critical care medicine
How To Do Peripheral Vein Cannulation, Ultrasound Guided
Step by Step Description of US Guided Peripheral Vein Cannulation
The Step-by-Step Description of Procedure is the same as when ultrasonographic guidance is not used and is not described here. Check that the ultrasound machine is configured and functioning correctly: Set the machine to 2-D mode or B mode and ready to acquire appropriate imaging documentation as per institution protocols. Ensure that the screen image correlates with the spatial orientation of the probe as you are holding and moving it. This almost always means orienting the probe marker to the left of the operator, not patient. The side-mark on the probe corresponds to the marker dot/symbol on the ultrasound screen. Adjust the screen settings and probe position if needed to attain an accurate left-right orientation. Place a tourniquet proximal to a prospective insertion site and do a preliminary, nonsterile ultrasound inspection to identify a suitable vein. A preferred vein segment is straight, wide, relatively close to the surface, and distinct from any nearby artery. Use a transverse (cross-sectional, short-axis) view, and adjust the gain on the console so that the blood vessels are anechoic (appear black on the ultrasound screen) and the surrounding tissues are gray. Set maximum depth at the surface of a bone, so as to view the entire field. Slowly slide the probe from proximal to distal along the veins, and adjust/rotate the probe so that the vein is under the center of the probe. Adjust maximum depth to roughly twice the distance from the surface to the candidate vein. After identifying a suitable cannulation site, remove the tourniquet. Generally, veins are larger, thin-walled, and ovoid (rather than thick-walled and round) and are more easily compressed (ie, by pressing with the probe) than arteries. Press lightly to avoid distorting or hiding the venous lumen. Venous thrombosis disqualifies the vein for cannulation; it may appear as an echogenicity (gray irregularity) in the lumen but often is diagnosed because the thrombosed vein is incompressible. Step-by-Step Description of Procedure as described above. Reapply the tourniquet proximal to the anticipated needle-insertion point. Two layers of gel are used. Apply one layer to the probe footprint and cover it with a sterile transparent dressing—tightly applied to eliminate air bubbles underneath. Then apply sterile lubricant to the on the outside of the covered probe. Begin with the transverse (short-axis) view: Place the probe footprint on the skin, transverse to the vein. Select a segment of the vein as the target entry site and center this image on the ultrasound screen, which centers the vein under the probe. Move the probe to a preliminary position justdistalto the target vein entrance site. Insert the angiocatheter, with the needle bevel facing up, into the skin. Very slightly tilt the probe, thereby fanning the imaging plane toward the angiocatheter to identify its tip. Once the tip is identified, move the probe proximally a couple of millimeters (closer to the intended target entrance site on the vein). Keep the probe still and advance the angiocatheter while watching the screen until the bright white dot representing the tip of angiocatheter again appears. Repeat the process to advance the angiocatheter. You may prefer to maintain the transverse (cross-section) view throughout the cannulation. Slightly tilt the probe fore-and-aft as you advance the angiocatheter to continually reidentify the needle tip (disappearing/reappearing white dot) as it approaches the vein. Or, you may prefer to switch to the longitudinal (long-axis) view to see the angiocatheter lengthwise as it approaches and enters the vein. Turn the probe 90 degrees and maintain full longitudinal (in-plane) images of both the angiocatheter and the vein. As the angiocatheter meets the vein, you should see the needle first indent the superficial wall and then pop through the wall to enter the lumen. A simultaneous flash of dark red blood in the barrel of the syringe confirms intraluminal placement. Follow standard procedures for advancing the catheter, ensuring intravascular placement, wiping away ultrasound gel before securing the catheter, and beginning any infusion. 