Ultrasound Guided Peripheral Vascular Access

Cite this article as:
Trent Calcutt. Ultrasound Guided Peripheral Vascular Access, Don't Forget the Bubbles, 2021. Available at:
https://doi.org/10.31440/DFTB.23253

One of my favourite things in paediatrics is the expanding role of ultrasound guided vascular access.

When I started as a paediatric registrar, I’d just finished an adult ICU term where I’d become spent a majority of time supporting provision of a vascular access service, and as part of this had become a PICC line insertion instructor. Eventually, I got to the point where I dreamt of abstract grey shapes. But then I started a paediatric job in a regional hospital where it seemed that ultrasound was used for vascular access rarely if at all. Initially, I thought there must have been something different about paediatric vascular access that I was unaware of. One day, when looking after a young lady with Rett’s who was known to be difficult to cannulate, I reached for the ultrasound. In the five years since, ultrasound has been a standard part of my practice in achieving vascular access in children, with technique adapted to fit the age of the patient.

Ultrasound-guided vascular access and paediatrics seem like such a natural partnership. The concept of a DIVA (“difficult IV access”) patient is receiving increasing interest and research. Criteria for a DIVA can include prematurity, inability to see or feel a vessel, or an episode of multiple prior attempts. These criteria would be met by a huge number of the kids we care for, in particular toddlers or the previously premature infant. 

Chonky baby arm
Spot the veins

Why is ultrasound not the first-line adjunct in these tricky kids? It’s probably multifactorial, but certainly, ultrasound is more difficult in children than adults. Its utility is varied in the NICU context and for infants under 2.5kg, although can still have a role with a modification to technique. It’s also harder to learn ultrasound in a population who are scared, angry, impatient and poorly tolerant of a prolonged period of needle-through-skin. For these reasons, I think that there is less appeal to replace the familiar (cannulating without an ultrasound), with the unfamiliar (cannulating with an ultrasound). As I’d experienced, this also leads to a culture where ultrasound is infrequently utilized, decreasing the likelihood of implementation by new or more junior staff.

Once the learning investment is made to reach a proficient level of ultrasound competency (about 20 cannulas in adults) the potential benefits are significant. Decreased time spent performing a procedure, decreased number of attempts and subsequent patient trauma, and increased cannula longevity are all achievable.

I’ve spent a lot of time thinking success optimisation in paediatric ultrasound guided cannulation, both during my own development of proficiency and then in an effort to verbalize this skill when educating others. Below are my 5 top tips to enhance your ultrasound-guided cannulation skills:

I’m hoping that some of these words may help avoid some bits of the inevitable trial and error process that comes with learning a new skill.

There is sometimes a general impression of both practical and personal inconvenience in using ultrasound for vascular access. An ultrasound may not be nearby. There is the fear of “looking silly” in front of other people, as turning on, adjusting, and then physically coordinating the use of the ultrasound may be unfamiliar. During the period of establishing proficiency, an approach to decreasing this sense of unfamiliarity is to get in the habit of bringing the ultrasound with you do a cannula. Turn on and optimize the ultrasound to view vessels, and spend a period mapping out candidates for cannulation using your non-cannulating hand. Draw on the patient with a skin pen if you want to keep track of the best sites. Then, discard the ultrasound and cannulate using whatever technique is most familiar to you, but with the added knowledge of vessel location, depth, size, and direction. If this becomes a routine and almost ritualistic process, the mental barrier created by a lack of familiarity with ultrasound settings and holding the transducer should decrease over time. It is a relatively small step from performing vascular mapping to placing a cannula under real-time ultrasound guidance.

The preparation otherwise is quite straightforward. In addition to the set up that you use for all other cannulas, you need the following four things:

  • An ultrasound with a linear array probe (the smaller the footprint and the higher the frequency, the better)
  • Sterile lubricating gel and some form of sterile barrier to cover your probe (this varies institutionally)
  • Cavilon wipe or skin prep (securement devices / dressings / tape doesn’t like to stick to ultrasound gel so will need some encouragement)
  • An extra person (one of your hands is out of action, so you need an additional person to perform the task that your non-dominant hand would normally do; this is typically stabilization of the distal limb)

The ultrasound sits on the opposite side of the bed to the operator, so as to minimize truncal movement in looking from the puncture site to screen. Aside from making sure the correct probe is selected, the only 3 settings you need to know how to adjust are depth (typically as shallow as possible), gain (similar to a ‘brightness’ setting to highlight blood-filled vessels), and a midline marker (for physical-digital landmark referencing).

