# Arterial Blood Sampling

## Overview

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

## Indications

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

## Contraindications

## Patient information and consent

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.”

## Preparation

###

### Documentation

### Equipment

## Site and Positioning

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

## Procedure

Follow medical asepsis with non-sterile gloves.

## Troubleshooting

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

two unsuccessful

two unsuccessful

Multiple attempts will cause pain and frustration and may damage soft tissue/vasculature or distort anatomy, compromising further attempts.

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.

## Risks

## References

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