Vascular Procedures

Fig. 15.1

Arterial and venous anatomy of the lower extremity

../images/323313_1_En_15_Chapter/323313_1_En_15_Fig2_HTML.png — Fig. 15.2

B-mode image of transverse view of left common femoral artery (CFA) and common femoral vein (CFV)

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Color Doppler image of left common femoral artery (red) and common femoral vein (blue)

../images/323313_1_En_15_Chapter/323313_1_En_15_Fig4_HTML.png — Fig. 15.4

(a) Common femoral vein – spectral Doppler waveform showing phasic flow. (b) Common femoral artery – spectral Doppler waveform showing pulsatility

A pseudoaneurysm or a false aneurysm is a collection of blood between one or two outer layers of an artery (media or adventitia), whereas true aneurysm is an outpouching with all three layers of the arterial wall. Femoral pseudoaneurysm is typically seen as a round sac adjacent to, and often with, a connecting cylindrical neck from the native common femoral artery. Depending on the degree of thrombosis, the internal appearance of the pseudoaneurysm varies. Partial rupture of the pseudoaneurysm may result in a complex, multilobed pattern with multiple communicating sacs, whereas complete rupture may lead to a more diffusely infiltrative hematoma. Ultrasound is the most rapid and best imaging modality for the evaluation of pseudoaneurysm. On B-mode imaging, a pulsatile anechoic saccular lesion is visualized in the soft tissue with variable echogenicity. When there is no intraluminal thrombus, it appears anechoic with swirling blood; when there is a thrombus, the echogenicity varies according to the age of the thrombus (Figs. 15.5 and 15.6). It may be difficult to differentiate a completely thrombosed pseudoaneurysm from a hematoma. On color Doppler a characteristic yin-yang sign may be visualized due to bidirectional swirling turbulent blood flow in the sac (Fig. 15.7). On pulsed-wave Doppler, a “To and Fro” Doppler pattern (blood entering the sac during systole and leaving during diastole) is found in the neck of pseudoaneurysm with preserved native arterial flow distal to the neck of the sac (Figs. 15.8 and 15.9) [18].

../images/323313_1_En_15_Chapter/323313_1_En_15_Fig5_HTML.png — Fig. 15.5

Femoral artery pseudoaneurysm. (a) Gray-scale ultrasonography shows a well-defined anechoic mass. (b) Color Doppler shows swirling blood flow pattern within the mass

../images/323313_1_En_15_Chapter/323313_1_En_15_Fig6_HTML.png — Fig. 15.6

Partially thrombosed femoral artery pseudoaneurysm (a) B-mode image. (b) Color Doppler image

../images/323313_1_En_15_Chapter/323313_1_En_15_Fig7_HTML.png — Fig. 15.7

Color Doppler images of three patients with femoral artery pseudoaneurysms demonstrating bidirectional swirling turbulent blood flow in the sac (a–c)

../images/323313_1_En_15_Chapter/323313_1_En_15_Fig8_HTML.png — Fig. 15.8

Pulsed-wave Doppler showing a “To and Fro” Doppler pattern (blood entering the sac during systole and leaving during diastole) in the neck of pseudoaneurysm

../images/323313_1_En_15_Chapter/323313_1_En_15_Fig9_HTML.png — Fig. 15.9

Spectral Doppler demonstrating preserved native arterial flow distal to the neck of the pseudoaneurysm sac

Indications

The size of the pseudoaneurysm is used as a guide to determine the treatment option. A conservative approach is generally adopted for a small-diameter (<3.0 cm) femoral artery pseudoaneurysms since they may thrombose spontaneously. With a favorable risk/benefit ratio, the indications for direct percutaneous thrombin injection are broad and involve almost all patients except those with rare contraindications. However, it is particularly indicated if the femoral pseudoaneurysms are painful, growing, and affecting ambulation.

Contraindications

The contraindications to direct percutaneous thrombin injection therapy include:

1.

Ruptured pseudoaneurysm
2.

Coexisting arteriovenous fistulous component
3.

Associated ipsilateral deep venous thrombosis
4.

Prior treatment/exposure to bovine thrombin due to concern for allergic reactions
5.

Increased risk of vessel thrombosis such as patients with hypercoagulable disorders
6.

Infected pseudoaneurysms or overlying skin erosion/breakdown due to risk of infection
7.

