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Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
Arterial Blood Gas - Analysis 1
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Arterial Blood Gas - Analysis 1

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  • 1. Arterial Blood Gas Analysis …..1 Dr Deopujari Pediatrician Nagpur
  • 2. The Goal : To provide simple and bedside approach to ABG report Not to: To teach physiology . To teach theories on acid-base regulation To look for alternative approaches to interpretation In details
  • 3. A Systematic and pointed ………approach Use of pH for Hydrogen Ion Activity …….. The credit (or Blame) for introducing the term pH, the negative log of hydrogen ion (H+) concentration, goes to S. P. L. Sørensen (1868-1939), who apparently was tired of writing seven zeros in a paper on enzyme activity and wanted a simpler designation…..?.
  • 4. H ION CONC. N.MOLS / L. pH 20 7.70 30 7.52 40 7.40 50 7.30 60 7.22 H ION OH ION 0 14 pH stand for "power of hydrogen" H+ = 80 - last two digits of pH
  • 5. The Anatomy of a Blood Gas Report ----- XXXX Diagnostics ------ Blood Gas Report 248 05:36 Jul 22 2000 Pt ID 2570 / 00 Measured 37.0 o C pH 7.463 pCO2 44.4 mm Hg pO2 113.2 mm Hg Corrected 38.6 o C pH 7.439 pCO2 47.6 mm Hg pO2 123.5 mm Hg Calculated Data HCO3 act 31.1 mmol / L HCO3 std 30.5 mmol / L BE 6.6 mmol / L O2 CT 14.7 mL / dl O2 Sat 98.3 % ct CO2 32.4 mmol / L pO2 (A - a) 32.2 mm Hg pO2 (a / A) 0.79 Entered Data Temp 38.6 oC ct Hb 10.5 g/dl FiO2 30.0 % Measured Values the most important Temperature Correction: Is there any value to it? Calculated Data: Which are the useful ones? Entered Data: As important
  • 6. Bicarbonate:----- XXXX Diagnostics ------ Blood Gas Report Measured 37.0 o C pH 7.463 pCO2 44.4 mm Hg pO2 113.2 mm Hg Corrected 38.6 o C Calculated Data HCO3 act 31.1 mmol / L HCO3 std 30.5 mmol / L BE 6.6 mmol / L O2 CT 14.7 mL / dl O2 Sat 98.3 % t CO2 32.4 mmol / L pO2 (A - a) 32.2 mm Hg pO2 (a / A) 0.79 Entered Data Temp 38.6 oC ct Hb 10.5 g/dl FiO2 30.0 % Henderson - Hasselbach equation: pH = pK + Log HCO3 Dissolved CO2
  • 7. ----- XXXX Diagnostics ------ Blood Gas Report Measured 37.0 o C pH 7.463 pCO2 44.4 mm Hg pO2 113.2 mm Hg Corrected 38.6 o C Calculated Data HCO3 act 31.1 mmol / L HCO3 std 30.5 mmol / L BE 6.6 mmol / L O2 CT 14.7 mL / dl O2 Sat 98.3 % t CO2 32.4 mmol / L pO2 (A - a) 32.2 mm Hg pO2 (a / A) 0.79 Entered Data Temp 38.6 oC ct Hb 10.5 g/dl FiO2 30.0 % Standard Bicarbonate: Plasma HCO3 after equilibration to a PCO2 of 40 mm Hg : reflects non-respiratory acid base change : does not quantify the extent of the buffer base abnormality : does not consider actual buffering capacity of blood Base Excess: D base to normalise HCO3 (to 24) with PCO2 at 40 mm Hg (Sigaard-Andersen) : reflects metabolic part of acid base D : no info. over that derived from pH, pCO2 and HCO3 : Misinterpreted in chronic or mixed disorders
