Page 152 - Basic Monitoring in Canine and Feline Emergency Patients

Table 7.2. A comparison of the transverse and longitudinal techniques for ultrasound-guided vascular access.

VetBooks.ir Vessel identification Transverse plane Longitudinal plane
Due to limited beam footprint, harder to align
Easier to identify vessel
US beam with vasculature
Vessels appear as anechoic circular Vessels appear as anechoic stripes with
structures hyperechoic walls (similar to an equal
sign)
Veins may collapse with pressure Veins will easily collapse with pressure
Arteries may have visible pulsation of blood Arteries may have visible blood pulsation
Arteries are more difficult to collapse Arteries are more difficult to collapse
Needle identification Appears as hyperechoic dot Appears as hyperechoic tube
Needle makes a bullseye sign when inside Easy to see needle profile within the vessel
the vessel lumen (hyperechoic tube within the vessel)
Can be hard to judge depth of needle until Easy to judge depth of needle insertion
inside vessel
Relatively easy to keep needle and vessel Hard to keep needle in plane with vessel
in same plane
Learning curve Larger probe footprint Smaller probe footprint
Easier to stay in plane with vessel Harder to stay in plane with vessel
Considered easier to learn Considered more technically challenging for
novice
Depth of structures Harder to adjust depth in real time Easy to adjust depth of approach in real time
Easier to utilize in deeper structures such Easier to utilize for superficial structures
as when there is neck pathology (edema, and use when normal neck anatomy
cellulitis, hematomas)
Harder to use when neck anatomy normal Easier to use when neck anatomy is normal
(structures too superficial)
US, ultrasound.

plane. To image the desired vessel, the operator For transverse orientation venipuncture, the opera-
should place the US probe with the notch/indica- tor should alter the image depth and focus so that the
tor pointed distally toward the point of catheter vessel is in the center of the US screen and appears as
insertion. When imaged in transverse the vessels an anechoic circle (Fig. 7.9A). The needle or intro-
appear as anechoic circles (Fig. 7.9A). When in ducer catheter should be held with the dominant
imaged in a longitudinal plane, the vessels appear hand and introduced through the skin 1–2 cm rostral
as parallel lines (similar to an equal sign) made up to the US probe and perpendicular to the indicator/
of the hyperechoic vessel walls and anechoic vas- notch on the linear transducer. The angle that the
cular lumen (Fig. 7.9B). To differentiate between needle or introducer catheter should be inserted into
vein and artery, the operator may look for pulsa- the skin is dependent upon the depth of the vessel
tion of the vessel (consistent with being an artery). and distance of insertion rostral to the US transducer
The operator may also observe that a vein will probe (for arterial catheterizations, the operator may
more easily collapse with pressure applied to it need a steeper angle of approach than a vein).
than an artery. Once the needle or introducer catheter are
4. Once the vessel is identified, the operator deter- inserted into the skin, the US probe can be moved
mines if he would like to catheterize in a trans- slightly rostrally to see the hyperechoic needle as it
verse or longitudinal plane. See Table 7.2 for the inserts into the anechoic vessel. Seeing the hypere-
pros and cons of each approach and below for a choic tip of the needle within the anechoic vessel
description. has been described as a ‘bullseye effect’ in the

144 D.M. Hundley