3.1 Positioning & Vascular Access Assessment

Positioning & Vascular Access Assessment

Cardiac-interventional cases go wrong as often from a poorly chosen stick and an unsecured patient as from a difficult coronary. American Registry of Radiologic Technologists (ARRT) Cardiac-Interventional Radiography Patient Care items B.6 and B.7 ask the R.T.(CI) to position the patient so imaging, sterile technique, and hemodynamics can proceed, then to assess vascular patency, peripheral pulses, anatomical location, and imaging before anyone picks up a needle.

Quick Answer: Strap, pad, and wedge the patient so they cannot contaminate the field or develop a pressure or plexus injury. Confirm dual palmar circulation before radial work (Allen test or Barbeau test). For femoral access, puncture the common femoral artery (CFA) over the medial femoral head—not above the inguinal ligament and not below the bifurcation.

Positioning (B.6): straps, padding, wedges, and arm boards

The table is narrow, the C-arm will swing through steep angles, and moderate sedation blunts the patient's ability to protect themselves. Positioning is a safety skill, not housekeeping. Decide the access plan first, then build the table around that plan. Tucking both arms in draw sheets and then announcing a right-radial percutaneous coronary intervention (PCI) means you will break the drape to free the wrist.

Velcro straps

Apply Velcro straps across the thighs or lower abdomen (below the planned sterile field) and, when the arms are tucked, across the forearms. The exam-relevant reason is not so the pictures look still. A startled or lightly sedated patient reaches toward the groin or wrist. That hand contaminates the field, dislodges a sheath, or flexes a radial wrist into spasm. Straps also keep the patient on the table when the operator uses steep Trendelenburg, reverse Trendelenburg, or aggressive table panning.

Trap: A strap across the chest restricts ventilation and fights defibrillation-pad and electrocardiogram lead placement. A strap that sits on the femoral access site is worse than no strap. Recheck strap tension after you rotate the table or drop the rail.

Padding and brachial plexus protection

Long fluoroscopy times on an unpadded table produce pressure injuries over the occiput, sacrum, heels, and elbows. Pad those points before the drape goes on; you will not get another clean look once the sterile field is up. Heels hang off many tables—foam or gel under the calcaneus is not optional on a two-hour case.

Arm position is a plexus problem. If the arms are tucked at the sides for femoral or jugular work, keep them slightly flexed at the elbow, palms toward the thigh, with foam between the arm and the metal rail. Extreme adduction against a hard rail, or letting the arm hang off the table, stretches the brachial plexus. Do not abduct an arm above 90 degrees on an arm board just to get it out of a femoral beam—that is a classic stretch injury. Watch the tucked elbow when the C-arm comes in for a steep left anterior oblique: the housing can crush an unprotected olecranon.

For radial access, use a dedicated arm board. The wrist is slightly extended and supinated, often with a small roll under the dorsum, and the board is locked so the arm cannot fall when the table moves. Slight extension opens the radial artery at the styloid; extreme hyperextension can flatten the artery and make the stick harder, not easier. The elbow stays padded. Left-radial cases need the same board on the left, not a tucked left arm and a hopeful drape.

Trap: Arms in the primary beam raise patient dose, raise scatter to the operator, and degrade image quality. Tucking is for femoral and jugular work. Radial work keeps that arm on a board, out of the thorax field of view.

Wedges

Wedges under the knees reduce lumbar strain and help an arthritic patient tolerate a long recumbent case. A small hip wedge can rotate the pelvis just enough to open a femoral puncture angle in a patient who cannot frog-leg. From an imaging standpoint, extra tissue in the beam is scatter. Support pannus so it does not hang through the collimated field, keep arms out of the thorax, and use wedges to reduce unnecessary bulk rather than as a substitute for collimation. Comfort is not cosmetic: a patient who is already in pain will move, which is how sterile fields and sheaths are lost.

Access assessment (B.7)

Assessment has four official leaves. Treat them as a sequence, not a menu you pick from after a failed stick.

Vascular patency: ultrasound, Allen test, Barbeau test

Ultrasound is the real-time patency test for femoral and jugular access: lumen size, plaque, thrombus, dissection flaps, and the CFA bifurcation are visible before the needle moves. For the wrist, ultrasound shows radial diameter (many operators want about 2 mm or larger), calcification, and loops that will fight a wire.