  • 8. ----- XXXX Diagnostics ------ Blood Gas Report Measured 37.0 o C pH 7.463 pCO2 44.4 mm Hg pO2 113.2 mm Hg Corrected 38.6 o C Calculated Data HCO3 act 31.1 mmol / L HCO3 std 30.5 mmol / L BE 6.6 mmol / L O2 CT 14.7 mL / dl O2 Sat 98.3 % t CO2 32.4 mmol / L pO2 (A - a) 32.2 mm Hg pO2 (a / A) 0.79 Entered Data Temp 38.6 oC ct Hb 10.5 g/dl FiO2 30.0 % Oxygenation Parameters: O2 Content of blood: Hb x O2 Sat + Dissolved O2 Oxygen Saturation: ( remember this is calculated ) Alveolar / arterial gradient: Arterial / alveolar ratio:
  • 9. Rt. Shift Lt.Shift
  • 10. Alveolar-arterial Difference Inspired O2 = 21 % piO2 = (760-45) x . 21 = 150 mmHg O2 CO2 palvO2 = piO2 – pCO2 / RQ = 150 – 40 / 0.8 = 150 – 50 = 100 mm Hg partO2 = 90 mmHg palvO2 – partO2 = 10 mmHg
  • 11. Alveolar- arterial Difference O2 CO2 Oxygenation Failure piO2 = 150 pCO2 = 40 palvO2= 150 – 40/.8 =150-50 =100 pO2 = 45 D = 100 - 45 = 55 Ventilation Failure piO2 = 150 pCO2 = 80 palvO2= 150-80/.8 =150-100 = 50 pO2 = 45 D = 50 - 45 = 5 PAO2 (partial pres. of O2. in the alveolus.) = 150 - ( PaCO2 / .8 ) 760 – 45 = 715 : 21 % of 715 = 150
  • 12. ----- XXXX Diagnostics ------ Blood Gas Report Measured 37.0 o C pH 7.463 pCO2 44.4 mm Hg pO2 113.2 mm Hg Corrected 38.6 o C Calculated Data HCO3 act 31.1 mmol / L O2 CT 14.7 mL / dl O2 Sat 98.3 % t CO2 32.4 mmol / L pO2 (A - a) 32.2 mm Hg pO2 (a / A) 0.79 Entered Data Temp 38.6 oC ct Hb 10.5 g/dl FiO2 30.0 % Oxygenation: Limitations of parameters: O2 Content of blood: Useful in oxygen transport calculations Derived from calculated saturation Oxygen Saturation: Ideally measured by co-oximetry Calculated values may be error-prone Alveolar / arterial gradient: Reflects O2 exchange with fixed FiO2 Impractical Differentiates hypoventilation as cause Arterial / alveolar ratio: Proposed to be less variable Same limitations as A-a gradient 20 × 5 = 100
  • 13. ----- XXXX Diagnostics ------ Blood Gas Report Measured 37.0 o C pH 7.463 pCO2 44.4 mm Hg pO2 113.2 mm Hg Calculated Data HCO3 act 31.1 mmol / L O2 Sat 98.3 % pO2 (A - a) 32.2 mm Hg Entered Data FiO2 30.0 % The Blood Gas Report: pH 7.40 + 0.05 PCO2 40 + 5 mm Hg PO2 80 - 100 mm Hg HCO3 24 + 4 mmol/L O2 Sat >95 Always mention and see FIO2 ----- XXXX Diagnostics ------ Blood Gas Report Measured 37.0 o C pH 7.463 pCO2 44.4 mm Hg pO2 113.2 mm Hg Corrected 38.6 o C pH 7.439 pCO2 47.6 mm Hg pO2 123.5 mm Hg Calculated Data HCO3 act 31.1 mmol / L HCO3 std 30.5 mmol / L BE 6.6 mmol / L O2 CT 14.7 mL / dl O2 Sat 98.3 % t CO2 32.4 mmol / L pO2 (A - a) 32.2 mm Hg pO2 (a / A) 0.79 Entered Data Temp 38.6 oC ct Hb 10.5 g/dl FiO2 30.0 % The essentials
  • 14. A ) low PAO2 ( Low Alveolar Pressure ) 1) low barometric pressure, 2) low fraction of inspired oxygen (FiO2) 3) Hypercarbia – elevated (PaCO2). B ) Wide A / a gradient ( Normal Alveolar pressure ) 1) Shunt ( cardiac or non cardiac ) 2) Diffusion abnormality Low PaO2 can be the result of
  • 15. Technical Errors Glass vs. plastic syringe: Changes in pO2 are not clinically important No effect on pH or pCO2 Heparin (1000 u / ml): Need <0.1 ml / ml of blood pH of heparin is 7.0; pCO2 trends down Avoided by heparin flushing & drawing 2-4 cc blood Delay in measurement: Rate of changes in pH, pCO2 and pO2 can be reduced to 1/10 by cooling in ice slush(4 o C) No major drifts up to 1 hour
  • 16. The Steps for Successful Blood Gas Analysis
