Arterial and venous anatomy of the upper extremity
Though less common, the great saphenous vein can also be located with ultrasound in the lower extremity and offers an alternative to the upper extremities for cannulation. This vein courses along the medial aspect of the lower extremity from the anterior aspect of the medial malleolus, along the medial calf, posterior to the medial condyle of the femur, along the medial thigh. In the thigh it courses anteriorly where it joins the femoral vein in the groin (Fig. 12.2). It is often cannulated at the level of the ankle. Due to its superficial nature, ultrasound use during cannulation may be challenging secondary to venous compression.
Fig. 12.2
Arterial and venous anatomy of the lower extremity
The external jugular vein is another viable alternative. Its course is along the lateral neck along the posterior border of the sternocleidomastoid muscle caudally. As it travels more proximally, it crosses anterior to the sternocleidomastoid muscle and enters the subclavian triangle to join the subclavian vein (Fig. 12.3). Though this vein often has good caliber and is easily accessible, it is easily compressible and use of a tourniquet is not possible in this area. Ultrasound can be used to cannulate an external jugular vein; however, adjustments need to be made to allow visualization. Patient positioning in reverse Trendelenburg can decrease the vein’s compressibility, and the operator must be extremely cognizant of the amount of pressure applied with the probe.
Fig. 12.3
Anatomy of the external jugular vein and surrounding structures
A similar technique can be used when utilizing ultrasound guidance for accessing the radial artery for arterial line placement as is used for peripheral venous access. Ultrasound guidance for arterial access can be useful when arterial pulses are not easily palpable (scar tissue, obesity, low blood pressure, etc.). The radial artery is very superficial in nature, coursing from the radial aspect of the wrist along the forearm to the antecubital fossa, where it joins the brachial artery. It is cannulated at the level of the wrist where it is found medial and proximal to the radial styloid and lateral to the flexor carpi radialis tendon.
Indications and Contraindications
The indications for ultrasound-guided PIV placement include any disease state or planned intervention which requires IV placement in patients who have proven or predicted difficult IV access. In situations where traditional methods of IV placement have failed or are predicted to fail, proceeding directly to ultrasound guidance is advised in most situations. Contraindications to ultrasound-guided PIV are similar to the contraindications for traditional IV placement including the presence of a dialysis fistula or catheter on the chosen limb, prior lymph node dissection of the affected limb, overlying infection or other overlying severe skin disease, known superficial thrombus in the target vein, or deep vein thrombosis in the ipsilateral limb. Relative contraindications include severe edema as the ability to detect extravasation is poor and use of the lower extremity veins in patients with diabetes as the ability to detect complications may be impaired by neuropathy.
Equipment
Necessary equipment for the procedure is listed in Table 12.1. The ultrasound machine utilized for the procedure is ideally a lightweight, sturdy, mobile unit with a user-friendly interface. A high-frequency (12-5 MHz) linear array transducer should be utilized as the target structures are very superficial. There are a variety of these transducers, including a traditional linear transducer, downsized linear transducers with smaller footprints, and the so-called hockey stick transducer.
Table 12.1
Necessary equipment for the placement of an ultrasound-guided peripheral intravenous catheter
Ultrasound machine with an appropriate high-frequency transducer
Non-sterile gloves
Mask and eye protection for the provider
Sterile ultrasound gel packets
Ultrasound probe cover/barrier
Alcohol or other disinfectant for skin preparation
Appropriate length and gauge IV catheter
Device or tape to secure the catheter
Barrier dressing
Saline flush
The placement of a PIV is a clean/aseptic, but not sterile, procedure. Traditional, non-sterile examination gloves should be utilized and should be latex-free as necessary to protect the patient and provider. As with any procedure with the potential for blood-borne pathogen exposure, mask and eye protection are recommended. Sterile gel should be utilized to minimize the infection as the skin will be breached. To protect the equipment and the patient, a single-use barrier adhesive or a single-use sterile probe cover should be utilized. Additionally, disinfectant for the patient’s skin should include chlorhexidine swabs or alcohol swabs for cleaning the skin prior to needle insertion.
A catheter of an appropriate gauge and length should be chosen. Standard length IV catheters (generally 24–44 mm) are usually not sufficient as the veins used for ultrasound-guided PIV placement are frequently deep. When longer catheters are utilized (generally >50 mm), there is a decreased failure rate of the catheter [18]. Appropriate choice of gauge should be determined by patient needs for rapid resuscitation or rapid administration of medications or blood products and by the chosen vein caliber.
An optional piece of equipment is the stand-off or gel pad which can be used to improve visualization of a very superficial vein. The decreased spatial resolution which is present in the first few millimeters of the near field on most ultrasound imaging can affect the ability of a practitioner to adequately visualize the most superficial veins. Using a fluid-filled stand-off between the patient and the ultrasound probe will increase the distance from the probe to the structure of interest, thereby increasing the spatial resolution of the structure. A small (100 ml) bag of saline can be used as well as a commercially available product (Fig. 12.4).
Fig. 12.4
Use of a saline bag as a stand-off for ultrasound imaging of superficial structures
Another optional and recommended piece of equipment is a catheter stabilization device. There are several commercially available products. These are used to secure the device to the patient’s skin. Given the increased depth at which these catheters are placed, there is greater potential for displacement of the catheter compared to traditionally placed IVs.
Pre-procedural Evaluation
Patient should be consented and counseled prior to procedure performance. The risks of the procedure are similar to those for traditional IV placement including infection, phlebitis, bruising, infiltration, arterial puncture, nerve damage, pain, and bleeding. These complications do occur with less frequency with ultrasound-guided PIV placement than with traditional techniques, however.