The Allen test screens the palmar arches. The patient makes a fist while you occlude both the radial artery and the ulnar artery. Open the hand (it should be blanched), then release the ulnar artery only. Return of palmar color within about 5–10 seconds supports ulnar collateral flow. Persistent pallor is an incomplete Allen test—do not cannulate that radial artery as if dual circulation were proven. A bounding radial pulse does not replace this step.

The Barbeau test replaces subjective color with a pulse-oximeter waveform on the thumb or index finger. Compress the radial artery and read the tracing:

Types A and B are the usual go patterns. Type D is a fail. The dual-circulation rationale is simple: radial artery occlusion (RAO) after sheath placement is not rare. If the ulnar artery and palmar arches supply the hand, RAO is usually tolerated. If they do not, a wrist stick becomes an ischemic hand. Document the type in the record the same way you document a pulse.

Peripheral pulses: palpation and Doppler

Palpate radial, ulnar, brachial, femoral, dorsalis pedis, and posterior tibial pulses as the case requires, and document them before you puncture. A bounding femoral pulse with an absent pedal pulse does not cancel every angiogram, but it should change the conversation about iliac disease, sheath size, and whether a closure device belongs in that groin. If you cannot feel a pulse, use a handheld Doppler and mark the signal. After the case, compare to the baseline. Loss of a previously documented Doppler signal is a vascular emergency, not a wait-and-see finding, and it is how you catch occlusion, embolism, or an over-tight hemostasis band while there is still time to fix it.

Anatomical location: femoral artery and vein, radial artery, jugular vein

CFA and femoral vein. The arterial target is the CFA over the medial femoral head on fluoroscopy, below the inguinal ligament and above the CFA bifurcation. Too high (above the ligament or clearly superior to the femoral head) risks retroperitoneal hemorrhage because you cannot compress the vessel against bone. Too low (below the femoral head, into the superficial femoral artery (SFA) or profunda femoris) risks thrombosis, dissection, arteriovenous fistula, and failed closure devices that were designed for the CFA. Remember NAVEL in the femoral triangle, lateral to medial: Nerve, Artery, Vein, Empty space, Lymph. The femoral vein is medial to the artery. A stick that is too medial is a venous or mixed puncture; a stick that is too lateral threatens the femoral nerve.

Radial artery. Right radial is the default for most operators standing at the patient's right. Left radial is the practical choice for left internal mammary artery (LIMA) graft angiography, because the path is more direct, and when the right radial is occluded, diminutive, or has a severe loop. Assess and document the wrist you actually intend to use. Dual circulation still applies on the left.

Internal jugular vein (IJ). Preferred for right-heart catheterization, temporary pacemaker wires, and some pulmonary procedures. The right IJ is a straighter shot to the superior vena cava and right atrium. This is a venous assessment: compressibility and ultrasound landmarks, not an Allen test. The carotid artery is typically medial to the IJ; a carotid puncture is the complication you are trying not to have.

Imaging: ultrasound and fluoroscopy

Ultrasound of the groin should show the CFA bifurcation. Puncture above it. Distinguish vein from artery: the vein is compressible, usually medial, and has a continuous or respirophasic Doppler signal; the artery is pulsatile, less compressible, and has a triphasic or biphasic arterial Doppler waveform. Fluoroscopy of the femoral head remains the landmark check even when ultrasound is used—confirm the needle is over the medial femoral head before you upsize the sheath. For IJ, ultrasound is the expected confirmation of location, not a landmark-only stick. For radial, ultrasound plus Barbeau or Allen is the pair; fluoro of the wrist is not a substitute for palmar-arch testing.

Femoral vs radial vs internal jugular assessment

Scenario

A 68-year-old is booked for elective PCI. The right radial pulse is 2+, but Barbeau compression of the radial artery flattens the oximeter tracing and it never returns (type D). The left radial is Barbeau B. Do not use the right radial because the pulse feels strong. Dual circulation failed on the right. Reposition with a left arm board, repeat the assessment, or move to a documented femoral plan with fluoroscopic femoral-head landmarks and ultrasound of the CFA bifurcation. Strap the unused arm so a startle cannot contaminate the new field.

Exam traps

• A strong radial pulse does not prove palmar collaterals. Barbeau type D is a fail even if the pulse is bounding.
• High femoral stick is the retroperitoneal-bleed answer. Arteriovenous fistula is more a low or side-wall problem that catches both artery and vein.
• IJ is a vein. You do not assess it with an Allen test, and you do not treat a carotid waveform as a successful venous access.
• Arms tucked is the femoral/IJ default; radial PCI that starts with both arms tucked is a positioning error, not a time-saver.