ABG  series<br />ANAS  SAHLE , MD<br />DAMASCUSE   HOSPITAL<br />
MORE  FORESTSMORE  OXYGENLONGER  LIFE<br />
Acid-Base Disorders and the ABG 1<br />
OUTLINE<br />ACID-BASE DISORDERS<br />HIGH  AG  METABOLIC  ACIDOSIS<br />NORMAL  AG  METABOLIC  ACIDOSIS<br />METABOLIC  A...
ABG - Introduction<br />Blood gas and pH analysis has more immediacy and potential impact on patient care than any other l...
Getting an arterial blood gas sample<br />
Blood Gas Report<br />Acid-Base Information<br /><ul><li>pH
PCO2
HCO3 [calculated vs measured]</li></ul>Oxygenation Information<br /><ul><li>PO2 [oxygen tension]
SO2 [oxygen saturation]</li></li></ul><li>Normal Ranges<br />PaO2 >80mm Hg<br />In supine posture PaO2=109-(0.43 Х age)<br...
Sampling errors -Air contamination<br />Most important change: PaO2 tends to increase towards 158mm Hg,<br />Less signific...
Anticoagulant effects<br />0.05ml of heparin(1,000units/ml) is required to anticoagulate 1 ml of blood.<br />Dead space of...
Time delay - metabolism<br />Samples should be analyzed within 20 min to avoid error.<br />Placing the sample in iced wate...
EXPECTED CHANGES IN <br />ACID-BASE DISORDERS <br />From: THE ICU BOOK - 2nd Ed. (1998) [Corrected]<br />
Overview of Acid-Base Physiology<br />
Henderson-Hasselbalch Equation<br />
Renal Regulation of Acid-Base<br />
Primary Acid-Base Disorders<br />As dictated by the Henderson-Hasselbalch equation, disturbances in either the respiratory...
Compensation<br />When a primary acid-base disorder exists, the body attempts to return the pH to normal via the “other ha...
Compensation (continued)<br />
The Arterial Blood Gas (ABG)<br />pH, pCO2, pO2 – Measured directly<br />HCO3-, O2 saturation (usually) – Calculated from ...
Practical Approach<br />1. Check the pH<br />If the pH < 7.37, acidemia (and at least 1 acidosis) is present.<br />If the ...
Practical Approach<br />2. Check the pCO2<br />pH < 7.37 and pCO2 < 40  metabolic acidosis<br />pH < 7.37 and pCO2 > 40 ...
Practical Approach<br />3. Choose the appropriate compensation formula<br />
Practical Approach<br />4. Determine if the degree compensation is appropriate<br />(If it isn’t, a second acid-base disor...
Practical Approach<br />5. Calculate the anion gap <br />Anion gap   =   [Na+]   –   ( [Cl-]   +   [HCO3-] )<br />If the a...
Practical Approach<br />6. If an elevated gap acidosis is present, calculate the delta-delta ratio, to determine if a seco...
Practical Approach<br />7. If a metabolic acidosis is present, check the urine pH.<br />Urine pH > 6.0 in the setting of a...
Practical Approach<br />8. Generate a differential diagnosis<br />If multiple disorders are present, they may be:<br />		A...
Differential Diagonsis for Acid-Base Disorders<br />
Summary of the Approach to ABGs<br />Check the pH<br />Check the pCO2<br />Select the appropriate compensation formula<br ...
Gap:gap ratio??<br />
AGc=AG +(2,5(4-alb))<br />Expected PCO2<br />
Case 1<br />A 26 year old man with unknown past medical history is brought in to the ER by ambulance, after friends found ...
APPROCHE 1<br />RESPIRATORY  ACIDOSIS<br />
Case 2<br />A 67 year old man with diabetes and early diabetic nephropathy (without overt renal failure) presents for a ro...
APPROCHE 2<br />Normal  AG METABOLIC  ACIDOSIS<br />
Case 3<br />A 68 year old woman with metastatic colon cancer presents to the ER with 1 hour of chest pain and shortness of...
APPROCHE 3<br />RESPIRATORY  ALKALOSIS<br />
Case 4<br />A 6 year old girl with severe gastroenteritis is admitted to the hospital for fluid rehydration, and is noted ...
APPROCHE 4<br />Pure metabolic Alkalosis<br />
Case 5<br />A 75 year old man with morbid obesity is sent to the ER by his skilled nursing facility after he developed a f...
APPROCHE 5<br />Respiratory Aci+High AG Metabolic Aci<br />
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ABG1 SERIES

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ABG1 SERIES

  1. 1. ABG series<br />ANAS SAHLE , MD<br />DAMASCUSE HOSPITAL<br />
  2. 2. MORE FORESTSMORE OXYGENLONGER LIFE<br />
  3. 3. Acid-Base Disorders and the ABG 1<br />
  4. 4. OUTLINE<br />ACID-BASE DISORDERS<br />HIGH AG METABOLIC ACIDOSIS<br />NORMAL AG METABOLIC ACIDOSIS<br />METABOLIC ALKALOSIS<br />OXYGENATION AXIES<br />A-a GRADIENT<br />
  5. 5. ABG - Introduction<br />Blood gas and pH analysis has more immediacy and potential impact on patient care than any other laboratory determination.(National committee for Laboratory Standards).<br />Cornerstone in the diagnosis & management of clinical oxygenation and acid-base disturbances.<br />Of all the concepts employed in the diagnosis and treatment of respiratory disorders, few are more important or less well understood than those of blood gas interpretation. <br />
  6. 6. Getting an arterial blood gas sample<br />
  7. 7.