As alluded to above, pre-scanning is a useful skill even in the absence of cannulating under real-time ultrasound guidance. It’s a good idea to scope out the most appropriate vessels and puncture sites prior to picking up your cannula. Essentially the objective is to place a cannula within a vessel with as few attempts as possible, as quickly as possible, with as little pain as possible, and in a site that will provide the greatest longevity. Characteristics of vessels that tend to correlate with these outcomes are:

  • long and straight stretches
  • vessel 6mm or less below the surface
  • vessels greater than 2mm in diameter
  • vessels that don’t cross a joint (provides freedom of movement and less extravasation)
  • vessels without upstream thrombosis or obstruction

Mid-forearm vessels often meet the above criteria.

The greater length of cannula able to be placed within the vessel can correlate with longevity, however larger cannula diameter may increase the phlebitis and decrease longevity. This requires consideration of the balance between length and diameter of device. Of the commonly available devices, a good balance is a blue cannula (22G). There are several specialised less widely available devices that are longer versions of small diameter cannulae (24G and 22G).

In practical terms, to find these vessels you can start in the antecubital fossa (more familiar area for most of us) and track them down, or plonk down on the forearm and pan circumferentially. Scanning in the short axis / transverse axis / cross-sectional view tends to work best in kids. To assess suitability, translate the probe up and down along a vessel to get an idea of the direction. If it’s running diagonally, rotate your probe until it’s running along the same plane as the vessel to act as a mental reminder of the angle/direction that you need to insert your cannula. Pick the specific spot on the vessel that you’d like to puncture, bearing in mind that you will be puncturing the skin millimetres back from that point. Pick the patch of the vein that is the longest, straightest, shallowest, and biggest. Have a second fallback site planned out elsewhere for if required. Lastly, make sure to track the vein proximally as far as you can to ensure that it doesn’t run into a large thrombosed/occluded/recannalizing patch of vessel.

Obscure angles make things more challenging, in my experience. Right angles and parallel lines are your friends because they assist in mental unburdening and allow you to devote energy to troubleshooting issues. As mentioned above, map the vessel prior to puncture. Part or all of a vein will often wander diagonally along its journey, so approaching from the wrong direction increases the likelihood of punching through the side of the vessel. The centre of the image corresponds to the arrow/marker along the long edge of the probe, so you have a reference point between digital (screen) and physical (skin). Use the ultrasound as a mental reminder of your plane of approach; rotate the probe until the vessel is consistently sitting in the very centre of your image as you plane up and down. In other words, the ultrasound image is perfectly perpendicular to the plane of the vessel.

Speaking of right angles, I prefer to keep the ultrasound at right angles to the surface that you’re scanning. Angling back and forth creates a loss of contact and a distorted image as the ultrasound bounces of structures and does not return to the transducer. This creates a less clear image where vessels artificially look larger. If you need to change your view, translate/glide the probe along the skin, rather than introducing angle. It can be useful to temporarily angle the transducer perpendicular to the shaft of the cannula if you lose sight of it as this will light it up more clearly.

This is a big one. Thinking of your cannulation as a two-phase puncture process is something that I find extremely helpful. Your objective is not to puncture the skin and end up inside the vessel in a single action, and in fact, attempting to do this seems decrease the likelihood of success. 

 

Puncture Phase 1

Puncture 1 is the process from skin puncture to positioning the tip of your cannula on the superficial wall of the vessel. To achieve this, align your probe to achieve a view with the vessel in the centre of the image. Puncture the skin with the cannula a few millimetres distal to the probe. This bit is painful, so do this with a decisive action so that 2-3 mm of the cannula is within the soft tissue. Increase your angle of insertion to 30-45°. Your next objective is to find the tip of the cannula. Moving your non-dominant (ultrasound) hand, translate/slide the probe towards the puncture site until a glimmering white dot becomes apparent in your image. Once you are convinced that you are viewing your cannula, you need to ensure that you are viewing the tip at all times.

