1 / 62

Simple Rules for the Interpretation of Arterial Blood Gases

Simple Rules for the Interpretation of Arterial Blood Gases. Nicholas Sadovnikoff, MD, FCCM Assistant Professor, Harvard Medical School Co-Director, Surgical Intensive Care Units Brigham and Women’s Hospital Boston, MA Kuwait City, Kuwait November 24, 2011. “Mantra”. 1 for 1 10 for 7 1

adamina
Download Presentation

Simple Rules for the Interpretation of Arterial Blood Gases

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Simple Rules for the Interpretation of Arterial Blood Gases Nicholas Sadovnikoff, MD, FCCM Assistant Professor, Harvard Medical School Co-Director, Surgical Intensive Care Units Brigham and Women’s Hospital Boston, MA Kuwait City, Kuwait November 24, 2011

  2. “Mantra” 1 for 1 10 for 7 1 4 2 5

  3. Mantra Metabolic Acidosis: 1HCO3 => 1PCO2 Metabolic Alkalosis: 10  HCO3 => 7 PCO2 Acute Resp Acid: 10  PCO2 = 1  HCO3 Chronic Resp Acid: 10  PCO2 = 4  HCO3 Acute Resp Alk: 10  PCO2 => 2  HCO3 Chronic Resp Alk: 10  PCO2 => 5  HCO3

  4. Examples pH = 7.33, PCO2=30, HCO3=15 diagnosis

  5. Examples pH = 7.33, PCO2=30, HCO3=15 Diagnosis: metabolic acidosis or Metabolic acidosis with respiratory compensation or metabolic acidosis with compensatory respiratory alkalosis

  6. Suggestion: Delete the word compensation from your acid base vocabulary.

  7. Mantra Metabolic Acidosis: 1HCO3 => 1PCO2 Metabolic Alkalosis: 10  HCO3 => 7 PCO2 Acute Resp Acid: 10  PCO2 = 1  HCO3 Chronic Resp Acid: 10  PCO2 = 4  HCO3 Acute Resp Alk: 10  PCO2 => 2  HCO3 Chronic Resp Alk: 10  PCO2 => 5  HCO3

  8. Definition Acidemia Acidosis

  9. Definition Acidemia – an abnormally low pH (high proton concentration)

  10. Definition Acidemia – an abnormally low pH (high proton concentration) Acidosis – a process which produces an excess of protons

  11. Example • pH=7.22, PCO2=38, HCO3=15 • diagnosis

  12. Example • pH=7.22, PCO2=38, HCO3=15 • diagnosis: Met and Resp acidosis or Undercompensated Met Acidosis

  13. Example • pH=7.38, PCO2=28, HCO3=16 • diagnosis

  14. Example • pH=7.38, PCO2=28, HCO3=16 • diagnosis: Met Acid with Resp Alk or Overcompensated Met Acid

  15. Example • pH=7.47, PCO2=47, HCO3=34 • diagnosis

  16. Example • pH=7.47, PCO2=47, HCO3=34 • diagnosis metabolic alkalosis

  17. Mantra Metabolic Acidosis: 1HCO3 => 1PCO2 Metabolic Alkalosis: 10  HCO3 => 7 PCO2 Acute Resp Acid: 10  PCO2 = 1  HCO3 Chronic Resp Acid: 10  PCO2 = 4  HCO3 Acute Resp Alk: 10  PCO2 => 2  HCO3 Chronic Resp Alk: 10  PCO2 => 5  HCO3

