I have had a few emails from nurses asking how they should best select the location to place a cannula. Here are some tips based on my own personal experience. You may well disagree with them, or you may have some better ideas of your own. Lets have a look.
I think 80% of the trick in performing a successful cannulation is in taking time to prepare your equipment and selecting the best available site.
- Long and Large: You want to pick a a large vein and then put a large cannula into it. In the emergency department setting we often need to deliver large volumes of fluid over short times. The larger the vein and the larger the cannula, the less resistance to rapid flows.
- Pure and Pink:There should be no evidence of thrombosis or damage to the valves from previous attempts at cannulation. The target area should be well perfused. It should not be in a zone of acute burns, wounds or infection. You should avoid attempting to cannulate over a bony prominence.
- Safe and secure: You should also consider both the security of the cannula and the comfort of the patient when considering placement. A cannula placed at the cubital fossa is likely to kink off every time the patient bends their arm. It can also be quite uncomfortable. Similarly, a cannula placed in the back of the hand is also likely to kink with movement of the hand. For some reason placing cannulas in the back of a patients dominant hand seems to be a favorite site for junior doctors.
scope the lay of the land.
OK. Before we begin machete-ing our way into the circulation, let us tighten up the tourniquet and give the veins a little time to fill. Some people swear by using an inflated BP cuff instead of a tourniquet to really buff up those veins. Other tricks used to get a little vein-o-erection include placing warm towels over the area, briskly tapping or slapping the area, letting the arm hang down over the edge of the bed (before applying tourniquet) ,Â and even using vasodilatory creams such as Nitrobid paste ( this sounds a little dicey to me). Start by inspecting the non-dominant arm, but if you cant find anything jumping out at you, check the other arm. Don’t forget to inspect the entire surface of the arm. Quite a few times I have battled to get a line in only to find veins the size of a garden hose on the underside of their arm. Never underestimate the importance of palpating. More experienced cannulators will probably tell you that they rely more on feel than on sight when searching for a vein.
Once the veins are on show… look to see if you have one that bifurcates ( like the inverted Y pictured). These veins are simply begging to be cannulated, and its a simple matter of inserting your needle through the bifurcation and up into the root vein. Sweet. One mistake many people make when attempting to access a straight vein is to approach from above. More often than not the vein will *roll* away from the needle. Particularly in older patients with more, well, older connective tissues. Approach from the side whilst at the same time stabilizing the vein with your other hand by applying gentle traction to the skin. Over time you can develop quite a sensitivity to the actual layers of resistance. The skin will often require some force to pierce, but don’t push too hard. Once through the skin the needle will advance easily until you feel a subtle ‘pop’ as you enter the vein. Advance the needle slowly to avoid skewering right through the vein. Known as pranging the vein. [Related articles: Zen and the art of cannulation. How to secure a cannula. Needle stick injuries. ]