Investigation Quiz 026

Scenario

A 47 year old man with a history of chronic liver disease and schizophrenia is brought to your emergency department by ambulance with acute confusion.

Arterial blood gas

Question

Describe and interpret his results (100%)

Answer

FACEM VAQ Exam 2012.2 – Question 3

  • The overall pass rate for this question was  67/104 (64.4%)
  • Pass Criteria
    • Recognition of serious nature of clinical presentation
    • Profoundly raise lactic acid
    • Primary metabolic acidosis with respiratory compensation, and coexistent respiratory alkalosis Profound hyponatraemia
    • HAGMA identified
    • Interpretation: HAGMA causes (ie hypoperfusive sate, toxicology) and hyponatraemia causes (ie SIADH)
  • Features of unsuccessful answers
    • Insufficient interpretation of HAGMA or hyponatraemia Calculation errors
    • Lack of identification of co-existent respiratory alkalosis

ACEM Fellowship Visual Aid Questions

 

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Comments

  1. Rum_boy says

    delta ratio worked out to be 0.46 indicating a mixed HAGMA and NAGMA.
    No mention in examiners reports of maybe a seizure secondary to severe hyponatremia, which may explain his confusion ( post ictal ) and also lactate ( although I do agree that it is higher than would be expected just post seizure, but definetly a contribvuting cause to whatever is the primary process)

    Any thoughts?

    • says

      Sounds reasonable.
      Another thing to consider is that the anion gap could also be falsely low due to hypoalbuminemia due to chronic liver disease.

      From http://lifeinthefastlane.com/education/ccc/anion-gap/ :

      the normal anion gap depends on serum phosphate and serum albumin
      the normal AG = 0.2 x [albumin] (g/L) + 1.5 x [phosphate] (mmol/L)
      albumin is the major unmeasured anion and contributes almost the whole of the value of the anion gap.
      every one gram decrease in albumin will decrease anion gap by .25 to .3 mmoles.
      a normally high anion gap acidosis in a patient with hypoalbuminaemia may appear as a normal anion gap acidosis.
      this is particularly relevant in ICU patients where lower albumin levels are common.

  2. Afzal Ali says

    i do not think there respiratory alkalosis because as per winter formula if it is Met. Acidosis then as per winter formula expected decrease in paco2 is = (1.5 x 9)+ 8 which is 21.5 & if you account for the SD of normal (+/-5) it is 16.5 which near normal so i do understand how can it be RESPIRATORY ALKALOSIS with difference 1.5. Rum_boy is absoultely right Delta ratio is 0.46 indicating a mixed HAGMA and NAGMA. So in nutshell if we account for REs Alkalosis then it is a triple disorder & if we minus Res Alkalosis then it a double disorder.

    Would like some to tell me if My assumption regarding Res. Alkalosis are right or wrong

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