Mike: Hello, I'm Mike Clarke, podcast editor for the Cochrane Library. The intravenous administration of fluids and drugs, and the drawing of blood samples requires the placing of a catheter or cannula into a vein using a needle in a procedure known as peripheral intravenous cannulation. There are different ways to guide the procedure and a new Cochrane Review from December 2022 looks at the effect of using ultrasound guidance. In this podcast, Edoardo Ostinelli from the University of Oxford talks with lead author Masafumi Tada from Kyoto University in Japan, about the review.

Edoardo: Hello Masafumi, first of all can you tell us some more about peripheral intravenous cannulation?

Masafumi: Hey Edoardo. Peripheral venous cannulation is one of the most essential procedures in medicine. The traditional approach involves visual inspection and palpation, which is known as the landmark method. However, this can sometimes be difficult and, if it fails, it can delay further treatment and laboratory tests. In those situations, a central venous line is often the next option but this may be associated with serious complications, and is a lengthy and expensive procedure compared to peripheral venous cannulation.

Edoardo: So, how might ultrasound help ensure that peripheral intravenous cannulation doesn’t fail?

Masafumi: Ultrasound can spot veins that aren't visible on the surface of the body and allows healthcare providers to see the needle and important surrounding structures, such as arteries and nerves, which should not be damaged. However, it also has some downsides, so it’s important to look at the evidence for its effectiveness, which is what we have done in this review.

Edoardo: What did you find?

Masafumi: We were interested in first-pass success, that is successful cannulation on the first attempt, overall success, and pain associated with the procedure. We found 16 clinical trials that had recruited a total of more than 2000 participants and compared peripheral intravenous cannulation using ultrasound guidance to the landmark method. As we expected, the impact of ultrasound guidance varied according to the difficultly of the cannulation process when using the landmark method, and so we analyzed the results based on the difficulty level as defined in each trial: easy, moderate, and difficult.

Edoardo: And what were the results according to these three different levels?

Masafumi: In what we can call “difficult participants”, we found low to very low certainty evidence that ultrasound guidance may increase the first-pass and overall success of cannulation, but it had no clear effect on pain.
In moderate participants, there was moderate to low certainty evidence that ultrasound guidance probably increased the first-pass success of cannulation, but the effect was smaller than in difficult participants. There was no clear effect on pain and no studies evaluated the overall success of cannulation for these participants.
In easy participants, we found moderate to high certainty evidence that ultrasound guidance decreased the first-pass success of cannulation and probably increased pain, but no studies evaluated the overall success of cannulation for easy participants. 

Edoardo: You’ve mentioned the certainty of the evidence, are there any other strengths and limitations with this research?

Masafumi: Yes, several. Firstly, the definition of the difficulty levels across the trials differed considerably, which challenged us to harmonise the levels. We redefined them based on the success rate of the landmark method, which allowed us to improve the certainty of evidence for the first-pass success of cannulation. Additionally, the magnitude of the effect was consistent between the two definitions of difficulty levels, suggesting that the results are robust. The definitions of puncture failure also varied among the trials, but we were not able to harmonise these data, which means that the results for the overall success of cannulation are less reliable.

Edoardo: Are there any other things to keep in mind when thinking about using ultrasound guidance?

Masafumi: Proficiency is essential. We saw this because the first-pass success rates varied widely in the trials, from 20% up to 80%, depending on how skilled people were in using ultrasound guidance. Adequate training and high case numbers are apparently crucial from a clinical standpoint, though our subgroup analysis didn't yield meaningful results.

Edoardo: Thanks Masafumi. If people would like to read your review, how can they get it?

Masafumi: Thanks Edoardo. To read the review online, they should go to Cochrane Library dot com and enter 'ultrasound and peripheral vein' in the search box to see the review near the top of the list.