I. V cunnulation

               Cunnulation 

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Intravenous Cannulation

Click here to jump to a particular section:-Equipment-Cannulation Protocol-Tips

Equipment

Cannula sizes:

Cannulae come in a variety of sizes. These are measured in 'Gauge' (ie. how many can be fitted into a tube of fixed diameter). This means that larger numbers, mean smaller diameter lumens: 

Blue 22G (very small - for difficult hand veins - useful in elderly patients with fragile veins)
Pink 20G (small - suitable for the majority of patients that require IV fluids)
Green 18G (average sized - suitable for IV fluids and smaller blood transfusions)
Grey 16G (large - for use in large blood transfusions and emergency use)
Brown 14G (very large and painful - again, for emergency use)

Equipment you will require for cannulation:

Cannula of preferred size (always take one extra of the same or smaller size just incase) 
Gloves (non-sterile)
Alcohol 'steri' wipe
Gauze or cotton wool
Tourniquet
5ml Normal Saline flush (as well as the IV fluid with giving set if you wish to administer IV fluids) 
Adhesive dressing (Vecafix/Tegaderm, etc.)
5-10ml syringe for the saline flush
Portable sharps bin

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The Procedure

Protocol:

1. Collect your equipment, introduce yourself to the patient, confirm their identity, explain what you are about to do, and obtain consent.

2. Apply a tourniquet to the upper arm (preferably use the non-dominant hand), and ask the patient to open and close their fist a few times. This will make the veins more prominent. If you are having difficulty finding a suitable vein, you can get the patient to ensure that their arm is 'hanging down' off the end of the bed or chair, and make sure that it is warm (you can also immerse in warm water if required). 

3. Select a vein which is palpable (does not have to necessarily be visible), and that runs straight for a few centimetres. The red arrow in the diagram highlights a popular site. If the cannula is for 'long-term' use, then situate it away from joints if possible as this is more convenient for the patient. Confidently visualise how the cannula will go along the vein - your aim is to pierce the skin and vessel wall in one swift manoeuvre - if you hesitate, then you are likely to just push the vessel wall to one side rather than penetrate it. 

4. Put your gloves on and swab around the potential entry site with one downwards sweep. Wait for the alcohol to dry (it can sting when wet).

5. Take the cannula and remove the plastic sheath covering the needle. Open the plastic wings and loosen the white cap without removing it completely. Inform the patient that they will experience a sharp scratch. Pull the skin back distal to your entry site, and introduce the needle into the vein at an angle of around 30^o to the skin, with the bevel facing upwards. Visualise the path of the vein, and try and make a small 'sweeping' arc, therefore introducing the cannula into the vein in one manoeuvre. The skin penetration is the most painful part, so you can usually move around to find the vein if required if you miss initially. Make sure that any subsequent attempts also involve firm movements - gentle prodding will only nudge the vein to one side and add to discomfort for the patient. Once the needle is in the vein, you will see a 'flashback' of blood into the barrel of the needle. 

6. Once you see the flashback, flatten the needle (more flush with the skin) and slide the cannula a couple of millimetres further forward. You can at this stage begin to slide the cannula further forwards into the vein, whilst at the same time retracting the needle. Some people prefer to do this as 'one move', whilst others like to nudge the cannula forward then pull the needle back a bit, then repeat until the cannula is firmly in the vein. 

7. Remove the tourniquet before fully retracting the needle. Before you remove the needle, take hold of the white cap that you had previously loosened. It can be useful to place a piece of gauze just beneath the end of the cannula and to raise the patient's arm at this point to help minimise any chances of making a mess with leaking blood. Then, remove the needle whilst pressing on the area of vein that you have just cannulated - this will block the cannula and will stop blood leaking backwards prior to you capping the cannula off. Once the needle has been removed, screw the white cap onto the end of the cannula. Nearly done! 

8. Dispose of your sharps immediately - do not leave them lying around. If you produce the sharps, you must take responsibility for disposing of them. 

9. Wipe off any blood with cotton wool/gauze, and secure your cannula with the adhesive dressing. It's easier if you take your gloves off before you do this, or the dressing will just stick to your gloves. 

10. Tell the patient that they may feel a cool sensation running up their arm. Flush the cannula with saline. The saline should run easily into the vein, and the 'window' where the flashback appeared should clear up. If it is painful, or you get a swelling/bleb beneath the skin. then the vein has 'tissued' (disintegrated) or your cannula is not sited in the vein. Stop flushing and remove the cannula, applying pressure with a gauze/cotton wool to prevent swelling. 

11. If required, attach the giving set of the intravenous fluid to the cannula (nurses can show you how to do this best), fill the little reservoir about three-quarters full, and adjust the speed of the drip to run as required. NB: rolling the little slider downwards = squeezes tubing = slower rate).

12. Set the desired infusion rate (count the number of bubbles per sec - there is a way of working this out that only nurses know!), note time that the infusion started, and record this on the fluid chart. 

12. Thank the patient, and clear up.

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Tips

Optimum site for a cannula:

The forearm veins are usually best. The dorsum (back) of the hand can be a little inconvenient for patients - as can joints. Foot veins are a last resort. Try and use the patient's non-dominant hand if possible so it minimises disruption to their activities. Be aware of avoiding A-V fistulae (for dialysis - pulsatile, bulging vessels with an audible buzzing hum).

Emergency cannula insertion:

The classic answer for this is to site 'two large bore (ie. grey or larger) cannulae, one into each antecubital fossa.'

 
 

 

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