Calc Function

    • Calcs that help predict probability of a diseaseDiagnosis
    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
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    • Numerical inputs and outputsFormula
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    • Suggested protocolsAlgorithm





    Chief Complaint


    Organ System


    Patent Pending

    Anion Gap

    Evaluates states of metabolic acidosis.


    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.



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    Next Steps
    Creator Insights


    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
    • Post-hypercapnia
    • Diuretics

    Respiratory Alkalosis: CHAMPS (think speed up breathing)

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


    • 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

    About the Creator
    Dr. Man S. Oh