Amy Yau Profile picture
Academic Nephrologist, FACP @AZ_Neph 🐻⬇️ • @BookBurton • Interests #electrolytes #kidneystones #uronephrology #onconephrology • Tweets are my own 🌷

13 Sep, 19 tweets

⁉️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.🌟

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

Skeletal muscle cells also have Cation/Cl exchanger and H/OrganicAnion (H/A) cotransport leading to 🌟differential effects on potassium🌟

In 🥬organic acidosis → ⬆️ more H/A activity → ⬇️less K efflux

In 💎mineral acidosis → ⬆️increased Cl/HCO3 exchange → ⬆️more K efflux

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)

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.⭐

⁉️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!)

In ⏲️acute acidosis, kaliuresis is inhibited by a multitude of mechanisms.

In ⏱️prolonged acidosis,
📌increase UrNa and UrCl support the theory ⬆️increased distal Na delivery is the key🗝️

🤔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!)

⏱️Prolonged acidosis can also directly ⬆️stimulate aldosterone secretion (independent of renin)

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.

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