DKA & acid-base analysis

We discussed a young male with no past medical history with 4 days of abdominal pain, nausea, vomiting, constipation found to be kussmaul breathing on physical exam. Patient presented with anion gap metabolic acidosis. 

Learn how to calculate acid base

  1. Anion gap = Na-Cl-bicarb
  2. Determine pH (7.35-7.45 is normal)
  3. Identify primary disorder (i.e. respiratory vs metabolic)
    • If metabolic: bicarb <22, think primary metabolic acidosis; if bicarb>28, think primary metabolic alkalosis
    • If respiratory: pCO2 <35, thik primary respiratory alkalosis; if pCO2>45, think primary respiratory acidosis
  4. To look for concomitant respiratory process on top of primary metabolic acidosis, calculate Winters Formula: expected pco2 = 1.5*(bicarb)+8
  5. To look for comitant metabolic process on top of primary metabolic process, calculate Delta gap:(patient’s AG – normal AG) – (patient’s bicarb-normal bicarb)
    • Delta gap>6 indicates metabolic alkalosis on top of AGMA 
    • Delta gap close to 0 is normal and indicates pure AGMA
    • Delta gap <-6 indicates NAGMA on top of AGMA  

Our patient had primary AGMA with metabolic alkalosis with superimposed respiratory acidosis. 

Learn differential for AGMA

  1. Glycols – ethylene glycol/propylene glycol 
  2. Oxoproline (acetaminophen)
  3. L-lactate
  4. D-lactate
  5. Methanol
  6. Aspirin
  7. Renal Failure
  8. Ketoacidosis

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