Radial artery access

Radial artery access is a minimally invasive approach for vascular access in interventional procedures. This route has widely been adopted since it reduced significantly the transfemoral-related complications. It is the recommended access route by the European Society of Cardiology for angiography and interventions in patients with ST-elevation myocardial infarctions¹.

Advantages

Compared to transfemoral or transbrachial access, the radial approach decreases the incidence of complications such as^2,3:

• access site bleeding

• pseudoaneurysm

• arteriovenous fistula

Disadvantages

• inability to use larger sheaths

• risk of radial artery spasm

• increased radiation exposure

• potential need for crossover to femoral access

• not adapted for lumbar and bronchial artery catheterization

Radial access is a harder technique compared to the femoral approach and is associated with a higher cannulation failure rate⁴ because:

• the distal radial artery has a small diameter

• existence of anatomical variants

• are more prone to thromboembolic disease than the femoral artery

Preprocedural assessment

Examination of radial pulse.

Confirm adequate collateral circulation to the hand, to ensure blood supply in case of radial artery spasm/occlusion by performing:

• Allen test

• Barbeau test

Ultrasound duplex assessment

• measure the diameter of the radial artery, to select the correct sheath size. The radial artery-to-sheath diameter should be <1

• verify the patency of the radial and brachial arteries and look for stenosis or thrombosis

Patient preparation

Monitoring with finger pulse oximeter of the accessed hand to assess the integrity of blood supply to the hand.

Anxiolytics and analgesics - to reduce the risk of radial artery spasm.

Sterilize the area from the mid-forearm to the flexor crease.

The groins can be sterilized to facilitate femoral access in case of radial cannulation failure or if mechanical support is needed.

The arm should not be flexed (could block the advancement of catheters and wires) but rather extended on a movable splint or arm board.

Material preparation

The material generally prepared consists of:

• short 5-6F sheath catheter (10 to 11 cm in length) - the size depends on the radial artery diameter

• for vessel puncture

  • 20 G angiocath - if double-wall through-and-through approach is to be used

  • or a micropuncture needle (19- 21G) for single-wall anterior puncture approach

• access wires

  • metallic access guidewire if a micropuncture needle is used, to avoid stripping the hydriophilic coating with the needle tip

  • hydrophilic access guidewire if an angiocath is used

• "radial cocktail"⁵

  • 1.25 mg of verapamil

  • 100 μg of nitroglycerin

  • 5,000 IU of heparin

Flush the sheath catheter and the tapered tip dilator. The access guidewire should be damped in heparinised saline.

Procedure

Local anesthesia

• lidocaine 1% mixed with Isosorbide dinitrate - to promote arterial dilatation.

Ultrasound-guided puncture of artery

• the distal artery is preferred over the proximal segment since it offers a better position for the patient and operator

• doublewall through-and-through approach or single-wall anterior puncture

• the needle tip should be headed towards the navigation direction (towards brachial artery), and should be at 45º from the skin surface.

• the transducer is placed 2.5 - 5 mm from the needle tip

Access wire exchange

• when the angiocath/needle tip is within the lumen of the artery, decrease the angle to the skin surface to allow the access wire to pass

• Insertion of the access wire

• advance the wire until it traverses the elbow

• any resistance is abnormal and require visualization under ultrasound/fluoroscopy.

The causes of guidewire resistance may be :

• extra-arterial location

• the wire is in a small branch

• wire in the subintimal position

Placement of sheath catheter

• slowly introduce the sheath over the wire

• remove dilator

• aspirate and flush heparinised saline

• the "radial cocktail" should be diluted with approximately 20 ml of aspirated blood and injected over one minute, to avoid patient discomfort during the injection⁶

Radial angiography

To confirm radial patency and to screen for loops and anomalies before introducing larger catheters.

Sheath fixation - optional

The sheath can be fixed with a transparent adhesive pad to prevent accidental removal during the procedure.

Complications

• radial artery occlusion - higher risk when the ratio of radial artery inner diameter to sheath catheter outer diameter < 1 ⁷

• radial artery injuries

  • intimal tears

  • medial dissections

  • chronic intima-media thickening

• sheath catheter thrombus migration

  • this complication happens following selective access catheters exchange, and to avoid it, an aspiration through the sheath catheter should be performed before insertion of the new catheter