1. Pediatrics
Kiyetta Alade, M.D., RDMS
Assistant Professor
Director, Pediatric Emergency Ultrasound
Section of Emergency Medicine
Department of Pediatrics
Baylor College of Medicine
Texas Children’s Hospital
Ultrasound Fundamentals
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Pediatrics
Goals and Objectives
•Describe and operate the basic functions of the
ultrasound machine
•Discuss the common pitfalls with ultrasound-guided
vascular access
•Integrate the “landmark technique” and dynamic
ultrasound when performing central venous
cannulation
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Gain
•Gain: Adjusts the intensity of returned echoes
shown on display
‐Increasing gain makes picture brighter
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Ultrasound Fundamentals
•Depth: Can be adjusted to ensure entire structure
of interest is on the screen
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Ultrasound Fundamentals
•Axial resolution: US machines ability to differentiate
objects in plane parallel to traveling wave
‐Increase frequency or decrease wavelength to
improve
•Lateral resolution: US machine’s ability to differentiate
objects in plane perpendicular to traveling wave
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Pediatrics
Resolution
•Low resolution (2-4 MHz)
‐Lower frequency
‐Deeper penetration
•High resolution (8-14 MHz)
‐High frequency
‐Poor penetration (best to image superficial structures)
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Probe Selection
•High frequency
‐Linear Array
•Low frequency
‐Curvilinear
‐Phased array
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Ultrasound Fundamentals
•Every probe has raised marker to correlate with the
side of the screen with some type of identifier (dot,
logo)
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Pediatrics
User Orientation
•Objects near the top of the screen correlate with
structures CLOSEST to the probe on the patient
•Objects near the bottom of the screen correlate
with structures furthest away from the probe on the
patient
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Pediatrics
Ultrasound Fundamentals
•D (doppler) mode: Senses the
movement of reflected US waves
toward and away from the probe by
color change or sound
‐Color represents flow toward or away from
probe… NOT arterial vs venous flow
‐(Blue Away Red Toward)
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Pediatrics
Procedural
•Static ultrasound
locates structure of
interest but not used to
guide procedure
‐LP
‐Thoracentesis
‐Paracentesis
‐I&D
•Dynamic ultrasound is
used to locate structure
of interest AND allow
direct visualization of
procedure in real time
‐Vascular access
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Pediatrics
The Agency for Health Care
Research and Quality (AHRQ)
•Supports the use of ultrasound guidance for the
placement of central venous catheters as a way to
improve success rates, reduce number of attempts
and reduce complications associated with their
placement
(AHRQ) AfHCRaQ. Making Health Care Safer. A Critical Analysis of Patient Safety
Practices. July 20, 2001.
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Probe Selection
•4-10 MHz frequency
•Linear Array
•Small to medium
footprint
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Vessel Selection
•Must be able to differentiate arteries from
veins
‐Compression (veins more compressible)
‐Distal Augmentation
‐Color flow (look for pulsations)
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Pediatrics
Screening Ultrasound
•Before preparing to cannulate a vessel you should
‐Screen the area of interest for a target
‐Evaluate the vessel size
‐Evaluate vessel compressibility
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Pediatrics
Screening Ultrasound
•Before preparing to cannulate a vessel you should
‐Ensure you are targeting the correct vessel
‐Measure the depth
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Transverse Approach
•With a transverse approach to vessel puncture you
should orient the probe with the marker to YOUR
left and the US screen in FRONT of you
‐This allows for easy manipulation
‐If on the screen the needle looks like it is to the right of the
vessel then you change direction more to the left
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Transverse Approach
•Locate target vessel in transverse plane
•Pucture skin adjacent to probe, locate needle
tip and follow it until it enters vessel
‐This requires you to move the probe as you advance the
needle (following the needle tip)
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Transverse Approach
•Able to visualize surrounding structures
•Have to locate needle tip through motion or comet
artifact
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Internal Jugular
•Position the ultrasound screen in front of you
•Orient the ultrasound probe with marker to YOUR
left
‐This allows you to move the probe in the SAME direction as
visualized on the screen
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Internal Jugular Central Line
•US guided central line placement still with
complications (fewer than landmark technique)
‐Puncture of posterior wall of vein
‐Cannulation of carotid artery
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Femoral Vein
•Complete overlap of femoral artery over
vein 4 cm below inguinal ligament about
half of the time
•At least 50% overlap of femoral artery
over vein in same location
Hughes, et al. Brit J Anes. Ultrasonography of the femoral vessel in the groin: implications
for vascular access. 2000:84(5):668-669
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Femoral Vein
•Position the ultrasound screen in front of you
•Orient the ultrasound probe with marker to YOUR
left
‐This allows you to move the probe in the SAME direction as
visualized on the screen
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Femoral Vein
•Single operator:
‐Hold probe with hand on outside of leg
•Left hand right leg
•Right hand left leg
‐Use free hand to access vein using Seldinger technique
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Femoral Vein
•Locate target vessel in transverse plane
•Measure depth of vessel
•Puncture skin at a ~ 30° angle (too sharp will inhibit
passing of guidewire)
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Remember
•ALWAYS
‐find potential puncture sight using landmark technique before
evaluating with US
•If time allows
‐Screen BOTH sides to determine the best site for needle
puncture
Remember high frequency give you better resolution (images) but has poor penetrationinto the tissue (need to focus on superficial structures).
If you apply enough pressure you WILL compress an artery (but less than the nearby vein)
Remember: The carotid is medial to the IJ. The probe marker is to YOUR left for venous access. If this is the right side of the neck then the carotid will be the small round structure slightly left and inferior to the large round IJ
Why is this important? This is important because if you are too far below the inguinal ligament the femoral artery will likely partially overlap the vein in at least half of the population