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    Patent Pending

    Anion Gap

    Evaluates states of metabolic acidosis.
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    INSTRUCTIONS

    We now have an ABG Analyzer to help with acid-base analysis as well.

    When to Use
    Why Use

    Determining if a patient's acidosis also has an elevated anion gap.

    Anion gap acidoses have a very different differential diagnosis than non-gap acidoses.

    mEq/L
    mEq/L
    mEq/L
    g/dL

    Result:

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    Next Steps
    Evidence
    Creator Insights

    Advice

    Anion Gap Metabolic Acidosis: MUDPILERS

    • Methanol - Uremia - DKA/Alcoholic KA - Paraldehyde - Isoniazid - Lactic Acidosis - Etoh/Ethylene Glycol - Rhabdo/Renal Failure - Salicylates

    Non-Anion Gap Acidosis: HARDUPS

    • Hyperalimentation
    • Acetazolamide
    • Renal Tubular Acidosis
    • Diarrhea
    • Uretero-Pelvic Shunt
    • Post-Hypocapnia
    • Spironolactone

    Acute Respiratory Acidosis (Chronic Respiratory Acidosis = COPD/restrictive lung dz): any hypoventilation state

    • CNS Depression (drugs/CVA)
    • Airway Obstruction
    • Pneumonia
    • Pulmonary Edema
    • Hemo/Pneumothorax
    • Myopathy

    Metabolic Alkalosis: CLEVER PD

    • Contraction
    • Licorice
    • Endo: (Conn's, Cushings, Bartter's)
    • Vomiting
    • Excess Alkali
    • Refeeding Alkalosis

    Respiratory Alkalosis: CHAMPS (think speed up breathing)

    • CNS disease
    • Hypoxia
    • Anxiety
    • Mech Ventilators
    • Progesterone
    • Salicylates/Sepsis

    Formula

    • Anion gap = Na – (Cl + HCO3-)
    • Corrected anion gap, mEq/L = Anion gap, mEq/L + [ 2.5 × (4 – albumin, g/dL) ]
    • Delta gap = Anion gap – 12 (normal anion gap)

    Facts & Figures

    Delta Ratio Interpretation:

    Delta Ratio... Suggests...
    < 0.4 Hyperchloremic normal anion gap acidosis
    < 1 High AG & normal AG acidosis
    1 to 2 Pure Anion Gap Acidosis
    Lactic acidosis: average value 1.6
    DKA more likely to have a ratio closer to 1 due to urine ketone loss
    > 2 High AG acidosis and a concurrent metabolic alkalosis
    or a pre-existing compensated respiratory acidosis
    Dr. Man S. Oh

    About the Creator

    Man S. Oh, MD, is a professor of medicine and the director of fluid and electrolytes in the Department of Nephrology at SUNY Downstate Medical Center.

    To view Dr. Man S. Oh's publications, visit PubMed