Dr Ranjith Kumar/ ABG notes

STEP 1: PH determination

(H+) = 80

STEP 2:

ACIDOSIS

RESPIRATORY

CO2

ACUTE CHRONIC

Valid ABG =

ABG INTERPRETATION

Normal 7.35 – 7.45

(H+) = 80 – LAST 2 DIGITS OF Ph (eg:7.23)

PH

(7.34-7.45)

ACIDOSIS

CHRONIC

METABOLOC

HCO3-

ALKALOSIS

RESPIRATORY METABOLIC

[H+] [HCO3

-]

Valid ABG = ---------------------- =24

P CO2

Page 1

METABOLIC

Dr Ranjith Kumar/ ABG notes Page 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

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 [HCO3-] falls by 4 for each 10-mm Hg decrease in PCO2

Acidosis Alkalosis Acidosis Alkalosis

1 2 3.5 4

ACUTE CHRONIC

Dr Ranjith Kumar/ ABG notes

� Respiratory compensation for metabolic disorder

Metabolic acidosis PCO2 = 1.5 × [HCO

Metabolic alkalosis PCO2 increases by 7 mm Hg for each 10 mEq/L increase in serum

� Mixed disorder

Corrected HCO3

compensation for metabolic disorder

= 1.5 × [HCO3-] + 8 ± 2

increases by 7 mm Hg for each 10 mEq/L increase in serum

Corrected HCO3- = Measured HCO3

- + Anion gap - 12

Met.Acidosis

Normal

Anion gap

10-12

Diarrhoea

RTA

urinary tract diversion

Ammoniam chloride intake

posthypocapnic

Positive

Anion gap

MUDPILES

Page 3

increases by 7 mm Hg for each 10 mEq/L increase in serum HCO3-

12