Central venous catheter position – Rapid atrial swirl sign (RASS)

Following internal jugular vein or subclavian vein catheter insertion, the correct positioning of the catheter can be evaluated by using the rapid atrial swirl sign (RASS). The tip of a central venous catheter should be positioned in a central vein between the superior vena cava and atrium.

9 mL of saline with 1 mL air mixture (shaken/agitated) is injected rapidly through the distal port of the central venous line while visualizing the right atrium in the subcostal 4-chamber view.

RV, right ventricle; RA, right atrium; LV, left ventricle; LA, left atrium.

• Immediate air bubbles: If a transient opacification in the right atrium appears immediately (< 2s) following the injection of the mixture the catheter is in the right position in a large central vein.
• Delayed air bubbles: If the opacification is delayed and appears slower (> 2s) the catheter is probably placed at an atypical position in the internal jugular, subclavian, or brachiocephalic vein.
• Absent air bubbles: If the opacification does not appear at all the catheter is probably malpositioned and may be placed in an artery or extravascular. 

RASS: Opacification of the right atrium after injection of agitated saline.

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