Plastic cannulas “vital” for patients at risk from needle infiltration

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Dori Schatell (Medical Education Institute, Madison, USA) spoke at the VEITH Symposium (15–19 November, New York City, USA) on the uses of plastic cannulas in vascular access, extolling the advantages brought by their flexibility. Conceding that they were not yet approved by the US Food and Drug Administration (FDA), Schatell argued that they presented several opportunities for clinicians.

Plastic cannulas have been used for 30 years or more in Japan, and 15 years in Europe, Australia, and New Zealand, but are not yet FDA-approved in the United States. That may be changing. Schatell argued that plastic cannulas should be considered for patients requiring more flexible access. Needle infiltration, which occurs more frequently with metal cannulas, can disrupt treatment and create a requirement for new procedures. A flexible cannula may reduce the risk of infiltration, she said, while also drawing attention to other scenarios in which plastic cannulas may be useful, such as for nocturnal haemodialysis during sleep, restless patients and children, as well as those with endovascular arteriovenous fistulas (AVFs) or metal allergies.

A direct statistical comparison was drawn by Schatell between plastic and steel. Referring to a study in the Journal of Vascular Access led by Sun Ryoung Choi (Hallym University Medical Center, Seoul, South Korea), she demonstrated that there is “no optimal flow, angle, depth or needle eye” to prevent wall sheer stress with steel cannulas, while plastic cannulas was associated with more stable arterial and venous pressures. Cannulation success generally was higher with a plastic rather than metal needle, and plastic use resulted in “less AVF injury, failure [and] haemostasis time.”

There was, however, a “learning curve” associated with plastic, Schatell suggested. Cannulation pain was generally found to be higher than with metal cannulas, but can be addressed with topical anaesthetics. Nurses also found cannulation more difficult at first [p = 0.084]. Despite these drawbacks, she said, plastic cannulas “save lives” by allowing earlier cannulation.  This conclusion she backed with reference to a Blood Purification-published study led by Krzysztof Letachowicz (Wroclaw Medical University, Wroclaw, Poland), which concluded in 2015 that “judicious” use of plastic cannulas “can minimise or even avoid catheter use.”

Though plastic cannulas initially cost more, Schatell said, their advantages resulted ultimately in savings for healthcare providers. She concluded by stating that they were “cheaper per patient” in part because they were both “less likely to harm the access” and “able to be used faster,” reducing the need to start haemodialysis with a risky central venous catheter.

“Blood vessels are flexible—but metal needles are rigid,” noted Schatell. “Getting plastic cannulas FDA-approved and in regular use is vital to reduce the fear, pain, and potential damage from metal needles and to help make home haemodialysis more possible for many.”

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