What is the ideal placement of a central line?
The right atrium is fine
The superior vena cava, brachiocephalic veins, and subclavian veins seem OK
Comparison with femoral lines
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
Tolerating unorthodox line position has certain advantages
Less repositioning or replacement of central lines
Line confirmation solely via ultrasonography
- [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 stopcock may produce more bubbles, a regular saline flush is easier and produces sufficient bubbles (Gekle 2015).
- 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.
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?).
- 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.
- Bubble test by 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.
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