The most important thing to remember is the only way to be certain that you are viewing the tip of your cannula is when the glimmering dot disappears when you move the probe 1mm proximally (away). It is frustratingly easy to think that you are viewing your cannula tip when instead you are halfway along the shaft, with the tip out the deep wall of the vessel. Maintain this view via a “walking” approach. For each 1-2mm advancement (step) of the cannula, make an equivalent proximal movement with your ultrasound probe (step). Move the ultrasound away so that you cannot see cannula tip anymore, and then advance the cannula into view. If needed, intermittently stop advancing your cannula and check your tip position as described above. I find advancing at 30-45° until you reach the vessel works well as minimal cannula is wasted on the journey there.

If you find yourself wandering off track, keep the ultrasound focused around the vessel as the centre of your image (as this is your target). Correcting if off centre is slightly counterintuitive. Move your cannulating hand away from the direction that you want to move your cannula tip (ie- moving right will move the tip left). Continue inserting until your cannula tip is sitting at 12 o’clock on top of your vessel. As you reach this point, the tip of the cannula may gently tent the roof of the vessel, turning an “O” shape into a “❤️” shape. This is a good test of correct positioning. Once you’ve reached this point, you’re ready for puncture phase 2!!

 Puncture Phase 2

Puncture 2 is the process of entering the vessel to feeding your cannula fully in. With the tip of your cannula in view and the roof of the vessel tented (❤️), continue incrementally advancing your cannula with tiny movement, walking the ultrasound forward to ensure the tip remains in view (as above). Gently decrease your angle of insertion so that the superficial wall is not tenting towards the deep wall but rather into the potential space of the proximal vessel. Eventually, your tented vessel (❤️) will suddenly encompass the cannula and return to a circular shape (O). This may be associated with a tactile pop. You can check for flashback for additional confirmation of vessel puncture, but I prefer to not take my eyes off the ultrasound screen at this point.

Continue decreasing your angle of insertion to maintain the tip of the cannula in the top 50% of the vessel (keep the sharp bevel away from the deep wall). This may eventually require you be pushing the cannula into the skin, which really requires your assistant to get out of the way. Don’t lose site of your tip! Continue to step forward; cannula then ultrasound. To check whether you are in the vessel and not in soft tissue or dragging on the vessel wall, waggle the tip of the cannula around gently (left, right, up, down). There should be absolutely no distortion of the soft tissue surrounding the vessel; completely free cannula tip movement. I tend to leave the metal stylet in until the plastic catheter is fully inserted to the hub because of greater visibility and added rigidity. This does, however, carry the risk of puncturing the back or sidewall of the vessel if you don’t keep a close eye on your cannula tip. At the very least, ensure 3-4mm of the cannula is inside the vessel lumen prior to gliding the plastic catheter off (to avoid tissuing / tearing the vessel roof). Once this is done, you’ve just successfully place a real-time ultrasound-guided cannula! Well done!

I think it’s reasonable with each healthcare interaction to measure success both in the resolution of issue (beneficence) and in minimization of harm / traumatic experience (non-maleficence). Vascular access is our commonest painful procedure, hence representing a significant potential burden of pain, anxiety, and trauma. Undertaking steps to minimize vascular access attempts, maximize speed/efficiency, and maximize cannula longevity are important considerations in the healthcare interaction. Even if we manage to achieve the elusive goal of a single puncture hospital admission, this still requires a single puncture. 

This discussion is not really directed towards addressing the specifics of analgesia and sedation but suffice to say that time permitting these should be used and optimized readily. A topical anaesthetic is valuable, although in the case of an ultrasound-guided cannula application by the operator is useful in ensuring good placement. Evidence is increasingly suggesting that topical anaesthetic is appropriate in all ages including neonates.

The power of social stories, rehearsal, music therapy, and just general distraction cannot be undervalued. There is a multitude of approaches to this. 

Unfortunately, it is not an uncommon experience to be in a situation where vascular access is required with a degree of clinical urgency. In this circumstance, oral/intranasal/topical medication may have not had time to work, and a specialist in distraction may not be readily available.

In this circumstance, I have found that playing calm and quiet music more useful than positioning a video in front of a child. Maintaining a minimum of people speaking, and using quiet calm voices is valuable. I have had some success using the ultrasound itself as a distraction modality while telling the child a story of the “doughnut that has lost its hole” (vein and cannula tip respectively) as the tip tracks toward the vessel. A variant is the “star that fell from the sky into the lake” (cannula tip and vein respectively). There are many approaches to pain reduction through distraction.

It is my sincere hope that these tips are of some practical and clinical value in your cannulating endeavours. If it makes a difference for a single child, then surely it’s worth it. Good luck!

