medical laboratory technology

1. Arterial blood gas analysis
Adarsh Benny

2. Arterial blood gas analysis
•ABG measurements are done to assess adequacy
of oxygenation and ventilation
•To evaluate acid base balance

4. The instrument used is called as blood gas analyser

5. Parameters measured
• Measured parameters
• pH (7.34- 7.44 )
• pCO2 (35-45mm Hg)
• pO2 (80-100mmHg)
• Na+ (135-145mmol/L)
• K+ (3.5-4.5 mmol/L)
• Ca++
• Glucose

6. • Calculated parameters
• HCO3- (bicarbonate) (22-26mEq/L)
• std HCO3- (standard bicarbonate)
• TCO2 (Total CO2)
• Base excess
• S02 (saturated oxygen)

7. Principles
•Potentiometry
•Measurement of potential difference when current is zero
•Used to measure; pH, pCO2, Na+, K+, Ca++
•Voltametry
•Measurement of current when external voltage is applied
•Used to measure; pO2

8. Collection of sample
• Arterial blood is collected from the radial artery in a
syringe
• Anticoagulant used is heparin
• After drawing the blood gently mix by rolling it
between your palms.
• If any air bubbles are seen, it needs to be expelled out
• Needle cap should be closed and put in ice box
• Send to laboratory immediately.

11. Analysis
•Before analysis, gently mix blood by rolling it
between your palms.
•Inject the sample directly into the inlet from the
syringe.
•Ensure that the blood in the syringe is not
coagulated by expelling a drop on tissue paper

12. PRECAUTIONS
•If any air bubbles are seen, it needs to be
expelled out
•Needle cap should be closed
•Transportation should be done in ice box
•Analysis should be done immediately

13. Errors in ABG analysis
•Delayed collection
•Improper labeling
•Inappropriate container- Clotting of blood
•Inappropriate anticoagulant

14. Pre analytical variables
•Improper labeling
•Inappropriate container- Clotting of blood
•Inappropriate anticoagulant
•Presence of air bubbles in the syringe
•If the Needle cap is not closed
•Improper transportation (Transportation should be done
in the ice box)