Ultrasound-guided peripheral venous cannulation uses real-time (dynamic) ultrasound to guide venipuncture and a catheter-over-needle technique to place a peripheral intravenous catheter (cannula), usually into a deep, nonpalpable vein of the upper arm.
Ultrasound guidance can facilitate peripheral vein catheterization, especially of deep, nonpalpable veins. This topic will focus on the use of ultrasonography to guide IV placement. The actual procedure for starting an IV is the same as when ultrasonography is not used and is described in detail in How To Do Peripheral Vein Cannulation.
Indications for US-Guided Peripheral Vein Cannulation
Difficulty in identifying suitable peripheral veins for cannulation in patients who do not otherwise require a central venous catheter
Contraindications to US-Guided Peripheral Vein Cannulation
Absolute contraindications
None
Relative contraindications
Untrained or inexperienced ultrasound operator
There are some relative contraindications to using certain sites for IV placement, but once an appropriate site is identified, there are no contraindications to use of ultrasonography.
Complications of US-Guided Peripheral Vein Cannulation
None
There are some complications of IV placement, but these are unrelated to use of ultrasonography.
Equipment for US-Guided Peripheral Vein Cannulation
In addition to standard equipment needed to start an IV, operators will need the following:
Ultrasound machine with high frequency (eg, 7.5 MHz or higher), linear array probe (transducer)
Transparent probe cover (eg, sterile dressing, single-use probe cover)
Sterile, water-based lubricant, single-use packet (recommended over multi-use bottle of ultrasound gel)
Additional Considerations for US-Guided Peripheral Vein Cannulation
There are, in general, 2 views used in ultrasound-guided peripheral venous cannulation. The short-axis (transverse, cross-sectional) view usually is preferred because it is easy to obtain and is the best view for identifying veins and arteries and their orientation to each other. However, the transverse view shows the needle only in cross-section (hyperechoic [white] dot), and the needle tip can be distinguished only by the appearance and disappearance of the white dot as the imaging plane traverses past needle tip.
The long-axis (longitudinal, in-plane) ultrasound view is technically more difficult to obtain (must keep probe, vein, and needle in one plane), but the entire needle (including the tip) is imaged continuously, which ensures accurate intraluminal placement. Increasing narrowness of peripheral veins increases the difficulty of obtaining the longitudinal view.
Relevant Anatomy for US-Guided Peripheral Vein Cannulation
Peripheral veins may be superficial or deep. Typically, ultrasonographic guidance is needed when superficial veins are not visible or palpable. Typical targets for ultrasound-guided IV placement include
Deep forearm veins
The brachial vein (there are typically 2 brachial veins that lie on either side of the brachial artery in the medial upper arm)
Positioning for US-Guided Peripheral Vein Cannulation
Rest the body part being cannulated on a comfortable surface, and adjust the position to optimally expose the site (eg, to cannulate a brachial vein or the basilic vein, abduct and externally rotate the arm to expose the medial upper arm).
Step-by-Step Description of US-Guided Peripheral Vein Cannulation
The procedure for preparing the site and inserting and securing the IV catheter is the same as when ultrasonographic guidance is not used and is not described here.
Prepare the ultrasonography device and identify a candidate vein
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.
Insert the peripheral venous catheter using ultrasound guidance
Prepare your IV equipment and the insertion site 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 just distal to 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.
Aftercare for US-Guided Peripheral Vein Cannulation
Replace or remove catheters within 72 hours of placement.
Warnings and Common Errors for US-Guided Peripheral Vein Cannulation
Always maintain ultrasound visualization of the needle tip during insertion.
A needle can appear to be within the lumen of the vein without actually puncturing the vein. Continue to advance the catheter within the vein under ultrasound guidance until a pop is felt or a flash of blood is seen in the catheter chamber.
Tips and Tricks for US-Guided Peripheral Vein Cannulation
Copious gel or lubricant is not necessary and can obscure the probe center marker.
Gel from single-use packets is recommended over bottled ultrasound gel.
