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How to survive a gas attack
- 1. How to Survive a in 10 minutes… A Talk by Chris Nickson
- 2. No $ Photo by Misserion
- 3. Overview A-a Gradient Compensation Strong Ions Anion Gap
- 4. All about A-a gradients (not really…)
- 5. A-a gradient = PAO2 – PaO2
- 6. PAO2 = FiO2 (PB – PH20) – (PaCO2/R)
- 7. Quick check: expected PaO2 = %FiO2 x 5
- 8. Caveats: high PaCO2 A-a gradient varies with age and FiO2
- 9. Rule of thumb: expected A-a gradient = (age/4) + 4
- 10. Be a Compensation King (or Queen)
- 11. Respiratory compensation = rapid Metabolic compensation = slow
- 12. Metabolic compensation The 1-2-3-4-5 Rule
- 14. 1
- 15. 1 2
- 16. HCO3 1 2
- 17. HCO3 1 4 2
- 18. HCO3 1 4 2 5
- 19. HCO3 1 4 2 5 acute chronic
- 20. HCO3 10 mmHg 1 4 PaCO2 2 5 acute chronic
- 22. PaCO2 = 1.5 x HCO3 + 8 (+/-2) if metabolic acidosis PaCO2 = 0.7 x HCO3 + 20 (+/-5) if metabolic alkalosis
- 23. Rule of thumb: If pH = 7.xy then PaCO2 ≈ xy
- 24. Strong ions… WTF?
- 25. The real determinants of pH are: Strong ions Weak acids [ATOT] PCO2
- 26. Strong Ion difference: Na – Cl <38 = NAGMA >38 = metabolic alkalosis
- 27. EMCrit by Scott Weingart http://emcrit.org/podcasts/acid-base-i/ Acid-Base Physiology by Kerry Brandis http://www.anaesthesiamcq.com/AcidB aseBook/ABindex.php
- 28. High Lactate with Normal Anion Gap… WTF?
- 29. Anion gap Na – (HCO3+Cl) Normal = 8-12 mM LTKR
- 30. Anion gap is only ~50% sensitive for lactic acidosis
- 31. What causes a low anion gap?
- 32. Low Anions: Albumin High Cations Bromism Analytical error
- 33. Correcting for low albumin is essential AGadj = AGobs + 0.25 x (42 - Albobs)
- 34. THE END http://lifeinthefastlane.com/education /clinical-cases/ http://lifeinthefastlane.com/exams/fac em-fellowship/vaq-subject/ http://lifeinthefastlane.com/exams/cic m-fellowship/saq-keyword/
- 35. THE END http://lifeinthefastlane.com/education/clinical-cases/ http://lifeinthefastlane.com/exams/facem-fellowship/vaq-subject/ http://lifeinthefastlane.com/exams/cicm-fellowship/saq-keyword/
Notes de l'éditeur
- Photo by Misserion
- Normal Aa gradient increases 5-7 mmHG for every 10% increase in FiO2 due to the overcoming of hypoxic vasoconstriction opening blood flow to poorly ventilated lung areas.
- Adams et al. included all ED patients over a seven month time period in whom a lactate level was measured for any reason. They considered an AG >12 abnormal and conducted sensitivity analyses of the AG for detecting the presence of a lactate >2.5 mmol/L. The AG was 52.8% sensitive, 81.0% specific with a negative predictive value of 89.7% for the prediction of lactic acidosis.(Adams BD, Bonzani TA, Hunter CJ. The anion gap does not accurately screen for lacticacidosis in emergency department patients. Emerg Med J. 2006;23(3):179-182.)