Successful completion of any procedure requires careful preparation. Attention to patient positioning and a priori collection of needed equipment is mandatory. Additionally, predicting difficult access and the use of techniques to aid vasodilation will greatly facilitate successful cannulation. The use of topical anesthetics may be useful in some populations, especially in pediatric patients.

Patient Positioning

 

Mise-en-Place

 

Tricks to Promote
Vasodilation

 

Topical Anesthesia

Patient Positioning

As with any procedure, positioning of both the patient and the performer should be optimized. The patient should be seated or in a reclining position for comfort and safety. Immobilize the extremity, particularly for pediatric or uncooperative patients. Keep the extremity in full extension to make the vein taut, and place the intended cannulation site in a dependant position to engorge the vein.
Mise-en-Place
In French, and in cooking, this means to lay out all of your expected ingredients and equipment ahead of time, prepared and within reach. It is often beneficial to have a selection of IV catheters available as well as extra blood tubes, tape, etc., should additional supplies be required.
Predicting Difficult Access and Promoting Vasodilation

Difficult Access

Conditions that may predict difficult access include:

  • Dehydration/intravascular depletion
  • Chronic illness with venous scarring from frequent IV access
  • IV drug use with venous scarring
  • Obesity
  • Significant edema
  • Tortuous, fragile vessels due to advanced age
  • Thin vessel walls due to age, steroid use, certain disease conditions

When presented with these situations, using the vasodilating techniques below may facilitate cannulation. If you are unsuccessful, Alternative Techniques may be required.

 
Promoting Vasodilation

Tourniquets should always be used when drawing blood or starting an IV. The tourniquet prevents venous return of blood, causing the vessel to dilate.

 

If a suitable vein is not identified after the application of a tourniquet, having the patient hold the extremity in a dependent fashion will also help to engorge the vessel.

 

Lenhardt and associates showed in a randomized trial that actively warming patient's hands with a warming mitt prior to cannulation reduced the time needed to complete the procedure and increased success rates. (Lenhardt, 2002) While these warming mitts will not likely be available at your institution, cheap and conveinent alternatives (such as having the patient hold the hand in a bowl of warm water, or applying a heating blanket or hot-water bottle) will likey have the same effect.

Topical Anesthesia

While anesthesia is not routinely utilized for intravenous cannulation, its use should be considered in special situations. Topical anesthetics are often used for venepuncture on children, to reduce anxiety and pain. (Arrowsmith)

EMLA (eutectic mixture of local anesthetics) cream contains 2.5% lidocaine and 2.5% prilocaine. It is applied as a thick dollop of cream to the area of venepuncture, and then covered with an occlusive dressing such as Tegaderm. While it provides excellent anesthesia, it must remain on the skin for 60 minutes prior to the procedure to achieve maximum tissue preparation. (Wong) EMLA is extemely safe to use, but it should not be left on for more than two hours. Cases of methemoglobinemia have been reported (Hahn; Jakobson), however these are exceedingly rare and in most cases involved large doses of EMLA which were in contact with the skin for an extended period of time.

 

LET (lidocaine 4%, epinephrine 0.1%, tetracaine 0.5%) can also be used in a similar fasion to EMLA. It too is generally safe, however should not be used on areas of the body without collateral circulation (such as the fingers, toes, ears and penis) because the epinephrine can cause local tissue ischemia. This is more of a concern when LET is used on lacerations. (Wheaton)

 
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