Skyler Lentz
Skyler Lentz

@SkylerLentz

11 تغريدة 32 قراءة Mar 21, 2023
🧪Can you have a metabolic acidosis with a normal plasma bicarbonate?
Lessons learned from a case
👇
#FOAMed #foamcc
1/
A patient presents ill after being found down and altered
Sepsis from a pneumonia is suspected
Labs:
Na 130 K 5.0 Cl 75 Bicarb 25
Cr 3.8 BUN 120 (Acute renal failure)
Glucose 520 (h/o type 2 DM)
Lactate 3
Ca 13.0
pH 7.41 pCO2 45
2/
Is there an acidosis?
The pH is normal, bicarb is normal 🧐
What’s the anion gap?
130 – [75+25] = anion gap of 30
There is an elevated anion gap = there IS a high anion gap metabolic acidosis (HAGMA)
3/
Lesson: always calculate an anion gap, even if bicarb is normal
What is going in our case?
Use Delta-Delta equation to figure it out
Delta (change in anion gap) - Delta (change in bicarb) = ± 5 in pure HAGMA
4/
Our case
Delta Anion Gap-Delta Bicarbonate
Anion gap up by 18 (30 - normal of 12)
Bicarb up by 1 (25 - normal of 24)
Bicarb should be ~ 6 if pure HAGMA (24-18)
Instead, it is 25 in our case
The bicarbonate is elevated from what is predicted based on the anion gap
5/
Must mean there is a metabolic alkalosis!
First what is the anion causing the gap?
Measure what you can:
Lactate-minimally elevated
Renal failure might be contributing
Ketones?
Beta-hydroxybutyrate is highly elevated suggesting ketoacidosis we suspect DKA
6/
What about the metabolic alkalosis?
History usually helpful
Most common causes are GI losses of hydrogen ions (vomiting or NG output) with hypovolemia and diuretic use
This person had been 🤮, they did not take diuretics
But why the hypercalcemia?
7/
Urine chloride was low suggesting a chloride responsive met alkalosis (typical of excessive vomiting and HCl loss)
But they had had also been taking a lot of antacids chronic stomach pain
So, probably component of milk-alkali syndrome from excess calcium carbonate intake
8/
Treatment?
Supportive as long as they’re making urine
Usual treatment of DKA (Insulin and fluids)
Normal saline (sodium chloride) was used preferentially to correct hypovolemia and replete Cl
Electrolyte repletion
9/
The anion gap rapidly improved
Bicarb up to 38 after anion gap resolved
Bicarb returned to normal next day after maintenance normal saline infusion and improving renal function
Hypercalcemia resolved
10/
Final thoughts 📜
1.You CAN have a metabolic acidosis with a normal bicarb
2.Always calculate an anion gap
3.Use Delta anion gap-Delta Bicarbonate to identify mixed acid base disorder
4.Metabolic alkalosis from hypovolemia and vomiting-treat with NS
11/

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