Inserting an intravenous cannula

How to insert a cannula:

1. wash hands
2. obtain consent (skip this if patient is unconscious)
3. prepare all necessary items (dressing tray, proper size cannula, tourniquet, alcohol/iodine/chlorhexidine swab, sterile dressing)
4. apply tourniquet
5. look for suitable superficial vein
   • good veins are visible, palpable, fairly straight and not too close to a joint
6. put on gloves
7. prepare skin with swab
8. if using cannula larger than 20G, inject a little local anaesthetic subcutaneously with a 25G needle at the site where you wish to puncture with the cannula.
9. take cannula (ensure cannula is working by moving cannula freely over needle) and puncture skin next to vein at an angle of about 15^o to skin
10. move cannula and needle so that it pierces the vein. look for a flashback of blood in the cannula indicating that it is in the vein.
11. advance the cannula and needle about 5mm further into the vein with cannula flush with skin (the idea is to try to avoid breaking through the other side of the vein).
12. advance cannula over needle into vein, keeping the needle steady at all times.
    • if cannula does not enter the vein properly, do not attempt to reinsert needle into cannula. remove the whole thing and try again.
13. withdraw needle.
14. free backflow of blood indicates that the canula is in the right place. apply digital pressure above cannula to stop blood flow.
15. attach syringe with saline to cannula and flush the cannula to ensure that it is patent.
16. attach blue cap to cannula
17. release tourniquet
18. apply dressing and transparent adhesive dressing over site.
19. dispose of needles into a sharps container. dispose of gloves and syringes into specialised containers for contaminated items.

Call for help and supervision if uncertain.

If needing blood for laboratory analysis, in addition to the usual technique of cannula insertion, a syringe of appropriate size (10 ml will suffice for most things, 20 ml if blood cultures are to be taken) can be used to take blood directly from the cannula. This is done directly following removal of the needle and before the cannula is flushed. The tourniquet should not be removed (but should be loosened) while the syringe is being inserted and removed.

This technique requires patients to have only one needle inserted, and is thus far less painful. It is often important to insert cannulas and take blood at the same time, for example when seeing acutely unwell medical patients, or acute trauma patients.