How to take an Arterial Blood Gas sample

Introduction

Introduce yourself

Check patient details:

• Ensure the patient is not on any anticoagulants
• Check platelets are not low & confirm coagulation blood results are normal
• Take note of whether the patient is requiring oxygen & record how much (e.g. 15L)

Explain procedure:

“I need to take a sample of blood from an artery in the wrist to assess the oxygen levels in your circulation. It will be a little painful, but will only take a short time”

Gain consent

Allen’s Test:

1. This test involves the assessment of the arterial supply to the hand
2. Ask the patient to raise their hand & make a fist for 30 seconds
3. Apply pressure over both the radial & ulnar artery at the wrist, occluding them
4. Then ask the patient to open their hand, which should appear blanched
5. Remove the pressure from the ulnar artery, whilst maintaining pressure over the radial
6. If there is adequate blood supply from the ulnar artery, colour should return within 7 seconds

If colour does return within 7 seconds, this is considered a “negative” result.
Alternatively, if the colour does not return within the timeframe, this is considered a “positive” result.
A positive result suggests that the ulnar arteries supply to the hand is inadequate.
This suggests that sampling from the radial artery on the hand is unsafe, due to the reliance on the radial artery to supply the majority of the hands tissues.
It should be noted that there is no evidence performing this test reduces the rate of ischaemic complications of arterial sampling.

Gather equipment

Arterial blood gas needle - heparinised 

Alcohol swabs

Gauze

Tape

Taking the sample

Wash hands

Position patients arm -  ideally the wrist should be extended to make the artery more superficial

Palpate radial artery - most pulsatile on the lateral anterior aspect of the wrist

Put on gloves 

Clean the site with an alcohol wipe

Attach needle to the syringe & expel the heparin 

Inserting the needle:

• Use one hand to palpate the radial artery
• Ensure you fully understand the course of the artery
• Insert the needle using your other hand at an angle of 30 degrees
• Aim towards the pulsation you are palpating with your non-dominant hand
• As you puncture the artery, you should observe bright red blood flashback into the needle
• The needle should begin to self-fill, in a pulsatile manner
• Once the required amount of blood has been collected, quickly remove the needle
• You should immediately press down firmly with some gauze over the site
• You need to press down firmly for at least 5 minutes, to prevent haematoma formation
• Some ABG needle sets come with a rubber block, to insert the used needle tip into
• Remove the needle from the syringe & discard into a sharps bin
• Place a cap on the syringe, and fill the cap with blood

To complete the procedure

Dress puncture site

Thank patient

Remove gloves and wash hands

Take blood gas sample to an analyser as soon as possible to ensure accurate results