General Principles of Endovascular Therapy: Access Site Management




Historical Background


Throughout the 1940s and early 1950s, angiographic procedures required surgical exposure with placement of a blunt metal trocar and were often cumbersome and dangerous. A percutaneous approach was first described by Jönsson in 1949 with passage of a blunt trocar into the thoracic aorta via the common carotid artery. Seldinger’s report in 1953 was the first description of a soft, polyethylene catheter rather than a rigid metal trocar to achieve percutaneous access, which made the technique safer and, as a consequence, was widely adopted. With use of an introducer needle, followed by a “leader” or guidewire, a flexible catheter could be easily inserted into the artery or vein over a wire. This technique facilitated supine positioning of the patient, allowed repetitive contrast injections, and minimized bleeding at the access site. Subsequent development of catheters of different shapes allowed a range of angiographic imaging via the common femoral artery.




Indications


The common femoral artery is the most common axial vessel used to gain intravascular access for catheter-based procedures. This site allows wires and catheters to be placed in the aorta, as well as branch vessels to lower and upper extremities, renal and visceral vessels, and cerebral arteries. For atherosclerotic occlusive and aneurysmal disease, angiography is usually reserved for patients in whom delineation of the arterial anatomy and related vascular pathology is required for evaluation and treatment.


Although atherosclerotic occlusive disease remains the most common problem treated in the endovascular suite, less common indications for angiography via a common femoral artery access site include treatment of gastrointestinal bleeding, traumatic arterial injuries, arteriovenous fistulas, pseudoaneurysms and true aneurysms, arteriovenous malformations, tumor chemoembolization, and symptomatic uterine fibroids.


Although less common since the advent of duplex ultrasonography, historically, axial veins had been used as access sites for ascending and descending phlebography to evaluate lower extremity venous insufficiency and deep venous thrombosis. With the development of a growing array of catheter-based approaches for disorders of the venous system, the site for venous access is selected based on the task. For example, selected access points may include the common femoral, femoral, popliteal, posterior tibial, great saphenous, small saphenous, dorsal pedal, median antecubital, brachial, basilic, axillary, subclavian, and internal jugular veins. Common indications for percutaneous access via an axial vein includes placement and retrieval of inferior vena cava filters, as well as treatment of acute thrombosis of the femoral-popliteal, iliofemoral, and axillary-subclavian veins. Somewhat less common indications include treatment of chronic venous obstruction with angioplasty and stenting, pelvic congestion treated with sclerotherapy and embolization, pulmonary arteriography for diagnostic and therapeutic intervention, portal vein hypertension with transjugular intrahepatic portosystemic shunting, and venous blood sampling of adrenal and renal veins.




General Considerations for Access


Access Site


The location of the planned diagnostic or therapeutic intervention dictates the selection of left- or right-sided access sites, as well as the choice of an antegrade or retrograde approach in which access is obtained with the intent of passing a catheter in the same direction as or opposite to blood flow, respectively. The farther the planned task is from the access site, the less responsive catheters and wires may be in performing the procedure. This factor, as well as characteristics of the vascular pathway, including the presence of tortuosity, dilated or aneurysmal regions, and stenotic, calcified, compressed, or thrombosed segments, may also influence the selected access site. Other considerations include vessel diameter in relation to the diameter of the catheter required for the procedure, local vascular disease, scarring around the access site, and body habitus.


Coagulation


Review of the patient’s history, including use of medications, should be performed to assess risk of bleeding or thrombosis. For example, patients with renal failure, liver insufficiency, or other bleeding diatheses may need ultrasound guidance or use of a micropuncture needle. Likewise, repletion with appropriate blood products or use of a closure or compression device may be required upon completing the procedure.


The American College of Chest Physicians proposed guidelines for antithrombotic prophylaxis in patients receiving warfarin therapy with different risk factors ( Tables 3-1 and 3-2 ). If the annual risk for thromboembolism is low, warfarin therapy can be withheld for 4 to 5 days before a procedure without “bridging” with therapeutic subcutaneous low-molecular-weight heparin or intravenous unfractionated heparin. Bridging anticoagulation is recommended in patients with a history of a mechanical heart valve, atrial fibrillation, or venous thromboembolism who are at high risk for thromboembolism (e.g., known thrombophilia or hypercoagulable state, rheumatic atrial fibrillation, or arterial or venous thromboembolism within preceding 1-3 months) or moderate risk for thromboembolism (e.g., thromboembolism within preceding 6 months or atrial fibrillation with ejection fraction of less than 40% and valvular heart disease). Bridging therapy with low-molecular-weight heparin would need to be stopped 24 hours before the procedure. Bridging therapy has been associated with an increased risk of bleeding, including pseudoaneurysm formation after arterial puncture.



TABLE 3-1

Patients Who Should Receive Bridging Heparin: Risk for Thromboembolism




































High Moderate Low
Inherited thrombophilia Arterial or venous thromboembolism within 3-6 mo Arterial or venous thromboembolism after >6 mo
Unknown hypercoagulable state Atrial fibrillation with multiple risk factors for embolism (e.g., ejection fraction less than 40%, diabetes, hypertension, valvular heart disease) Atrial fibrillation without multiple risk factors for embolism
Arterial or venous thromboembolism within 3 mo Mechanical heart valve in aortic position
Rheumatic atrial fibrillation
Atrial fibrillation with history of embolism
Mechanical heart valve in mitral position
Intracardiac thrombus

Adapted from Jaffer AK, Brotman DJ, Chukwumerije N: When patients on warfarin need surgery. Cleveland Clinic J Med 70:973-984, 2003.