  18. Example • pH=7.51, PCO2=42, HCO3=34 • diagnosis

  19. Example • pH=7.51, PCO2=42, HCO3=34 • diagnosis Met and Resp alkalosis

  20. Example • pH=7.42, PCO2=52, HCO3=34 • diagnosis

  21. Example • pH=7.42, PCO2=52, HCO3=34 • diagnosis metabolic alkalosis and respiratory acidosis

  22. Example pH=7.35, PCO2=60, HCO3=32 diagnosis

  23. Example pH=7.35, PCO2=60, HCO3=32 diagnosis chronic respiratory acidosis

  24. Example pH=7.25, PCO2=60, HCO3=26 diagnosis

  25. Example pH=7.25, PCO2=60, HCO3=26 diagnosis acute respiratory acidosis

  26. Example pH=7.30, PCO2=60, HCO3=29 diagnosis

  27. Example pH=7.30, PCO2=60, HCO3=29 diagnosis acute on chronic resp acid

  28. Example pH=7.45, PCO2=25, HCO3=17 diagnosis

  29. Example pH=7.45, PCO2=25, HCO3=17 diagnosis chronic respiratory alkalosis

  30. Mantra Metabolic Acidosis: 1HCO3 => 1PCO2 Metabolic Alkalosis: 10  HCO3 => 7 PCO2 Acute Resp Acid: 10  PCO2 = 1  HCO3 Chronic Resp Acid: 10  PCO2 = 4  HCO3 Acute Resp Alk: 10  PCO2 => 2  HCO3 Chronic Resp Alk: 10  PCO2 => 5  HCO3

  31. Example pH=7.33, PCO2=30, HCO3=15 Na= 147, Cl=110 diagnosis

  32. What is an Anion Gap? • Qualitative • Quantitative • Why not include H+ ? K+ ?

  33. What is an Anion Gap? • Qualitative – unmeasured anions • Quantitative - Na+ - Cl– - HCO3– • Why not include H+ - too small K+ - always ~ 4

  34. DDx of AG Met Acid • Ketones • Uremia • Salicylates • Methanol • Alcohols • Lactate • Ethylene Glycol • What are the unmeasured anions?

  35. Additional Rule The HCO3 normally falls 1 for every 1 increase in anion gap, with the exception of sepsis.

  36. The Anions of Sepsis • HPLC studies have failed to identify the anions responsible for the  AG in sepsis. • Lactate accounts for a portion. • H+ is likely from ATP hydrolysis which drives the fall in bicarbonate and is not coupled to lactate production.

  37. What Lowers Anion Gap? • Hypoalbuminemia • Lithium • Myeloma

  38. Example • pH = 7.20, HCO3=10, PCO2=25 • Na=140, Cl=110 • diagnosis

  39. Example • pH = 7.20, HCO3=10, PCO2=25 • Na=140, Cl=110 • diagnosis AG Met acid and Non-AG met acid

  40. DDx of NonAG Met AcidUSED CARS • Ureterosigmoidostomy / Fistulae • Saline • Early Renal Failure • Diarrhea • CAI • AAs • RTA • Supplements

  41. Urine Anion Gap • UAG = Na+ + K+ - Cl- • largely reflects NH4+ and therefore is usually negative due to renal ammoniagenesis • In non-AG metabolic acidosis, a negative UAG implies extra-renal cause of the disorder. • If positive, renal ammoniagenesis is likely impaired.

  42. Example • pH = 7.35, HCO3=19, PCO2=35 • Na=140, Cl=100

  43. Example • pH = 7.35, HCO3=19, PCO2=35 • Na=140, Cl=100 • diagnosis AG metabolic acidosis and metabolic alkalosis

  44. Example • pH = 7.31, HCO3=15, PCO2=30 • Na=138, Cl=112 • diagnosis

  45. Example • pH = 7.31, HCO3=15, PCO2=30 • Na=138, Cl=112 • diagnosis non AG metabolic acidosis

  46. Example • pH = 7.12, HCO3=10, PCO2=33 • Na=138, Cl=95 • diagnosis

  47. Example • pH = 7.12, HCO3=10, PCO2=33 • Na=138, Cl=95 • diagnosis AG metabolic acidosis and metabolic alkalosis and respiratory acidosis

  48. Example • pH = 7.38, HCO3=14, PCO2=23 • Na=138, Cl=95

  49. Example • pH = 7.38, HCO3=14, PCO2=23 • Na=138, Cl=95 • diagnosis AG metabolic acidosis and metabolic alkalosis and respiratory alkalosis

  50. Example • pH = 7.40, HCO3=24, PCO2=40 • Na=140, Cl=96 • diagnosis

More Related