1. This station is a procedure that you should be familiar with. It can be extended to involve interpretation of blood gas results.

2. Introduce yourself to the patient, explain what you would like to do and obtain consent. This is an uncomfortable procedure, you should let the patient know this.

3. Gather the necessary equipment. This is a blue (23 G) needle, 2ml syringe with heparin, a cap for the syringe, a plastic bung, (usually all provided in a pack) alcohol gel, cotton wool, gloves and a sharps bin.

4. Put on your gloves and attach the needle to the heparinised syringe.

5. Position the patient’s arm with the wrist extended.

6. Locate the radial artery with your index and middle fingers. Perform Alan’s test where you compress both the radial and ulnar arteries at the same time. The hand should become white, release the ulnar artery and the colour should return to the hand. This ensures that there will still be a blood supply to the hand should the ABG cause a blockage in the radial artery.

7. Take the cap off the needle, flush the heparin through the syringe and again locate the radial artery using your non-dominant hand.

8. Let the patient know you are about to proceed and to expect a sharp scratch.

9. Insert the needle at 30º to the skin at the point of maximum pulsation of the radial artery. Advance the needle until arterial blood flushes into the syringe. PLEASE NOTE, THE NEEDLE SHOULD BE INSERTED AWAY FROM THE HAND, NOT TOWARDS IT AS SHOWN IN THE PICTURE.

10. The arterial pressure will cause the blood to fill the syringe.

11. Remove the needle/syringe placing the needle into the bung. Press firmly over the puncture site with the cotton wool. Press for 5 minutes.

12. Remove the needle and discard safely.

13. Cap the syringe, push out any air in the syringe and send immediately for analysis ensuring that the sample is packed in ice.

14. Blood gas interpretation is a clinical skill you should know. Before attempting to interpret the results you should know whether the patient was on room air or on oxygen when the sample was taken, and if on oxygen, what concentration. It is also useful to know whether the patient has a temperature or not, this should be clearly written on the sample.

15. The table below shows the changes in CO₂ and bicarbonate concentrations in different situations.

© Matthew Green and Laura Henderson 2006.