The preferred limb should be chosen on each patient depending on patient factors, and the limb should be evaluated for an ideal vessel. Unpaired veins (those without a paired artery) are ideal but not always available. An ideal vessel is one that is superficial and of larger caliber and can be accessed without damaging other structures (arteries, nerves, tendons, etc.). Success rates in placing ultrasound-guided PIVs are improved when veins that are greater than 4 mm in size and are at a depth between 3 mm and 15 mm are utilized [19]. Size of the vessel is the most important predictor of success [20]. Additionally, when possible, the catheter should not be larger than 1/3 of the vessel diameter to decrease the possibility of vein thrombosis.
Peripheral veins can be distinguished sonographically from superficial arteries using several techniques. The first and easiest is to use compression. With B-mode imaging, the operator can visualize the compression of a peripheral vein using light pressure applied to the patient’s skin with the ultrasound probe (Fig. 12.5a, b). Venous structures will compress and collapse with little pressure, and arteries compress less easily. A potential drawback to this technique is in hypotensive patients because the pressure required to compress an artery is less and it may be mistaken for a vein. In these situations, veins will still require less compression for complete collapse than an artery, and this must be distinguished by the operator. Another confounder is when venous congestion occurs due to patient factors or a very tight tourniquet. In these situations, the pressure required to compress a vein is greater and may approach the pressure required to compress an artery, decreasing the ability to distinguish the two.
Fig. 12.5
(a) B-mode image of a peripheral vein and artery without compression. (b) The same vessels with compression applied with the ultrasound probe. Note the compression of the artery but not the vein
Doppler, either pulsed wave or color, can be used to distinguish peripheral veins from arteries. Using pulsed wave Doppler, the sample gate is placed over the vessel in question and a waveform obtained. A pulsatile waveform will confirm that the vessel is an artery (Fig. 12.6). A vein may have low continuous flow, intermittent low level flow, or none at all (Fig. 12.7). Augmentation, whereby the operator squeezes the limb distal to the transducer during the ultrasound examination, can be utilized. With augmentation, veins will demonstrate a sudden increase in return which will be visualized on the Doppler waveform (Fig. 12.8). Color Doppler is used similarly to pulsed wave Doppler. The color box is placed over the vessel in question. Pulsatile flow will confirm an artery, and low continuous flow, intermittent low level flow, or no flow can confirm that it is a vein. Vein augmentation can also be visualized as a sudden increase in flow within a vessel when distal compression is applied to the limb. One potential problem when using Doppler to distinguish arteries from veins can occur if the tourniquet is causing impedance of arterial flow. In this situation, the arterial waveforms may appear dampened or non-existent and may lead to misidentification of an artery as a vein.
Fig. 12.6
Pulsed wave Doppler waveform of a peripheral artery
Fig. 12.7
Pulsed wave Doppler waveform of a peripheral vein demonstrating phasic flow
Fig. 12.8
Pulsed wave Doppler waveform of a peripheral vein with augmentation
The patency of the chosen vein should also be confirmed prior to procedure. A superficial thrombus may appear as an echogenic or isoechoic area within the vessel (Fig. 12.9). Alternatively, a thrombus can be anechoic, and the chosen vein should be confirmed to have full compression in B-mode imaging.
Fig. 12.9
B-mode image of a superficial venous thrombosis
Performing the Procedure
Once the patient has been consented (as required by local policies), the procedure and the patient confirmed, the appropriate vessel evaluated and chosen, and all equipment ready, the patient and operator should be positioned properly. Procedural success is improved with good operator and patient positioning. The operator should be in a seated position with all equipment within arm’s reach. It is ideal to have the ultrasound machine placed on the patient’s contralateral side directly in the operator’s field of view when performing the cannulation (Fig. 12.10). Any positioning which requires the operator to turn their head to look from their procedural field to the ultrasound machine should be avoided.
Fig. 12.10
Ideal positioning of the ultrasound machine and the operator with the ultrasound machine on the patient’s contralateral side and in full view of the operator
Real-time ultrasound guidance should be used to visualize the catheter entering the vein, and this is best facilitated using the in-plane approach. The use of the in-plane approach for real-time visualization of needle guidance allows the operator to continuously visualize the needle tip and improves visualization of the needle at the time of vessel puncture [21].
A tourniquet should be placed to distend the veins. The appropriate preset should be selected on the ultrasound machine and the chosen vein visualized. Once the appropriate vein is visualized and confirmed in the short axis, the probe should be turned into the longitudinal plane of the vein (Fig. 12.11a, b). The skin surface where the needle will enter the skin should be cleansed with a chlorhexidine swab or other disinfectant per institutional policy for PIV placement. A large transparent tegaderm can be applied to the footprint of the transducer which will prevent contamination of the transducer with blood. Care must be taken not to trap any air bubbles between the tegaderm and the transducer. The non-dominant hand of the operator should stabilize the probe with the hand firmly planted on the patient’s extremity. With the dominant hand and the needle bevel facing up, the operator should puncture the skin with the needle using in-plane approach (Figs. 12.12 and 12.13). Care should be taken not to damage the probe surface with the needle tip. In order to enter the skin, the probe can be rocked, lifting the end closest to the needle using a “ski-lift maneuver” [22]. The needle tip should be visualized at all times as it is advancing, and if it cannot be visualized, it should not be advanced. Maintaining a shallow angle of approach will improve visualization of the needle because it will allow a more perpendicular angle between the ultrasound waves and the needle surface. Once the needle tip enters the vessel, the needle angle should be flattened and advanced to ensure that the entire catheter tip is within the vessel walls (Fig. 12.14).
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