Simple rules for the interpretation of arterial blood gases l.jpg
Sponsored Links
This presentation is the property of its rightful owner.
1 / 62

Simple Rules for the Interpretation of Arterial Blood Gases PowerPoint PPT Presentation


  • 613 Views
  • Uploaded on
  • Presentation posted in: General

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

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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


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

4

2

5


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


Examples

pH = 7.33, PCO2=30, HCO3=15

diagnosis


Examples

pH = 7.33, PCO2=30, HCO3=15

Diagnosis:

metabolic acidosis or

Metabolic acidosis with respiratory compensation

or

metabolic acidosis with compensatory respiratory alkalosis


Suggestion:

Delete the word compensation from your acid base vocabulary.


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


Definition

Acidemia

Acidosis


Definition

Acidemia – an abnormally low pH (high proton concentration)


Definition

Acidemia – an abnormally low pH (high proton concentration)

Acidosis – a process which produces an excess of protons


Example

  • pH=7.22, PCO2=38, HCO3=15

  • diagnosis


Example

  • pH=7.22, PCO2=38, HCO3=15

  • diagnosis:

    Met and Resp acidosis

    or

    Undercompensated Met Acidosis


Example

  • pH=7.38, PCO2=28, HCO3=16

  • diagnosis


Example

  • pH=7.38, PCO2=28, HCO3=16

  • diagnosis:Met Acid with Resp AlkorOvercompensated Met Acid


Example

  • pH=7.47, PCO2=47, HCO3=34

  • diagnosis


Example

  • pH=7.47, PCO2=47, HCO3=34

  • diagnosismetabolic alkalosis


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


Example

  • pH=7.51, PCO2=42, HCO3=34

  • diagnosis


Example

  • pH=7.51, PCO2=42, HCO3=34

  • diagnosisMet and Resp alkalosis


Example

  • pH=7.42, PCO2=52, HCO3=34

  • diagnosis


Example

  • pH=7.42, PCO2=52, HCO3=34

  • diagnosismetabolic alkalosis andrespiratory acidosis


Example

pH=7.35, PCO2=60, HCO3=32

diagnosis


Example

pH=7.35, PCO2=60, HCO3=32

diagnosischronic respiratory acidosis


Example

pH=7.25, PCO2=60, HCO3=26

diagnosis


Example

pH=7.25, PCO2=60, HCO3=26

diagnosisacute respiratory acidosis


Example

pH=7.30, PCO2=60, HCO3=29

diagnosis


Example

pH=7.30, PCO2=60, HCO3=29

diagnosisacute on chronic resp acid


Example

pH=7.45, PCO2=25, HCO3=17

diagnosis


Example

pH=7.45, PCO2=25, HCO3=17

diagnosischronic respiratory alkalosis


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


Example

pH=7.33, PCO2=30, HCO3=15

Na= 147, Cl=110

diagnosis


What is an Anion Gap?

  • Qualitative

  • Quantitative

  • Why not include H+ ? K+ ?


What is an Anion Gap?

  • Qualitative – unmeasured anions

  • Quantitative - Na+ - Cl– - HCO3–

  • Why not include H+ - too small K+ - always ~ 4


DDx of AG Met Acid

  • Ketones

  • Uremia

  • Salicylates

  • Methanol

  • Alcohols

  • Lactate

  • Ethylene Glycol

  • What are the unmeasured anions?


Additional Rule

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


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.


What Lowers Anion Gap?

  • Hypoalbuminemia

  • Lithium

  • Myeloma


Example

  • pH = 7.20, HCO3=10, PCO2=25

  • Na=140, Cl=110

  • diagnosis


Example

  • pH = 7.20, HCO3=10, PCO2=25

  • Na=140, Cl=110

  • diagnosisAG Met acid andNon-AG met acid


DDx of NonAG Met AcidUSED CARS

  • Ureterosigmoidostomy / Fistulae

  • Saline

  • Early Renal Failure

  • Diarrhea

  • CAI

  • AAs

  • RTA

  • Supplements


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.


Example

  • pH = 7.35, HCO3=19, PCO2=35

  • Na=140, Cl=100


Example

  • pH = 7.35, HCO3=19, PCO2=35

  • Na=140, Cl=100

  • diagnosisAG metabolic acidosis andmetabolic alkalosis


Example

  • pH = 7.31, HCO3=15, PCO2=30

  • Na=138, Cl=112

  • diagnosis


Example

  • pH = 7.31, HCO3=15, PCO2=30

  • Na=138, Cl=112

  • diagnosisnon AG metabolic acidosis


Example

  • pH = 7.12, HCO3=10, PCO2=33

  • Na=138, Cl=95

  • diagnosis


Example

  • pH = 7.12, HCO3=10, PCO2=33

  • Na=138, Cl=95

  • diagnosisAG metabolic acidosis andmetabolic alkalosis andrespiratory acidosis


Example

  • pH = 7.38, HCO3=14, PCO2=23

  • Na=138, Cl=95


Example

  • pH = 7.38, HCO3=14, PCO2=23

  • Na=138, Cl=95

  • diagnosisAG metabolic acidosis andmetabolic alkalosis andrespiratory alkalosis


Example

  • pH = 7.40, HCO3=24, PCO2=40

  • Na=140, Cl=96

  • diagnosis


Example

  • pH = 7.40, HCO3=24, PCO2=40

  • Na=140, Cl=96

  • diagnosisAG metabolic acidosis and Metabolic alkalosis


Example

  • pH = 7.40, HCO3=24, PCO2=40

  • Na=140, Cl=104


Example

  • pH = 7.40, HCO3=24, PCO2=40

  • Na=140, Cl=104, albumin=1.1


Last rule!

  • For every 1.0 g/dl that the serum albumin is below 4.0, the upper limit of the anion gap is decreased by 2.5

  • Normal upper limit = 12

  • Alb 3.0 upper limit = 9.5

  • Alb 2.0 upper limit = 7.0

  • Alb 1.9 upper limit = 4.5


Example

  • pH = 7.40, HCO3=24, PCO2=40

  • Na=140, Cl=104, albumin=1.1


Example

  • pH = 7.40, HCO3=24, PCO2=40

  • Na=140, Cl=104, albumin=1.1

  • Diagnosis:Anion Gap Metabolic AcidosisMetabolic Alkalosis


Dogmatic Statement

  • You cannot interpret arterial blood gases without looking at the electrolytes.


Dogmatic Statement

  • You cannot interpret arterial blood gases without looking at the electrolytes.

  • Be sure to check the albumin as well.


Summary

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


Summary

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

But don’t forget to check the anion gap and the serum albumin!


Thank you for your attention

Metabolic Acidosis: 1HCO3 => 1PCO2

Metaboli 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

But don’t forget to check the anion gap and the serum albumin!


Thank you for your attention


  • Login