TABLE 3-2

Protocol for Low-Molecular-Weight Heparin as a Bridge for Patients on Warfarin






































Before Procedure After Procedure
If preoperative INR is 2-3:
Stop warfarin 5 days before procedure Restart low-molecular-weight heparin 24 hr after procedure
If preoperative INR is 3-4.5:
Stop warfarin 6 days before procedure Restart warfarin 24 hr after procedure
Start low-molecular-weight heparin 36 hr after last warfarin as follows: Daily PT and INR until INR is in therapeutic range
Enoxaparin (Lovenox) 1 mg/kg SC q12h or Discontinue low-molecular-weight heparin when INR is between 2 and 3
Enoxaparin (Lovenox) 1.5 mg/kg q24h
Dalteparin (Fragmin) 120 unit/kg SC q12h or
Dalteparin (Fragmin) 200 unit/kg SC q24h
Give last dose of low-molecular-weight heparin 24 hr before procedure
Ensure that INR is <1.8 prior to initiating procedure

INR, International normalized ratio; PT, prothrombin time; SC, subcutaneously.

Adapted from Jaffer AK, Brotman DJ, Chukwumerije N: When patients on warfarin need surgery. Cleveland Clinic J Med 70:973-984, 2003.


Patients who have had placement of a bare metal coronary stent within 6 weeks should have aspirin and clopidogrel continued during the periprocedural period. Likewise, continuing aspirin and clopidogrel is recommended if a drug-eluting coronary stent has been placed within the previous 12 months. Indeed, patients may be loaded with antiplatelet medications to minimize the risk of platelet thrombus formation if femoral, renal, or carotid angioplasty and stenting are anticipated.


Laboratory Testing


Basic testing should include an international normalized ratio (INR), a complete blood count to assess hemoglobin level and platelet count, and a serum creatinine to assess overall renal function.


Patient Positioning


Each area of the body that needs to be accessed percutaneously requires specific positioning to optimize success. Access to vessels in the femoral region requires the patient be in the supine position with arms to the side. A large abdominal panniculus should be taped so that it pulls the abdominal skin and adipose tissue superiorly to expose the groin area. Access in the popliteal fossa requires the patient be in the prone position. Access to the posterior tibial vessels requires the patient be in the supine position with the knee slightly flexed and externally rotated. Access to the brachial region requires the arm to be positioned perpendicular to the body. For access to the axillary region, the patient is best positioned by putting the hand behind the head. Access to the jugular vein is facilitated by elevating the patient’s shoulders to extend the neck, placing the patient in the Trendelenburg position, and turning the patient’s head away from the intended puncture site.


Anesthesia


The large majority of patients undergoing catheter-based procedures require short-acting intravenous sedatives, pain management with small doses of short-acting narcotics, and administration of local anesthesia at the access site. The importance of managing these three regimens cannot be underestimated in obtaining safe percutaneous access. With the exception of initial pain from injection of local anesthesia, obtaining access to axial vessels should be anxiety and pain free. Patients not meeting these criteria are more difficult to access because they may move suddenly and the potential for incomplete diagnosis, treatment, or avoidable errors is increased as a result of the operator’s desire to then rush through the procedure. A small minority of patients require general anesthesia as a result of overwhelming anxiety, prolonged procedure time, inability to remain immobile during the procedure, or anticipated pain that may be difficult to tolerate. Conversely, the rare patient who may not be able to tolerate intravenous sedation, such as a frail elderly patient or one with sleep apnea, may be better served with local anesthesia alone.


Ultrasound Guidance


Ultrasound guidance is a common adjunct to percutaneous access of axial vessels and is mandatory for accessing vessels that cannot be easily palpated. These include virtually all commonly accessed veins in the extremities. Other indications include obesity and edema or when accessing the jugular vein or an axillary or proximal brachial artery, where there may be an increased risk of injury to adjacent structures.


Direct visualization of the needle entering an axial vessel using ultrasound requires anticipation and timing of where the needle will be in relation to the depth of the vessel. When the transverse view is used for access, the point of skin puncture varies in terms of its distance from the ultrasound probe. This means that as the vessel becomes deeper, the distance between the needle puncture and where the ultrasound probe lay on the skin increases ( Fig. 3-1 ). Conversely, use of the longitudinal view of the ultrasound probe requires meticulous attention to maintaining the needle constantly in a single plane of view for direct visualization. Central to both techniques is the need for slow hand adjustments when using the ultrasound probe.




Figure 3-1


Relative positioning of the ultrasound probe and arterial entry needle. A , Retrograde access of the left common femoral artery is achieved by positioning the entry needle several centimeters away from the ultrasound probe. The path of visualization of the ultrasound probe should intersect with the trajectory of the needle and the common femoral artery. B , If the entry needle is placed too close to the ultrasound probe, access requires the needle to be positioned almost 90 degrees to the skin, which is not favorable for passing either subsequent guidewires or sheaths.

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Mar 13, 2019 | Posted by in VASCULAR SURGERY | Comments Off on General Principles of Endovascular Therapy: Access Site Management
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