Ultrasound scan (USS) guided cannulation is a technique to obtain peripheral vascular access under ultrasound visual guidance. It is particularly useful when peripheral venous access is difficult. It is essential you are confident with cannulation before attempting USS guided cannulation.

This article describes the equipment required and method for performing USS guided cannulation.

Venous access is required for blood sampling and/or the administration of intravenous drugs or fluids but this is not possible due to:

• Repeated failed attempts.
• Inability to palpate or visualise suitable veins due to dehydration, oedema or body habitus.
• Previous repeated intravenous access.

• Cannula – NB: USS cannulation usually uses deeper veins than regular cannulation; therefore a larger cannula is required to ensure enough of the catheter is in the vein to reduce the risk of extravasation. A minimum 18G (green) cannula is recommended.
• Equipment tray
• Tourniquet
• Apron
• Disposable gloves
• Alcohol/antiseptic wipes
• Cannula bung
• 10ml 0.9% saline flush
• Sterile gauze
• Clear cannula dressing
• Blood collection tubes (if required)
• Blood collection tube adaptor (if required)
• Ultrasound machine with linear probe
• Sterile ultrasound probe cover
• Sterile ultrasound gel
• Standard ultrasound gel

Part 1: Preparation and target vein identification

1. Have the patient laying down in a bed with their left or right arm exposed and elbow extended. Support the arm with a pillow if needed.
2. Position the ultrasound machine screen directly in front of you, ideally on the opposite side of the bed from you.
3. Place your cannulation equipment tray within easy arms reach.
4. Alter the ultrasound probe settings if necessary (this will vary depending on the machine, a vascular preset and depth of 2cm is recommended).
5. Apply the tourniquet.
6. Apply standard ultrasound gel to the probe and run the probe distally from the antecubital fossa in a transverse position.
7. Identify an appropriate vein:
   • Ensure it is a vein (compressible and non-pulsatile).
   • Aim to avoid veins next to arteries (non-compressible and pulsatile) and nerves. The brachial vein is deeper than the cephalic and basilic vein and has an artery and nerve close by.
   • Aim to find a vein between 0.3 and 1.5cm in depth.
   • Aim to find a vein greater than 0.4cm in diameter.
   • Aim to find a straight vein (move the probe up and down the vein, if it stays in the centre of the screen then the section scanned is straight).
8. Remove the tourniquet.
9. Clean the probe and target site.

An optimal set up for USS, aim to keep the target vein and ultrasound screen directly infront of yourself.

The deep and superficial veins of the arms. The cephalic and basilic veins are good options.
Source: OpenStax College, Wikimedia Commons, 29 June 2013.

Part 2: USS guided cannulation (for steps 6 to 13 please use the diagram attached below to aid understanding).

1. Wash your hands and don your apron and disposable gloves.
2. Clean the target site with antiseptic wipes.
3. Apply sterile gel to the end of the probe, then apply the sterile probe cover and secure with a rubber band. Reapply sterile gel to the end of the covered probe.
4. Reapply the tourniquet.
5. Relocate the target vein with the probe in your non-dominant hand in a transverse position and hold this position.
6. Pierce the skin with the cannula at 30-45 degrees and 0.5 to 1cm distally from the probe and then stop advancing.
7. Move the probe toward the cannula until the tip of the cannula is seen on the screen (the cannula will appear as a bright white circle on the USS screen).
8. Advance the probe away from the cannula until the cannula disappears from the USS screen.
9. Advance the cannula until the tip reappears on the USS screen.
10. Repeat steps 8 and 9 until the tip of the cannula is in the target vein on the USS screen.
11. Once in the vein, flatten the angle of the cannula, move the probe away from the cannula again and advance the cannula until it reappears on the USS screen.
12. Repeat step 11 to advance approximately 5mm into the vein and until the tip of the cannula is in the centre of the vein.
13. Withdraw the needle and advance the catheter of the cannula until all of the catheter is in and the needle tip is in the end of the cannula.
14. You can turn the probe into a longitudinal view to confirm the cannula is in the vein (also look for flashback in the cannula to confirm).
15. Remove the probe.
16. Secure the cannula with tape and place sterile gauze under the end of the cannula.
17. Optional: if you are taking blood samples then withdraw the needle and quickly insert the blood tube adaptor and draw blood samples.
18. Remove the tourniquet and flush the cannula with saline which should have minimal resistance and no localised swelling.
19. Apply the cannula dressing with the current date.
20. Dispose of the cannula in the sharps bin and clean/dispose of remaining equipment.
21. Remove the ultrasound probe cover and wipe down the machine and return it to the appropriate place.
22. Document the location and size of cannula used and that it was done under USS guidance.

A diagram outlining continuously advancing the cannula tip and ultrasound probe.

Written by Dr Jesse Chan (FY3)