Metabolic Acidosis

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🌱 來自: Huppert’s Notes

Metabolic Acidosis🚧 施工中

Metabolic Acidosis

↓pH, ↓ HCO3–, (Immediate respiratory compensation = Hyperventilation ↓PaCO2)

•   Clinical features: Hyperventilation (Kussmaul’s respirations if pH <7.2); decreased cardiac output and tissue perfusion due to decreased response to catecholamines

•   Calculate anion gap (AG): Anion Gap = Na+ – (Cl– + HCO3–)

-   Increased anion gap: There are mnemonics like “MUDPILES” or “GOLD MARK,” but simpler to consider four buckets:

•   Ketoacidosis (DKA, starvation, alcohol use)

-   Pearl: SGLT2 inhibitors are associated with euglycemic ketoacidosis (glucose <200 mg/dL). A normal serum glucose does not rule out ketoacidosis if these medications are being taken!

•   Lactic acidosis (hypoperfusion, bowel ischemia, seizures)

-   L-lactic acidosis = Hypoperfusion and type B causes

-   D-lactic acidosis = Bacterial overgrowth, DKA or propylene glycol infusion. Of note, D lactic acidosis is NOT measured by laboratory lactate measurement.

•   Renal failure (decreased excretion of NH4+ and other acids)

•   Intoxication (aspirin, methanol, ethylene glycol)

-   Check osmolar gap (Measured serum osms – calculated serum osms)

-   Calculated serum osms = 2(Na+) + Gluc/18 + BUN / 2.8 + EtOH / 4.6

-   Pearl: Measure serum ethanol and incorporate into the serum Osm calculation to avoid a false-positive osmolar gap if it is present.

-   Normal anion gap: Check urine anion gap = Urine (Na+ + K+ – Cl-)

•   Renal losses (positive urine anion gap): Proximal/distal tubular acidosis, acetazolamide, spironolactone

•   GI or other extra-renal losses (negative urine anion gap): Saline administration, diarrhea, pancreatic or small bowel fistulas or drains

•   Hypoaldosteronism

•   Appropriate respiratory compensation? Winter’s formula: PaCO2 = 1.5(HCO3–) + 8 ± 2

-   If PaCO2 falls within the excepted range, then the patient just has a metabolic acidosis

-   If the actual (i.e., measured) PaCO2 is higher than the calculated PaCO2 using Winter’s formula, then the patient has a metabolic acidosis + respiratory acidosis

-   If the actual (i.e., measured) PaCO2 is lower than the calculated PaCO2 using Winter’s formula, then the patient has a metabolic acidosis + respiratory alkalosis

•   Treatment: Treat the underlying cause; PO alkali supplementation (sodium bicarb, sodium citrate, potassium citrate) for chronic causes; IV sodium bicarb if pH <7.1