How To Do Peripheral Vein Cannulation, Ultrasound-Guided

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

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

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.