Arterial Blood Sampling

Arterial Blood Sampling - Cover

This module describes how to obtain an arterial blood sample for blood gas analysis.


  1. To obtain blood for arterial blood gas analysis (ABG)
  2. To obtain blood for investigations if venous sampling has failed

  1. Damaged or infected skin or distorted anatomy at the site

  2. in the limb

  3. Severe

    in the limb

  4. Consider the risks and benefits in patients with coagulopathy or anticoagulation with warfarin or heparin, or recent use of

    medication (aspirin is fine)


Always verify your patient’s identity and obtain informed consent before proceeding.

How do I explain this procedure?

“We need to draw some blood from an artery for testing.”

What can my patient expect?

“You may feel a sharp sting when I insert the needle. I will only draw a little blood. The test results will come out within a few minutes.”

What is my patient’s role?

“Let me know if you have any allergies or a bleeding tendency, or use blood thinners. Fearing blood or needles is normal, but tell me if you have fainted from it. Keep as still as possible. If you feel strange sensations or severe pain, tell me immediately. Afterwards, press firmly on the area with cotton wool to prevent bleeding.”


Arterial Blood Sampling - Equipment

Documentation

  1. Patient notes

  2. Patient labels

Equipment

  1. Non-sterile gloves

  2. Alcohol-based hand rub

  3. Alcohol swab

  4. Heparinised syringe OR 2 ml syringe, blunt fill needle and

  5. Winged set (butterfly needle)

  6. Cotton wool and plaster


Arterial Blood Sampling - Site

The preferred site is the radial artery in the wrist. The patient’s arm should be supinated and the wrist dorsiflexed 40°. Before puncturing a radial artery, perform the modified Allen test to see if it is suitable. If neither radial artery is usable, you may use the femoral artery in the groin, or the brachial artery in the upper arm. In these cases the patient should be supine with the leg in neutral, or with the arm supinated and extended respectively.

Modified Allen Test

  1. Ask the patient to make a tight fist.

  2. on both the radial and ulnar arteries

  3. Instruct the patient to open their fist - their hand should be

    .

  4. Release only the ulnar compression.

  5. to the entire hand within 15 seconds (positive test).

  6. If colour does not return, ulnar circulation to the hand is

    and radial artery puncture is contraindicated. Try the other hand, then move to femoral or brachial sites.


Follow medical asepsis with non-sterile gloves.

  1. If not using a heparinised syringe,

    a syringe.

  2. Perform hand hygiene and don gloves.

  3. Palpate the position of the arterial pulse with the non-dominant hand. It is useful to make a gentle indentation with your nail to mark this spot or the tip of a needle cap.

  4. Clean this area with a swab and allow it to dry. Do not touch this area again. Attach the needle to your syringe.

  5. You may wish to palpate again with one finger above and one finger below the puncture site before inserting the needle. Tense the skin by placing the thumb/finger of your non-dominant hand below the puncture site.

  6. Insert the needle at a 45° angle with the bevel up. Advance until you enter the artery; you should see blood (flashback) pulsing into the tubing. Withdraw the plunger slowly to fill the syringe. If the flashback does not pulsate, you may have hit a vein — see Troubleshooting.

  7. Withdraw the needle and apply firm pressure to the site with a cotton ball. Allow the patient to take this over and continue for 5 minutes.

  8. Remove and discard needle in a sharps container.

  9. If there is air in the syringe, hold it upright and gently push the plunger to expel the air.

  10. Cap the syringe with a stopper.

  11. Gently up-end the syringe a few times to mix blood with heparin.

  12. Dispose of medical waste safely.

  13. Label the syringe with a patient sticker and take it for

    analysis.

  14. Record completion of the procedure in patient notes.


I have not achieved flashback.

Withdraw until just the tip of the needle is in the puncture site. Make sure you are palpating the pulse, adjust your angle, and try again. If you cannot palpate the pulse anymore, abandon the attempt for now, as there is probably arteriospasm. After

attempts, call a senior for assistance.

I’ve achieved flashback, but it is not pulsatile.

You may have hit a vein. Try re-angling your needle. If still unsuccessful, try again with a new needle and a different entry point. Flashback that appears non-pulsatile may also occur if the patient is in shock, or in cardiac arrest. This may still be arterial blood.

I don’t have a winged set (butterfly needle).

Use a 22 G needle and draw up 2 ml of air into the syringe before entering the artery. The blood should fill the syringe spontaneously in a pulsatile manner.


  1. Local hematoma, pain, or excessive bleeding at the site

  2. Injury to nerves and other local structures

  3. Infection at the site

  4. Sharps injury to healthcare personnel

  5. Vasovagal response (fainting)


  1. Brzezinski M, Luisetti T, London MJ. Radial artery cannulation: a comprehensive review of recent anatomic and physiologic investigations. Anesth Analg. 2009 Dec. 109(6):1763-81.
  2. WHO Guidelines on Drawing Blood: Best Practices in Phlebotomy. Geneva: World Health Organization; 2010. Available from: https://www.ncbi.nlm.nih.gov/books/NBK138661/
  3. Davis MD, Walsh BK, Sittig SE, Restrepo RD. AARC clinical practice guideline: blood gas analysis and hemoximetry: 2013. Respir Care. 2013 Oct;58 (10):1694-703.
  4. O’Connell C. Arterial Puncture. In: Essential Clinical Procedures, Third Edition. Philadelphia: Elsevier; 2013. p. 63-70.
  5. Dev SP, Hillmer MD, Ferri M. Videos in clinical medicine. Arterial puncture for blood gas analysis. N Engl J Med. 2011;364(5):e7. doi:10.1056/NEJMvcm0803851