APPROACHES FOR ENDOVASCULAR ACCESS
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As is the case for any procedure, proper patient positioning and access is vital to achieving successful outcome and minimizing morbidity. For acute stroke intervention using endovascular techniques, patients are placed supine on the angiography table. Both groins are prepared in usual sterile fashion so as to provide immediate access to a second puncture site should one be needed or if the first cannot be successfully accessed. For femoral access, an imaginary line between the anterior superior region of the iliac spine and the pubic tubercle is visualized; a puncture site is localized three finger-breadths below this line. The groin may be imaged using AP fluoroscopy. The acetabulum may be used as a bony landmark for access to the artery; puncture site should ideally be in the inferior third of the head of the femur. A local anesthetic is then used to infiltrate this area, and a needle is thrust in at a 45-degree angle toward the umbilicus. Some interventionists incise the skin before performing the puncture. The needle may sometimes be used to palpate the bounding pulse of the femoral pulse and redirected to the point where the pulsations are best appreciated.
Once excellent arterial blood return through the puncture needle is visualized, the operator’s left hand stabilizes the needle, while a j-shaped wire is inserted through the needle with the right hand. The needle is removed, and a 5-French sheath is inserted over the wire and attached to a heparinized-saline flush. A diagnostic catheter is inserted through the sheath and advanced into the aortic arch over a hydrophilic guide wire. Diagnostic angiography is performed to elucidate the angiographic anatomy responsible for the patient’s neurological condition.
The femoral artery is an excellent choice for access in the setting of acute stroke interventions for several reasons, including ease of access, familiarity with the approach, and the ability of the vessel to accommodate large sheaths. A population of patients exists, however, in whom femoral access is difficult or associated with increased morbidity.16,17 As much as 10% of the general population may have severe peripheral vascular disease, femoral artery occlusion, previous femoral artery bypass graft placement, or morbid obesity precluding successful negotiation of diagnostic and/or guiding catheters beyond the aortoiliac junction.16,17 The transradial or transbrachial approach is becoming an alternative to transfemoral access for this patient population.
With the advent of smaller delivery apparatus for endovascular thrombolysis, 5-French sheaths are needed to allow delivery of the associated balloons, stents, snares, and other devices within the extracranial and intracranial circulation. Cardiologists have long been using the transradial and transbrachial approach for angioplasty and stenting, as the radial artery can accommodate up to an 8-French sheath quite well.18,19 Some investigators have placed 8-French sheaths with low rates of complication and permanent occlusion of the radial artery.20 These large sheaths must be immediately removed following the procedure to minimize the chances for radial artery occlusion. Additionally, a mixture of heparin (5000 international units/ml), verapamil (2.5 mg), lidocaine (2%, 4 ml), sodium bicarbonate (42 mg), and nitroglycerin (0.2 mg) is infused through the introducer sheath to relieve and/or prevent vasospasm immediately following insertion of the sheath.
We caution that patients must demonstrate adequate collateral circulation of the hand through the ulnar artery via an Allen test (following continuous compression of both the radial and ulnar arteries during finger extension, the ulnar artery is released; and the duration of time necessary to achieve visual capillary refill and at least 92% oxygen saturation at the finger pads is measured).21 Although several investigators have demonstrated the effectiveness of transradial cerebral angiography and intervention in the elective setting, the transradial approach should be considered in the setting of acute stroke should the transfemoral approach not be feasible.22-24 Contraindications to the transradial approach include a failed Allen test and chronic occlusion of either the ipsilateral subclavian artery or the brachiocephalic trunk.
Reprinted with permission from Mohr JP, Choi DW, Grotta JC, Weir B, Wolf PA (eds): STROKE: PATHOPHYSIOLOGY, DIAGNOSIS, AND MANAGEMENT (4th edition), pp. 1475-1520 (chapter 78), Copyright Elsevier 2004. Permission has been granted to reproduce this material in online electronic format for non-exclusive world English rights