Vascular Access: Professional Tips

Educational Objectives

The goal of this program is to improve the implementation of vascular access techniques. After hearing and assimilating this program, the clinicians will be better able to:

1. Optimize the characteristics of needles used to gain vascular access.
2. Employ appropriate techniques for achieving vascular access.
3. Use appropriate imaging strategies to ensure safe and accurate vascular access.

Summary

Needle sizing conventions: needles are measured in gauges (G), starting from 1 G; in the early 1800s, a push for standardization led to the Birmingham Wire Gauge and French (F) sizing systems; dividing F size by 3 gives the diameter; the term “micropuncture” has replaced “fine needle” (ie, any needle <20 G or 2.5 F)

Needle wall thickness: the thicker the wall, the stiffer the needle and the more likely it is to move in a straight line; the Seldinger technique uses 18-G needles, whereas the modified Seldinger technique uses micropuncture (21 G) needles; 18-G needle is seen on ultrasonography (USG), does not bend when advanced, and since luminal diameter is large, the working wire can be passed easily; micropuncture needles accept only half-thick wires but are safer as the hole created is smaller; the modified Seldinger technique has an extra step where access is upsized with a transitional system to advance the working wire, since the column strength of half-thick wires is too weak to prevent kinking and bending

Wire bending: wires bend even if inserted for short distances, as refraction applies to anything that is changing interface; each transition through a layer of tissue distorts the angle of approach of the needle; the stiffer a needle is, the more it can resist distortion; though it cannot be controlled, it should be expected and compensated for; if inserted at a 90-degree angle, needle stiffness does not matter much; the more the angle deviates from 90 degrees, the worse the distortion; the critical angle increases with change in density from one tissue plane to the other; if the change in density is great, the needle reflects off the target; for bone biopsies, the critical angle is 90 degrees

Compensating for refraction: the further the angle of approach from 90 degrees, the harder it is to keep the needle on course; the provider should course-correct along the way; every time the tissue plane changes, the needle can slide off course, especially if the plane is curved or dense or if the angle of approach is flat; it may be necessary to pull back and reapproach before reaching the desired location for puncture; the entire needle and target should be visualized on imaging

Needle bevels: the size of the defect depends on the angle of the bevel of the needle; vascular access is done with a dissecting needle, which separates tissues, as opposed to a coring needle, which removes tissue; the bevel has a complex shape with multiple planed angles that push tissue aside with minimal injury; this minimizes the defect needed to allow the body of the needle to enter the target; when the needle is removed, tissue springs back to fill the space that was pushed away; the more acute the tip of the needle, the less traumatic it is; conic tips are good for sampling or injecting fluids but cannot be used for vascular access since a wire has to be delivered (a Quincke-like tip is generally required); minimally traumatic bevels have long bevels, but since the aperture is long, it is more difficult to complete the procedure once the target is reached

Aperture length: if inserted into identical vessels, a 90-degree bevel cores the vessel and creates a large hole, a 45-degree bevel creates a smaller defect but has to be pushed in further for the entire luminal aperture to enter the intravascular space, and this is even more of an issue for a 22-degree bevel; modern machining attempts to minimize the tradeoff between defect size and aperture length; the needle may appear to be in the vessel, but the aperture may be in the vessel wall; this can cause problems when hitting small targets; technique should be informed by the tradeoff between aperture length and how traumatic the needle is; the solution lies in how USG is used to guide the needle; the entry point, trajectory, depth, and force of entry are determined by USG

Role of USG: performing thoracentesis and chest tube insertion with the patient supine in an anterolateral position protects neurovascular structures, but this approach requires USG guidance; it also allows the use of thin chest tubes that are more comfortable, safer, and efficacious; this would not be possible if the blind method is simply augmented with USG