  • 17. Step 1 Look at the pH Is the patient acidemic pH < 7.35 or alkalemic pH > 7.45 Step 2 Who is responsible for this change ( culprit )? Acidemia: With HCO3 < 20 mmol/L = metabolic With PCO2 >45 mm hg = respiratory Alkalemia: With HCO3 >28 mmol/L = metabolic With PCO2 <35 mm Hg = respiratory The culprit BICARB pH CO2 pH BICARB pH CO2 pH
  • 18. Step 3 If there is a primary respiratory disturbance, is it acute? (Acute)change in pH = 0.08 for 10 mm change in PCO2 (Chronic)change in pH = 0.03 for 10 mm change in PCO2
  • 19. Step 4 If the disturbance is metabolic is the respiratory compensation appropriate? For metabolic acidosis: Expected PCO2 = (1.5 x [HCO3]) + 8 ) + 2 (Winter’s equation) ( Last two digits of pH ) For metabolic alkalosis: Expected PCO2 = 6 mm for 10 mEq. rise in Bicarb. If : actual PCO2 more than expected : additional respiratory acidosis actual PCO2 less than expected : additional respiratory alkalosis The last two digits
  • 20. Step 4 cont. If there is metabolic acidosis, is there a wide anion gap ? Na - (Cl - + HCO3 - ) = Anion Gap usually <12 If >12, Anion Gap Acidosis : Methanol Uremia Diabetic Ketoacidosis Paraldehyde Infection (lactic acid) Ethylene Glycol Salicylate Common pediatric causes 1) Lactic acidosis 2) Metabolic disorders 3) Renal failure
  • 21. th step Clinical correlation
  • 22. HCO3 META.pH PCO2 pH RESP. Same direction Opposite direction Same direction
  • 23. 24 CO2 BICARBONATE = H ION CONC. 24 40 = 960 BICARBONATE = H ION CONC. 960 24 = H ION CONC. = 40 N.MOLS / L. H+ N.MOLS / L. = 80 - last two digits of pH N.MOLS / L. N.MOLS / L.
  • 24. Primary lesion Primary lesion compensation pH HCO3 CO2 METABOLIC ACIDOSIS HYPER VENTILATION BICARB CHANGES pH in same direction
  • 25. Primary lesion compensation pH HCO3 CO2 METABOLIC ALKALOSIS HYPO VENTILATION BICARB CHANGES pH in same direction
  • 26. Primary lesion compensation pH CO 2 BICARB Respiratory acidosis CO 2 CHANGES pH in opposite direction
  • 27. pHCO2+H20=H2CO3 = H + HCO3 + HCO3 HCO3 RESP. ACIDOSIS ALKALOSIS META. ACUTE RISE : PCO2 10 : pH .08 CHRONIC RISE : PCO2 10 : pH .03 PCO2 HIGH H HIGH HCO3 +
  • 28. Primary lesion Primary lesion compensation pH CO 2 BICARB Respiratory alkalosis CO 2 CHANGES pH in opposite direction
  • 29. CO2 + H20 = H2CO3 = H + HCO3 + pH HCO3 LOW H IONS …LOW HCO3 RESP. ALK. ACID. META. ACUTE FALL : PCO2 10 : pH .08 CHRONIC FALL: PCO2 10 : pH .03 CO2 +
  • 30. Pco2 of 10 pH Acute change .08 Chronic change .03
  • 31. INTERPRETATION OF A.B.G. FOUR STEP METHOD OF DEOSAT 1) LOOK FOR pH 2) WHO IS THE CULPRIT ? 3) IF RESPIRATORY ACUTE / CHRONIC ? 4) IF METABOLIC / COMP. / ANION GAP CLINICAL CORRELATION
  • 32. compensation considered complete when the pH returns to normal range Clinical blood gases by Malley
  • 33. COMPENSIONLIMITS METABLIC ACIDOSIS CO2 = Up to 10 ? METABOLIC ALKALOSIS CO2 = Maximum 6O RESPIRATORY ACIDOSIS BICARB = Maximum 40 RESPIRATORY ALKALOSIS BICARB = Up to 10
  • 34. ----- XXXX Diagnostics ------ Blood Gas Report Measured 37.0 o C pH 7.523 pCO2 30.1 mm Hg pO2 105.3 mm Hg Calculated Data HCO3 act 22 mmol / L O2 Sat 98.3 % pO2 (A - a) 8 mm Hg D pO2 (a / A) 0.93 Entered Data FiO2 21.0 % Case 1 16 year old female with sudden onset of dyspnea. No Cough or Chest Pain Vitals normal but RR 56, anxious.
