USS guided IVs

JC: Long lines for USS guided peripheral IVs. St Emlyn's

The placing of peripheral IVs is arguably the most common procedure that we do in the ED. However, although common, it’s not always easy and on those occasions when it’s difficult and needed quickly, it can be one of the most challenging procedures we do.

In recent years we have seen the widespread adoption of IO access as an alternative, and also the development of technologies such as ultrasound to help. Ultrasound in particular has allowed us to find veins that are seemingly invisible to the naked eye or to touch1. I use it regularly to find veins and to then guide the needle tip into the vein.

If you’re not doing this yet, or want a reminder then please pop overt to 5-min Sono for a reminder of the technique and for some very practical top tips.

Ultrasound guided IVs are not perfect though. Past work suggests that we often end up going for ‘deeper’ veins which inevitably leads to less cannula in the vein, which then means a higher failure rate. This has led to the development of longer IV cannulas, and more recently ultralong cannulas (up to 20cm long) to try and improve success and survival rates. This month we have a randomised controlled trial that aims to assess the potential survival benefits of ultralong IV cannulas​2​.

What kind of paper is this?

This is a randomised controlled trial which is exactly what we want to see in a trial testing a clinical intervention.

Tell me about the patients.

This was a ED based study which importantly looked at a subgroup of patients requiring IV access, notably those who were deemed to be difficult access. This is important as we only really want to study this question in patients in whom we would try the intervention. It’s important that they screened out those who were considered ‘easy’.

What did they do?

Patients were randomised to either a standard long line (SLL), which was 4.78 inch in length, or a ultra- long line (ULL) which was 6.35cm in length. Both were 20G cannulas which in the UK is pink in colour (so fairly small). The ultra-long catheters were B. Braun Introcan Safety intravenous catheters. The standard catheters were 4.78-cm, Becton Dickinson Insyte Autoguards.

Cannulas were placed under USS control using a linear high frequency probe in the same way that we would do in Virchester. According to the study protocol the lines should have been placed in the upper arm, proximal to the antecubital fossa.

What were the outcomes?

The primary outcome was median catheter survival time. They powered the study to detect a 30 hour difference between the two techniques. That’s quite a long time in my opinion. Personally I’d consider a much shorter time to be clinically important, but obviously larger numbers of patients would have been required to detect a smaller difference. Analysis was by intention to treat.

A number of secondary analyses were planned. Many were relevant to us here in Virchester such as success rate to cannulate and infection rates. In addition they looked to measure the length of catheter in the vein as previous studies have shown this to be a critical determinant of longeivity.

You might argue that this is a rather circular argument. If we know that catheter length is a determinant of longevity then ‘surely’ a longer cannula would be better? Perhaps, but there must be a point at which the benefit of length diminishes and so I think it is worth including in the research protocol.

What did they find?

270 patients were randomised on the intention to treat protocol. Of those 257 were included in the final analysis. Patients appear to be similar at baseline

Success at achieving access was similar between the two IVs.

The authors’ primary analysis was by intention to treat. In that analysis of 257 patients there was a difference of 44 hours in the average survival rate of the catheters (5.7 vs. 3.9 days). A per-protocol analysis (of 194 patients) also showed a benefit to long lines, but we must be mindful that this is a large number of patients who failed to follow protocol either by leaving within 24 hours, or by having insertions in the forearm.

The risk of losing an ultralong line was roughly 50% less that that of losing a standard IV.

The authors also looked to see if the length of cannula in the vein affected how long the IV remained usable. In keeping with past studies, more line in the vein made a difference. They found that IVs lasted longer if >2.75cm remained in the vein once inserted.

The most common reasons for needing a cannula change (in both groups) was infection or infiltration (into soft tissues).

What does this mean.

USS guided IVs are increasing in popularity in our practice. In Virchester most people use standard IV cannulae, which often leads to failure (Ed – it’s on my list of things to sort out). Our experience matches previous studies where survival of this approach is often very poor, especially when ‘deeper’ veins are cannulated​2–5​.

This study tells us again that catheter length is important as it allows more cannula to reside within the vein​6,7​, with perhaps a distance of 2.75cm being important (you can estimate this using USS). If you don’t have the super long cannulae in your department, it’s worth opting for at least an 18G (green) as these are often longer that the standard 20/22G sizes. We all know that bigger is better too, right?

What about Midlines?

You may have heard of these over on the EMCRIT site. Essentially it’s a similar concept, using even longer catheters (8-25cm) for peripheral access. It’s worth reading an excellent review on these from Scott Weingart here​8​. The related paper​9​ describes the use of midlines in critical ill patients, which is probably where I see them being used. For standard ED patients I think a longer IV is enough, but for those with very difficult access heading to ICU/HDU then perhaps we do need to look at midlines too (Ed – a question for another day, but interested to hear if anyone is using them in the UK).

Scott has done a great video on midlines here. It clearly shows them to be a different device and technique to the usual USS based lines.

