Ultrasound-guided vascular access: Trends and perspectives

Patient and technical considerations

The implementation of a simple three-step UGVA technique (pre-procedural scanning, real-time ultrasound-guided cannulation, post-procedural scanning) maximizes success rates and decreases complications in the intensive care unit (ICU). A pre-procedural scan is recommended to guide the selection of an optimal target vessel. Usual criteria for the selection of an optimal vein are:

Normal venous patency (venous collapse during breathing or compression without signs of thrombosis)

Easy accessibility (relatively short distance from the skin surface to the vessel wall)

Adequate size (vessel size less than three times the caliber of catheter may carry a greater risk for thrombosis)

Absence of anatomical variation

Intended purpose of cannulation (i.e., neck surgery often requires infraclavicular vascular access)

Intended duration for catheter placement (i.e., a cancer patient receiving chemotherapy often requires long-term vascular access)

Complication rates after the implementation of landmark techniques differ between sites ( Chapter 10 ). The internal jugular vein carries the highest risk of accidental arterial puncture and hematoma, the subclavian carries the highest risk for pneumothorax, hemothorax, and catheter malposition, while the femoral vein carries the highest risk for thrombosis and infection ( Table 11-1 ). The subclavian vein is considered advantageous in the ICU (compared to the internal jugular or the femoral vein) as it carries the lowest infection risk. However, recent studies show that Chlorhexidine gluconate -impregnated sponge dressing when used with the standard care decreases the incidence of major catheter-related infections from 1.4 to 0.6 per 1000 catheter-days. The American Society of Anesthesiologists Task Force on Central Venous Access recommends the use of a central line insertion work and safety checklist and bundling of required equipment to minimize errors, risk of infection, and complications. These measures have shown reduction (up to 66%) in central line-associated bloodstream infections.

Preprocedural tips

A few practical tips when performing an ultrasound-guided central venous cannulation for the first time include:

• The implementation of a strict sterilization process including use of a sterile probe cover and gel ( Figure 11-1 )

  

• Avoid applying extreme probe pressure on the vessel as normal veins are collapsible vessels

• Optimize the two-dimensional image: center the image on the screen and adjust depth, gain and focus, while obtaining the proper orientation of anatomy with standardization of the dot on the left ( Chapter 1 ).

• When a clear two-dimensional image of the vein is obtained check its patency by applying probe pressure to exclude thrombosis (Video 11-1).

Notably, a thorough preprocedural scan at a prospective region of interest (ROI) should be performed because of the frequent finding of venous and arterial asymmetry between symmetric sites. In that sense, anatomic diversities may exist as well in occasional patients (e.g., duplicated femoral vein). Venous compressibility and patency should be examined because exclusion of thrombosis is mandatory ( Chapter 9 ). The latter is more commonly observed at the common femoral vein site than at other cannulation sites, and ultrasound monitoring of a central line may reveal cases of catheter-related thrombosis ( Figure 11-2 ). Occasionally, trauma to the venous wall, trapped air, hematomas, arteriovenous fistulas, or injuries to nonvascular adjacent structures may be identified after a “clumsy” blind attempt or multiple blind penetrations, which could produce local trauma ( Figure 11-3 ). Estimating vessel size is equally important, as previously mentioned. The size of the internal jugular vein can be evaluated before and after a Valsalva maneuver, which may make a relatively small-caliber vessel that is seemingly difficult to catheterize become robust and easy to puncture. Moreover, the diameter of the internal jugular vein is usually found to be larger when the vessel is depicted in the lower neck area (scanning caudally toward the clavicle) than in the upper neck area (scanning cranially toward the mandible). When planning on catheterizing the internal jugular or subclavian vein, the pleura should be assessed for a sliding lung while identifying the vasculature.

Visualization of the vasculature is most often done with B-mode ultrasound. When compared with B-mode, use of the color Doppler mode for vascular access has been associated with a longer learning curve, longer insertion time, and higher cost. Although in the vast majority of cases the absence of Doppler capability does not preclude safe catheterization, it can be of assistance when identification of the target vasculature is difficult. Color Doppler and pulsed wave Doppler are useful techniques that facilitate the differentiation between arterial and venous pulsation. The use of ultrasound for vascular access has been shown to decrease the need for correction of coagulopathy before insertion of the catheter. In the hands of experienced operators, when favorable vasculature is visualized, UGVA has been demonstrated to be safe and successful, with a low rate of complications. ^,