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Ultrasound Intravascular Access


Ultrasound Intravascular Access

Article Author:
Michael Currie
Article Author:
Bo Zhu
Article Author:
Rishik Vashisht
Article Author:
David Elkin
Article Editor:
Martin Huecker
Updated:
10/15/2020 8:43:06 AM
For CME on this topic:
Ultrasound Intravascular Access CME
PubMed Link:
Ultrasound Intravascular Access

Introduction

Ultrasound (US) guidance for intravenous (IV) access has been well documented for more than 20 years and is now routine in many settings for non-emergent central line placement and difficult peripheral IV access. The safety and high success rate of US-guided IV access have been proven in the literature, and this effectiveness is the reason for such widespread integration in emergency departments. While not as common, ultrasound can also be utilized for arterial access and cannulation. Once mastered, the procedure is simple, effective, safe, and presents little to no increased risk or contraindications. Limitations to the use of US for IV access include the availability of US machines and training required.

Anytime a procedure is considered, the alternatives should be considered as well. The primary alternatives to US-guided IV access are anatomic landmark-guided placement (traditional), intraosseous access, or not obtaining IV or IO access (using intramuscular and oral routes). Other alternative adjuncts to aid in IV access include devices made for trans-illumination.[1][2][3]

Anatomy and Physiology

One must differentiate between artery and vein before cannulation. This can be done using knowledge of anatomy as well as the different characteristics seen on US. Veins should be easily compressible when pressure is applied using the US probe, whereas arteries will generally not collapse. In addition to this, when pressure is applied there often will be a pulsatile movement of the arteries. Arteries also have slightly thicker and hyperechoic walls when compared to the veins.

With hypotension or vessel calcifications, these differences may not be as noticeable. In these cases, the color flow mode or Doppler mode may assist in differentiating between the artery and vein. When using color flow mode, it is important to remember that the different colors do not inherently represent artery or vein but instead the direction of blood flow towards or away from the probe, so the operator should be careful to slightly angle probe and interpret the color based on the probe’s angulation. When using Doppler flow, the artery should show a much greater variation in the velocity waveform as compared to the vein.

Once the proper vessel is identified, follow the path of the vessel to identify any branching or tortuosity that may complicate the cannulation. This can be done in longitudinal or transverse planes.[4][5][6]

Indications

Ultrasound guidance may be indicated in any patient, though is typically prioritized for patients who have difficult IV access (either known previously or suspected), high-risk procedures such as internal jugular venous access, or patients who have already had failed attempts at IV access.[7][8][9]

Patients with suspected difficult access may include IV drug users or hemodialysis patients, hypotensive/dehydrated patients, coagulopathic patients, pediatric patients, or obese/edematous patients.

The procedure may be required for imaging (use of contrast), delivery of medications/fluids/blood, or diagnostic purposes. 

US guidance also can be used for arterial access for arterial blood samples for diagnostic purposes as well as lines for monitoring purposes.

Contraindications

There are no absolute contraindications to the use of US for IV access, although inadequate training or experience may lead to incorrect identification of structures and subsequent complications. A second relative contraindication would be failed attempts or when the time is critical, in which case intraosseous access point or landmark identification may lead to quicker access.

Other relative contraindications include those for traditional IV access: burn, infection, or injury at the site of access; mastectomy, DVT, or AV fistula on the side of access. Clinical judgment must be used in these instances.

As use becomes more widespread, the lack of training or experience will become less common. Many medical schools have begun implementing US curricula, and residency programs with ultrasound fellowship-trained faculty are increasing in number.

Equipment

Aside from the supplies necessary for vascular access, an ultrasound machine with a high-frequency capable probe is all that is necessary. If the procedure is for central access, full sterile precautions are also required.

Clinicians should be familiar with the specific US machine of the home institution, as there are some differences in design. The US probe indicator is a bump or marking on the side of the probe, which correlates with a marker on one side of the screen  (generally the left) for location identification. The probe indicator should be oriented to correlate with the side of the screen that the marker is on so that the movements of the probe correlate with the movements seen on the screen. This usually is achieved by keeping the probe marker facing towards the patient's right side. The machine also should have markers vertically on the screen to indicate the depth of structures seen, which can be adjusted based on the depth of the target vessel. Long angiocatheters should be used in deep vein access.

