Importance of Catheter Length for Ultrasound-Guided Cannulation of Peripheral Veins

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We read with great enthusiasm the article by Ueda and Hussey1 describing their dynamic ultrasound-guided technique and congratulate them on their excellent study. We use a very similar technique for reliable successful venous cannulation on patients with difficult intravenous (IV) access. We especially appreciate their study design incorporating only obese patients, a patient population that represents a challenge in obtaining IV access. Our suggestion to readers attempting to implement this technique concerns the importance of catheter selection, specifically with regard to its length, a critical element of this technique that was not mentioned in the article.
In our experience, use of this ultrasound-guided technique without proper catheter length can leave patients at high risk for IV infiltration and related morbidity including compartment syndrome and extravasation of vasoactive or vesicant medications.2,3 The reason for this is 3-fold. First, this technique is specifically designed to target deep structures, veins that cannot be seen by the eye alone. The authors note that the proper technique involves an entry approach of 15° to 30° and a skin entry point approximately 1 cm distal to the chosen venipuncture point. With such a trajectory, the distance from skin entry to the venipuncture point is >1 cm (1.16 cm with a 30° approach). This means that at best, using a standard 1.25 in (3.18 cm) IV catheter, only about 2 cm of the catheter will reside in the vein. This length is decreased to as little as 1.18 cm if the vein depth is increased to 1 cm with a 30° insertion that is common in obese patients. Second, epidermal translation relative to the vein can displace the catheter tip outside the venous lumen. This is particularly true in obese or older patients with loose, redundant skin at the arm. The secured catheter hub can easily translate the 1- to 2-cm distance needed to expel the catheter tip. Third, in obese patients especially, the large volume arm can easily hide any early evidence of infiltration. Swelling may not be readily apparent especially if the arms are tucked. Similarly, in these high volume compartments, lack of dripping of the IV line is an unreliable marker for infiltration. A large volume of infiltrate and medication can be delivered through the large bore IV before there is any clue that there is a problem.
For these reasons, we strongly urge readers to use the longer 2-in catheters for ultrasound-guided IV insertions. These catheters will ensure that a safe length of catheter remains within the vein, a length that is less likely to dislodge even with significant translation of overlying skin. The authors’ dynamic technique is a truly invaluable development from the frontier of point-of-care ultrasound, one we encourage all readers to learn, but like all new techniques it has its own unique risks and considerations.

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