Return of the king: Can ultrasound revive the subclavian line?

Central lines are typically placed in either the internal jugular, femoral, or subclavian vein.

The femoral site is useful, particularly in emergent circumstances (as it is usually accessible even in crashing patients, and generally safe and feasible even without ultrasound). However, it is—probably—associated with a higher risk of line infection. Conversely, the IJ is almost always a piece of cake under ultrasound guidance, and is—maybe—fairly clean, which has led it to be the site of choice in most teaching facilities.

But what happened to the subclavian?

Ultrasound killed the subclavian line…

The wane of the subclavian and coincident ascendancy of the IJ were both driven by the increasing prevalence of ultrasound. Once upon a time, central lines were placed “blind,” purely using anatomic landmarks. As bedside ultrasound became increasingly available, and evidence showed it to generally increase success and reduce complications, ultrasound-guided line placement has gradually become the standard of care. Landmark-guided placement is not extinct, but is certainly going the way of the manual gearbox.

This has shifted the balance of power. The IJ is such a chip shot using ultrasound that it’s almost too easy, while traditional wisdom dictates that subclavians cannot be placed using ultrasound.

This is because the standard placement uses the clavicle itself as a landmark, the needle slipping just underneath the bone to access the vein.

The site of traditional subclavian line placement, directly beneath the clavicle itself (as demonstrated by Mr. Badpaint).

This placement offers the most reliable physical landmarks, steering clear of the artery and the underlying lung. However, the ultrasound cannot be used here, because the site is completely occluded by bone. Sound waves cannot penetrate bone.

… and ultrasound can save it

The solution is simple. By following the vein out laterally, you will find that it sweeps down, curving inferiorly and clearing the clavicle. At this location, ultrasound can see it easily.

The lateral site for ultrasound-guided line placement.

(Formally, at this point, an anatomist would probably consider this the axillary vein.  Call it what you will.)

From a technical perspective, this is not the easiest line, and perhaps a poor choice for novices (e.g. residents on their first few lines). However, it is not rocket science. The challenges:

  • It is fairly deep, which can make good visualization difficult. However, it is not dramatically deeper than a femoral line.
  • The lung can closely underly the vein, making it possible to penetrate the vessel and cause a pneumothorax. However, as long as visualization is good, cautious placement without backwalling should be possible, and by exploring with ultrasound you can often identify a point with a good margin of safety between vessel and pleura.
  • The vein is sometimes small-caliber and hard to identify. Trendelenburg is helpful, or conscious patients can Valsalva to distend the vein. Color Doppler can help confirm vessels as well.
  • Sometimes, you simply can’t see very much. Of course, sometimes the landmarks fail as well. The difference is that if your ultrasound view is poor, you’ll know before you break the skin, and can simply move to a different site.

On the other hand, there are also some profound advantages to the lateral, ultrasound-guided subclavian line.

It is clean

The best-known benefit to the subclavian site has always been sterility. The literature has consistently shown subclavian lines to develop fewer line infections than alternate sites.

The reason can be appreciated by anyone who spends some time in the ICU and watches the fate of lines after several days of dwell time. Femoral lines sit deep in wet, moist folds of skin and are bathed in urine and stool. IJs are surrounded by facial hair, dribbled with spittle and vomit, and their dressings never, ever fully adhere.

But subclavians? They live in the center of the chest, far from any sources of contamination. They are easily prepped and cleaned, and permit a flat, perfect, well-adhered and easily-maintained dressing. They are lovely.

They are elegant

Femoral lines require navigating past a pannus, sometimes involving awkward taping and leg manipulation. IJ lines are even less fun. Simply reaching the head of the bed in an ICU (never mind positioning a table nearby) can be difficult, requiring reconfiguration of the entire room. Once you’re there, the procedure occurs “diagonally,” the entire activity taking place half-sideways in the angle formed by the neck and shoulder. It is characterized by awkwardness and sadness and is never satisfying.

On the other hand, subclavians are a pleasure. The side of the bed is easily reached, and the ultrasound positioned just as easily directly across. The procedure takes place on a flat surface, orthogonal to your body. It is comfortable, elegant, and ergonomic.

They are safe, even in coagulopathy

The argument against subclavians has always been the risk of mechanical complications during placement. Ultrasound dramatically reduces this. Both the lung and the adjacent artery can be visualized and avoided.

Blind subclavians are considered a “non-compressible” site, and therefore contraindicated in patients at high-risk for bleeding. Although data on this is scant, I believe the ultrasound-guided subclavian is an exception. By moving laterally and avoiding the clavicle, it becomes possible to apply direct pressure to the puncture site. This can be proven by a simple test: using the ultrasound probe, apply pressure until the vein (and even the artery if you’d like) visibly collapses. You can easily demonstrate the ability to completely occlude the vessels here.

To me, this makes it arguably the site of choice even in thrombocytopenic, coagulopathic patients. Femoral punctures are compressible, but overpenetration can cause retroperitoneal hemorrhage which can be life-threatening. IJs are compressible, but a hematoma there could theoretically compromise the airway in a non-intubated patient. The lateral subclavian is easily compressible, and bleeding here is usually benign.

Hail to the king

The death of the subclavian line was heralded too soon. There are still clinicians uttering the notion that “you can’t use the ultrasound for subclavians.” In reality, it’s not only possible, it’s so straightforward that you’ll need to look for reasons not to do it.

The ultrasound-guided subclavian is my go-to site. It is clean, elegant, safe, and satisfying. It is the king of lines. Let’s bring it back.

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