With this technique it is important to keep the

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With this technique, it is important to keep the transducer steady over the center of the vessel. If the needle is misdirected out of the plane (seen as losing the image of the needle), the needle should be withdrawn toward the skin and redirected. Do not redirect the ultrasound beam to find the needle, instead redirect the needle toward the beam . Figure 15.15 Guidewire (arrow) visualized within vein. Note reverberations (*) distal to the wire. Procedural ultrasound 285 Vascular access
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(A) (B) Figure 15.16 Catheter (arrow) visualized within the vein in ( A ) transverse and ( B ) longitudinal views. Figure 15.17 Subxiphoid view of the heart with right atrium (RA), right ventricle (RV), left ventricle (LV), and liver (L) visible. Several mL normal saline is pushed into the central line and a blush of agitated saline (microbubbles) is visible as it enters the right atrium (arrow, center ). The microbubbles then spread throughout the right side of the heart ( right ). This effect occurs almost instantly and lasts just a few seconds. 286 Procedural ultrasound Vascular access
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When visualizing the long axis of the needle and vessel, the entire length of the needle (including the all-important tip) can be visualized ( Figure 15.19 ). For the novice user, it can be challenging to correlate movements of the needle with changes in appearance of the image on the screen. However, it is important to stress that the ultimate goal of ultrasound use is vessel Figure 15.18 Long-axis positioning. Note that the needle and the vessel are both in the plane of the ultrasound beam. Figure 15.19 Long-axis visualization of the needle puncturing the vessel. The arrows point out the highly conductive metal needle with reverberation artifact emanating parallel to it. Procedural ultrasound 287 Vascular access
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cannulation. Thus, one cannot lose sight of the syringe and needle during the procedure. It is easy to focus on the screen and miss a flash of blood, or to focus on the syringe and miss the needle veering dangerously off course on the screen. With practice, it becomes easier to simultaneously focus on the screen and the syringe, just as one focuses on both the road ahead and the rearview mirror when driving a car. It is also quite useful to apply negative pressure on the syringe as soon as the tip of the needle punctures the skin. Creating a slight vacuum using only one hand on the syringe is a useful skill to develop for many procedures involving a needle. As soon as a vessel is punctured, the negative pressure will facilitate the flash. With a bit of practice this sudden pressure change can be felt by the operator, providing an add- itional sensory clue to successful cannulation (in addition to seeing a flash and visualizing tenting of the vessel wall on ultrasound). Scanning tips ³ Tilt probe toward needle tip when using a short-axis approach.
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