Arterial Blood Gas Collection (OSCE)

Introduction 

1. Greet patient and introduce yourself 👋
2. Confirm patient details ✍ 
3. Make a note of the delivery device if patient is receiving oxygen therapy (increases PaO2) ✍ 
4. Briefly explain the procedure in a patient friendly manner 
5. Identify any absolute contraindications (peripheral vascular disease in limb/arteriovenous fistula/ cellulitis) 
6. Identify any relative contraindications (impaired coagulation) 
7. Check if the patient is allergic to local anaesthetic 
8. Get patient consent ✅ 
9. Ensure patient is sitting with wrist exposed 
10. Check the patient is not in any pain 
11. Wash hands ✋ 

Equipment 

💉 Disposable gloves ✋ 

💉 Apron 

💉 Sharps bin 🗑

💉 Gauze/cotton wool 

💉 Tape 

💉 70% isopropyl alcohol wipe 

💉 Arterial blood gas syringe (pre-heparinised) 💉

💉 Bung/cap 

💉 23 G blood gas needle 💉

💉 25 to 27 G Subcutaneous needle 💉

💉 1 to 2 ml syringe for lidocaine 

💉 1mL 1% Lidocaine  

Modified Allen’s Test 

1. Occlude the radial and ulnar arteries by applying pressure over them whilst the patient clenches their fist ✊ 
2. Ask the patient to unclench their fist and check it looks ‘blanched’ for confirmation that you successfully occluded the arteries ✋ 
3. Maintain pressure over the radial artery, but remove it from the ulnar artery 
4. Assess whether normal colour returns to the hand within 5 to 15 seconds (indicates the ulnar artery has sufficient blood supply ⏱ 
5. If it takes longer than 5 to 15 seconds for the colour to return to the hand, it indicates that the patient has poor collateral circulation and arterial blood gas sampling should NOT be performed ❌ 

Preparation 

1. Collect unpackaged equipment on a tray 
2. Prepare the ABG syringe by attaching the needle 💉
3. Place the patient’s hand on a pillow, extended 20 to 30° 📐

ABG Sampling 

Palpate the radial artery: 

1. Palpate the radial artery on the patient’s non-dominant hand, identifying the most pulsatile part, this is the ideal puncture site 
2. Clean the identified site with the alcohol wipe, allow it to dry 
3. Wash hands ✋ 
4. Put gloves and apron on ✋ 

Administer local anaesthetic: 

1. Prepare lidocaine 
2. Administer it over the puncture site, subcutaneously 
3. Wait for at least 1 minute to allow the anaesthetic to work ⏱ 

Arterial Puncture: 

1. Uncover the ABG syringe  
2. Flush the heparin from the syringe 💉
3. Hold patient’s extended wrist 
4. Use your non-dominant hand to palpate the radial artery, 1cm above the puncture site 📏
5. Inform the patient you are ready to insert needle 💉
6. Insert needle at a 30 to 45° angle 📐
7. Insert the needle further into the artery until you observe flashback 💉
8. The ABG syringe should begin filling 
9. Remove the needle from the artery when you have the required amount of blood 💉
10. Apply pressure to the puncture site with some cotton wool or gauze 
11. Tape the cotton wool or gauze in place on the skin 
12. Apply the safety measure to the needle (cover it with a clip or bung) ❗ 
13. Discard the ABG needle appropriately into the sharps bin 🗑
14. Put the cap on the ABG syringe, and expel any air 
15. Label the patient’s details on the ABG sample ✍ 
16. Tell patient to continue applying pressure for 3 to 5 minutes ⏱ 

ABG ranges: 

💉 pH: 7.35 ➡ 7.45 

💉 PaCO2: 4.7 ➡ 6.0 kPa/35.2 ➡ 45 mmHg 

💉 PaO2: 11 ➡ 13 kPa/82.5 ➡ 97.5 mmHg 

💉 HCO3–: 22 ➡ 26 mEq/L 

💉 Base excess (BE): -2 ➡ +2 mmol/L 

Completion  

1. Tell the patient the examination is complete ✅ 
2. Thank patient 
3. Dispose of all equipment appropriately 
4. Wash hands ✋ 
5. Take ABG sample for analysis immediately❗ 
6. Document ABG results in patient’s medical records ✍ 

Summary:

1. Greet the patient and explain the procedure
2. Perform the Modified Allen's Test
3. Palpate the radial artery
4. Administer local anaesthetic
5. Perform arterial puncture
6. Complete the procedure by thanking the patient and dispose of equipment appropriately