Central venous catheter placement is an essential procedure in emergency medicine, with the internal jugular vein (IJV) the most commonly accessed site. However, in certain situations such as abnormal neck anatomy, presence of a cervical collar, IJV thrombosis, or active cardiopulmonary resuscitation, the subclavian vein (SCV) may be a better option.^1,2 Also, because of the SCV’s fixed position under the clavicle, size variations are less common (unlike the often collapsed IJV noted in patients with severe dehydration or sepsis). Cannulation of the SCV may also improve patient comfort while reducing rates of infection and thrombosis when compared to the IJV and femoral vein.^3,4

Classically, landmark-based SCV cannulation is performed below the clavicle. In contrast, ultrasound guidance allows cannulation to occur both via the infraclavicular (at the junction of the axillary vein and SCV) and supraclavicular (where the SCV meets the IJV to form the brachiocephalic vein) approaches. When compared to landmark techniques, ultrasound guidance reduces the rates of arterial puncture, pneumothorax, brachial plexus injury, and hematoma formation.^5–8 With the supraclavicular approach, the SCV is often shallow and easily visualized as compared to the infraclavicular approach, making for an ideal site for central venous cannulation.^9,10

Our two-part series will discuss both the supraclavicular and infraclavicular approaches to ultrasound-guided SCV cannulation. Before attempting either of these more challenging ultrasound-guided SCV cannulations, we recommend novice sonographers obtain comfort with both the ultrasound-guided IJV or femoral vein cannulation as well as attain proficiency with in-plane needling technique.

With the supraclavicular approach, the SCV is often shallow and easily visualized as compared to the infraclavicular approach, making for an ideal site for central venous cannulation.

Anatomy

The SCV runs from lateral to medial under the clavicle, just anterior to the subclavian artery (SCA). As it approaches the heart, the SCV is joined by the IJV, forming the brachiocephalic vein. The supraclavicular approach attempts to cannulate the portion of the SCV just lateral to the clavicular head of the sternocleidomastoid muscle.⁸ The right SCV is preferred to the left since it forms a straighter angle with the IJV, offering a shorter distance for wire passage into the superior vena cava, avoiding proximity to the thoracic duct, which drains into the left SCV (see Figure 1).

Procedure

Set Up

As with all central venous access, standard sterile technique should be followed to minimize infection (sterile ultrasound probe cover and gel, drapes, etc.). Place the patient in a supine position and the ultrasound machine contralateral to the patient (eg, left side of the patient for right SCV cannulation) to allow for visualization of the screen and needle in a similar line of sight (see Figure 2).

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Figure 1. Surface anatomy of the right subclavian vein (SCV). Note the confluence of the SCV and internal jugular vein (IJV) to form the brachiocephalic vein.

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Figure 2. For a right SCV cannulation, the operator has placed the ultrasound system on the contralateral side. This ergonomic position allows for direct view of the ultrasound screen and site of needle entry without change in visual axis.

Survey Scan

Place a high-frequency linear transducer (eg, 13–6 MHz) on the lateral neck just above the clavicle to locate the IJV and carotid artery (see Figure 3A). Slowly trace the IJV caudally (toward the chest) into the supraclavicular fossa until the probe abuts the clavicle (see Figure 3B). While visualizing the most promximal/caudal aspect of the IJV, angle the probe anteriorly to visualize the confluence of the IJV and SCV (see Figure 4). At this proximal location, the SCV lies anterior to the SCA, and the operator should dynamically fan the probe from a posterior to anterior position to identify both vessels.

A clear view of the often shallow and large SCV can make for a relatively simple access site. Unfortunately, variation in vascular anatomy always exists, and in some patients, clear SCV visualization can be difficult.

Ultrasound-Guided SCV Cannulation

After clear ultrasonographic visualization of the SCV is obtained, place a small skin wheal just lateral to the ultrasound transducer. Unlike the classic ultrasound-guided IJV cannulation, SCV cannulation will require the use of in-plane technique (see Figure 5).

Enter the skin just lateral to the transducer at an angle that will intersect the SCV at the desired location (this angle will depend on patient body habitus and probe size). Slowly advance the needle under ultrasound guidance, gently aspirating the syringe for flashback and ensuring that the needle tip is clearly visualized as it transverses soft tissue and finally enters the SCV. Confirmation of venous access is performed in a similar manner to other central venous cannulation sites (checking for nonpulsatile dark blood, ultrasound-guided visualization of the guidewire, etc.). A postprocedure chest radiograph will determine the location of the catheter tip and identify most pneumothoraces.

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Figure 3. (A) In a transverse plane on the neck, locate the thyroid, IJV, and carotid artery (CA) deep to the sternocleidomastoid (SCM) muscle. (B) Slide the transducer down the IJV into the supraclavicular fossa until the subclavian artery (SCA) is noted.

Figure 4. Angle the probe anteriorly (solid yellow arrow) to visualize the SCV as it joins the brachiocephalic vein (BCV). The external jugular vein (EJV) may be seen joining the SCV at this location.

Figure 5. An in-plane technique will be used with the needle entering the skin just lateral to the ultrasound transducer. The operator should use the nondominant hand to stabilize the transducer on the patient’s neck. SCV; IJV; BCV.

Summary

The supraclavicular approach to ultrasound-guided SCV cannulation may be ideal in certain scenarios and safer than the landmark-based SCV central line placement.^2,3,11 We recommend this access site as an alternative for providers comfortable in procedures requiring in-plane needle visualization. Using a pragmatic ultrasound-based approach to central venous cannulation that relies on visualized patient anatomy, operator skill, and the clinical scenario allows emergency physicians to become adept at an often challenging aspect of emergency care.

Dr. Lieu and Dr. River are ultrasound fellows at Highland Hospital, a member of Alameda Health System, in Oakland, California.

Dr. Mantuani is assistant director of emergency ultrasound at Highland Hospital.

Dr. Nagdev is director of emergency ultrasound at Highland Hospital and assistant clinical professor (volunteer) of emergency medicine at the University of California, San Francisco.

References

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