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How to survive a gas attack

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Slides for a short talk on some tips and tricks for trainees when interpreting ABGs (arterial blood gases). Talk given at the free registrar's day at Bedside Critical Care 2013 in the Whitsunday Islands.

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How to survive a gas attack

  1. 1. How to Survive ain 10 minutes… A Talk by Chris Nickson
  2. 2. No $ Photo by Misserion
  3. 3. Overview A-a GradientCompensation Strong Ions Anion Gap
  4. 4. All aboutA-a gradients(not really…)
  5. 5. A-a gradient = PAO2 – PaO2
  6. 6. PAO2 = FiO2 (PB – PH20) – (PaCO2/R)
  7. 7. Quick check:expected PaO2 = %FiO2 x 5
  8. 8. Caveats: high PaCO2A-a gradient varies with age and FiO2
  9. 9. Rule of thumb:expected A-a gradient = (age/4) + 4
  10. 10. Be aCompensation King (or Queen)
  11. 11. Respiratory compensation = rapidMetabolic compensation = slow
  12. 12. Metabolic compensation The 1-2-3-4-5 Rule
  13. 13. 1
  14. 14. 12
  15. 15. HCO312
  16. 16. HCO31 42
  17. 17. HCO31 42 5
  18. 18. HCO31 42 5acute chronic
  19. 19. HCO310 mmHg  1 4PaCO2  2 5 acute chronic
  20. 20. Respiratory compensation
  21. 21. PaCO2 = 1.5 x HCO3 + 8 (+/-2) if metabolic acidosisPaCO2 = 0.7 x HCO3 + 20 (+/-5) if metabolic alkalosis
  22. 22. Rule of thumb:If pH = 7.xy then PaCO2 ≈ xy
  23. 23. Strong ions… WTF?
  24. 24. The real determinants of pH are: Strong ions Weak acids [ATOT] PCO2
  25. 25. Strong Ion difference: Na – Cl <38 = NAGMA>38 = metabolic alkalosis
  26. 26. EMCrit by Scott Weingarthttp://emcrit.org/podcasts/acid-base-i/ Acid-Base Physiology by Kerry Brandishttp://www.anaesthesiamcq.com/AcidB aseBook/ABindex.php
  27. 27. High Lactate withNormal Anion Gap… WTF?
  28. 28. Anion gap Na – (HCO3+Cl)Normal = 8-12 mM LTKR
  29. 29. Anion gap is only ~50% sensitivefor lactic acidosis
  30. 30. What causes alow anion gap?
  31. 31. Low Anions: Albumin High Cations Bromism Analytical error
  32. 32. Correcting for low albumin is essentialAGadj = AGobs + 0.25 x (42 - Albobs)
  33. 33. THE ENDhttp://lifeinthefastlane.com/education /clinical-cases/http://lifeinthefastlane.com/exams/fac em-fellowship/vaq-subject/http://lifeinthefastlane.com/exams/cic m-fellowship/saq-keyword/
  34. 34. THE END http://lifeinthefastlane.com/education/clinical-cases/http://lifeinthefastlane.com/exams/facem-fellowship/vaq-subject/http://lifeinthefastlane.com/exams/cicm-fellowship/saq-keyword/

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