ARIEL L. SHILOH, LEWIS A. EISEN, MICHAEL BLAIVAS and DIMITRIOS KARAKITSOS

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).⁶ A pre-procedural scan is recommended to guide the selection of an optimal target vessel.^4–6 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)⁷

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.⁸ 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.⁹ These measures have shown reduction (up to 66%) in central line-associated bloodstream infections.¹⁰

Preprocedural tips

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

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.¹¹ 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.¹² 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.^13,14

Variations in technique

One-person (two-hand) and two-person (three-hand) techniques have been described for USGV. In the one-person technique, the operator controls the transducer with the nondominant hand and the needle with the dominant hand. An assistant, also in full sterile barrier precautions, is required to hold the probe for the two-person technique. The one-person technique is reported to be learned easily and is associated with improved first-pass and overall success of CVC placement when compared with the two-person technique.^2,11 When first learning the technique, many operators find the two-person technique easier. Eventually, most operators gravitate toward the one-person technique.

The ergonomics of UGVA is equally important. Ideally, the ultrasound machine should be placed on the contralateral side of the ROI while the operator stands at the cannulation site (Figures 11-4 and 11-5). Usually, the dominant hand of the operator holds the needle and the nondominant hand holds the transducer. Hence, the latter can be flexed slightly while resting on the body surface of the patient to stabilize the elbow in a comfortable position. Because the elbow of the operator remains stable, it is easier for the operator’s wrist to relax and sweep the transducer accurately while the needle is moved forward gently under the transducer in real time.

Variations on needle insertion have been described (Chapter 10). Real-time, dynamic visual guidance (free-hand access) throughout catheterization is always superior to marking a spot with ultrasound and then trying to locate a vessel without guidance (Figures 11-6 and 11-7).^{2,11,12, 13–16} As described previously, longitudinal visualization of the vessel allows improved and continuous visualization of the advancing needle tip but requires a more skilled operator, especially when attempting to catheterize small-caliber vessels. The transverse approach, though easier to learn, has been associated with an increased incidence of posterior wall perforation, probably because operators are often mistaking the shaft of the needle for the tip since it is easy to advance the tip of the needle past the ultrasound beam.

When using a transverse approach, we advocate using the “creeping” technique, in which the tip of the needle is visualized continuously, by using the following steps:

When using a longitudinal approach, the main technical difficulty is depicting a “steady” image of the target vein while advancing the needle. Performing synchronous manipulations (e.g., moving the needle while adjusting the ROI to depict the target vein) has been recommended. However, these manipulations may be dangerous, especially when performed by novice users. For example, when a desirable ROI is found after continuous manipulations, the needle, which is moving synchronously, thereafter may well have followed an out-of-plane course. Hence, it is safer to first identify a desirable image of the target vein and then advance the needle in real time while keeping that image intact. Finally, estimating the depth of the target vein from the skin surface is important because the distance may sometimes be greater than anticipated for various reasons (e.g., anatomic variations, trauma, obesity) and necessitate adjustments of the insertion angle and thereby increase the technical difficulty of the procedure.

Intraprocedural and postprocedural tips

For the most part, evaluation of target vessels is limited to the insertion point and what can be visualized immediately proximal and distal to the insertion site. Although a well-chosen site increases the success of catheter deployment and positioning, it does not guarantee success. When inserting a CVC into the internal jugular or subclavian vein, the rib cage obscures further evaluation of the vessel downstream. 13–16 Fragou et al demonstrated that the contralateral vasculature could be visualized by an assistant while advancing the guidewire to assess for potentially misdirected catheter deployment.¹⁷ If the guidewire is seen in the contralateral vasculature, attempts could be made to redirect the wire. In addition, the guidewire should always be visualized within the vein before any dilation is performed to prevent potential catastrophic arterial damage (Figure 11-8).

After the procedure the pleura should once again be visualized and assessed for lung sliding to ensure that pneumothorax is not present (Chapter 19). If difficulty was encountered despite using UGVA, such as an inability to thread the guidewire or unexpected resistance in catheter deployment, the vasculature should be scanned for the potential development of a hematoma, pseudoaneurysm, or arteriovenous fistula (Chapter 8).

Simulation training and echogenic technology

In recent years, implementation of simulation-based training for CVC insertion has been increasing. Such training has resulted in a significant reduction in mechanical and infectious complications and an increase in ultrasound use.¹⁸ At the present time, simulation mannequins and vascular task trainers, compatible with ultrasound, can be used to improve the skills of novice and less experienced operators.

Optimal image acquisition can be affected and deteriorated by subcutaneous air, obesity, trauma, and mechanical ventilation in the ICU. Such factors often make continuous visualization of the tip of the needle a challenge. The use of echogenic vascular cannulas, which have the potential to improve image acquisition and thus needle visualization, has been shown to improve success rates in technically difficult cases of vascular access.^19,20 Etched reflectors on the tip of the vascular cannula improve visualization of the needle independent of the angle of insertion, in a method analogous to a bicycle reflector (see Figure 11-8). Recent, preliminary data have demonstrated improved continuous needle visibility and decreased access times and technical complexity of UGVA when using echogenic needle technology in either a longitudinal or transverse approach.^19,20

Pearls and highlights

References