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Bloedgas Workshop

Bloedgas Workshop. Laura Kater Emergency Physician Rode Kruis Ziekenhuis, Beverwijk ROD 17.01.2013. What will we discuss. Warming up Aa gradient Arterial vs venous blood gas. 1kPa = 7.5 mmHg. Warming up. 35 yo female D yspnea FiO2 100%

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Bloedgas Workshop

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  1. Bloedgas Workshop Laura Kater EmergencyPhysician Rode Kruis Ziekenhuis, Beverwijk ROD 17.01.2013

  2. Whatwill we discuss • Warming up • Aa gradient • Arterialvsvenousblood gas

  3. 1kPa = 7.5 mmHg

  4. Warming up

  5. 35 yo female • Dyspnea • FiO2 100% • ABG: pH 6.76 pCO2 72 Bic 10 BE -26.0 pO2 24 Sat 94

  6. 31 yo male • Dyspnea • FiO2 100% • ABG: pH 6.72 pCO2 87 Bic 11 BE -28.7 pO2 301 Sat 97

  7. 94 yo female • Dyspnea • FiO2 4 ltr O2 = ongeveer 30%? • ABG: pH 7.15 pCO2 55 Bic 19 BE -10.2 pO2 62 Sat 83

  8. Aa Gradient

  9. Aa gradient = alveolarminusarterialoxygenpressure pAO2 – paO2

  10. pAO2: calculation paO2: measurementin arterialblood gas

  11. Why is this important?

  12. pAO2 pAO2 (mmHg) = 7x %O2 – paCO2 – 10 So at room air: 7x21 – 40 – 10 = 97 mmHg

  13. Example • 65 yo, room air (FiO2 21%) • ABG 7.44 / 29 / 88 / 19 / -3 / 95% • pAO2 = 7x21 – 29 – 10 = 108 mmHg • paO2 in ABG = 88 mmHg • Difference= Aa gradient = 20 mmHg

  14. Is thatnormal???

  15. Aa gradient Aa max = age/ 3 + pAO2 / 5 – 23 Ourpt: 65 / 3 + 108 / 5 – 23 = 21.67 + 21.6 – 23 = 20.27 Calculated gradient was 20.

  16. Anotherone 61 yo, FiO2 30% ABG 7.02 / 22 / 146 / 6 / -24 / 98% pAO2 = 7x30 – 22 – 10 = 178 mmHg paO2 = 146 Aa gradient = 32 Aa max forthisage: 61/3 + 178/5 – 23 = 20.3 + 35.6 – 23 = 32.9 Conclusion: normalAa gradient

  17. En nu? 30 yo, non rebreather (FiO2 +/-80%) ABG: 7.40 / 40 / … / 25 / 0 / 100% What pO2 do youexpect? pAO2 = 7x80 – 40 – 10 = 510 mmHg Max Aa gradient = 30/3 + 510 / 5 – 23 = 10 + 102 – 23 = 89 ExpectedpaO2 in ABG is about421 mmHg

  18. Last… 74 yo, room air ABG: 7.42 / 39 / 62 / 25 / 1 / 90% pAO2 = 7x21 – 39 – 10 = 98 mmHg paO2 =62 Aa gradient = 36 Aa max = 74/3 + 98/5 – 23 = 24.7 + 19.6 – 23 = 21 Aa gradient 15 mmHgto high = low paO2 Pulm.problem?, shunt / VQ mismatch?

  19. Lifeinthefastlane.com

  20. Arterial or Venous

  21. Usebloodgasin ED • acid-base status pH, bicarbonaat • respiratoryfunction pCO2, sometimes pO2

  22. Whyvenous? • Painfularterialpunction • Hematomaafterart.punction • Easy to sample a venousonewhenyou’realreadydrawingbloodfor standard labs

  23. BUT Is avenousbloodgasclinical equivalent toarterial?????

  24. EMRAP june 2008 summarizesa few publications: (www.emrap.org)

  25. A few publicationsin: Annalsof EM april 1998 In diabeticketoacidosis in adults the venousblood gas measurementsaccuratelydemonstrate the degree of acidosis. Meandifferencebetweenarterialandvenous pH was 0.03 (range 0.0-0.11)

  26. EM Journal sept 2001 strong correlationbetweenarterialandvenous pH, difference 0.4.

  27. Journal EM jan 2002 Verygood agreement in pH withvenous samples being -/-34 units lowerthanarterial samples. pCO2 on average 5.8 mmHghigher in venous samples

  28. Canadian Journal EM 2002 pH art anvenousdifference 0.36 pCO2 6 mmHg HCO3- 1.5

  29. Annals of EM 2005 verygoodcorrelationbetweenarterialand venous pH and HCO3-

  30. EM Australasia feb 2006 in ptswith DKA the weightedaveragedifferencesbetweenarterialandvenous pH was 0.02 bic -1.88

  31. For details look at the studies

  32. Resus.me Cliff Reid:

  33. Professor Anne-MareeKelly, June 2009 • pH - Close enough agreement forclinicalpurposes in DKA, isolatedmetabolicdisease; more workneeded in shock, mixed disease • Bicarbonate- Close enough agreement forclinicalpurposes in most cases; more workneeded in shock, mixed disease, calculatedvsmeasured gap • pCO2 – NOT enough agreement forclinicalpurposes; potential as a screening test • Base excess – Insufficient data

  34. Limand Kelly Eur J of EM 2010 Availableevidencesuggeststhatthere is good agreement for pH and HCO3 valuesbetweenarterialandpVBGresults in patientswith COPD, but notfor pO2 or pCO2. Widespreadclinicaluse is limitedbecause of the lack of validation studies on clinicaloutcomes

  35. Questions???

  36. Take home message • When in doubt of a pulmonaryproblemcausinghypoxia, use the Aa gradient tocalculateif the oxygenyougiveyour patiënt correlateswith the paO2 in the ABG • Thinkbeforeyouaskforan ABG. What do youneedtoknow, will a venousblood gas do? • When in need of an ABG: localanesthesia.

  37. Thankyou!

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