REBEL Cast Ep78: Length Matters – At Least When it Comes to US-Guided Peripheral IV Catheters

Background: Peripheral intravenous (PIV) access is one of the most commonly performed invasive procedures in unwell patients.  Although, most patients can have PIVs placed by palpation, there is a subset of patients with difficult vascular access that will require ultrasound-guided peripheral IVs. We have covered this topic before with Jacob Avila (The Ultrasound Podcast, 5 Minute Sono) in REBEL Cast Ep 62. One thing we did not cover was catheter dwell rates.  Catheter dwell rate is an important endpoint as it takes time to perform the procedure, but more importantly for the patient, premature IV failure can include complications such as infiltration, phlebitis, ischemia, necrosis, as well as delays in receiving medications. Therefore, an important concept worth covering is the length of the catheter that is in the vein.

Midline catheters, which we have also covered on REBEL EM are catheters with lengths of 6 to 20cm and represent a potential solution.  These catheters have high success rates and longevity, but insertion requires institutional protocols and specialized training.  A nice go between is the peripheral ultralong catheter (ULC), which is 6.35cm. As with anything new in medicine, it is important to review the evidence to ensure we are performing best practices for our patients.

REBEL  Episode 78 – Length Matters – At Least When it Comes to US-Guided Peripheral IV Catheters?

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From Research to Practice Ep4.0 – Length Matters in US-Guided Peripheral IVs


What They Did:

  • Single site, prospective nonblinded, 2-arm randomized clinical trial of catheter survival in the US
  • Patients randomized to:
    • Standard long catheter (SLC): 4.78cm, 20g (Becton Dickinson Insyte Autoguard)
    • Ultralong catheter (ULC): 6.35cm, 20g (B. Braun Introcan Safety)


  • Primary: Median duration of catheter survival
  • Secondary: Optimal length of catheter in the vein to maximize survival
  • Additional IV-Related Endpoints:
    • 1st stick success
    • Time to insertion
    • Number of attempts
    • Thrombosis
    • Infection


  • Age ≥18 years
  • Self-reported difficult vascular access PLUS any one of the following…
    • History of requiring 2 or more IV attempts on a previous visit
    • Previous requirement for a rescue catheter (US-guided IV catheter)
    • Midline catheter
    • Peripherally indwelling central catheter (PICC)
    • End-stage renal disease (ESRD)
    • Receiving dialysis
    • Injection drug use
    • Sickle cell disease


  • Previously enrolled
  • Withdrew from study
  • Presented when trained IV-line inserters unavailable


  • 257 patients randomized
    • Most common location of US-Guided IVs:
      • Basilic: ≈40%
      • Brachial: ≈35%
      • Cephalic: ≈20%
    • Most IV-line inserters were physicians: ≈67%
    • Diameter of vein accessed: 0.3cm
    • Depth of vein accessed: 1.0cm
    • Distance from Antecubital Fossa ≥2.5cm: ≈75%
    • Angle of Insertion:
      • 0 – 30°: ≈55%
      • ≥31°: ≈30%
    • Length of Catheter in Vein:
      • >3.0cm: ULC 55.7% vs SLC 30.9%
      • 75 – 3.0cm: ULC 6.9% vs SLC 11.1%
      • 5 – 2.75cm: ULC 6.1% vs SLC 7.9%
      • ≤2.5cm: ULC 6.1% vs SLC 30.9%
    • Median Survival Time (Primary Outcome):
      • ULC: 136hrs or 5.7d (95% CI 116 to 311hrs)
      • SLC: 92hrs or 3.9d (95% CI 71 to 120hrs)
      • Absolute difference: 44hrs (95% CI 2 to 218hrs)
      • Unadjusted HR: 0.54; 95% CI 0.35 to 0.82 (Intention-to-Treat)
      • Adjusted HR: 0.44; 95% CI 0.28 to 0.70 (Per Protocol)
    • Optimal Catheter Length in Vein (Secondary Outcome):
      • >2.75cm in Vein: Median survival of 129hrs or 5.4d (95% CI 102 to 202hrs)
      • ≤2.75cm in Vein: Median survival of 75hrs or 3.1d (95% CI 52 to 116hrs)
      • Absolute difference: 54hrs (95% CI 10 to 134hrs)
      • Unadjusted HR: 0.52; 95% CI 0.32 to 0.83 (Intention-to-Treat)
      • Adjusted HR: 0.51; 95% CI 0.32 to 0.81 (Per Protocol)
    • No statistical difference in any of the additional IV-related endpoints (ULC vs SLC):
      • 1st Stick Success: 74.1% vs 79.4%
      • Number of Attempts: 1.4 vs 1.3
      • Time to Completion: 6.9min vs 5.9min
      • Zero cases of deep vein thrombosis or infection
    • Therapy Completion:
      • 7% of patients in the ULC group reached completion of therapy compared to 57.9% in the standard long group
      • On average, ULC group required a mean 0.48 rescue catheters to reach completion of therapy compared with 0.91 in the SLC group
    • The most common causes for IV removal were:
      • Infiltration: 6 cases in ULC vs 16 cases in SLC
      • Phlebitis: 3 cases in the ULC vs 11 cases in SLC