Challenges in cannulation

Cite this article as:
Vicki Currie. Challenges in cannulation, Don't Forget the Bubbles, 2021. Available at:
https://doi.org/10.31440/DFTB.33103

A look at paediatric cannulation. The good, the bad and the seemingly impossible.

We have all been there – coming onto a busy shift and a child who is well known for having ‘difficult’ vascular access needs a cannula.

It can be a heart sink moment when you realise that the team from the previous shift have already tried and failed. You feel your palms begin to sweat as the nursing staff tell you that access was a huge problem on the last admission. The father of the child tells you that you can have ‘just one go’.

But what really affects the chances of success of getting that tricky cannula in? Are there any modifiable factors that make it easier or harder? And how can we feel more confident in paediatric cannulation?

What is the evidence?

There are several factors that have been shown in the literature to negatively impact the success rates of paediatric cannulation:

  • Use of previous central venous access
  • Obesity
  • Attempts in the hand and lower legs
  • Non-black / non-white race
  • Poor cooperation of the child
  • Lack of confidence prior to the procedure

A recent study by Maduemem et al looked at the ‘Challenges Faced by Non- Consultant Hospital Doctors (NCHDs) in Paediatric Peripheral Intravenous Cannulation in Ireland.’ It aimed to evaluate the level of confidence of NCHD’s and looked to identify the factors that positively or negatively impacted confidence. This is a unique piece of research that is one of the first qualitative studies looking at the level of confidence in doctors in peripheral intravenous cannulation (PIVC).

Maduemem, K., Umana, E., Adedokun, C. et al. Challenges Faced by Non-consultant Hospital Doctors in Paediatric Peripheral Intravenous Cannulation in Ireland. SN Compr. Clin. Med. 2021

The team performed a cross-sectional national survey in 12 hospitals in Ireland using paper-based questionnaires. The survey captured data on the respondents’ clinical demographics (primary speciality, number of years postgraduate experience), clinical experience with PIVC (any paediatric clinical experience, number of children cannulated in preceding three months etc), the level of confidence in paediatric PIVC and potential factors influencing confidence in PIVC.

The primary outcome was the level of confidence in cannulation, measured by a five-point Likert scale assessing the overall level of confidence with ‘agree and strongly agree’ determined as a good level of confidence. Secondary outcomes were self-rated success in PIVC, previous experience and the effect of parental presence during the procedure.

The study had 202 respondents (45% response rate). The median number of years postgraduate experience for SHO level was three years (IQR 2-4) and at registrar level seven years (IQR 5-10.5). Interestingly ALL respondents had carried out paediatric cannulation in the preceding three months with 76% performing the procedure at least 10 times during the three-month time frame.  Despite 89% of respondents rating their performance as at least average, less than half (48%) of respondents reported themselves as feeling confident with the procedure.

Only 29% of respondents were reported as feeling confident in attempting PIVC that had been unsuccessful by a colleague. 37% of the cohort felt anxious when asked to perform PIVC in children, unsurprisingly with NCHD’s below registrar level feeling more anxious than their registrar counterparts.

What was driving this anxiety? More than half of the respondents (56%) stated that nursing staff and parental presence were sources of anxiety with 52% preferring to carry out this procedure without parents present.

Specific phrases that were noted by participants to have an adverse effect on confidence before the procedure were phrases which I’m sure the majority of us have heard before:

So what can we do?

Practice, practice and more practice

The study found that levels of confidence increased with seniority so encouraging junior colleagues and supporting them to perform cannulation is key. Including sessions on simulated patient arms to practice venepuncture may be a useful adjunct for clinicians with limited previous exposure.

Think before we speak

The phrases we use prior to performing a procedure can be powerful – not just the ones we say to ourselves but those we utter to colleagues. Feeding back to colleagues that phrases were unhelpful or signposting to the above study, in a polite way, might be a good way to raise awareness of the impact such phrases can have.

We all have seen the effect a ‘fresh set of eyes’ can have on that difficult cannula. So, if you are the person attempting after a colleague has already had a go, then be confident and try to start from fresh.

What about ultrasound?

Ultrasound guidance as an adjunct to PIVC has been shown to increase the success of the first attempt with good training in the use of ultrasound a big factor in first attempt success.

