So there have been several questions put forth recently about ultrasound in the literature. So I have decided to create a post once a month which will tackle a specific topic in Emergency Medicine Ultrasound.
This month we are going to talk about the use of ultrasound to confirm central line placement.
How many times have you had a patient who was septic or unstable and needed to use the newly placed central line ASAP, only to have to wait for X-ray? Why not use bedside ultrasound to confirm that your line is in good position and that there are no pneumothoracies? Can it be done?
Let's first discuss what are the potential complications of central line placement. Major complications include pneumothorax, catheter tip misplacement which may cause intravascular or intracardiac injury, arterial puncture, hematomas and neural injury. CXR identifies the presence of a pneumothorax and verifies the catheter's position, but it can be difficult to assess the location of the catheter tip when it is near the right atria. Catheter tips left in the right atria may lead to thrombosis or perforation.
Ultrasound use to confirm central line placement has been studied in the critical care literature for 10 years now. Maury et al first described using ultrasound to replace CXR in 2001 by performing a combination of limited bedside echo, vascular imaging of the subclavian and internal jugular veins and thoracic sonography to identify pneumothorax. This study showed that ultrasound identified the only pneumothorax in the study group and found 9 out of the 10 catheter tip misplacements. It also showed that bedside ultrasound could be performed significantly faster than CXR. More recently Vezzani et al used contrast enhanced cardiac ultrasound (used agitated saline to create microbubbles which will appear as turbulent flow through the vessel- see video below) to further demonstrate catheter tip position. This study described a concordance with CXR of 95% for catheter tip misplacement and 98% for pneumothorax. These studies show significant promise in using ultrasound to rule out two of the complications of central line placement in the chest. But what about arterial puncture? Gillman et al reported that ultrasound could be used to decrease the number of intraarterial dilations by confirming that the guidewire was in the vein not the artery prior to dilation. Although a review study, this showed that by using ultrasound to confirm that the guidewire is in the vein and not the artery prior to dilation of the vessel, no arterial dilations occurred.
Venous Catheter Flush from
UF-Jax Emergency Medicine on
Vimeo.
So what does this mean for us in the ED? How can we put these articles into practice?
Using ultrasound for dynamic cannulation of the IJ has been well documented in the literature. Tracking the needle tip or "walking down the vein" will allow you to visualize the needle going through the vein wall and ensure that you are within the vessel wall. I agree with Gillman et al, that once you place the guidewire and prior to dilation, you should visualize the IJ in the long axis plane. This "check step" will ensure that 1) you are in the vein and not the artery and 2) that you have not penetrated the posterior wall of the vessel and 3) that the guidewire is headed down toward the chest and the heart. Compression of the vessel while the guidewire is in place will also aid in confirmation that you are in a vein.
Once you have completed your line, a quick look at the lungs for pneumothorax can be done from apex to base on each side. This can be done rapidly and can be extremely helpful in your intubated patients who are in a supine position. We know that air rises to the least dependant area, thus ultrasound may be better at picking up ptx in these patients than the initial CXR. Thus, use the same linear probe that you used to place the line and slide down the chest wall, stopping briefly at each interspace to look for the slide sign.
Once the lungs have been evaluated, then the heart can be examined. Use the subxiphiod view to evaluate it the catheter tip is in the IVC and then the right atria. Although contrast ultrasound does give slightly more information, it is not necessary to identify the catheter tip in the heart. If you can see the tip, then it is easy to pull the line back.
Any thoughts on the feasibility of using ultrasound in this way?
References:
Ultrasonic Examination: An Alternative to Chest Radiography after Central Venous Catheter Insertion? Maury E, Guglielminotti J, Alzieu M, Guidet B, Offenstadt G. Am J Respir Crit Care Med. 164: 403-405, 2001.
Ultrasound Localization of Central Vein Catheter and Detection of Postprocedural Pneumothorax: An Alternative to Chest Radiograph. Vezzani A, Brusasco C, Palermo S, Launo C, Mergoni M, Corradi F. Critical Care Medicine. 38(2):533-538, February 2010
Ultrasound confirmation of guidewire position may eliminate accidental arterial dilation during central venous cannulation. Gillman LM, Blaivas M, Lord J, Al-Kadi A, Kirkpatrick AW. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine. 18:39, 2010