Inability to access the site for injection due to scarring

Equipment/Probe Selection

An ultrasound system capable of adequate image quality and soft tissue penetration is essential. The ultrasound system should have a linear array transducer, although obese patients may require the use of a curvilinear probe. Color and pulsed-wave Doppler capability are important adjuncts.
Recombinant or bovine thrombin (100–1000 units/ml).
20 G or 22 G needle with syringe.
Local anesthetic (1% lidocaine).
25 G needle for anesthetic infiltration.
Sterile drapes, gown, gloves, mask, and cap.
Sterile ultrasound probe cover.
Gauze.

Preparation/Pre-procedural Evaluation

Ultrasound assessment of the pseudoaneurysm involves scanning the suspected area in two orthogonal planes and documenting the following: site of origin of the aneurysm (common femoral vs. femoral/deep femoral artery), waveform pattern of outflow artery, size of the aneurysm, number of lobes and the dimensions of each lumen, and length and diameter of the neck of the aneurysm. After evaluating the extent of the pseudoaneurysm in two orthogonal planes, it is time to prepare for thrombin injection. The procedure should be performed under standard hospital sterile procedure guidelines similar to that of a central line placement. The ultrasound transducer should be disinfected and then sterilely dressed in an appropriate sterile ultrasound transducer sheath cover. Sterile gel should be utilized once the injection site has been prepped according to hospital sterile procedure guidelines. Prior to the procedure, it is important to check for vascular compromise distal to the location of the pseudoaneurysm, and in the case of the femoral artery pseudoaneurysm, the posterior tibial and dorsalis pedis pulses should be assessed with palpation or Doppler signals should be documented. In-plane needle visualization and guidance is likely to yield the best results in avoiding nearby structures and injection of thrombin into the injured artery. Local anesthetic administration under dynamic ultrasound guidance can be exceedingly helpful which allows depositing anesthetic throughout the path of the needle. A thin needle (20–22 G) can be utilized for thrombin injection. Using a 25 or 27 G needle will make it harder to visualize the needle on ultrasound. A small syringe can be used to draw thrombin (recombinant or bovine) for injection [19].

Procedure

The injection should be performed under real-time ultrasound guidance. Using B-mode imaging, the sterile needle should be placed to one side of the long axis of the linear array transducer directly in the middle of the transducer. The needle is slowly introduced through the skin under real-time ultrasound guidance. Once the needle tip and shaft are identified, after having been inserted several millimeters under the skin, the needle tip is directed into the sac of pseudoaneurysm. The operator should take extreme care to direct the needle tip to the periphery of the aneurysm away from the neck of pseudoaneurysm. This reduces the possibility of thrombin administration into the pseudoaneurysm neck and, possibly, into the arterial circulation. Under ultrasound guidance, the sac is injected with 0.1 mL aliquots of thrombin until the blood flow in the sac is successfully obliterated. Alternate color Doppler and B-mode assessments should be performed to assess for thrombosis and disappearance of color signal and confirm pseudoaneurysm closure. After successful thrombosis is accomplished, the distal arterial circulation is assessed and compared with pre-procedural findings. For patients in whom thrombin is not initially successful, repeat injection can be attempted. The patient must remain supine after the procedure and should be observed for 6 hours. Thereafter, the native common femoral artery should be assessed with Doppler ultrasound to confirm patency. An ultrasound should ideally be performed the following day to confirm hemostasis (Figs. 15.10, 15.11, and 15.12) [19, 20].

../images/323313_1_En_15_Chapter/323313_1_En_15_Fig10_HTML.jpg — Fig. 15.10

Ultrasound-guided thrombin injection

../images/323313_1_En_15_Chapter/323313_1_En_15_Fig11_HTML.jpg — Fig. 15.11

Echogenic needle tip (arrow) is visualized in B-mode in the pseudoaneurysm sac

../images/323313_1_En_15_Chapter/323313_1_En_15_Fig12_HTML.png — Fig. 15.12

(a) Pseudoaneursym sac prior to thrombin injection. (b) Post thrombin injection, successful thrombosis (arrow) is accomplished

Complications

The most serious complications following thrombin injection are arterial thrombosis or distal embolization, which are extremely rare (<1%). Other potential complications include allergic reactions related to bovine thrombin, infection, pseudoaneurysm rupture, and inadvertent injection of the thrombin into adjacent structures instead of pseudoaneurysm [19, 20].