This is not a mandatory or even optional skill in general paediatric training in the UK. Experience is often gained from placements in PICU, ED or time with anaesthetic colleagues. Courses are becoming more frequent . If you have the opportunity or access to learn this skill from a colleague (paediatric or adult trained) it can be extremely useful.

Vein finders (infra-red lights that magically show veins through the skin) and the cold light that can often be found on the neonatal unit (used to look for evidence of pneumothorax) can be useful adjuncts too.

Are there any scores that can predict if a child’s access is going to be difficult?

The Difficult Intravenous Access (DIVA) prediction score is based upon four variables that are proportionally weighted. The variables are: vein palpability, vein visibility, age (infants score higher) and a history of prematurity. A score > 4 equates to a 50% increase in the likelihood of failure rate with first attempt.

But if a child has a high score, what next? Some difficult access pathways have been proposed with the utilisation of ultrasound, early contact with anaesthetic colleagues to help with access and consideration of midline/ PICC/ CVC in children who are particularly difficult. In practice, highlighting children early who have factors that put them at higher risk of being difficult and early escalation to senior colleagues, limiting attempts and utilisation of some of the steps mentioned can be helpful.

Keep things calm and pain free…

Optimisation of the position of the child and parents can help to not just keep the environment a calmer place but can reduce anxieties all round. The classic ‘bear hug’ position with a parent on a chair and the child chest to chest can provide not only comfort but easy access to limbs.

The use of freeze spray or anaesthetic creams on the area you are going to attempt cannulation can help to reduce pain as well as child and parental anxiety.

The use of distraction techniques can also reduce the child’s perception of pain. Singing, a YouTube video, home video on a smartphone or even bubbles can be easily done whilst attempting cannulation.

And if despite all of this you are still unsuccessful then limit yourself to a maximum number of attempts – usual practice is two to three (two attempts usually for more junior colleagues) before you ask for additional help. This ensures that there are still some veins left for that fresh set of eyes to have a look at. It also gives the child, parent and other staff helping a break from the procedure and means you don’t become super task-focused. In a situation where the child is unwell and access just needs to be attained, this is a different matter, and you will hopefully have multiple people around with lots of sets of eyes.

PIVC in children is tough, it is a skill that takes years to get right and still people who have been doing it for years can have a bad day where they just cannot get that cannula in. Keep practising, keep smiling, think about the words you use in relation to the procedure and how they can affect others and don’t forget the bubbles!

References

Bauman M, Braude D, Crandall C. Ultrasound-guidance vs. standard technique in difficult vascular access patients by ED technicians. Am J Emerg Med. 2009;27(2):135–40.

de Negri DC, Avelar AFM, Andreoni S, et al. Predisposing factors for peripheral intravenous puncture failure in children. Rev Latam Enfermagem. 2012;20(6):1072–80.

Larsen P, Eldridge D, Brinkley J, Newton D, Goff D, Hartzog T, et al. Pediatric peripheral intravenous access: does nursing experience and competence really make a difference? J Infus Nurs. 2010;33(4):226–35.

Maduemem, K., Umana, E., Adedokun, C. et al. Challenges Faced by Non-consultant Hospital Doctors in Paediatric Peripheral Intravenous Cannulation in Ireland. SN Compr. Clin. Med. 2021. https://doi.org/10.1007/s42399-021-00881-9

Nafiu OO, Burke C, Cowan A, et al. Comparing peripheral venous access between obese and normal weight children. Pediatr Anaesthesia. 2010;20:172–6.

Petroski A, Frisch A, Joseph N, Carlson JN. Predictors of difficult pediatric intravenous access in a community emergency department. J Vasc Access. 2015;16(6):521–6.

Sou V, McManus C, Mifflin N, Frost SA, Ale J, Alexandrou E. A clinical pathway for the management of difficult venous access. BMC Nurs. 2017 Nov 17;16:64. doi: 10.1186/s12912-017-0261-z.

Vinograd AM, Chen AE, Woodford AL, Fesnak S, Gaines S, Elci OU, et al. Ultrasonographic guidance to improve first-attempt success in children with predicted difficult intravenous access in the emergency department: a randomized controlled trial. Ann Emerg Med. 2019;74(1):19–27.

Yen K, Riegert A, Gorelick MH. Derivation of the DIVA score: a clinical prediction rule for the identification of children with difficult intravenous access. Pediatr Emerg Care. 2008 Mar;24(3):143-7. doi: 10.1097/PEC.0b013e3181666f32.