Personnel

Most trained personnel do not require any additional individuals for the procedure. The individual responsible for US-guided IV access may vary based on the institution and the vessel to be accessed but may include technicians, nurses, advanced practice clinicians, and physicians.

Preparation

As with most procedures, the preparation is crucial for obtaining US-guided IV access. This may vary depending on whether a peripheral or central vein is being attempted. Universal precautions always should be observed to decrease the risk of infection transmission.  

Prior to starting the procedure, discuss with the patient what will occur to help relieve anxiety. Consent can be obtained if time permits.  

The following materials should be available at the bedside: IV starting kit (tourniquet band, appropriate length IV catheter, antiseptic solution), IV flushes/saline lock, ultrasound with the high-frequency linear probe, sterile gel, and sterile probe cover. For peripheral IV access, a thin adhesive dressing such as Tegaderm may be used to cover the ultrasound probe.

Common sites when performing US-guided IV access include the superficial veins of the hand and forearm, antecubital fossa, external jugular vein, or the deeper basilic, brachial, or cephalic veins of the upper arm. When identifying the deep upper arm veins, the easiest approach is usually from the medial side of the arm. For central IV access, sites include femoral, subclavian, or internal jugular.

Technique

Different approaches involve static versus real-time and longitudinal versus transverse.

In the static approach, the vessel is identified and a skin marking is made at the sight of proper needle entry point. The course of the vein and anticipated point of vessel contact also may be marked. The probe is then put down, the site is sterilized, and IV access is attempted. This approach alleviates the need for a sterile probe covering and the need to maintain the ultrasound probe on the patient during the procedure. The success rate is much lower for this method when compared to the real-time method.

In the real-time approach, a sterile probe cover is placed on the US probe, and the US is used to visually guide the needle dynamically during the procedure. The success rate for this method is higher, allowing for a fewer number of attempts and higher patient satisfaction.

With the longitudinal approach,  the vessel appears as a long cylindrical structure. This provides the advantage of visualizing the entire needle while attempting to cannulate the vessel. The ultrasound probe, for the most part, remains still while the needle is guided into place. The beam of the ultrasound, the needle, and the vessel must all remain in the same plane during this view which makes lateral movements of the needle difficult and the lateral position of the needle relative to the vessel hard to identify. This approach is more difficult on curving or tortuous vessels. 

With the transverse or short axis approach, the vessel appears as a circular structure. Needle identification is done by visualizing the hyperechoic needle tip. This is best done by maintaining the bevel of the needle facing the ultrasound probe. In this approach, the US probe must be moved along with the needle to track the tip as you attempt to reach the vessel, and it is important to maintain visualization of the needle tip at all times since visualization of the entire needle is not possible as in the longitudinal approach. Losing sight of the needle tip can lead to puncturing adjacent structures or puncturing through the back wall of your intended vessel. This can be done with a combination of slight movements of the needle back and forth while observing the surrounding tissue for movement, and fanning the probe back and forth until the needle tip is found. Once the needle enters the vessel with either approach, the needle should be advanced while remaining in the vessel until the angiocatheter can be advanced into the vessel. With the longitudinal approach, it is usually easier to visualize entry into the vessel, since the entire needle and length of the vessel is visible on the screen. In the transverse approach, the needle can be “walked” in by slight advancements of the needle followed by a slight fanning of the probe, paying careful attention to maintain the needle tip in the center of the vessel at all times. These two approaches may be used independently or together, depending on the operator's comfort level and needs during the procedure. 

Procedure

1. Explain and discuss the procedure (including what to expect, risks, benefits, and alternatives) and consent the patient (if required).

2.  Collect equipment (see preparation section).

3.  Identify a site. Use the high-frequency probe and scan at desired locations to identify the best access site. Consider relative contraindications, depth of vessel, size and shape/path of the vessel, overlying structures such as nerves or other vessels that may be in your anticipated path, and impact the site will have on the patient’s comfort and range of movement. Optimal needle entry point may be marked at this time if desired.