  8. 8.
  9. 9.
  10. 10. Blood Gas Report<br />Acid-Base Information<br /><ul><li>pH
  11. 11. PCO2
  12. 12. HCO3 [calculated vs measured]</li></ul>Oxygenation Information<br /><ul><li>PO2 [oxygen tension]
  13. 13. SO2 [oxygen saturation]</li></li></ul><li>Normal Ranges<br />PaO2 >80mm Hg<br />In supine posture PaO2=109-(0.43 Х age)<br />PaO2=100mmHg in 10 year old child, PaO2 falls approximately 5mmHG for every 10 years upto 90 years.<br />5 mmHg higher in the sitting position that supine position<br />
  14. 14. Sampling errors -Air contamination<br />Most important change: PaO2 tends to increase towards 158mm Hg,<br />Less significant change: PaCO2 falls, pH rises<br />All air bubbles should be expelled immediately<br />All samples with visually apparent froth should be discarded.<br />
  15. 15. Anticoagulant effects<br />0.05ml of heparin(1,000units/ml) is required to anticoagulate 1 ml of blood.<br />Dead space of a standard 5ml syringe with 22G needle is 0.2ml; i.e. filling the syringe dead space with heparin provides sufficient volume to anticoagulate a 4ml blood sample.<br />Heparin – weak acid equilibrated with room air<br />Initially PaCO2 falls, <br />In extreme dilution pH and bicarbonate falls<br />PaO2 usually unchanged.<br />
  16. 16. Time delay - metabolism<br />Samples should be analyzed within 20 min to avoid error.<br />Placing the sample in iced water slows metabolism to 10%.<br />
  17. 17. EXPECTED CHANGES IN <br />ACID-BASE DISORDERS <br />From: THE ICU BOOK - 2nd Ed. (1998) [Corrected]<br />
  18. 18. Overview of Acid-Base Physiology<br />
  19. 19. Henderson-Hasselbalch Equation<br />
  20. 20. Renal Regulation of Acid-Base<br />
  21. 21. Primary Acid-Base Disorders<br />As dictated by the Henderson-Hasselbalch equation, disturbances in either the respiratory component (pCO2) or metabolic component (HCO3-) can lead to alterations in pH.<br />
  22. 22. Compensation<br />When a primary acid-base disorder exists, the body attempts to return the pH to normal via the “other half” of acid base metabolism.<br /> Primary metabolic disorder  Respiratory compensation<br /> Primary respiratory disorder  Metabolic compensation<br />
  23. 23. Compensation (continued)<br />
  24. 24. The Arterial Blood Gas (ABG)<br />pH, pCO2, pO2 – Measured directly<br />HCO3-, O2 saturation (usually) – Calculated from pH, pCO2, and pO2<br />
  25. 25. Practical Approach<br />1. Check the pH<br />If the pH < 7.37, acidemia (and at least 1 acidosis) is present.<br />If the pH > 7.43, alkalemia (and at least 1 alkalosis) is present. <br />
  26. 26. Practical Approach<br />2. Check the pCO2<br />pH < 7.37 and pCO2 < 40  metabolic acidosis<br />pH < 7.37 and pCO2 > 40  respiratory acidosis<br />pH > 7.43 and pCO2 < 40  respiratory alkalosis<br />pH > 7.43 and pCO2 > 40  metabolic alklosis<br />
  27. 27. Practical Approach<br />3. Choose the appropriate compensation formula<br />
  28. 28. Practical Approach<br />4. Determine if the degree compensation is appropriate<br />(If it isn’t, a second acid-base disorder is likely present)<br />
  29. 29. Practical Approach<br />5. Calculate the anion gap <br />Anion gap = [Na+] – ( [Cl-] + [HCO3-] )<br />If the anion gap is elevated, an elevated gap metabolic acidosis is likely present.<br />
  30. 30. Practical Approach<br />6. If an elevated gap acidosis is present, calculate the delta-delta ratio, to determine if a second metabolic disorder is present.<br />Delta–Delta = Measured anion gap – Normal anion gap<br /> Normal [HCO3-] – Measured [HCO3-]<br />
  31. 31. Practical Approach<br />7. If a metabolic acidosis is present, check the urine pH.<br />Urine pH > 6.0 in the setting of an acidosis  Suggests RTA<br />
  32. 32. Practical Approach<br />8. Generate a differential diagnosis<br />If multiple disorders are present, they may be:<br /> All related to the same process<br /> All independent of one another<br />
  33. 33. Differential Diagonsis for Acid-Base Disorders<br />
  34. 34. Summary of the Approach to ABGs<br />Check the pH<br />Check the pCO2<br />Select the appropriate compensation formula<br />Determine if compensation is appropriate<br />Check the anion gap <br />AG=NA – (HCO3 + CL):12<br />If the anion gap is elevated, check the delta-delta<br />G:G Ratio =Δ AG (12-AG m) Δ HCO3 (24-HCO3 m)<br />If a metabolic acidosis is present, check urine pH<br />Generate a differential diagnosis<br />
  35. 35.
