ABG

1. ABG analysis
By Dr. Anna Khurshid

2. INTRODUCTION
• Interpreting an arterial blood gas (ABG) is a crucial skill for Physicians,
Nurses, Respiratory Therapists, and other health care personnel. ABG
interpretation is especially important in critically ill patients.
• The following six-step process helps ensure a complete interpretation of
every ABG. In addition, you will find tables that list commonly encountered
acid-base disorders.
• Many methods exist to guide the interpretation of the ABG. This discussion
does not include some methods, such as analysis of base excess or
Stewart’s strong ion difference. A summary of these techniques can be
found in some of the suggested articles. It is unclear whether these
alternate methods offer clinically important advantages over the presented
approach, which is based on the “anion gap.”

3. What is ABG Test?
•Anarterialbloodgas(ABG) testmeasures
oxygenandcarbondioxidelevelsinblood. It
alsomeasuresbody’sacidbase(pH) level,
whichisnormallybalancedwhenhealthy.
blood gas analyzer

4. OBJECTIVE:
•1.UnderstandABG and its terms .
•2.Know some of the indications and
contraindications for performing an
arterial puncture.
• 3.Be able to demonstrate the technique
for performing an arterial puncture.

5. Components of ABGs:
• PCO2 (ventilation) – Partial Carbon Dioxide
• PaO2 - (oxygenation) –Partial Oxygen
• HCO3 – (metabolism) -Bicarbonate
• O2Sat – Oxygen Saturation
• pH –Acid/Base balance
• BE – Base excess

6. Continued:
• The arterial blood gas provides the following values:
•pH _ Measurement of acidity or alkalinity, based on
the hydrogen (H+) ions present.
•The normal range is 7.35 to 7.45
•PaO2 _ The partial pressure of oxygen that is
dissolved in arterial blood.
•The normal range is 80 to 100 mm Hg.

7. • SaO2 _The arterial oxygen saturation.
• The normal range is 95% to 100%.
• PaCO2 _The amount of carbon dioxide dissolved in
arterial blood.
• The normal range is 35 to 45 mm Hg.
• HCO3 _The calculated value of the amount of
bicarbonate in the bloodstream.
• The normal range is 22 to 26 mEq/liter

8. B.E. (Base Excess):
• The base excess indicates the amount of excess or
insufficient level of bicarbonate in the system.
• The normal range is –2 to +2 mEq/liter.
• (A negative base excess indicates a base deficit in the
blood.)

10. INDICATIONS :
# Assess the ventilatory status, oxygenation and
acid base status.
# Assess the response to an intervention.
# Regulate electrolyte therapy.
# Establish preoperative baseline parameters.

11. Arterial blood gas test results may show
whether:
1. Your lungs are getting enough oxygen.
2. Your lungs are removing enough Carbon
dioxide .
3. Your kidneys are working properly.

13. Equipments for the Analysis of
ABG:

14. HOW TO DRAW AN ABG..???
• Equipments
• Site Selection
• Contraindication
• Puncture procedure
• Post puncture procedure
• Sample handling

15. Structure and function of
equipment:

16. Equipments :
1.One 1 cc to 5 cc vented, pre-heparinized,
plastic syringe.
2.One 20 - 25 gauge 1 –1 1/2” needle Longer
needles for brachial and femoral artery
puncture.
3. One Biohazard labelled plastic bag.
4. Two 1 x 1 inch sterile gauze.
5. Alcohol prep pad.

17. Continued……..
6. Specimen/Patient label .
7. Iodine pad.
8. One adhesive bandage .
9. Lab Form .
10. Ice Box.
11.Gloves.
12.Apron.

19. Site selection:
• Radial Artery _ 45 degree insertion angle.
• Brachial Artery _60 – 90 degree insertion angle.
• Femoral Artery _90 degree insertion angle.
• Dorsalis Pedis Artery.
• Posterior Tibial artery.

21. Site selection:
•1. Radial artery is always the first choice because it
provides collateral circulation.
• A. Palpate the right and left radials arterial pulse and
visualize the course of the artery.
• B. Pick strongest pulse .* if radial pulse weak on right,
move to left.* if pulse on left weak, then try brachial.
• 2. Brachial used as alternative site .
• 3. Femoral is the last choice in normal situations,
highest complication rate.

22. Contraindications:
• No absolute contraindications.
• Dialysis shunt – choose another site.
• Mastectomy – use opposite side.
• Patient on anticoagulant/aspirin therapy – may
have to hold .
• pressure on puncture site longer than normal .

23. Site specific contraindication :
1.Radial : Burgers' disease.
• Raynaud’s disease.
•Absent Ulnar collateral circulation.
•AV dialysis shunt.
2.Femoral: Local infection.

24. Punctureprocedure:
1. Check for orders .
2.Explain the patient about compression of puncture site .
3. Make positive patient I.D.
4. Put on gloves.
5. Assemble needle to syringe.
a. keep needle sterile.
b. eject excess heparin and air bubbles .
c. pull back syringe plunger to at least 1 cc.

25. Puncture procedure : Allen’s Test.
•When using Allen's test for collateral circulation:
A. In conscious and cooperative patient:
1. Compress ulnar and radial arteries at wrist to obliterate pulse.
2. Have patient clench and release pulse until hand blanches.
3. With radial still compressed, release pressure on ulnar artery.
4. Watch for pinkness to return should “pink up “ within 10-15 seconds.
B. In an unconscious patient:
1. compress ulnar and radials.
2.Elevate hand above head , squeeze hard.
3. Release ulnar and lower hand below heart.

26. Palpate right and left radial arteries noting maximum pulse.
The one with strongest pulse will be your site of entry.

27. Puncture Procedure:
• Drape the bed and stabilize the wrist in that position that gives maximum
pulse (hyper- extended , using a rolled up towel if necessary).
• Prepare the site.
• Clean the chosen area with alcohol and with iodine.
• Secure needle to syringe and remove the cap from needle.
• Pierce the skin at puncture site (keep needle angle constant, bevel of needle
up or into the arterial flow).
• Slowly advance in one plane.
• When the artery is punctured , blood will enter the syringe – “flash”.
• Slowly allow the blood to fill the syringe.
• If no blood appears , remove ,change needle and start again.

28. • Upon removal of needle , hold pressure on puncture site for at least 5
minutes.
• Pressure may need to be held longer(>5 minutes) if the patient is on anti-
coagulant therapy.
Check for:
• a. Bleeding
• b. movement of fingers and tingling sensation
• c. pulse distal to puncture

29. Post puncture procedure:
1. Remove any air bubbles from sample and cap syringe.
• Dispose of needle in sharps container.
2. Roll syringe to mix heparin with sample.
3. Immerse in ice.
4. On lab slip indicate:
a. FIO2.
b. Patient temperature.
c. Ventilator parameters.
5. Deliver to lab.

30. Sample handling:
•Sample should be analyzed as soon as possible .
•–If iced sample can be stored ,
•»Glass syringe – 1 hour .
•»Plastic syringe – 15 minutes.
•Remember: Blood is living tissue that continues to
consume O2 and produce CO2 .

31. ABG Specimen Collection/Handling:
• Transport specimen to laboratory in a biohazard container.
• Analyze specimen on an instrument that has been recently calibrated.
• Temperature correction specimen in analyzer.