Cannulation – 9 Tips for Success

“Give me six hours to chop down a tree and I will spend the first four sharpening the axe” – Abraham Lincoln

Outlined here are 9 tips on cannulation. A tricky skill to become proficient at when starting out as a medical student/intern – it can soon become your strong suit. The quote above should be your mantra when attempting to cannulate a patient – take your time finding the vein before making your attempt…although dont take six hours, and your cannula probably doesn’t need to be sharpened!

Step 1: CALM DOWN – whether inserting a small cannula for an elective procedure or a behemoth during a cardiac arrest – take a few seconds to calm yourself -relax and glove up with a pair of dry hands.

Step 2: GET COMFORTABLE – Do not try to cannulate a patient while you are leaning over a bed rail  or reaching over the opposite side of their bed. Lie the patients arm in a comfortable position. Get yourself a chair if that makes you more comfortable.

Step 3: TAKE YOUR TIME – Take your time finding a vein, do not take your time entering the vein when you puncture the skin.

Step 4: TRACTION – Hold traction on the skin before you cannulate to help keep the vein in place. Try to maintain traction with your spare hand until the cannula is fully placed.

Step 5: GO BIG – Often whilst a junior doctor if having difficulty with a cannula – they may convince themselves to use only the smallest cannula available (Usually 22Ga) – smaller cannula = bigger chance of getting into the vein, right? The problem with using small cannula’s in large veins is that the sheath may lack the strength to push along the wall of vein – resulting in a kinked cannula. If you suspect this to be the case – do not be afraid to use a larger cannula. The moral: Sometimes if the vein’s big, a bigger cannula is actually easier.

Step 6: THE ANGLE – Did they teach you to enter at 45 degrees and then level out? Rubbish! The entry angle should be shallower for veins closer to the surface, and steeper for deeper veins.


Step 8: LET THERE BE LIGHT: Use a flashlight to illuminate the vein – Apply a bright flashlight firmly to the skin and move it until you see the veins. Veins = dark while Tissue = orange/illuminated. Try it out on your own hand! Works best in a dark room – perfect for the intern on night shift!

Step 9: TIGHTEN THAT TOURNIQUET: Make sure to ask the patient. When starting out, some students may not tighten the tourniquet adequately to fill the distal venous system.

Step 10BONUS STEP: We all have good and bad runs. You cannot control everything in medicine. Know when to ask for senior help and always put the patient first.


Other Techniques for the difficult vein (or the flustered intern!)

  1. Rest the hand in a dependent position off the bed/chair
  2. Warm water
  3. Never be afraid to ask for help – think of the patient
  4. Grab the portable ultrasound machine
  5. Check the legs

Miscellaneous: If the patient has very good veins – it is possible through ’emptying the vein’ to see where the venous valves are. Avoiding penetrating these venous valves may decrease the pain experienced by patients.

Video Demonstrating Valve Locating – Credit Pieter Peach


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