Ultrasound Guided Vascular Access

Daniel Duque, MD RDMS, Assistant Professor, Department of Emergency Medicine, Mount Sinai School of Medicine, Elmhurst Hospital Center and Stuart Kessler, MD, FACEP, Associate Professor, Department of Emergency Medicine, Mount Sinai School of Medicine, Elmhurst Hospital Center

Establishing central vascular access in an emergency department setting can be problematic. Factors that impede successful cannulation include obesity, anatomical variants, hypotension and intravenous drug abuse. Serious technique related complications include pneumothorax, pneumomediastinum, hemothorax, hematoma and AV fistula. Use of bedside ultrasound facilitates successful cannulation while decreasing complication rates.

The Department of Health and Human Services in its 2001 Agency for Healthcare Research and Quality Report and The British National Institute of Clinical Excellence in 2002 recommended the use of ultrasound guidance in central venous cannulation. These recommendations stem from convincing literature showing that the use of ultrasound increases first attempt success, decreases the number of attempts, decreases rates of arterial punctures and leads to successful cannulation in patients who fail the landmark technique.

Two recent studies have demonstrated the superiority of ultrasound guided central venous access. Hilty et al enrolled 40 patients in an attempt to compare success and complication rates between ultrasound guided line placement and standard landmark technique.

1 The group that utilized ultrasound guidance had a 90 % successful cannulation rate vs. 65% in the landmark group. The group that used ultrasound guided placement averaged 2.3 needle passes per patient vs. 5 needle passes per patient in the landmark group. Patients in the group that used ultrasound guidance had 0% arterial puncture vs. 20% in the group that used landmarks. Slama M and colleagues
also demonstrated superiority of ultrasound guided venous cannulation.

2 This study enrolled 79 patients. The group that utilized ultrasound guidance had a 100% successful cannulation rate vs. 76% cannulation rate in the group that utilized standard landmark techniques.

Emergency physicians who are incorporating ultrasound guided procedures into their practice should have formal training in general emergency ultrasound. Although specific guidelines do not dictate how much training is needed to perform the procedures, several courses are available for individual training. In order to develop better hand eye coordination, the techniques can also be practiced on commercial or hand made phantoms.

Ultrasound guidance can also aide in peripheral vein access. This is particularly useful in patients that may have short ED visits. The basilic, antecubital and cephalic veins can all be visualized and successfully cannulated with the use of ultrasound.

Needle guides are available on many ultrasound systems but many practitioners feel they are unnecessary. The guides are designed to keep the needle centered in the ultrasound beam which can be helpful in the early stages of training. However, the angle of entry cannot be changed thus surrendering an element of control. In addition, the needle guides are offered in only one particular axis (long or short) and cannot be changed. Thus the procedure can only be performed in the axis dictated by the particular guide.

Dynamic ultrasound (real time ultrasound) and static ultrasound are the two basic techniques utilized in ultrasound assisted procedures. When using dynamic ultrasound the anatomy and needle are visualized with the ultrasound machine throughout the entire procedure. The needle or the ultrasound artifact it produces are visualized thus assuring correct vessel cannulation. When using static ultrasound, the anatomy is surveyed with ultrasound prior to performing the procedure. A point of entry in the skin is identified and the procedure is then performed without continuous ultrasound visualization.

Although both techniques can be utilized, dynamic imaging is superior and is used in most studies. When using dynamic imaging, the transverse (short axis) or longitudinal (long axis) approach may be used. Keep in mind that the ultrasound beam is only 1-2 mm thick thus making visualizing the needle difficult. Ring down artifact (comet tail artifact), which is caused by reverberation of sound waves, and soft tissue displacement help to locate the needle.

A study conducted by M. Bliavis concluded that the transverse approach was more successful with less attempts and required less redirection than the longitudinal approach.

3 The transverse approach is accomplished by centering a cross sectional view of the vessel on the center of the screen. This approach avoids inadvertent arterial puncture but cannot always visualize the needle. Instead it relies on soft tissue displacement to confirm needle placement. The main disadvantage to the transverse approach is the potential for double wall puncture (puncture of the proximal and distal walls of the vessel). The longitudinal approach is accomplished by placing the probe to show a long view of the vessel. The needle tip is seen
throughout the procedure preventing double wall puncture. The major disadvantage to the longitudinal approach is that only one vessel can be seen at a time, thus the potential that the artery can be inadvertently punctured. The internal jugular, femoral and subclavian veins can all be successfully cannulated using these techniques.

Dynamic ultrasound guidance can be performed with one or two operators. When two operators employ the freehand technique, the first operator conducts the procedure while the second operator holds the transducer. The major disadvantage to the freehand approach is that both operators must be familiar with ultrasound and probe placement. The other option is to perform the procedure with a single operator. When using this technique, one operator holds both the transducer and the needle while cannulating the vessel. This technique requires more practice and better hand eye coordination. Personal preference and number of operators available usually dictate which technique is used.

While performing dynamic ultrasound guidance the vein must be distinguished from the artery. Compression is the only reliable method to make this distinction. Although Doppler is an alternative method to distinguish artery from vein it is not as reliable as compression.

The development of ultrasound training programs in emergency medicine residencies is creating a generation of physicians skilled in ultrasound guided line placement. With proper training every emergency medicine physician can incorporate this skill into their practice. The ability to reduce complication rates makes the acquisition of this skill desirable and beneficial.

References
1. Hilty WM, Hudson PA, Levitt MA, Hall JB: Real time ultrasound guided femoral vein catherization during cardiopulmonary resuscitation. Ann Emerg Med 1997; 29 331-7
2. Slama M, Novara A, Safavian A, Ossart M : Improvement of internal jugular vein cannulation using an ultrasound-guided technique. Intensive Care Med 1997; 23:916-9
3. Blaivas M: Short-axis versus long-axis approaches for teaching ultrasound-guided vascular access on a new inanimate model. Acad Emerg Med 2003;10(12): 1307-11