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The "C" Technique

A practice that is much too common, and much too dangerous.

by Shanise Keith • March 07, 2022

Technical, Safety


If you read my story last month regarding a recent experience I had while having my blood drawn, then you may remember me describing a certain technique used by the phlebotomist performing the draw. I am specifically talking about the "C" technique (also known as the 'window' technique), or the practice of placing a thumb and pointer finger from the same hand above and below the puncture site to help anchor the vein during needle insertion. 

This technique is widely used to help pull the skin taut and keep the vein still, but it is actually a pretty hazardous practice. The CLSI GP41 Phlebotomy Standards specifically state; 

"Hold the patient's arm firmly distal to the intended puncture site. Draw the skin taut to anchor the vein 1 to 2 inches (2.5 to 5.0 cm) below and to the side of the venipuncture site (see Figure 4). NOTE: Anchoring the vein from above is not recommended due to the risk of an accidental needlestick." 

Any jump or unexpected movement from the patient could cause the needle to be pulled out of the skin and potentially stabbed into that upper finger - something that I once personally witnessed happen to an experienced nurse who used this technique. The patient was very needle-phobic and moved suddenly during the draw. The needle came out of the skin, went into the nurse's finger, passed completely through her finger and into the patient again. Both of them had to have exposure testing, and the patient had to have another venipuncture done to collect the original samples and the subsequent tests for the exposure. That day did nothing to lessen the patient's needle-phobia, and the nurse learned a harsh lesson. 

Using techniques like the "C" technique dramatically increase the chance of an injury or exposure to the collector. Not only does this technique place the phlebotomist at a much higher risk of exposure, but the fingers placed in such close proximity to the puncture site can also inadvertently increase the angle of needle insertion to be steeper than necessary to account for the thumb being in the way. As the standards state, anchoring can (and should) be pulled from below (or below and to the side) the venipuncture site. If you find yourself needing more control to anchor the skin, use more fingers. You can also pull gently to the side at the same time. Picture your fingers in more of an "L" or "V" shape pulling from below the site instead of a "C" shape that surrounds the site. This technique works very well, and is much safer. 

Placing a finger above the venipuncture site puts the sample collector directly in harm's way, and trusting a patient to behave perfectly during a draw is unrealistic. There have been many times where a patient has moved unexpectedly while I have been collecting blood, and can be very startling. Sometimes it's a reaction to pain or their fear of the venipuncture, sometimes it's due to absentmindedness, like automatically reaching for a phone when a text is received. Then there is also the unintended movement that can occur when someone may be on the verge of passing out. With so many reasons for why someone may move during a draw, we should take steps to ensure that when it happens (because it will) we are using the safest techniques available.


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exposure window C Technique GP41 technique

5 Comments

"C" anchoring

When I went through my Phlebotomy training we were taught to NEVER use this technique due to the exact dangers you have outlined in this article.

Greg King, 03/08/2022 09:32:45

Awareness

Thank you for sharing this information. As an instructor, students watch a lot of videos online and from people who are working in the field who are doing this technique is such a nightmare for me to hear. Spreading awareness how hazardous this technique is great!

Abigail Delos Reyes, 03/08/2022 10:01:50

The C Technique

In my 37 years of Phlebotomy, I have never been stuck with a needle while performing the C technique. I have been stuck with a dirty needle when the nurse released the pt before I took the needle out of the arm. I try not to use the technique, but in some cases, it works.

Renee Robidoux-Kwiatkowski , 03/08/2022 10:05:53

Visual Example

I'd love to see an image or video of proper vein stabilization and variations on proper vein stabilization. Thank you for considering.

Marlo Capoccia, 03/08/2022 10:52:18


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