OSCE - Arterial Blood Gas (Teaching)

Introduction

Introduce to the junior doctor, medical student, etc.

Find out the level of knowledge of ABG sampling.

Then explain the procedure as you go along.

Then introduce yourself to the patient and take consent that you are going to teach a junior doctor.

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)

Ensure they’re no contraindications to ABG sampling:
Absolute – Poor collateral circulation / PVD in the limb / Cellulitis surrounding site / AV fistula
Relative – Impaired coagulation (anticoagulation therapy / liver disease / low platelets <50 )

Explain procedure to patient:

“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:

This test involves the assessment of the arterial supply to the hand

Ask the patient to raise their hand & make a fist for 30 seconds

Apply pressure over both the radial & ulnar artery at the wrist, occluding them

Then ask the patient to open their hand, which should appear blanched

Remove the pressure from the ulnar artery, whilst maintaining pressure over the radial

If there is adequate blood supply from the ulnar artery, colour should return within 7 seconds

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

Lidocaine (1%) – with small needle/syringe for administration

Preparation

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

Infiltrate 0.1-0.2mls of 1% lidocaine subcutaneously over the planned puncture site (unless its an emergency)

Ensure to aspirate prior to injection of local anaesthetic

Allow 60 seconds for the local anesthetic to work

Attach needle to the syringe & expel the heparin

Taking the sample

1. Use one hand to palpate the radial artery – ensure you assess the course of the artery

2. Insert the needle using your other hand at an angle of 30 degrees

3. Aim towards the pulsation you are palpating with your non-dominant hand

4. As you puncture the artery, you should observe bright red blood flashback into the needle

5. The needle should begin to self-fill, in a pulsatile manner

6. Once the required amount of blood has been collected, quickly remove the needle

7. You should immediately press down firmly with some gauze over the site

8. You need to press down firmly for at least 5 minutes, to prevent haematoma formation

9. Some ABG needle sets come with a rubber block, to insert the used needle tip into and some needle have a security cap.

10. Remove the needle from the syringe & discard into a sharps bin

11. Place a cap on the syringe

To complete the procedure

Dress the puncture site

Thank patient

Remove gloves and wash hands

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

Closing statements

Answer any questions the junior doctor may have during the whole process.

Ask the junior doctor to read about the indictions of doing an ABG and to discuss in 1-2 weeks time.

To perform the procedure under supervision and complete a DOPS.

Thank the junior doctor

Input from Geeky Medics

OSCE - Arterial Blood Gas (Teaching)