General Principles of Endovascular Therapy: Access Site Management

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.

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.