Checklist
| Preparation | Wash – Name – Explain | |
| Check for allergies | ||
| Note inspired FiO2 | ||
| Position patient appropriately for procedure | ||
| Clean preparation surface | ||
| Gather equipment | Clean equipment tray | |
| Wash hands | ||
| Skin cleaning equipment | ||
| Blood gas syringe with needle | ||
| Gauze | ||
| Plaster | ||
| Safe sharps disposal | ||
| Site identification & cleaning | Return to patient | |
| Wash hands | ||
| Select appropriate site | ||
| Identify appropriate artery (Allen’s test) | ||
| Clean skin | ||
| Allow skin to dry | ||
| Arterial puncture | Wash hands and put on gloves | |
| Expel air/heparin from blood gas syringe (if required) | ||
| Insert needle into artery | ||
| Observe pulsatile filling | ||
| Cover site with gauze | ||
| Withdraw needle | ||
| Apply pressure to gauze | ||
| Dispose of sharps safely | ||
| Attach cap/bung to sample syringe | ||
| Ensure haemostasis | ||
| Cover wound | ||
| Finishing | Label sample at bedside | |
| Dispose of all waste appropriately | ||
| Wash hands | ||
| Transport sample to analyser |
Explanation
Preparation
Wash, name, explain:
- Wash your hands
- Introduce yourself by name and role
- Check the patient’s name and date of birth
- Explain the task and get consent
- Check whether the patient has any known allergies, e.g., to plasters
“Hello, I’m one of the doctors. I’ve been asked to take a blood sample from you. This will involve inserting a small needle into an artery in your arm. It may be a little painful, but it should not take long. You can ask me to stop at any time. Would that be okay?”
It is important to note of the concentration of oxygen that the patient is breathing (FiO2) at the time the sample is taken, as this will affect the arterial blood gas oxygen level (PaO2) result. If the patient is breathing room air, the FiO2 is 21%. If the patient is on oxygen therapy, the FiO2 will reflect the concentration of oxygen they are receiving.
Position the patient appropriately for the procedure. For an arterial blood gas sample, ensure the patient is sitting in a comfortable position, able to fully extend their arm at the elbow, and that you can comfortably access the procedure site. You may wish to place a pillow under the patient’s arm for support.
Clean your preparation space, typically a clinical trolley, using appropriate surface cleaning agents.
Gather Equipment
Clean an equipment tray and place it on your preparation surface. Wash your hands again after cleaning surfaces.
Gather the following equipment and place it in your clean tray, ensuring that key parts remain protected:
- Skin cleaning apparatus – usually alcohol-based
- Arterial blood gas syringe and needle – these usually come together in a kit, with the syringe pre-heparinised. If the needle is not already attached, you will need to attach it and expel any air or heparin in the syringe through the needle. The kit should also come with a bung or a cap for the syringe once the sample has been taken and the needle disposed of.
- Gauze
- Plaster
- Safe sharps disposal e.g., sharps bin
Site Identification & Cleaning
Return to the patient, wash your hands, and confirm that they are still happy to proceed.
Generally, arterial blood gas sampling is performed using the radial artery, and this explanation will describe the procedure from this site. Less commonly, the brachial artery is used, and in an emergency a sample can be taken from the femoral artery.
Ask the patient if they have a preference for which arm you take the sample from. Ensure that there are no contraindications to using an arm (e.g., upper limb peripheral vascular disease or fistula).
Ensure there is good collateral blood supply to the hand by performing the Allen’s test. To do this, hold the patient’s wrist and occlude both the radial and the ulnar arteries. Ask the patient to clench their fist, then open it after five seconds. The patient’s palm should be pale and blanched. Release pressure over the patient’s ulnar artery. If the hand reperfuses, then there is adequate collateral blood supply to the hand from the ulnar artery, indicating that the hand does not get its blood supply solely from the radial artery, which would be a contraindication to arterial sampling at that site.
Palpate the radial artery and familiarise yourself with its course at the wrist. Clean the skin over the chosen site using the appropriate equipment for at least 30 seconds, then allow the site to air dry for a further 30 seconds.
Arterial Puncture
Wash your hands and put on your gloves. Do not touch the site you have cleaned.
Ensure the sampling needle is attached to the syringe, and expel any air and heparin through the needle if required. Unsheathe the arterial blood gas needle. Using your non–dominant hand, palpate the radial artery and tether the skin just proximal to the arterial puncture site to locate the artery and minimise movement whilst maintaining a clean procedure site. Insert the needle into the artery at an angle of approximately 30-45° to the skin.
If the needle is correctly positioned in the artery, you should observe a flashback of blood into the needle, and the syringe should start to self–fill with each arterial pulsation.
Once you have taken the required samples, place gauze over the insertion site, remove the needle, and immediately apply firm pressure. Continue to apply firm pressure for 3-5 minutes. You may find it helpful to ask the patient or an assistant to continue to apply pressure if they are able to do so.
Dispose of the needle safely and attach the cap or bung to the sample syringe, then invert the syringe gently.
Ensure pressure is applied until the site has stopped bleeding. This may take longer if the patient is taking anticoagulants. Once haemostasis has been established, cover the site with a plaster.
Finishing
Confirm that the patient is feeling well.
Ensure you label the sample syringe at the bedside with the patient’s details. Dispose of all waste appropriately and clean your tray and trolley. Wash your hands.
Transport the sample to a blood gas analyser as soon as possible to obtain the most accurate results.
Last updated Mar 2025
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