Visualization: during vascular access, the biggest complications in the groin occur when access is too high and the vessel cannot be compressed; with imaging, it is safe to access vessels lower in the groin as long as they are large enough; the epigastric vessels curve around the peritoneal wall and travel on top of the peritoneum and underneath the rectus muscles; this can be identified on the abdominal wall and, once traced back to the groin, the needle can be inserted anywhere below its level of origin, whether arterial or venous; another useful tip is to look for the saphenous vein in the anterior medial thigh; it is close to the skin and has a fascial sheath that looks like an eye; this can be traced back to the saphenofemoral junction, which is a safe place for venous access; such landmarks can increase comfort, speed, and safety of the procedure; for small patients, ensure direct visualization

Vessel size: any device large enough to occlude flow through a vein will result in thrombosis, which can obstruct the vasa vasorum; it takes ≈2 wk for obstructed veins to die and be replaced by scar tissue; if the segment is short, it causes stenosis; if long, the vein can be occluded; risk for thrombosis depends on the relationship between the luminal diameter of the vessel and the size of the device being placed (≈25% is safe); larger things should be removed as soon as possible; interventional radiology can be contacted for vascular access before elective procedures if necessary

Neck vessels: the relationship of the internal jugular vein (IJV) and common carotid artery (CCA) varies with neck position, head turning, and shoulder movement; the IJV is usually lateral, anterior, and larger than the CCA; the only reliable way to tell them apart is to push down with the USG probe and see which one collapses first (find the trachea with USG, slide down to the thyroid gland and laterally until the vessels are seen, and push to assess compressibility); seeing 2 vessels running together at this level is reliable and ensures safe access even if the view becomes distorted later; arterial blood in hypoxic patients may appear dark, and propofol can make venous blood look arterial; in patients with prior central venous access, the anterior jugular vein (AJV) can be enlarged

Other considerations in the neck: the right subclavian artery (SA) often rises above the clavicle and into the neck, especially when extended, but the left SA does not; the vertebral artery may be fairly anterior in the lower neck as it does not enter the vertebral foramen of the spine until the sixth cervical vertebra (C6); C7 has an empty hole; the most common sites of inappropriate access in the neck are the SA and vertebral artery; depending on patient positioning and setup, blood may not be seen in the hub despite correct access; if the access looks good on USG, the physician should not push further as it can lead to other vessels being punctured (risk for this increases the lower the neck is accessed)

Anterior errors: with intravenous placement, there is a step-off from the needle to the device; the needle must be pushed in until the catheter is in the vessel to ensure access; the single wall technique is now standard; blood in the hub means that only the tip of the needle is in the lumen; the rest of it may still be in the wall, in which case passing a wire may be met with resistance, and pushing past it will dissect the wall; ensure the needle has passed through the anterior wall before passing the wire; using the back end of the wire is dangerous as it is sharp and can perforate vessels; the solution is to approach the vessel until the tip of the needle is on the wall and use a single forceful forward push with a twist to force the wall to release the needle without needing to advance further; under USG guidance, if tissue is seen around the needle tip, this maneuver can be used

Posterior errors: the double puncture technique involves advancing the needle toward or into the posterior wall to get the anterior wall to release; it is safe as long as it is recognized and the needle is withdrawn; the needle should be freely mobile before the wire is passed; changing the angle once in the vessel and seeing or feeling it move ensures that it is not embedded in the back wall; the wire can catch on to nearby valves, curl, and push the needle out; flattening the angle directs the wire to the centerline, where valves are open

Radiographic evaluation of line placement: if uncertain about an access attempt, an x-ray should be ordered; once a device is inserted, there can be serious consequences, and only a surgeon should remove it; arteries and veins cannot be seen on x-ray; the confluence of the brachiocephalic veins is higher in the chest than the aortic arch and forms the superior vena cava (SVC); if the common channel is long, the wire is driven downward; if it is high up, the merging is more horizontal and the wire can cross into the other side of the chest; a wire in the SA will go down into the arch and back up; passing a wire straight down below the diaphragm on the right of the spine ensures correct access to the SVC; the azygos system drains into the SVC above the carina; a wire in the azygos will travel posteriorly and to the left before continuing caudally; such a course should raise suspicion