4.  Prepare the site as follows:

  • Topical Anesthetic: Depending on the individual and situation, consider using a local anesthetic such as a topical eutectic mixture of lidocaine and prilocaine or a vapocoolant spray.  
  • Warming: Consider local warming of the site. While it is used in cases when the vessel is small or there is a reason for vasoconstriction, it has been shown to improve first stick success and to decrease time to access. Two minutes of heat was shown to counteract vasoconstriction noted after use of a eutectic mixture of lidocaine and prilocaine.
  • Tourniquet: When used, a tourniquet should be placed three to four centimeters (cm) proximal to the insertion site. This may be adjusted depending on the length of the needle used. 
  • Clean the site: Clean the site with an alcohol prep pad or other antiseptic pad/solution provided in IV starter kit/central line kit.
  • Unlock the needle cap:  Most needles have a cap that may be hard to remove one-handed, so it is beneficial to have the needle set up and ready.
  • Ensure saline lock and cap are attached, pre-flushed, and that they are easily reached along with the transparent patch to and any other securing dressing to be used.

5. Apply Tegaderm cover or sterile probe cover, depending on the procedure.

6.  Identify the location and vessels with the ultrasound, making sure to verify vein and/or artery.  Align the targeted vessel with the middle of the probe and screen in short or long axis (user preference).

7.  Advance the needle using the guidance of the US in real time and visualize the insertion of the needle into the vessel.  Maintain vision on the screen during the procedure to prevent loss of sight of the needle and vessel position. Look for blood return ("flash") in the hub. Some individuals find it beneficial to visualize further advancement within the vessel to ensure that when the catheter is advanced off the needle, it is well within the vessel. 

8.  Advance the catheter from the needle into the vessel. Withdraw the needle manually or with the needle’s adjunct, as some needles may come with a button for a spring-loaded withdrawal of the needle.

9.  Draw any blood required for diagnostic purposes.

10.  Attach the pre-flushed syringe to the catheter and secure the site with the dressing(s) chosen. Any remaining gel should be cleaned from the site before dressing. Otherwise, adhesive dressings are likely to fail.

11.  Remove the tourniquet and flush the tubing to ensure easy flushing and that the catheter/fluid did not infiltrate. While flushing, it may be helpful to place the probe back on the patient to observe the target vessel. There often will be a slight dilation of the vessel during the flush which can help confirm proper placement. 

Complications

There are no complications specific to the US for IV access as compared to the traditional method of IV access without US use.

A published study suggests that peripheral IV catheters placed under US guidance may fail earlier than expected, with an average life of approximately 26 hours. The shorter functional duration may be due to the patients who require this modality or the individual placing the catheter, rather than the use of US itself.

Clinical Significance

In summation, the benefits of US guidance for vascular access are seen in both adult and pediatric patients. A primary benefit is to increase success rate, which has been shown multiple times in both pre-identified subgroups of difficult patients and non-selected outpatients. With this success rate, the use of ultrasound for vascular access has been shown to decrease the need for central line placement. US guidance leads to an increased rate of first attempt success, a faster time to IV access, and higher patient satisfaction.

Enhancing Healthcare Team Outcomes

All healthcare workers who start peripheral or central lines should be familiar with the use of ultrasound. This non-invasive technology can be useful in patients with difficult intravenous access. While not as common, ultrasound can also be utilized for arterial access and cannulation. Once mastered, the procedure is simple, effective, safe, and presents little to no increased risk or contraindications. Limitations to the use of US for IV access include the availability of US machines and training required.

Anytime a procedure is considered, the alternatives should be considered as well. The primary alternatives to US-guided IV access are anatomic landmark-guided placement (traditional), intraosseous access, or not obtaining IV or IO access (using intramuscular and oral routes). Other alternative adjuncts to aid in IV access include devices made for trans-illumination.

Today, there are several types of portable US probes that can be sterilized for use on almost any part of the body. However, healthcare workers do need to acquire the skill to use US.



Contributed by Bradley Presley, MD

References

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