Download - How to survive a gas attack
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How to Survive a
GAS ATTACK!in 10 minutes…
A Talk by Chris Nickson
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No $
Photo by Misserion
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Overview
A-a GradientCompensation
Strong IonsAnion Gap
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All aboutA-a gradients(not really…)
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A-a gradient = PAO2 – PaO2
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PAO2 = FiO2 (PB – PH20) – (PaCO2/R)
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Quick check:expected PaO2 = %FiO2 x 5
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Caveats:high PaCO2
A-a gradient varies with age and FiO2
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Rule of thumb:expected A-a gradient =
(age/4) + 4
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Be aCompensation
King (or Queen)
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Respiratory compensation = rapid
Metabolic compensation = slow
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Metabolic compensation
The 1-2-3-4-5 Rule
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1
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12
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12
HCO3
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1 42
HCO3
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1 42 5
HCO3
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1 42 5
HCO3
acute chronic
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1 42 5
HCO3
acute chronic
10 mmHg
PaCO2
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Respiratory compensation
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PaCO2 = 1.5 x HCO3 + 8 (+/-2) if metabolic acidosis
PaCO2 = 0.7 x HCO3 + 20 (+/-5) if metabolic alkalosis
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Rule of thumb:If pH = 7.xy then
PaCO2 ≈ xy
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Strong ions… WTF?
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The real determinants of pH are:
Strong ionsWeak acids [ATOT]
PCO2
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Strong Ion difference:
Na – Cl
<38 = NAGMA>38 = metabolic alkalosis
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EMCrit by Scott Weingart http://emcrit.org/podcasts/acid-base-i/
Acid-Base Physiology by Kerry Brandishttp://www.anaesthesiamcq.com/AcidB
aseBook/ABindex.php
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High Lactate withNormal Anion Gap… WTF?
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Anion gap
Na – (HCO3+Cl)
Normal = 8-12 mM
LTKR
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Anion gap is only ~50% sensitive
for lactic acidosis
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What causes a low anion gap?
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Low Anions: Albumin
High Cations
Bromism
Analytical error
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Correcting for low albumin is essential
AGadj = AGobs + 0.25 x (42 - Albobs)
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THE END
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http://lifeinthefastlane.com/exams/facem-fellowship/vaq-subject/
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THE END
http://lifeinthefastlane.com/education/clinical-cases/http://lifeinthefastlane.com/exams/facem-fellowship/vaq-subject/http://lifeinthefastlane.com/exams/cicm-fellowship/saq-keyword/