Pearls/Pitfalls

A thorough assessment of pseudoaneursym should be performed prior to the procedure to determine the risk and benefit of the procedure. Thrombin injection is effective in patients who are already receiving anticoagulation with heparin or warfarin. A second injection can be performed if initial injection is not successful. Bovine thrombin is a foreign substance and, as such, may cause an allergic reaction after repeated exposures. Although downstream embolization is extremely rare, it may well be that some thrombin does in fact leave the pseudoaneurysm sac and travel into the native artery and systemic circulation. Pitfalls largely include the general mistakes providers make with ultrasound-guided procedures: advancing the needle without visualization and injury of nearby structures.

Integration into Clinical Practice

Femoral artery pseudoaneurysm after cardiac catheterization is not common but a well-recognized complication. Patients with femoral artery pseudoaneurysm are often initially evaluated in the emergency department. Providers with ultrasound skills can rapidly evaluate these patients for the presence of pseudoaneurysm. Depending on the practice setting and availability of resources, same providers can perform the thrombin injection in conjunction with cardiology consultation.

Evidence

Compelling evidence exists regarding the effectiveness of thrombin injection for pseudoaneurysm treatment. A recent study by Ehieli et al. looked at 326 patients who underwent thrombin injection for femoral artery pseudoaneurysm formation. The procedure was successfully completed in 98.2% of cases. Complete thrombosis of the psuedoaneurysm was achieved in 74.5% of patients within the first 24 hours. Those patients who required a second injection had a 97% success rate [14]. In a study done by Paulson et al., percutaneous ultrasound-guided thrombin injection had a high success rate of 96%, in comparison to the 74% success rate of ultrasound-guided compression [21]. In another prospective non-randomized study of femoral artery pseudoaneurysms treated with thrombin injection, the overall success rate was 97% and was not adversely affected by anticoagulation use [19].

Key Points

Use in-plane needle visualization and guidance for best results.
Follow sterile precautions as with other similar procedures like central venous access.
Alternate between B-mode and color Doppler assessments during thrombin injection to detect for thrombosis and disappearance of color signal.
Maintain the needle tip in the periphery of the aneurysm sac and direct the needle away from the neck of the sac.
Use a curvilinear probe to assess the aneurysm sac in obese patients.
Do not inject a pseudoaneurysm with a sac size <1 cm because of risk of arterial thrombosis.
Use the minimal amount of thrombin required to occlude the pseudoaneurysm, and always perform post-procedural assessment, including Doppler and color flow imaging of the native femoral artery.
Anticoagulated patients are less likely to have complete thrombosis.

Peripherally Inserted Central Catheter (PICC) Placement

Peripherally inserted central catheters (PICCs) are useful in patients with limited peripheral venous access or in those who require intermediate-term access. Ultrasound guidance has been shown to have a significant impact on the overall clinical performance of PICCs. With ultrasound guidance, the practice of placing PICCs in the antecubital veins has been completely abandoned. By placing the PICCs in the deeper veins in the upper arm, ultrasound guidance has been associated with a 95–99% success rate and a considerable reduction in early and late complications [22]. Ultrasound guidance helps reduce complications such as inadvertent puncture of the brachial artery and median nerve. Ultrasound is a valuable tool for selecting the most appropriate vein prior to the procedure and for the navigation of the catheter. Typically, access is through the cephalic, basilic, or brachial veins of the upper arm. The paired brachial veins follow the brachial artery, but the cephalic and basilic veins have no accompanying artery. Due to their variable location, smaller size, and lower patency rates, blind procedures can be challenging. The use of ultrasound guidance for PICC placement has been shown to increase overall success rates while decreasing risk of phlebitis and thrombosis [23, 24].

Anatomy

PICC lines are often placed in the superficial veins proximal to the antecubital fossa (usually in the basilic, brachial, or cephalic veins) (Fig. 15.13).

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Venous anatomy of the lower extremity

Sonographic anatomy of peripheral veins is discussed in Chap. 12. Briefly, many of the vessels targeted for cannulation occur as paired artery and vein, and they must be distinguished from each other. While both are tubular and have an anechoic lumen, the artery has a thicker wall and may demonstrate visible pulsations. Veins are more readily compressible than arteries, are often larger than their arterial counterpart, and contain valves (Fig. 15.14). Although usually not necessary, color and spectral Doppler can be used to distinguish arteries from veins by virtue of flow direction and pulsatility.

../images/323313_1_En_15_Chapter/323313_1_En_15_Fig14_HTML.png — Fig. 15.14

B-mode image of (a) brachial veins, (b) basilic vein, (c) cephalic vein, (d) axillary vein