Is it in? Well, flush the line

Clinical Scenario: 

You are working in the TCC when an ESRD patient presents with fever and hypotension, RN’s are able to attain a small IV, but knowing the patient will need abx and IVF, you prepare to place a central venous catheter (CVC). Under ultrasound guidance you place a triple lumen catheter.  You aspirate dark red blood and are confident it is venous. The follow up chest xray shows a cvc with an awkward course to the heart. You send off a blood gas, and are setting up to tranduce the line.  While waiting, you wonder is there another method to confirm CVC placement?

Literature Review:
Approximately three million CVC’s are placed every year in the US. Complication rates vary by source but the most commonly cited rate is around 10%, including arterial puncture, hematoma, pneumothorax, chylothorax, arrhythmia and air embolus . The use of ultrasound during CVC placement has reduced the complication rate to around 3%.  (1) In 2010 Liu et al described the novel use of bedside ultrasound (2D) and a saline flush,to confirm catheter placement in the SVC. The method involves flushing 10ml saline throught the most distal CVC port, while performing a cardiac ultrasound either in the subxiphoid or parasternal view. 

Horowitz et al 

Flushing of the saline causes immediate turbulence in the right atrium and ventricle, that is easily viewable on ultrasound.(1) Prekker et al also reported on using this technique with success, adding that saline can be flushed immediately after venous puncture but before the guide wire or CVC is placed. (2) In 2014 Horowitz et al performed a prospective blinded study testing whether flushed saline under cardiac US could accurately confirm femoral line placement.  In their study, all patients had an arterial line and a femoral CVC placed, then a blinded EM physician performed subxyphoid cardiac ultrasound while a provider flushed either the arterial line or venous CVC. The EM physician would either say "venous" or "arterial" based on the presence of a + flush sign (See image) . The study results showed 100% sensitivity and 90.3% specificity. (3) In other words, the presence of +flush test was always associated with venous CVC. There were zero incidences of an arterial flush being identified as venous. However, approx 10% of venous CVC's were incorrectly identified by negative flush test (specificity 90.3%). 

Take home points:
Rapid assessment of CVC placement can be achieved by saline flush and cardiac ultrasound. A +flush sign has been shown to be 100% sensitive for a venous CVC. However more studies are needed at this time as most literature is focused on case series, with only one prospective randomized study. 

Submitted by Louis Jamtgaard, PGY-3 @Lgaard
Faculty Reviewed by Deb Kane

References

1) Liu et al. Evaluation of proper above-the-diaphragm central venous catheter placement: the saline flush test. Am J Emerg Med. 2011 Sep;29(7):842.e1-3. doi: 10.1016/j.ajem.2010.06.025. Epub 2010 Sep 25.

2) Prekker ME Rapid confirmation of central venous catheter placement using an ultrasonographic "Bubble Test".Acad Emerg Med. 2010 Jul;17(7):e85-6. doi: 10.1111/j.1553-2712.2010.00785.x.

3) Horowitz R¹The FLUSH study--flush the line and ultrasound the heart: ultrasonographic confirmation of central femoral venous line placement. Ann Emerg Med. 2014 Jun;63(6):678-83. doi: 10.1016/j.annemergmed.2013.12.020. Epub 2014 Jan 15.