed.ncbi.nlm.nih.gov/21980112/
In 💎mineral acidosis → ⬆️increased Cl/HCO3 exchange → ⬆️more K efflux
pubmed.ncbi.nlm.nih.gov/21980112/
Differences in K shift may also be due to 🌟insulin (not well defined)
acidosis → insulin release → ⬆️increase Na/K activity🌟 → K shift into cell
(It is not clear if organic acidosis causes MORE insulin release than mineral)
pubmed.ncbi.nlm.nih.gov/15153570/
pubmed.ncbi.nlm.nih.gov/3884666/
Despite knowing acidosis and hyperkalemia go hand in hand, does giving bicarb help shift K?
Anecdotally, giving bicarb does not❌ always help shift hyperkalemia.
For any given HCO3 or pH, Na/H and Na/HCO3 activity is higher in acidosis, so ⭐bicarb shifts more K in acidosis.⭐
pubmed.ncbi.nlm.nih.gov/8840939
⁉️But, you may ask, what about the kidneys?!!!!⁉️
📊What is the net effect of acidosis on renal potassium handling?
Studies show there are differential effects of 🧪acidosis and UrK, likely based on the length of acid infusion
⏲️Acute acidosis (hours) → no change in UrK
⏱️Prolonged acidosis (days) → increase UrK (and total body K lowering!)
pubmed.ncbi.nlm.nih.gov/3884666/
pubmed.ncbi.nlm.nih.gov/3105328/
In ⏲️acute acidosis, kaliuresis is inhibited by a multitude of mechanisms.
pubmed.ncbi.nlm.nih.gov/21980112/
In ⏱️prolonged acidosis,
📌increase UrNa and UrCl support the theory ⬆️increased distal Na delivery is the key🗝️
pubmed.ncbi.nlm.nih.gov/11344560/
pubmed.ncbi.nlm.nih.gov/3105328/
🤔There are 🍀4 possible explanations why distal Na delivery increases...(see gif)
In some cases of acidosis, excretion of 🙀non absorbable acidic anions increase distal Na delivery too (a 5️⃣th explanation!)
pubmed.ncbi.nlm.nih.gov/21980112/
⏱️Prolonged acidosis can also directly ⬆️stimulate aldosterone secretion (independent of renin)
pubmed.ncbi.nlm.nih.gov/3105328/
In summary,
📌Acutely, 💎mineral acidosis associated with ⭐more profound hyperkalemia than 🥬organic due to ⭐cell shifting
📌Chronic acidosis increases UrK due to ⭐increased distal Na delivery and aldo
Comments, gripes, and suggestions welcome.
pubmed.ncbi.nlm.nih.gov/21980112/
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