Ultrasound G.E.L. – Simplified CVC Confirmation

Originally published on Ultrasound G.E.L. on 7/31/17 – Visit HERE to listen to accompanying PODCAST! Reposted with permission.

Follow Dr. Michael Prats, MD (@PratsEM), Dr. Creagh Bougler, MD (@CreaghB), and Dr. Jacob Avila, MD (@UltrasoundMD) from Ultrasound G.E.L. team!

Simplified point-of-care ultrasound protocol to confirm central venous catheter placement: A prospective study

World Journal of Emergency Medicine – Pubmed Link

Take Home Points

1. A single 5 cc saline push can likely confirm correct line placement when you see flow in the right atrium immediately afterwards. If you don’t see it → could still be okay.

2. This study did not demonstrate statistically significant time difference between ultrasound and chest xray confirmation.

Background

Central venous catheters are a vital tool in the critically ill patient. Traditional teaching after placement of a supradiphragmatic central line is to confirm correct catheter tip location with a chest xray. Point of care ultrasound is now being used to place central venous catheters and also to identify pneumothoracies which are a potential complication of catheter placement. Recently ultrasound has been used to confirm central venous access in lines placed above the diaphragm. The idea is that you already have the ultrasound there from your procedure, so now you just look at the heart, squirt some saline into your line, and confirm that it gets to the right atrium quickly. Some protocol can involves a lot of bells and whistles like finding a three way stop cock, agitating some saline, taking the square root of the volume divided by the body surface area of the patient….okay, I am exaggerating. The fact is that almost all of these protocols are actually pretty simple, but these authors wanted to make it even easier and faster so you have no excuse.

Questions

How accurate is a single view ultrasound protocol for confirming central venous access placement?

Is ultrasound faster than chest xray at confirming central venous access?

Population

Single center, urban, academic level 1 trauma center

Patients in emergency department and intensive care unit

Between January 2012 and May 2015

Inclusion

• getting a supra-diphragmatic central venous catheter

Exclusion

• <18 years old
• Unable to obtain informed consent
• Not presenting between the hours of 8am and 12 am

Who did the scans?

Emergency Medicine resident physicians

Intensive care unit resident physicians

Both stated to be “familiar with cardiac views” but no specific training for this study

Design

Prospective convenience sample

Ultrasound confirmed placement defined as echogenic, turbulent flow in right atria immediately after injection

Accuracy of ultrasound confirmed placement compared to radiology interpreted chest xray

Appropriate positioning defined as CVC tip at or immediately above the right atrium on chest xray

Times between ultrasound completion and chest xray completion compared

Intervention

1. Supradiaphragmatic central venous line was placed
2. Ultrasound performed (see “Scan” below)
3. 5 cc of sterile, non-agitated, normal saline was rapidly pushed through CVC
4. Chest xray performed immediately afterwards (but ultrasound not allowed to delay CXR)

The Scan

1-5 MHz phased array probe used

Parasternal long, apical four chamber, or subcostal views obtained with patient supine

Color or spectral doppler was not utilized (B-mode only)

Here’s how you place a central line with ultrasound

Here’s how you confirm it with ultrasound

Results

78 patients enrolled

• 17% in ED, 83% in ICU
• 43 (55%) in right Internal jugular
• 21 (27%) in left internal jugular
• 9 (12%) in left subclavian
• 5 (%) in right subclavian

Primary Outcomes

Test Characteristics for POCUS in confirmation of correct CVC placement

Sensitivity 86.8% (CI 77.1-93.5)

Specificity 100% (CI 15.8-100.0)

Mean time to completion:

POCUS 27.6 minutes (CI 20.3-35)

Chest xray 37.6 minutes (CI 30.3-45.0)

*Not statistically significant difference p = 0.07

Median time to completion:

POCUS 16 minutes (IQR 10-29)

Chest xray 32 minutes (IQR 19-45)

Other Findings

There were only two malpositioned lines in this study (confirmed on CXR) – coiling in the neck and into contralateral subclavian. No turbulent flow seen in either of these cases.

10 patients had negative ultrasound exam (no turbulent flow) but chest xray confirmed accurate placement.

Limitations

With only two malpositioned lines, it hard to say how reliable the 100% specificity really is. With more malpositioned lines, we may have seen some false positives.

What in the world took so long to do a single view ultrasound? – authors hypothesize that ICU residents not as familiar with ultrasound or may have been “distracted by other tasks”

Robust hospital wide POCUS program at this institution – as usual, the amount of training will affect your results; however, there was no specific training given in this study.

The study sonologists were also the ones who had placed the CVC – could have had confirmation bias based on how the procedure went.

Take Home Points

1. A single 5 cc saline push can likely confirm correct line placement when you see flow in the right atrium immediately afterwards. If you don’t see it → could still be okay.

2. This study did not demonstrate statistically significant time difference between ultrasound and chest xray confirmation.

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