How To: DIY Ultrasound Guided Peripheral IV Phantom

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Introduction

Ultrasound-guided venous access has become a core skill for both emergency medicine providers, and nursing staff, to help facilitate difficult access. While clinical experience is critical to learning this technique, phantoms are also a necessary component, specifically with regards to developing both fine-motor skills and spatial orientation. In this post, we provide a step-by-step guide to creating a high-quality, affordable, phantom that can be used for educational purposes at large conferences or for small group training sessions.

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1. The Set Up

The Mold: water, metamucil, gelatin, citric acid, blue food coloring

The Veins: animal balloons, red food coloring

The Container: supply case ( 5.08 x 5.25 x 1.9 )

The Tools: sharpie, scissors, syringe, sharp knife or razor blade, large whisk (not shown)

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2. Create your Container

We chose the above container because it only requires 500 ml of gelatin mixture, it is plastic (which allows us to cut into it), and it has a lid which allows for easy transport and keeps the phantom fresh.

What you will be doing is creating small slits in the sides of the container to allow for the vessels to "float" and avoid having to pour gelatin in two steps which is both time consuming and messy.

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 2a. Measure out vessel depth and location

I like to place the vessels 1.5 cm below the surface of the gelatin mold. Using the thick plastic line near the opening of the box, measure 1.5 cm down from here. Measure 4 cm from each side of the box and connect everything with lines. The areas that cross will be where your vessels will go. Repeat this process on opposite side.

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2b. Puncture four small slits in container

Now it's time to make small cuts in the plastic container which will allow the vessels to "float." I sit by the stove when doing this and turn on vent above to prevent significant inhalation of burning plastic fumes. Hold the tip of sharp knife or razor knife directly in flame until it turns red. Then quickly push knife into plastic at each line intersection, making approximately a 7-8 mm slit. You may have to re-heat knife between punctures.

Your container is now ready to be used, onto creation of your vessels.

 

 

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2. Create your Vessels

The red food coloring adds an extra element to your phantom by making the "flash" in the angio-catheter chamber visible.

Fill your syringe with colored water and inject into balloon until it is plump. Next, make sure to get all the air out of the balloon that may have become trapped by holding the balloon vertical, allowing the air to rise to the top, and then tying this off. Continue to tie off the ends of the balloon and trim down with scissors until the vessel is just longer than the width of your container.

Make sure to leave around 1 cm of balloon on each side of your knots as you will need this to pull the vessels through the slits in the container.

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3. Cannulate your Container 

Take each balloon vessel and thread the ends through the slits in your container. Note as shown in the image that the knot will get caught up on the slit. I use the end of my scissors to pry open the slit slightly, allowing the knot to be pulled through with a little bit of force.

Once the knot is through, pull the balloon vessel out about 1 cm. This will allow the container to "auto-seal." so you do not have to worry about leaking when pouring in the gelatin mold.

This is the hardest step in constructing your phantom so do not be dissuaded if it takes you a few tries.

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4. Make your Gelatin Mold

Now it's time to make your gelatin mold. Here are the amounts required for a 500 ml gelatin mold. You can multiply these amounts as needed if making multiple models at a time:

Water: 500 ml

Gelatin: 40 grams (~3.5 Tbsp)

Metamucil: 20 grams (~1.75 Tbsp)

Citric Acid: 1 Tbsp

Blue Food Coloring: 1 tsp

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4a.  Combine ingredients

Heat up the water in a large pot until it just begins to boil. At this point turn down heat so that water stays warm but is not bubbling. Too much heat will cause the mixture to froth and overflow.

Now add your ingredients, I do the gelatin first as this is the most difficult.  It is critical to whisk the water the entire time while adding the gelatin slowly. If you dump the gelatin in all at once, it will form large clumps and ruin your phantom. I would also follow this same technique when adding the other ingredients.

Once all ingredients have been well combined and your mixture has thickened you are ready to pour your gelatin mold into your container.

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4b. Pour the mold

Pour gelatin mold into your container, up to the thick plastic line. Allow the mold to cool for 10-15 minutes, then close lid and place in the fridge overnight to set.