Device placement: depends on the type of device and duration of use; central venous catheters (CVCs) were found to cause pericardial tamponade and death; when the arms, neck, and chest wall are moved, the CVC moves as well; as it has a fixed length and point of entry, movement leads to these complications; the effect is worse for longer catheters and in the arms; forward motion of the CVC is less of a concern if the device is soft and small, and if the vector of movement is away from the wall; a catheter pointing toward the wall can irritate, kill, or perforate the wall; vesicants can injure the vessel wall and cause thrombosis; a line coming in from the left side has to cross the midline, exerting lateral force into the wall of the SVC when it moves; left-sided lines should be placed deeper to prevent this; catheter tip position is dynamic and can change between radiographs; to maximize function and minimize trauma to the caval wall, longer lines are safer; this is particularly true for dialysis catheters and other permanent lines; the device tip is targeted to sit at or just below the caval-atrial junction, ie, 2 vertebral bodies below the carina

Femoral lines: faster flow and larger vessels are safer; the inferior vena cava (IVC) is long enough that any catheter with a tip near the diaphragm will be off the wall; if there is lateral motion, it should not be left in for long; a femoral line pushing on the lateral wall of the IVC above the junction of the iliac veins is dangerous as every time the groin moves, the line will traumatize the IVC; in particular, this is responsible for IVC stenosis in children; compression can reliably identify vessels in the groin as well

Readings

Abolhassani N, Patel RV. Deflection of a flexible needle during insertion into soft tissue. Conf Proc IEEE Eng Med Biol Soc. 2006;2006:3858-3861. doi:10.1109/IEMBS.2006.259519; Chen SS, Prasad SK. Long saphenous vein and its anatomical variations. Australas J Ultrasound Med. 2009;12(1):28-31. doi:10.1002/j.2205-0140.2009.tb00004.x; Franco-Sadud R, Schnobrich D, Mathews BK, et al. Recommendations on the use of ultrasound guidance for central and peripheral vascular access in adults: A position statement of the Society of Hospital Medicine. J Hosp Med. 2019;14(9):E1-E22. doi:10.12788/jhm.3287; Gonçalves AC, Cavassana S, Chavarette FR, et al. Variation of the penetration effort in an artificial tissue by hypodermic needles. J Healthc Eng. 2020;2020:8822686. Published 2020 Sep 14. doi:10.1155/2020/8822686; Gorgone M, O'Connor TP, Maximous SI. How I Teach: Ultrasound-guided Peripheral Venous Access. ATS Sch. 2022;3(4):598-609. Published 2022 Oct 26. doi:10.34197/ats-scholar.2022-0029HT; Maecken T, Marcon C, Bomas S, et al. Relationship of the internal jugular vein to the common carotid artery: implications for ultrasound-guided vascular access. Eur J Anaesthesiol. 2011;28(5):351-355. doi:10.1097/EJA.0b013e328341a492; Saugel B, Scheeren TWL, Teboul JL. Ultrasound-guided central venous catheter placement: a structured review and recommendations for clinical practice. Crit Care. 2017;21(1):225. Published 2017 Aug 28. doi:10.1186/s13054-017-1814-y; Song IK, Kim EH, Lee JH, et al. Seldinger vs modified Seldinger techniques for ultrasound-guided central venous catheterisation in neonates: a randomised controlled trial. Br J Anaesth. 2018;121(6):1332-1337. doi:10.1016/j.bja.2018.08.008; Taslakian B, Ingber R, Aaltonen E, et al. Interventional radiology suite: a primer for trainees. J Clin Med. 2019;8(9):1347. Published 2019 Aug 30. doi:10.3390/jcm8091347.

Disclosures

For this program, members of the faculty and planning committee reported nothing relevant to disclose.

Acknowledgements

Dr. Miller was recorded at the 62nd Clinical Conference in Pediatric Anesthesiology, held February 16-18, 2024, in Anaheim, CA, and presented by the Pediatric Anesthesiology Foundation and Children's Hospital Los Angeles. For information about upcoming CME activities from this presenter, please visit www.peds-gas.org. Audio Digest thanks the speakers and presenters for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 1.50 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

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Lecture ID:

AN662101

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.