Central venous catheters (CVCs) are widely used in the resuscitation and treatment of critically ill and injured patients.  Standard practice necessitates verification of line placement when inserted above the diaphragm.  This has traditionally been accomplished in most institutions by use of post-insertion chest radiography, which will both identify the tip of the catheter at the cavoatrial junction and rule out pneumothorax ipsilateral to the insertion site.  However, portable imaging is not rapidly available at all institutions, and other care may preclude obtaining immediate imaging studies.  Care in resource poor and mobile settings (e.g. helicopter transport) does not permit radiography for confirmation.  Additionally, supine chest x-ray has been shown to be inferior to ultrasonography in ruling out pneumothorax [1, 2].  Point of care ultrasonography (POCUS) can be utilized in these situations to facilitate rapid confirmation and use of CVCs.  This technique has been studied previously, going back nearly a decade [3, 4], yet has not been widely adopted by physicians.  We outline this technique to permit the use of POCUS to confirm line placement.

 The Technique

In addition to the standard kit used for CVC placement, the only additional equipment necessary is a 3-way stopcock to prepare agitated saline in a 10 cc syringe.

 Once the line has been placed, secured, and dressed using standard techniques, the operator switches to the phased  array probe on the ultrasound machine.  A standard sub-xyphoid view is used to image the heart, ensuring the superior vena cava (SVC), right atrium (RA), ventricle (RV), and tricuspid valve  (TV) are seen along the same axis.  The catheter tip can be seen as a hyperechoic structure at the cavoatrial junction, with streak artifact extending beyond the tip into the far field (Figure 1).  After obtaining this view, a volume (5-10 cc) of agitated sterile saline is injected into the distal (e.g. brown) port of the CVC rapidly while the ultrasound view is obtained.  The agitated saline provides contrast and should be seen rapidly flowing from the SVC, into the RA and the RV (Video 1).

Once echocardiography has confirmed placement, attention can be turned to evaluation for pneumothorax.  Using a high-frequency linear probe, the ipsilateral lung can be scanned anteriorly to identify lung sliding, absence of a lung point, and the presence of a lung pulse (for left-sided lines) using standard techniques (Videos 2-3).  M-mode can also be used to identify the presence of the “seashore sign”.

Discussion

POCUS has the benefit of being rapid, cost effective, and permits immediate use of the CVC.  It requires no additional equipment or training beyond basic ultrasonographic skills.  As ultrasound is increasingly being taught in medical schools and residencies, and has become adopted as a critical skill in surgery, emergency medicine, and critical care, the techniques needed to use POCUS for CVC confirmation should not be unfamiliar to those placing these lines.

References 

1. Dulchavsky SA, Schwarz KL, Kirkpatrick AW, et al. Prospective evaluation of thoracic ultrasound in the detection of pneumothorax. J Trauma 2001; 50:201-205.

2. Wilkerson RG, Stone MB. Sensitivity of bedside ultrasound and supine anteroposterior chest radiographs for the identification of pneumotho- rax after blunt trauma. Acad Emerg Med 2010; 17:11–17.

3. Gekle et al. Saline Flush Test. J Ultrasound Med 2015; 34:1295–1299

4. Liu YT, Bahl A. Evaluation of proper above-the-diaphragm central venous catheter placement: the saline flush test. Am J Emerg Med 2011; 28: 842.E1–842.E3.