So don’t confuse midlines with USS placed IVs, they are similar in concept but different.

Final thoughts.

For those of us struggling in Virchester the message here is that we need to order some longer IVs for the difficult to cannulate patients.




  1. 1.
    Egan G, Healy D, O’Neill H, Clarke-Moloney M, Grace PA, Walsh SR. Ultrasound guidance for difficult peripheral venous access: systematic review and meta-analysis. Emerg Med J. August 2012:521-526. doi:10.1136/emermed-2012-201652
  2. 2.
    Bahl A, Hijazi M, Chen N-W, Lachapelle-Clavette L, Price J. Ultralong Versus Standard Long Peripheral Intravenous Catheters: A Randomized Controlled Trial of Ultrasonographically Guided Catheter Survival. Annals of Emergency Medicine. January 2020. doi:10.1016/j.annemergmed.2019.11.013
  3. 3.
    Bahl A, Hang B, Brackney A, et al. Standard long IV catheters versus extended dwell catheters: A randomized comparison of ultrasound-guided catheter survival. The American Journal of Emergency Medicine. April 2019:715-721. doi:10.1016/j.ajem.2018.07.031
  4. 4.
    Elia F, Ferrari G, Molino P, et al. Standard-length catheters vs long catheters in ultrasound-guided peripheral vein cannulation. The American Journal of Emergency Medicine. June 2012:712-716. doi:10.1016/j.ajem.2011.04.019
  5. 5.
    Keyes LE, Frazee BW, Snoey ER, Simon BC, Christy D. Ultrasound-Guided Brachial and Basilic Vein Cannulation in Emergency Department Patients With Difficult Intravenous Access. Annals of Emergency Medicine. December 1999:711-714. doi:10.1016/s0196-0644(99)70095-8
  6. 6.
    Fields JM, Dean AJ, Todman RW, et al. The effect of vessel depth, diameter, and location on ultrasound-guided peripheral intravenous catheter longevity. The American Journal of Emergency Medicine. September 2012:1134-1140. doi:10.1016/j.ajem.2011.07.027
  7. 7.
    Pandurangadu AV, Tucker J, Brackney AR, Bahl A. Ultrasound-guided intravenous catheter survival impacted by amount of catheter residing in the vein. Emerg Med J. July 2018:550-555. doi:10.1136/emermed-2017-206803
  8. 8.
    Weingart S. Midlines part 1. EMCRIT. Published 2019. Accessed 2020.
  9. 9.
    Spiegel RJ, Eraso D, Leibner E, Thode H, Morley EJ, Weingart S. The Utility of Midline Intravenous Catheters in Critically Ill Emergency Department Patients. Annals of Emergency Medicine. December 2019. doi:10.1016/j.annemergmed.2019.09.018

Cite this article as: Simon Carley, "JC: Long lines for USS guided peripheral IVs. St Emlyn's," in St.Emlyn's, January 25, 2020,

4 thoughts on “JC: Long lines for USS guided peripheral IVs. St Emlyn's”

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  3. I was a fan of the ones I used to have access to. Tended to use while doing my anaesthetics block but I would happily use them in ED for ongoing benefit for the patient.

    If the patient has features like high BMI, oedematous and poor peripheral veins which had necessitated me looking with ultrasound in the first place, that same patient is probably going to have a miserable admission with repeated cannula attempts (especially when factoring in the misinformed decisions to remove a cannula after 3 days just because/because policy) and need for regular bloods (the brand we used could have blood aspirated from it) which are unlikely to get easier I’ve on the ward. I’d happily just place one of these as it doesn’t tend to add a huge amount more time. Can share the SOP I made at the time.

  4. Dr Nathan Littley

    Some really great points well made and a topic i have a strange passion for.
    Few additions from my experience as the on call anaesthetist who gets asked to help with these things…
    1. You don’t get length of cannula benefit until you go to 16g grey – they’re 45mm so almost always long enough to get decent length of cannula in vein. Use local anaesthetic! (Why are we so reluctant to do this, it’s not a sign of failure it’s just nicer for the pt, especially when it’s tricky and takes longer)
    2. Most radiology depts won’t do contrast injection through longer lines/midlines (because Hagen Poiseuille, length limits flow rate) – if that’s the reason for the line stick with the cannula even if it’s only temporary. They can be persuaded through an 8cm PowerWand but they’re specifically rated for 3 goes at contrast only as the pressures are higher.
    3. If the patient looks tricky from the outset, get your US from the outset. Nobody enjoys repeated attempts, least of all the patient. 2 failed attempts = try an alternative. Look up dynamic needle tip technique, practice on models and good veins so the tricky one won’t be tricky at all.
    4. If you’ve asked the anaesthetist for help, ask to observe and learn what they do differently- not a lot most of the time but they’ll have some pearls to share I’m sure, and an extra pair of hands is almost always useful in these circumstances.

Thanks so much for following. Viva la #FOAMed

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