Does central line position matter? Can we use ultrasonography to confirm line position? (2024)

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Introduction

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Suppose you just placed the central line shown above. Does it need to be repositioned?

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I was trained that the tip of the central line must lie in the lower portion of the superior vena cava. If the line was in the right atrium, it would cause cardiac perforation. If the line was too high, then vasopressors would sclerose the vein. At that time we were very interested in mixed venous oxygen saturation and central venous pressure, further mandating placement in the superior vena cava. With newer evidence and changes in our management of sepsis, how should we position central lines now?

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What is the ideal placement of a central line?

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The right atrium is fine

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Traditionally atrial placement was feared due to possible risk of cardiac perforation. However, this problem seems limited to older, stiffer central lines. A review concluded that the risk of cardiac perforation from a catheter in the right atrium is currently an “urban legend” (Pittiruti 2015). Hemodialysis catheters achieve better flow rates in the right atrium, so some nephrology guidelines recommend intentional placement in the atrium. Catheter placement within the right atrium does not appear to increase arrhythmia significantly (Vesely 2003; Torres-Millan 2010).

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The superior vena cava, brachiocephalic veins, and subclavian veins seem OK

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Traditional teaching was that infusion of vasopressors at these sites could cause vascular damage. However, we are now comfortable infusing vasopressors through peripheral veins as well as through midline catheters (which often terminate in the subclavian vein). Thus any large vein is probably fine for vasopressors.

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Observational studies correlate lines placed more peripherally with increased thrombosis among oncology patients receiving permanent indwelling ports for chemotherapy. However, these studies are not applicable to short-term non-tunneled catheters placed in critically ill patients. For example, outpatients are much more active than ICU patients and this could lead to repetitive irritation of the vein.

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It is commonly feared that a left-sided central line with its tip riding against the superior vena cava (as shown above) could eventually puncture the vessel. However, as with cardiac perforation, there is little evidence to support this with modern catheters. Superior vena cava perforation is indeed a complication of central line placement, but these rare events seem to occur during line placement (e.g. due to forcing deep passage of the dilator). Modern case reports describe this as occurring immediately or within 24 hours of catheter insertion, reflecting procedural injury rather than delayed injury from the catheter itself (1). Thus, repositioning a catheter away from the wall of the superior vena cava may be unnecessary.

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Comparison with femoral lines

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Malposition of femoral central venous catheters is virtually unheard of. Why? Because we don't check them. If we routinely obtained an X-ray after every femoral catheter, we would discover that these lines are not always where we intended (for example, one report suggested that 4.5% lie in the lumbar vein; Gocaze 2012). Nonetheless, nothing bad seems to happen (although a hemodialysis catheter in the lumbar vein won't work). Overall this supports the concept that the exact location of central lines may not matter.

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Bottom line on ideal line location?

“There are no conclusive studies on optimal catheter tip positioning.”
– Frykholm et al.Clinical Guidelines on Central Venous Catheterization 2014

There is no clear evidence what the best position is. Although “malpositioning” of central lines is common, this is well tolerated (Pikwer 2008). These lines are placed for a short period of time and usually aren’t used for anything tremendously irritating (i.e. hydrochloric acid, chemotherapy). Line placement in the right atrium, superior vena cava, brachiocephalic veins, and subclavian veins occurs frequently and seems to be safe. There is less evidence to support the safety of lines aberrantly placed in the internal jugular pointing upwards towards the head (example below), so my practice is to avoid this.

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Tolerating unorthodox line position has certain advantages

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Less repositioning or replacement of central lines

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Placing a new central line exposes the patient to all of the risks of central line placement. Repositioning a line is preferable, but unnecessary manipulation of the line could increase the risk of infection. Both maneuvers cause patient discomfort, consume time, and often lead to repeated X-rays.

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Line confirmation solely via ultrasonography

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If we can accept a line tip position anywhere from the subclavian vein to the right atrium, this facilitates replacement of the post-procedure X-ray with ultrasonography.

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Ultrasonographic approach to verifying central line placement

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• [a] Rule out pneumothorax with lung ultrasound.
• [b] Examine the internal jugular veins with ultrasonography (excluding the site of catheter placement, if it was placed in one). This should exclude a misdirected catheter pointing upwards into the head (as shown below; Zanobetti 2013).
• [c] Inject a saline flush into the distal port of the catheter while visualizing the right atrium on echocardiography. Appearance of bubbles within the right atrium proves that the catheter is either within the atrium or the venous system. Although agitation of the saline using a three-way stopco*ck may produce more bubbles, a regular saline flush is easier and produces sufficient bubbles (Gekle 2015).

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Appearance of microbubbles in the heart more than 2 seconds after injection of agitated saline suggests a distal location of the catheter (e.g. within the subclavian vein; Duran-Gehring 2014). This ought to be OK as long as catheter malposition within the internal jugular vein is excluded. An X-ray should be considered however.

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Ultrasonography has important advantages compared to chest X-ray:

• Ultrasonography is faster, allowing immediate use of the catheter in emergent situations.
• Ultrasonography has been proven to have superiorperformance for the detection of pneumothorax, perhaps the most important post-procedural complication.
• Chest X-ray will be fooled by rare anatomic variants (e.g. persistent left superior vena cava), which may cause the line to look like it is overlying the lung or aorta. In these situations, the saline flush test will correctly indicate that the line is within the venous system (Prekker 2010).
• Chest X-ray may be fooled by improperly placed lines which are nonetheless overlying the superior vena cava and thus appear to be correctly placed on a portable radiograph (e.g. this case by ScanCrit blog). In these situations, the saline flush test should to reveal that the line is not in the venous system.

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Overall ultrasonography is probably superior to X-ray at rapidly and definitively answering the two relevant clinical questions (Is there a pneumothorax? Is the catheter in a intrathoracic vein?).

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Currently it remains the norm to obtain a post-procedure X-ray. Eventually this practice may be abandoned, as was the practice of obtaining mandatory daily chest X-rays in every intubated patient. This could save ~500 million dollars every year in the USA (2).

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• The ideal placement of the central line tip is unknown.
• Placement of central lines within the right atrium appears safe, and is specifically recommended by some guidelines for hemodialysis catheters.
• Central lines terminating in the brachiocephalic trunk or subclavian vein are probably fine to use for most critical care applications (other than, for example, measurement of central venous pressure or mixed venous oxygen saturation).
• A combination of lung ultrasonography, internal jugular vein ultrasonography, and cardiac ultrasonography with a microbubble injection usually allows immediate exclusion of pneumothorax and proof that the catheter is in a intrathoracic vein. Ultrasonography may be superior to chest X-ray for confirmation of line placement.

[PLEASE NOTE: This post has been updatedslightly with a short new post adding some details and newer information. The material here is still correct, so start with this post.]

Notes

[2] It is estimated that 3 million central lines are placed annually in the United States, with a chest radiograph costing almost $200. This figure doesn't take into account the number of dollars wasted repositioning or replacing central lines that are probably fine to begin with.

More information

• Bubble testby Mount Sinai Emergency Medicine Ultrasound
• Saul et al. The ultrasound-only central venous catheter placement and confirmation procedure. J Ultrasound Med 2015; 34: 1301-1306.

Image credits: Torso image from https://en.wiktionary.org/wiki/torso