The next day your mold will be ready to use!

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5. Use your Mold 

The mold is probably good for ~ 50-100 IV insertion attempts and can be used at multiple training sessions, though I probably would not keep it for more than 2 weeks. Here are a few other tips:

- The gelatin mold should be chilled until just prior to use to keep it firm; clean surface with water after use, pat completely dry, and store back in fridge to increase longevity.

- To optimize movement of probe along the surface of gelatin mold, be sure to apply a generous quantity to the surface.

- If you notice the balloons appear flat after multiple cannulations, you can refill by directly accessing them through the gelatin under ultrasound guidance and injecting slowly until they appear plump again (do not over pressurize or you may damage the phantom or cause a leak).

Questions?

Leave a comment or email us at ucsdultrasound@gmail.com

The POCUS ATLAS-11

The effect of vessel depth, diameter, and location on US guided peripheral intravenous catheter longevity

Background

Nearly 30% of all patients who visit the ED in the US each year will require venous access. Bedside ultrasound-guided peripheral IVs (USGPIV) offer an alternative to central venous cannulation and external jugular cannulation for patients in which PIV access cannot be obtained, thereby reducing the risks of infection and the need for additional resources that are associated with the aforementioned procedures. The downside to USGPIVs lies in the longevity of this method of venous access, which introduces complications such as extravasation, tissue necrosis and disruption of access.  Failure rates are high, with 8% of them failing within the first 8 hours, and 47% failing within the first 24 hours. The authors of this weeks article speculate that this is due to the nature of the vessels targeted by ultrasound (US), being that they are often deeper and smaller veins in locations that are otherwise difficult to access without specialized imaging. This article will explore the influence of various vessel characteristics on the success and longevity of the USGPIVs, including vessel depth, diameter, and location.

The effect of vessel depth, diameter, and location on US guided peripheral intravenous catheter longevity

Clinical Question

How do specific characteristics of a vessel determine the success and longevity of a USGPIV?

Methods & Study Design

  • Design
    • A retrospective chart review of a previously gathered database of difficult intravenous access (DIVA) patients who underwent USGPIV placement in the ED
    • Data included images and measurements of the vessel’s depth, diameter and location as well as survival time of the IV
  • Population
    • Urban tertiary care center with a 4-yr EM residency and an US fellowship
    • Study period: Dec 2007-May 2008
  • Inclusion criteria
    • All DIVA patients: A DIVA patient is defined as someone with 2 failed peripheral IV attempts or a history of DIVA with inability to visualize or palpate a target vein on physical exam
    • DIVA patient must have underwent successful USGPIV placement in ED
  • Exclusion criteria
    • There were no specific exclusion criteria however patients were excluded for several reasons:
      • 18 for inability to establish USGPIV using study protocol
      • 12 for lack of charting to accurately determine time of IV removal
      • 2 for failure of consensus of at least 2 of the 3 blinded independent chart reviewers on timing or outcome of IV
  • Intervention
    • USGPIVs were placed by 2 PGY-2s, 1 PGY-3, and 1 US fellow, all met ACEP guidelines (at least 10 USGPIVs previously performed)
      • Successful IV placement was defined as aspiration of 5 mL of blood and ability to flush the line without resistance
      • Only 20-gauge, 48-mm-long (Angiocath Autoguard;BD Medical Systems, Sandy, UT) catheters were used for USGPIV placement
      • During USGPIV placement, vessels were measured for depth and diameter, and location was noted on a diagram of the upper extremity
  • Outcomes
      • Failure rate of USGPIV based on depth, diameter, and location
        • 2 blinded independent chart reviewers followed successfully placed USGPIVs for 48 hours or until failure, whichever came first
        • Failures were defined as IVs that infiltrated, dislodged, stopped working or were discontinued prematurely
        • IVs removed on patients that no longer required access were not considered failures

