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Practical Procedures
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Hints and tips
Special groups
Cannula sizes

  • Tourniquet
  • Gloves
  • Hazardous material container
  • Alcohol swab
  • Gauze or cotton
  • 5-ml syringe with saline
  • Cannula
  • Vecafix™ (or similar approved IV dressing)

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  • Tell the patient who you are and what you are going to do.
  • Attach the tourniquet to the upper arm.
  • Examine and palpate the arm for a vein. Look at
    – the back of the hand – this is a common site but can be fragile and mobile in the elderly
    – the antecubital fossa will always have a vein but might be uncomfortable for the patient
    – the anatomical snuffbox at wrist
  • Swab the selected vein.
  • Anchor the vein and insert the cannula at a 30° angle to the skin (Fig. 2). Advance until you feel give in the vein wall.
  • Watch for flashback at the base of the cannula.
  • Pull back the needle part of the cannula (the stylet) 1–2 mm and watch blood flow into the plastic tubing.
  • Slide the needle back while advancing the cannula into the vein.
  • Remove the needle completely and place the cap on the end of the cannula.
  • Dispose of the needle immediately. Tape down using Vecafix™.
  • Flush with 5 ml normal saline.

Fig. 2 Cannulation of a vein. Ensure that the stylet and cannula have entered the vein (A) before withdrawing the stylet and advancing the cannula (B).

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  Hints and tips

Finding the vein is the most important part of the exercise. If you have problems, try the following:

  • After putting on the tourniquet, ask the patient to drop the hand by the side and to clench and unclench the fist. Do something else in the meantime (e.g., draw-up your saline, open up the cannula).
  • If you cannot feel a vein in one arm, do not attempt to go in blind – stop and review the other arm.
  • If you still have no luck, ask the patient to put both hands in some warm water to help vasodilation
  • If you become really desperate, try sticking GTN patches to the antecubital fossa veins
  • Foot veins are sometimes used, but this can be painful for the patient and should only be used as a last resort.

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  Special Groups

The reservations made about groups such as IV drug abusers and renal patients in the Venipuncture section also apply here.

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  Cannula sizes

Fig. 3 shows the different sizes, colors, and uses of some common cannulas.

Fig. 3 Examples of some common cannulas and their uses. (G = gauge)

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