Metabolic Acidosis on the NCLEX
Anion gap vs non-anion gap, MUDPILES, treatment.
Metabolic acidosis is low pH from non-respiratory cause. Anion gap classifies it.
ABG pattern
pH <7.35, HCO3 <22. CO2 may drop as compensation.
Anion gap = Na - (Cl + HCO3)
Normal 8-12. Elevated >12 = anion-gap acidosis.
Anion gap causes (MUDPILES)
Methanol, Uremia, DKA, Propylene glycol, Iron/Isoniazid, Lactic acidosis, Ethylene glycol, Salicylates.
Non-anion gap causes
Diarrhea, RTA, TPN, hyperchloremic from NS.
Treatment
Treat cause. Sodium bicarbonate if pH <7.1 or severe symptoms. Insulin for DKA. Dialysis for severe renal/toxic causes.
Frequently asked
Compensation rate metabolic acidosis?
Winter's formula: expected CO2 = 1.5 × HCO3 + 8 ± 2.
Bicarbonate in DKA?
Not routine, only severe acidosis (pH <6.9). Insulin closes the gap.
Quick check
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