Results

  • Calculated USGPIV survival curves for vessels at given depths and location from Fields et al.
    • Statistical Analysis
      • Vessel depth divided into 3 zones: shallow (0.4 cm), intermediate (0.4-1.19 cm), and deep (≥1.2 cm); Intravenous diameter was divided into 4 groups (<0.3, 0.3-0.39, 0.4-0.49, and ≥0.5 cm);
      • Vessel location was divided into proximal (brachial region) and distal (antecubital fossa, forearm, or hand veins).
      • Kaplan-Meier estimator was used to measure time-to-failure and remove potential confounder of IVs that were removed for discharge or no longer needed
    • Findings
      • At 48 hrs, 48 (32%) had failed because of dislodgment, infiltration, or patient discomfort
        • 20 (42%) infiltrated
        • 11 (23%) dislodged
        • 16 (33%) were not flushing
        • 1 removed for discomfort
        • 36 (24%) were removed for routine reasons
        • 67 (44%) were still in place and without incident
        • There was no difference in patient characteristics of IVs that failed vs. those that did not fail
      • Kaplan-Meier Survival Analysis 
        • Depth: Survival probability excellent (1.00) for shallow vessels, moderate (0.62) for intermediate vessels, poor (0.29) for deep vessels STRONGEST PREDICTOR
        • Location: antecubital fossa or forearm associated with improved survival when compared with proximal placement in brachial or basilic vein (0.93 vs. 0.71)
        • Diameter: no significant difference
        • For each increase of 0.2 cm in depth, odds of failure at 48 hrs increases by hazard ratio of 1.36
        • Placement in proximal vs. distal location increases odds of failure by hazard ratio 2.76

Strengths & Limitations

  • Strengths
    • No difference in patient characteristics between failed and successful USGPIVs
    • Recruited difficult IV access patients from urban academic tertiary ED which is likely representative of true difficult access patient population and can be generalized to other EDs
    • 2 independent reviewers used for retrospective chart review
  • Limitations
    • Outcome variable (survivability) was gathered retrospectively; potential bias in rapid realization of IV failure and clear documentation
    • Possible that failed catheters were documented as “removed” because they were no longer needed or another access was obtained
    • Did not account for certain factors: nature of the infusion, how often IV accessed, movement of extremity, use of fixation device
    • Only assessed using 20-gauge, 48-mm IV
    • Small group of sonographers performed data collection, they may be more skilled than general population of emergency physicians

Author's Conclusions

“Ultrasound provides a useful rescue method for establishing IV access in patients with DIVA. The current study reveals 2 factors that significantly affect the durability of these IVs— depth and location. Using a 48-mm catheter, vessels of 1.2 cm or more deep have a high likelihood of USGPIV failure and should only be cannulated when other options are not available. Vessels of less than 0.4 cm deep yield the best USGPIV longevity. Forearm and antecubital sites are more enduring than those in the upper arm. Understanding of these associations will help the sonologist select the optimal vessel for successful USGPIV cannulation and longevity.”

Our Conclusions

Depth should be the primary consideration when selecting a vessel for USGPIV access. Due to high immediate failure rates, vessels of 1.2 cm deep or more deep should be avoided and other means of obtaining venous access should be considered. Providers should also take into consideration the location of IV placement. If it is anticipated that a patient will require IV access for longer than the immediate stay in the emergency department, then proximally-located IVs should be avoided given their high failure rate at 18 hours. This failure may be explained by the fact that proximal vessels are located closer to the axilla and usually embedded in looser skin containing more subcutaneous fat with greater potential for dislodgment upon movement of the extremity. Therefore, providers should consider how long the patient will be requiring access as well as how often the patient will be required to move the extremity in making decisions regarding venous access.

The Bottom Line

USGPIVs that are placed in more superficial (<1.2 cm) and distal (forearm/antecubital space) veins have a significantly higher likelihood of survival at 48 hours and these factors should strongly be considered when evaluating for a target for IV placement.

Authors

This post was written by Courtney Shay, MS4 at George Washington University. It was reviewed by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Fields JM, e. (2017). The effect of vessel depth, diameter, and location on ultrasound-guided peripheral intravenous catheter longevity. - PubMed - NCBI Ncbi.nlm.nih.gov. Retrieved 10 November 2017, from https://www.ncbi.nlm.nih.gov/pubmed/22078967