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 ultrasound to guide IV placement. The actual procedure for starting an IV is the same as when ultrasound is not used and is described in detail in How To Insert a Peripheral Intravenous Catheter.
Indications
Difficulty in identifying suitable peripheral veins for cannulation in patients who do not otherwise require a central venous catheter
Contraindications
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 ultrasound.
Complications
Complications are uncommon and include:
Local infection
Venous thrombophlebitis
These are the same complications of IV placement (without ultrasound), but these are unrelated to use of ultrasound.
Other complications include:
Extravasation of infused fluids into surrounding tissues
Arterial puncture
Hematoma or bleeding
Damage to the vein
Nerve damage
Catheter embolism
Equipment
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
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
Peripheral veins may be superficial or deep. Typically, ultrasound 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
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 Procedure
The procedure for preparing the site and inserting and securing the IV catheter is the same as when ultrasound guidance is not used and is not described here.
Prepare the ultrasound device and identify a candidate vein
Check that the ultrasound machine is configured and functioning correctly: Set the machine to 2-dimensional mode or B mode and ready it 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. To achieve this correlation 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 is a contraindication for cannulating the thrombosed vein; thrombosis may appear as an echogenic gray irregularity (rather than black) in the lumen. 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 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.
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.
Alternatively, 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, the needle should first indent the superficial wall and then pop through the wall to enter the lumen. A simultaneous flash of dark red blood will appear in the flash chamber of the angiocatheter and confirms intraluminal placement of the tip of the needle.
Advance the needle an additional 1 to 2 mm, to ensure that the tip of the catheter also has entered the vein. This step is done because the needle tip slightly precedes the catheter tip.
Hold the needle steady and slide the entire length of the catheter over the needle and into the vein. The catheter should slide easily and painlessly. Remove the needle.
If resistance or pain occurs, assume that the catheter is not in the vein. If you can no longer visualize the angiocatheter within the lumen of the vein, you will need to stop the attempt and start over at a new site.
Once the catheter is successfully placed, withdraw any blood needed for laboratory testing, remove the tourniquet, place some gauze underneath the hub, apply fingertip pressure to the skin proximal to the catheter tip (to compress the vein and limit blood loss from the hub), and connect the IV infusion or saline lock.
Begin the IV infusion/establish the saline lock
Attach the end of the IV tubing or the saline lock to the catheter hub.
Begin the infusion or flush the saline lock (inject about 5 mL of saline in rapid, small pulses). Fluid should flow freely.
If fluid extravasates or does not flow freely, remove the catheter, apply a dressing over the area with gentle pressure, and insert a new catheter at another site.
Dress the site
Wipe all blood and fluid from the site, being careful not to disturb the catheter.
Cover the catheter with a transparent occlusive dressing.
Loop the IV tubing (or saline lock tubing) and tape it to the skin away from the IV insertion site, to help prevent accidental traction on the tubing from dislodging the catheter.
Write the date and time of IV cannulation on the dressing.
Apply an immobilization board as necessary.
Aftercare
Replace or remove catheters within 72 hours of placement.
Warnings and Common Errors
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
Copious gel or lubricant is not necessary and can obscure the probe center marker.
Sterile water-based lubricant, single-use packet (recommended over multi-use bottle of ultrasound gel) 1
Reference
1. Guideline for Ultrasound Transducer Cleaning and Disinfection. American College of Emergency Physicians. Approved June 2018; Revised April 2021. Accessed April 2025.
