Radial Artery Sheath Insertion

The radial artery access sheath is used to gain arterial access and facilitate the insertion of catheters or other equipment for diagnostic and vascular interventions.[1]  Compared with procedures performed via the commonly used femoral artery access route, procedures performed via the radial artery route allow shorter recovery time, earlier ambulation, earlier discharge, and lower incidences of access-site complications, as well as being advantageous for patients with occlusive aortoiliac disease or peripheral vascular disease.

However, specific challenges exist in using radial artery sheath access. The radial artery is smaller than the femoral artery, and thus, more finesse and experience are required to access this vessel. In addition, a smaller sheath precludes the use of larger catheters and equipment, which may be needed for major operations. Finally, radial artery spasm is a risk, necessitating routine use of antispasmodic medications.

Indications for radial artery sheath insertion include the following:

• Coronary angiography and percutaneous coronary interventions
• Neuroangiography and possibly neurointerventions ^{[2, 3, 4]}
• Assisting with other endovascular thoracoabdominal procedures ^{[5, 6]}

Absolute contraindications for radial artery sheath insertion include the following:

• Patients with an abnormal Allen test result
• Patients who require support devices such as an intra-aortic balloon pump (IABP) or other devices that are not compatible with sheaths smaller than 7 French
• Patients with known congenital or noncongenital vascular anomalies of the upper limb
• Patients with known upper-limb peripheral vaso-occlusive disease, including thromboangiitis obliterans (Buerger disease) and Raynaud disease

Relative contraindications for radial artery sheath insertion include the following:

• Patients with chronic renal failure who require consideration of an arteriovenous fistula in the upper limb
• Patients whose radial artery is being considered as a conduit for coronary artery bypass grafting (CABG)
• Patients requiring angiographic evaluation of internal mammary artery (IMA) grafts after CABG; in such cases, access may be obtained via the ipsilateral radial artery (ie, the left radial artery for a left IMA graft and the right for a right IMA graft) because the contralateral IMA is very difficult or impossible to access and carries an increased risk of vascular complications

Anatomy

Before attempting to insert a radial artery sheath, the operator should be familiar with the anatomy of the blood supply to the hand. The radial artery is a branch of the brachial artery, originating above the elbow. It passes down the forearm between the tendons of the brachioradialis and the flexor carpi radialis and winds around the lateral aspect of the radius. It then crosses the floor of the anatomic snuffbox to pass between the two heads of the first dorsal interosseous muscle to join the deep palmar arch.

The collateral circulation is supplied via the ulnar artery and should be assessed by performing the Allen test. This can be done either visually or with oximetry. An abnormal Allen test result is a contraindication for radial access.

Two types of needles are commonly used for arterial puncture, as follows:

• A micropuncture needle, which is placed by using a Seldinger technique with a guide wire
• A cannula-over-needle, which is then used to upsize to a sheath over a guide wire

The choice of the needle set is dictated by the operator’s preference and familiarity.[7] Depending on the procedure, different diagnostic and guiding catheters can subsequently be inserted through the sheath. Various kits that include both the needle and the radial sheath are available (see the image below).

Basic setup for insertion of 6-Fr radial sheath.

The equipment list for radial artery sheath insertion includes the following:

• Local anesthetic agent of choice
• Topical anesthetic (optional)
• Needle (ie, a micropuncture needle or a cannula-over-needle assembly; see the first image below)
• Guide wire – A 0.021- to 0.025-in. uncoated or hydrophilic wire is used to exchange the needle for the sheath
• Radial artery sheath – This may range from 4 to 7 French in size (the authors recommend a sheath length of 10 cm) and should come with a dilator assembly (see the second image below)
• Skin scalpel
• Antispasmodic agent of choice (eg, verapamil 2-5 mg)
• Medical towel or hyperextension splint for positioning
• Alcohol-based sterilizing solution (eg, chlorhexidine)
• Angiography drapes
• Sterile gloves and gown

Radial artery sheath insertion. Shown are micropuncture needle (above) and cannula-over-needle (below).

