- Definition: pH < 7.35 due to HCO3⁻ < 24.
- Compensation: Hyperventilation (↓ pCO2).
- Anion Gap (AG): Na⁺ - (Cl⁻ + HCO3⁻). Normal = 8–12.
- High AG Metabolic Acidosis (MUDPILES)
- Mechanism: Accumulation of organic acids (unmeasured anions) consuming HCO3-.
- Measured anions are Cl- and HCO3-. Others are all unmeasured.
- Methanol (Vision loss)
- Uremia
- DKA
- Propylene glycol
- Iron / INH
- Lactic acidosis (Shock, Metformin) t
- Ethylene glycol (Calcium oxalate crystals)
- Salicylates (Mixed Met Acidosis + Resp Alkalosis)
- Normal AG Metabolic Acidosis (HARDASS)
- Mechanism: Direct loss of HCO3- or impaired acid excretion (Hyperchloremic).
- Hyperalimentation
- Acetazolamide
- RTA (Types 1, 2, 4)
- Diarrhea (#1 cause, Urine AG is Negative)
- Aldosterone antagonists
- Saline infusion
- Key Calculations
- Winter’s Formula: Checks compensation.
- Exp pCO2 = 1.5 × [HCO3⁻] + 8 ± 2
- Urine AG: (Urine Na + Urine K) - Urine Cl.
- Negative: Diarrhea (Gut loss).
- Positive: RTA (Renal loss).