Radial Artery Sheath Insertion Technique

Most radial artery sheaths have a hydrophilic coating to minimize vasospasm. ^[8] Agents such as diltiazem, verapamil, nitroglycerin, papaverine, or adenosine may be given in addition to prevent radial artery spasm; they may be administered during sheath advancement through the guide wire, after completion of the procedure but before removal of the radial sheath, or both.

Heparin is routinely given to prevent thrombosis at the site of sheath insertion. The amount used ranges from 40 to 70 U/kg, depending on the duration and degree of vascular intervention required. Heparin may be administered either via the arterial sheath or intravenously (IV). When given intra-arterially, it is often diluted with the patient’s own blood, which can be extracted from the sidearm.

Sheath insertion with cannula-over-needle

After the wrist has been appropriately prepared, palpate for the radial artery (see the image below). Infiltrate local anesthetic subcutaneously at least 2 cm proximal to the radial styloid process (in the region where the radial artery pulse is best appreciated) to form a small wheal.

Insert the cannula-over-needle through the skin at an angle of approximately 45°, directing it proximally toward the radial artery at its expected course. Advance the device slowly until pulsatile bright (arterial) backflow of blood is achieved and is visible in the needle (see the image below). Gently feed the cannula through, and remove the needle. Backflow of blood through the cannula should still exist.

Unsuccessful radial artery puncture commonly provokes radial artery spasm, temporary loss of the radial pulse at the site of puncture, and hematoma formation. In this situation, the following measures may be attempted:

• Wait several minutes while applying pressure over the puncture site to ensure hemostasis, then reattempt arterial puncture
• Give IV fluid and a further bolus of midazolam (eg, 1 mg) to alleviate spasm
• Move to a site proximal to the original site

After the artery has been successfully punctured, introduce the guide wire through the cannula. Once the guide wire has been smoothly advanced through the device, remove the cannula while leaving the guide wire in place (see the image below); the guide wire will be used to guide the sheath into the radial artery. To avoid accidental embolization of the guide wire, the length of wire left exposed outside the patient must always be greater than the length of the sheath. Always hold onto the wire with a hand.

Difficulty in advancing the guide wire may be caused by the artery being in spasm, the wire entering a small branch vessel, or the needle partly entering or having gone through the vessel wall. In this situation, the following measures may be attempted:

• Confirm that the needle remains in the correct vessel by removing the wire and observing arterial flow (blood from a venous puncture dribbles out and is nonpulsatile, and venous blood is darker than arterial blood)
• Retract the wire, spin it gently, and try advancing it again
• Try a hydrophilic-coated wire
• Manipulate the angle of the bevel by rotating the needle

Introduce the sheath (with the dilator inserted) over the guide wire into the radial artery. A small superficial skin incision may be made where the guide wire enters through the skin to facilitate smooth passage of the sheath. If resistance occurs, the tip of the wire may be watched via fluoroscopy. If resistance is met and the sheath is definitely in the artery, the guide wire may be removed, and verapamil 2.5-5 mg, nitroglycerin 200 µg, or both may be injected through the sheath dilator.

After the insertion of the sheath, if passing a 0.035-in. guide wire is difficult, angiography may be performed to check the arterial anatomy.

Once the sheath is fully advanced, the guide wire and the dilator assembly may be removed (see the image below). After the removal of the dilator, the sidearm may be used for administration of compatible medications (eg, heparin, verapamil, and nitroglycerin; diazepam must not be administered intra-arterially).

Inject antispasmodic agents (eg, verapamil 2.5-5 mg ^[9] diluted in blood) through the sheath via the sidearm. Anticoagulants (eg, heparin 5000 U) may be administered either via the sheath or IV, depending on the procedure performed. If necessary, the sheath may be secured with a transparent bandage.

In some cases, the sheath proves difficult to remove, usually as a consequence of vasospasm. In this situation, the following measures may be attempted:

• Wait, then reattempt sheath removal while applying gentle traction
• Gently rotate the sheath during removal
• Give additional doses of sedative or antispasmodic agents and reapply gentle traction

Sheath insertion with micropuncture needle

In general, sheath insertion with the micropuncture needle is similar to sheath insertion with the cannula-over-needle. However, the needle must be held steady once backflow occurs. Advance the guide wire through the needle in the same fashion as for the cannula-over-needle technique, again taking care not to lose the guide wire. If the wire advances smoothly, remove the needle while keeping the wire in place, then proceed with the introduction of the sheath as described above.

Complications of radial artery sheath insertion include the following ^[10] :

• Local bleeding at the access site
• Forearm hematoma due to a side-branch vessel perforation
• Pseudoaneurysm formation
• Radial artery occlusion (RAO)/thrombosis ^{[11, 12, 13, 14]}  - This may be less likely with a sheath technique than with a sheathless technique ^[15]
• Brachial artery thrombosis

Rashid et al, in a review of RAO after transradial interventions, reported postintervention RAO rates ranging from less than 1% to 33%. ^[16] In this review, a higher heparin dose was the most efficacious means of reducing RAO; shorter compression times were also found to reduce RAO. Distal puncture sites (0-1 cm from the styloid process) may be associated with higher RAO rates after transradial interventions. ^[17]

In a study of cases of RAO arising after radial artery access in patients requiring repeat cardiac catheterization, Schulte-Hermes et al found that it was feasible to gain access to an occluded radial artery by means of percutaneous transluminal angioplasty. ^[18]

Distal transradial access (DTRA) has been advocated as having several potential advantages over conventional transradial access (TRA), including greater operator and patient comfort, faster hemostasis, and lower risk of proximal RAO. In a study by Oliveira et al (N = 3683), the use of DTRA as standard for routine coronary interventions was found to be safe and feasible. ^[19]

The DISCO RADIAL (Distal vs Conventional Radial Access) trial (N = 1307) compared conventional TRA (n = 657) with DTRA (n = 650) for coronary angiography and intervention; the primary endpoint was the incidence of forearm RAO assessed by vascular ultrasonography at discharge. ^[20] The two approaches had equally low RAO rates. DTRA was associated with a higher crossover rate but a shorter hemostasis time. In the authors' view, conventional TRA remains the gold-standard vascular access in this setting, but DRA is a valid alternative.