Technique 4: Cannulation

Advanced procedure (not recommended)

Advantages:
Blood is literally "on tap". Disadvantages:
This is an advanced technique which requires specialist equipment. It's also extremely fiddly and carries great risk to the bottom.

The risks:
Very high .
You will be using a hypodermic needle (cannula) which carries a high risk of viral transmission if sharps injury occurs. You will be entering a blood vessel and leaving a foreign object in place which means there is a very high risk of introducing things into the blood stream that could cause serious (if not fatal) injury to the bottom. These include: Bacteria (which may cause infection of the blood stream) (See Technique 3.) Air: which can cause air embolus (see Technique 3.) Foreign object (cannula tip): This occurs when the tip of the cannula breaks off in the blood vessel and travels around the blood stream eventually lodging somewhere where the vessels narrow. If it lodges in the heart or lungs the consequences can be fatal. The risk of the tip of the cannula breaking off is high when the needle is moved backwards and forwards in the cannula tube whilst it is being introduced into the vessel. This is most often due to inexperience or poor technique.

Preparation
Where possible choose veins which are:

• Felt easily and feel "bouncy"
• On the dominant side
• Away from any cuts, scratches, skin problems

Equipment list

• Venous cannula of appropriate size (usually 20 or 22g)
• Tourniquet (soft, quick release)
• cannula dressing or tape
• Alcohol swab
• Non-sterile gloves
• Sharps container
• Cotton wool balls
• 10 ml syringe(s)

The Procedure

• Wash your hands & put on non-sterile gloves
• Find a suitable vein by having the donor:
  • Open & close the fist
  • Lower the arm below the heart
  • Wrap the arm in something warm or immerse in warm water
  • Apply a soft, quick release tourniquet
• Feel for the vein
• Clean the skin over the vein with an alcohol wipe & allow to dry (approx 30 seconds)
• Check all packaging is in date and intact (not torn or wet)
• Remove the cannula from the packaging and check all parts are working
• Loosen the white cap
• Remove the protective sleeve from the needle taking care not to touch it at any point in the procedure
• Holding the cannula in your dominant hand, stretch the skin over the vein (which should also anchor the vein) with your non-dominant hand
• Insert the needle (bevel side up) at an angle of 10-45o to the skin (this will depend on vein depth.)
• Observe for blood in the flashback chamber
• Lower the angle of the cannula & needle and advance 2mm
• Gently advance the cannula over the needle looking for “secondary” flashback along the cannula length
• Release the tourniquet
• Applying gentle pressure over the vein (beyond the cannula tip) remove the white cap from the needle
• Remove the needle from the cannula and dispose of it into a sharps container
• Attach the leur lock cap & secure the cannula with an appropriate cannula dressing or tape
• Collect blood as you require using a suitable, sterile syringe.

lili (July 2008)