  36. 36. Gap:gap ratio??<br />
  37. 37.
  38. 38. AGc=AG +(2,5(4-alb))<br />Expected PCO2<br />
  39. 39. Case 1<br />A 26 year old man with unknown past medical history is brought in to the ER by ambulance, after friends found him unresponsive in his apartment. He had last been seen at a party four hours prior.<br />ABG: pH 7.25 Chem 7: Na+ 137<br /> PCO2 60 K+ 4.5<br /> HCO3- 26 Cl- 100<br /> PO2 55 HCO3- 25<br />
  40. 40. APPROCHE 1<br />RESPIRATORY ACIDOSIS<br />
  41. 41. Case 2<br />A 67 year old man with diabetes and early diabetic nephropathy (without overt renal failure) presents for a routine clinic visit. He is currently asymptomatic. Because of some abnormalities on his routine blood chemistries, you elect to send him for an ABG.<br />ABG: pH 7.35 Chem 7: Na+ 135<br /> PCO2 34 K+ 5.1<br /> HCO3- 18 Cl- 110<br /> PO2 92 HCO3- 16<br /> Cr 1.4<br />Urine pH: 5.0<br />
  42. 42. APPROCHE 2<br />Normal AG METABOLIC ACIDOSIS<br />
  43. 43. Case 3<br />A 68 year old woman with metastatic colon cancer presents to the ER with 1 hour of chest pain and shortness of breath. She has no known previous cardiac or pulmonary problems.<br />ABG: pH 7.49 Chem 7: Na+ 133<br /> PCO2 28 K+ 3.9<br /> HCO3- 21 Cl- 102<br /> PO2 52 HCO3- 22<br />
  44. 44. APPROCHE 3<br />RESPIRATORY ALKALOSIS<br />
  45. 45. Case 4<br />A 6 year old girl with severe gastroenteritis is admitted to the hospital for fluid rehydration, and is noted to have a high [HCO3-] on hospital day #2. An ABG is ordered:<br />ABG: pH 7.47 Chem 7: Na+ 130<br /> PCO2 46 K+ 3.2<br /> HCO3- 32 Cl- 86<br /> PO2 96 HCO3- 33<br />Urine pH: 5.8<br />
  46. 46. APPROCHE 4<br />Pure metabolic Alkalosis<br />
  47. 47. Case 5<br />A 75 year old man with morbid obesity is sent to the ER by his skilled nursing facility after he developed a fever of 103° and rigors 2 hours ago. In the ER he is lucid and states that he feels “terrible”, but offers no localizing symptoms. His ER vitals include a heart rate of 115, and a blood pressure of 84/46.<br />ABG: pH 7.12 Chem 7: Na+ 138<br /> PCO2 50 K+ 4.2<br /> HCO3- 13 Cl- 99<br /> PO2 52 HCO3- 15<br />Urine pH: 5.0<br />
  48. 48. APPROCHE 5<br />Respiratory Aci+High AG Metabolic Aci<br />
  49. 49. Case 6<br />A 25 year old man with type I diabetes presents to the ER with 24 hours of severe nausea, vomiting, and abdominal pain.<br />ABG: pH 7.15 Chem 7: Na+ 138<br /> PCO2 30 K+ 5.6<br /> HCO3- 10 Cl- 88<br /> PO2 88 HCO3- 11<br /> Cr 1.1<br />Urine pH: 5.0<br />
  50. 50. APPROCHE 6<br />HIGH AG Metabolic.Acidosis + RESPIRATORY ACIDOSIS<br />
  51. 51. Case 7<br />A 62 year old woman with severe COPD comes to the ER complaining of increased cough and shortness of breath for the past 12 hours. There are no baseline ABGs to compare to, however, her HCO3- measured during a routine clinic visit 3 months ago was 34 mEq/L.<br />ABG: pH 7.21 Chem 7: Na+ 135<br /> PCO2 85 K+ 4.0<br /> HCO3- 33 Cl- 90<br /> PO2 47 HCO3- 34<br />Urine pH 5.5<br />
  52. 52. APPROCHE 7<br />CHRONIC RES.ACI + NORMAL AG MET.ACI<br />
  53. 53. Case 8<br />A 36 year old man with a history of alcoholism is brought to the ER after being found on the floor of his apartment unresponsive, soiled with vomit, and with an empty pill bottle nearby.<br />ABG: pH 7.03 Chem 7: Na+ 134<br /> PCO2 75 K+ 5.2<br /> HCO3- 19 Cl- 90<br /> PO2 48 HCO3- 20<br />Urine pH 5.0<br />
  54. 54. APPROCHE 8<br />RES.AC+High AG MET.AC +concomitant M.ALK<br />
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