Pediatric emergency medicine trisk 4512 4512
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Prior to performing the procedure, the intended target vein should be identified
and confirmed first in the transverse plane and then in the longitudinal plane. On
ultrasound, veins are characterized by their easy compressibility, color flow, and
Doppler waveforms. Placing gentle pressure on the probe, the walls of vein
should collapse. In contrast, arteries will pulsate and the walls of the arteries will
resist collapsing when compressed ( Videos 131.21 and 131.22 ). Both veins
and arteries have characteristic patterns when assessed with color Doppler (
Video 131.23 ).
Once the vein is identified, the depth to the center of the vein should be
measured. When the needle is inserted into the skin, it is traveling along the
hypotenuse of a right triangle, and the distance it must traverse before hitting the
vein should be calculated.
In the static approach, once the vasculature and surrounding anatomy are
imaged, the position of the vein should be marked on the skin at two points along
the path of the vessel. The ultrasound probe is then set aside and the procedure
continues using the landmarks identified with ultrasound, but without active
ultrasound assistance. This method does improve success rates, although
complications are reduced further when using dynamic ultrasound.
The dynamic method uses ultrasound in real time to visualize the needle
puncturing the vein. It is important that the ultrasound machine be positioned in
front of the proceduralist, making direct visualization possible. The transducer
marker should face to the left, the same direction as the marker on the screen.
This is critical when redirecting the needle; as the needle is moved toward the left
of the probe, it moves toward the left side of the screen.