Radial artery sheath insertion. Shown are 5-Fr and 6-Fr radial access sheath with dilator inserted through sheath ready to be used.

Anesthesia

A combination of local anesthesia and light sedation is often effective before the procedure. A popular choice of local anesthetic is 1-2 mL of 1% lidocaine. Topical anesthetic cream can be applied to alleviate discomfort and reduce the amount of local anesthetic injected. Midazolam 1-5 mg for sedation is helpful to reduce vascular tone and the frequency of arterial spasm.

Positioning

All obstructing jewelry and clothing should be removed from the wrist that is being accessed. Intravenous access should always be obtained, preferably on the contralateral side; alternatively, central venous access may be obtained if necessary. The wrist should be shaved to remove excess hair if necessary. A medical towel can be placed underneath the wrist to keep it in hyperextension (see the image below), or a hyperextension splint can be applied.

Radial artery sheath insertion. Wrist is positioned by using medical towel. Hyperextension splint may also be used.

The skin is sterilized with an alcohol-based skin preparation. The groin should also be prepared for access in the event of a failed radial artery insertion. The angiography drape is applied so as to expose the wrist in an area where the radial artery pulse will be palpable.

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.

Radial artery sheath insertion. Palpate for radial artery at its expected course.

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.

Radial artery sheath insertion. Puncture radial artery using either micropuncture needle or cannula-over-needle assembly until flashback of arterial blood is observed.

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.

Radial artery sheath insertion. Insert guide wire through cannula/micropuncture needle. Once guide wire is sufficiently inserted, cannula/micropuncture needle is removed, leaving guide wire in place.

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).

Radial artery sheath insertion. Once radial sheath is sufficiently advanced, remove guide wire and dilator.

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.

The goals of pharmacotherapy are to reduce morbidity and prevent complications.

Class Summary

Anticoagulants prevent recurrent or ongoing thromboembolic occlusion of the vertebrobasilar circulation. In patients with heparin-induced thrombocytopenia, LVAD implantation has been performed successfully, albeit with additional risk, by using alternative anticoagulants.

Heparin

Heparin may be used if thrombocytopenia is not present. Heparin augments the activity of antithrombin III and prevents the conversion of fibrinogen to fibrin. It does not actively lyse but is able to inhibit further thrombogenesis. Heparin prevents the recurrence of a clot after spontaneous fibrinolysis.

Heparin is routinely given to prevent thrombosis at the site of sheath insertion. The amount used ranges from 40-70 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.

Class Summary

Vasodilators dilate the mesenteric arterial system. Thereby, they reverse reactive arterial vasospasms. 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.

Papaverine

Papaverine is a benzylisoquinoline derivative that exerts a direct nonspecific relaxant effect on vascular, cardiac, and other smooth muscle. In the absence of peritoneal signs, it is the drug of choice for acute myocardial infarction (AMI) of arterial origin if angiography indicates good distal perfusion. Papaverine is advocated for the treatment of the widespread vasoconstriction that follows therapy for superior mesenteric artery (SMA) emboli by other modalities.

Nitroglycerin (Nitro-Dur, Nitro-Bid, Nitrolingual, Nitrostat)

Nitroglycerin produces vasodilator effects on the peripheral veins and arteries.

Class Summary

Agents that prevent radial artery spasm may be used.

Adenosine (Adenoscan, Adenocard)

When used in myocardial perfusion, scintigraphy reveals areas of insufficient blood flow. Adenosine increases blood flow and causes coronary vasodilation in normal coronary arteries, while it causes little or no increase in stenotic coronary arteries. Adenosine is also a short-acting agent that alters potassium conductance into cells and results in hyperpolarization of nodal cells.

Class Summary

Calcium channel blockers are used to prevent radial artery spasm.

Diltiazem (Cardizem, Dilacor XR, Diltzac, Matzim LA)

During depolarization, diltiazem inhibits calcium ions from entering slow channels and voltage-sensitive areas of vascular smooth muscle and myocardium.

Verapamil (Verelan, Calan)

Verapamil relaxes coronary vascular smooth muscle and produces coronary vasodilation.