  • Randomized patients appropriately, ensuring each individual patient has an equal probability to be assigned to one or the other treatment. This also allows for balancing of known and unknown confounders
  • US-guided PIVs were performed by attending physicians, resident physicians, advance practice providers, nurses, and technicians proficient in ultrasonography. This increases generalizability to many practice systems
  • Inserters saved both still images of the vein and cine loops of the catheter and stored them. These clips were then reviewed to measure the vein depth, vein diameter, as well as the catheter length and angle of insertion which objectively corroborates what the inserters were seeing
  • Integrity of catheter dwell time was done in real time and in person with research staff performing follow-up assessments in the hospital on the patients’ catheters within 24hrs and then daily for the life of the catheter. Catheters were deemed functional if they could be flushed with 5mL of saline solution without resistance
  • Baseline characteristics of patients were similar between groups 


  • This was a convenience sample of patients which can cause a sampling bias. The sample included may not be representative of an entire population (i.e. we don’t know how many patients that could have been enrolled were not enrolled)
  • Unblinded study: Obviously it is not possible to blind physicians to the length of the catheter, but outcomes could be assessed differently if the assessors know which participant was receiving which intervention (i.e. If you believe longer catheters will last longer, this could sway your assessment).
  • Departmental certification in US-guided vascular access involved attending a 2-hour vascular access didactic session follow by successful placement of US-guided PIVs in the ED, which may not be feasible in every institution
  • The timing and reason for catheter failure occurring before follow-up assessment were obtained from the chart. The actual time and reason for catheter failure may not be accurate as the data derived from the chart is only as good as the information that is put into the EMR
  • Concerns for superficial thrombophlebitis and DVT were assessed at physician discretion which may underestimate the rate of both
  • Most catheters were placed proximal to the antecubital fossa and therefore extrapolating results to other veins (distal to antecubital fossa) may not be possible
  • Catheter survival was not clearly defined in this study, which makes it a subjective outcome


  • US Guided PIV Access Technique Used in this Study:
    • Inserters were directed to avoid the antecubital fossa and place all US-guided PIVs at least 2cm proximal to this area
    • All catheters were placed with aseptic technique using a high-frequency linear transducer
    • Postinsertion, US-guided PIVs were confirmed for functionality by blood sampling and saline solution flush without resistance
    • Catheters were secured with a 3.5 x4-inch bordered dressing film (i.e. Tegaderm).
  • A significant number of patients were discharged ≤24hrs in both groups (ULC 31pts and SLC 21pts) and were included in the intention-to-treat analysis but not the per protocol analysis. This could significantly alter dwell times in the intention-to-treat analysis, however there did not appear to be any difference between the intention-to-treat analysis and per protocol analysis in terms of statistical significance
  • The one thing I loved about this paper is the authors make a recommendation on catheter length based on the depth of the vessel and inserter preference for the angle of insertion. If you are attempting access vessels deeper than 1cm you are more likely to get 2.75cm of catheter into the vessel with ultralong catheters regardless of the angle of insertion

Author Conclusion: “This study demonstrated increased catheter survival when the ultralong compared with the standard long ultrasonographically guided intravenous peripheral catheter was used, whereas insertion characteristics and safety appeared similar.”

Clinical Take Home Point: This study supports the contention that a longer length of catheter in the vein for US-guided PIVs in patients with difficult access increases the longevity of the catheter (The key is it is not the length of the catheter BUT the length of the catheter in the vein). ≥2.75cm of catheter in the vein leads to optimal catheter survival regardless of the catheter type.  Additionally, because these catheters have similar insertion technique as standard length catheters, no additional training is required for insertion competency.


Bahl A et al. Ultralong Versus Standard Long Peripheral Intravenous Catheters: A Randomized Controlled Trial of Ultrasonographically Guided Catheter Survival. Ann Emerg Med 2020. PMID: 31955940

For More Thoughts on This Topic Checkout:

Post Peer Reviewed By: Anand Swaminathan, MD (Twitter: @EMSwami)

Cite this article as: Salim Rezaie, "REBEL Cast Ep78: Length Matters – At Least When it Comes to US-Guided Peripheral IV Catheters", REBEL EM blog, April 2, 2020. Available at:

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