Abg
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This document provides instructions for interpreting arterial blood gas (ABG) results in 3 steps: 1) Determine pH and use it to identify acidosis or alkalosis. 2) Use pH and pCO2 values to classify acidosis or alkalosis as respiratory or metabolic, and as acute or chronic. 3) Examine bicarbonate levels to see if there is compensation for respiratory or metabolic disorders, and how to classify the compensation as acute or chronic. The document also provides formulas for calculating changes in bicarbonate and pCO2 levels during compensation, and discusses how to identify and classify mixed disorders.
![ABG INTERPRETATION
STEP 1: PH determination
-
[H+] [HCO3 ]
Valid ABG = ---------------------- =24
P CO2
Normal 7.35 – 7.45
(H+) = 80 – LAST 2 DIGITS OF Ph (eg:7.23)
STEP 2:
PH
(7.34-7.45)
ACIDOSIS
ALKALOSIS
RESPIRATORY
METABOLOC
CO2
HCO3-
ACUTE
RESPIRATORY
METABOLIC
CHRONIC
Dr Ranjith Kumar/ ABG notes
Page 1](https://image.slidesharecdn.com/abg-140209035839-phpapp02/85/Abg-1-320.jpg)
![To determine respiratory acidosis whether is acute or chronic:
ΔH
ΔPCO2
<0.3 Chronic Respiratory acidosis
>0.8 Acute Respiratory acidosis
0.3 – 0.8 Acute on Chronic
ΔH = Normal H+ (40) subtracted by Actual patient H+
ΔPco2 = (Patient PCo2 – 40)
Step 3: Compensation
Metabolic compensation for respiratory disorder
Acidosis
Alkalosis
1
2
ACUTE
Acidosis
Alkalosis
3.5
4
CHRONIC
Co2 we will take as 10 in every step
Respiratory acidosis
Acute
[HCO3-] increases by 1 for each 10-mm Hg increase in PCO2
Chronic
[HCO3-] increases by 3.5 for each 10-mm Hg increase in PCO2
Respiratory alkalosis
Acute
[HCO3-] falls by 2 for each 10-mm Hg decrease in PCO2
Chronic
[HCO -
Dr Ranjith Kumar/ ABG notes
3 ] falls by 4 for each 10-mm Hg decrease in PCO2
Page 2](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
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Abg
- 1. ABG INTERPRETATION STEP 1: PH determination - [H+] [HCO3 ] Valid ABG = ---------------------- =24 P CO2 Normal 7.35 – 7.45 (H+) = 80 – LAST 2 DIGITS OF Ph (eg:7.23) STEP 2: PH (7.34-7.45) ACIDOSIS ALKALOSIS RESPIRATORY METABOLOC CO2 HCO3- ACUTE RESPIRATORY METABOLIC CHRONIC Dr Ranjith Kumar/ ABG notes Page 1
- 2. To determine respiratory acidosis whether is acute or chronic: ΔH ΔPCO2 <0.3 Chronic Respiratory acidosis >0.8 Acute Respiratory acidosis 0.3 – 0.8 Acute on Chronic ΔH = Normal H+ (40) subtracted by Actual patient H+ ΔPco2 = (Patient PCo2 – 40) Step 3: Compensation Metabolic compensation for respiratory disorder Acidosis Alkalosis 1 2 ACUTE Acidosis Alkalosis 3.5 4 CHRONIC Co2 we will take as 10 in every step Respiratory acidosis Acute [HCO3-] increases by 1 for each 10-mm Hg increase in PCO2 Chronic [HCO3-] increases by 3.5 for each 10-mm Hg increase in PCO2 Respiratory alkalosis Acute [HCO3-] falls by 2 for each 10-mm Hg decrease in PCO2 Chronic [HCO - Dr Ranjith Kumar/ ABG notes 3 ] falls by 4 for each 10-mm Hg decrease in PCO2 Page 2
- 3. Respiratory compensation for metabolic disorder Metabolic acidosis PCO2 = 1.5 × [HCO3-] + 8 ± 2 Metabolic alkalosis PCO increases by 7 mm Hg for each 10 mEq/L increase in serum HCO 2 3 Met.Acidosis Normal Positive Anion gap Anion gap 10-12 MUDPILES Diarrhoea RTA urinary tract diversion Ammoniam chloride intake posthypocapnic Mixed disorder - Corrected HCO3 = Measured HCO3 + Anion gap - 12 HCO3- Dr Ranjith Kumar/ ABG notes Page 3