  • 35. Case 2 6 year old male with progressive respiratory distress Muscular dystrophy . ----- XXXX Diagnostics ------ Blood Gas Report Measured 37.0 o C pH 7.301 pCO2 76.2 mm Hg pO2 45.5 mm Hg Calculated Data HCO3 act 35.1 mmol / L O2 Sat 78 % pO2 (A - a) 9.5 mm Hg D pO2 (a / A) 0.83 Entered Data FiO2 21 % D CO2 =76-40=36 Expected D pH ( Acute ) = .08 for 10 Expected ( Acute ) pH = 7.40 - 0.29=7.11 Chronic resp. acidosis pH <7.35 :acidemia respiratory acidemia : co2 and pH Hypoxia Normal A-a gradient Due to hypoventilation
  • 36. Case 3 8-year-old male asthmatic; 3 days of cough, dyspnea and orthopnea not responding to usual bronchodilators. O/E: Respiratory distress; suprasternal and intercostal retraction; tired looking; on 4 L NC. ----- XXXX Diagnostics ------ Blood Gas Report Measured 37.0 o C pH 7. 24 pCO2 49.1 mm Hg pO2 66.3 mm Hg Calculated Data HCO3 act 18.0 mmol / L O2 Sat 92 % pO2 (A - a) mm Hg D pO2 (a / A) Entered Data FiO2 30 % 153-66= 87 pH <7.35 ; acidemia pCO2 >45; respiratory acidemia piO2 = 715x.3=214.5 / palvO2 = 214-49/.8=153 Wide A / a gradient Hypoxia WITH INCREASE IN CO2 BICARB MUST RISE ? Metabolic acidosis + respiratory acidosis 30 × 5 = 150 D CO2 = 49 - 40 = 9 Expected D pH ( Acute ) = 9/10 x 0.08 = 0.072 Expected pH ( Acute ) = 7.40 - 0.072 = 7.328 Acute resp. acidosis
  • 37. Case 4 8 year old diabetic with respi. distress fatigue and loss of appetite. ----- XXXX Diagnostics ------ Blood Gas Report Measured 37.0 o C pH 7.23 pCO2 23 mm Hg pO2 110.5 mm Hg Calculated Data HCO3 act 14 mmol / L O2 Sat % pO2 (A - a) mm Hg D pO2 (a / A) Entered Data FiO2 21.0 % pH <7.35 ; acidemia HCO3 <22; metabolic acidemia Last two digits of pH Correspond with co2 If Na = 130, Cl = 90 Anion Gap = 130 - (90 + 14) = 130 – 104 = 26
  • 38. ----- XXXX Diagnostics ------ Blood Gas Report Measured 37.0 o C pH 7.46 pCO2 28.1 mm Hg pO2 55.3 mm Hg Calculated Data HCO3 act 19.2 mmol / L O2 Sat % pO2 (A - a) mm Hg D pO2 (a / A) Entered Data FiO2 24.0 % Case 5 : 10 year old child with encephalitis pH almost within normal range Mild alkalosis Co2 is low , respiratory Co2 low by around 10 ( Acute ) by .08 (Chronic ) by .03 Bicarb looks low ? Is it expected ? More cases
  • 39. ABG OF THE DAY The arterial blood gas report : Room air pH 7.39 PCO2 l5mniHg HCO3 8mmol/L PaO2 90 mmHg PCO2 24 BICARBONATE H ION CONCENTRATION = = 45 nmol/lit
  • 40. 1) These findings are most consistent with…. a) Metabolic acidosis with compensatory Hypocapnia. b) Primary metabolic acidosis with respiratory alkalosis. c) Acute respiratory alkalosis fully compensated. d) Chronic respiratory alkalosis fully compensated. pH 7.39 PCO2 l5mniHg HCO3 8mmol/L PaO2 90 mmHg For metabolic acidosis: FULL COMPENSATION Expected PCO2 = (1.5 x [HCO3]) + 8 ) + 2 (Winter’s equation) PCO 2 ……SHOULD BE 20
  • 41. 2) What is the oxygenation status a) Normal oxygenation status b) Hypoxemia c) None of the above palvO2 = piO2 – pCO2 / RQ = 150 – 15 / 0.8 = 150 – 18 = 132 mm Hg 132 – 90 = 42 WIDE A / a gradient pH 7.39 PCO2 l5mniHg HCO3 8mmol/L PaO2 90 mmHg
  • 42. pCO2 pH 70 7.10 60 7.20 50 7.30 40 7.40 30 7.50 20 7.60
  • 43.  When pH is normal and: Bicarbonate is high ( Metabolic alkalosis + respiratory acidosis ) Bicarbonate is low ( Metabolic acidosis + resp. alkalosis)  Bicarbonate is normal and: anion gap is high ( Metabolic Acidosis + Metabolic alkalosis)  When bicarbonate is normal and: pH is in acidic range ( Chronic resp. acidosis + resp alk.) pH is in alkalemic range ( Metab.alk. + resp alk.)  Anion gap is elevated and: clinical and laboratory data suggest a diagnosis other than metabolic acidosis  PCO2 level and bicarbonates are shifted from normal in opposing directions.
  • 44. THANKS

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