How To Do Radial Artery Cannulation

In critically ill, unstable patients, especially those with refractory shock and respiratory failure, or in patients undergoing complex surgery with fluid shifts or blood loss:

• Continuous blood pressure measurement

• Repeated arterial blood gas measurements

• Repeated blood sampling for laboratory tests

Absolute contraindications

• An artery that is neither palpable nor detectable by ultrasonography (never try to cannulate a site simply because the artery is expected to be there)

• Unsuitable artery (eg, dialysis fistula at same limb, thrombosed or inaccessible artery, generalized limb ischemia)

• Inadequate collateral blood flow from ulnar artery circulation

• Full-thickness burns

• Local infection at the insertion site

Relative contraindications

• Coagulopathy (including therapeutic anticoagulation*) or recent/pending thrombolysis: The radial artery is the preferred arterial cannulation site in these situations; prolonged pressure (eg, 10 minutes or more) may be needed to stop bleeding/hematoma at the site.

• Local anatomic distortion (traumatic or congenital), or gross obesity

• History of prior surgery in the area

• Distal extremity ischemia/gangrene

* Therapeutic anticoagulation (eg, for atrial fibrillation) increases the risk of bleeding with radial artery cannulation, but this must be balanced against the increased risk of thrombosis (eg, stroke) if anticoagulation is reversed. Discuss any contemplated reversal with the clinician managing the patient's anticoagulation and then with the patient.

Complications include

• Hematoma

• Infection

• Damage to the artery

• Thrombosis (due to the catheter itself)

• Nerve damage

• Catheter misplacement

To reduce the risk of catheter-related infections, radial artery catheters should remain in place no more than 7 days and their transparent, occlusive dressings left undisturbed. Catheters should be removed as soon as they are no longer needed or if there are any signs of infection.

Rare complications include

• Distal ischemia and necrosis

• Pseudoaneurysm

• Arteriovenous fistula

• Cholesterol plaque (or atheroma); air, guidewire, or catheter embolism

Ischemia of the hand occurs rarely, due to thrombosis or embolism, intimal dissection, or arterial spasm. Collateral blood flow from the ulnar artery usually prevents significant ischemia. The risk of arterial thrombosis is higher in small arteries (explaining the greater incidence in women) and with increased duration of catheterization. The incidence of thrombosis and distal ischemia is much lower for femoral arterial catheterization. Occluded arteries nearly always recanalize after catheter removal.

Sterile procedure, barrier protection

• Sterile drapes, towels

• Sterile head caps, masks, gowns, gloves

• Face shields

Radial artery cannulation

• Arm board, gauze roll, and tape

• Sterile gauze (eg, 10 cm × 10 cm squares)

• 3-mL and 5-mL syringes

• Cannulation device (eg, integrated catheter and guidewire device; separate needle, guidewire and catheter; or peripheral venous angiocatheter [catheter-over-needle], 20 or 22 gauge)

• Blood pressure monitor; IV saline bag (500 mL), pressure bag, and hanger; integrated arterial pressure line or individual components (ie, pressure transducer, arterial line tubing [noncompliant pressure tubing], 3-way stopcocks)

• Nonabsorbable suture (eg, 3-0 or 4-0 nylon or silk)

An assistant or two is helpful.

• Arterial catheterization is done under universal (barrier) precautions and sterile conditions.

• A failed attempt to cannulate the radial artery may be followed by attempts more proximally, but only if arterial spasm does not occur and the radial pulse remains palpable. If the pulse is lost, further cannulation attempts of the artery—as well as of the ipsilateral ulnar artery—are prohibited.

• If the radial arteries cannot be cannulated, alternative arterial sites include brachial or dorsalis pedis arteries peripherally, or femoral or axillary arteries centrally.

Right Radial Artery

3D Model

• The radial artery lies close to the skin over the ventrolateral distal wrist, just medial to the radial head and lateral to the flexor carpi radialis tendon.

• Position the patient comfortably reclined or supine.

• Rest the patient's forearm supinated and with the wrist extended on the bed or a bedside table; support may be useful under the wrist.

• Stand or sit at the side of the bed so that your nondominant hand is proximal on the arm with the artery to be cannulated; this allows the natural movement of your dominant hand to insert the catheter in a proximal direction.

• Palpate the radial artery in detail with the tip of the index finger of your nondominant hand. Systematically palpate, release, and shift slightly over the artery, to precisely discern the center axis of the artery (the area of the strongest pulse).

• Some clinicians do the Allen test to determine whether there is sufficient collateral flow through the ulnar artery to perfuse the hand if the catheter occludes the radial artery. While the patient makes a tight fist, digitally compress both the ulnar and radial arteries. While continuing arterial compression, have the patient open the fist and spread the fingers, which should display a blanched palm and fingers. Then, release ulnar artery compression while maintaining radial artery compression. If the hand and fingers on the radial side reperfuse within 5 to 10 seconds, collateral circulation is considered adequate. Alternatively, just ascertain the presence of ulnar artery flow by palpation or Doppler evaluation.

• Supinate the forearm and tape both the hand and the mid-forearm to a dorsally placed arm board, with a gauze roll placed under the wrist to maintain moderate wrist extension.

Insert the needle into the artery

• Relocate the radial artery in the wrist as described previously, using your nondominant hand, and continue palpation to guide needle insertion into the artery.

• Using your dominant hand, hold the cannulation device between your thumb and forefinger. Orient the needle bevel facing up.

• Insert the cannulation device with the needle bevel facing up directly over the midline of the radial pulse at least 1 cm proximal to the radial head and advance it proximally (cephalad) at about a 30- to 45-degree angle into the skin, to intersect the artery.

• Steadily advance the cannulation device until a flash of bright red blood appears in the reservoir or barrel of the device, which indicates that the needle tip has entered the arterial lumen.

• Hold the device motionless in this spot.

If no blood flash appears after inserting a catheter-over-wire device 1 to 2 cm, slowly and gradually withdraw the device. If it had initially passed completely through the artery, a blood flash may now appear as the needle tip is withdrawn, passing back into the lumen. If a flash still does not appear, withdraw the device almost to the skin surface, change direction, and try again to advance it into the artery.

If no blood flash appears after inserting an angiocatheter 1 to 2 cm, hold the catheter steady and slowly withdraw the needle from it. A blood flash may appear if the needle tip alone had pierced the deep arterial wall. If a flash does not appear, keep withdrawing the needle until it is removed, and then slowly withdraw the catheter. If a flash appears, stop withdrawing and try to advance the catheter into the artery (some operators insert a guidewire before readvancing the catheter, to facilitate the catheter's passage into the arterial lumen).

If rapid local swelling occurs, blood is extravasating. Terminate the procedure: Remove the needle and use gauze pads to hold external pressure on the area for 10 minutes or more, to help limit bleeding and hematoma.

Insertion of an Arterial Cathe...

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• Not carefully determining the exact center of the pulse makes it more likely to miss the artery.

• Sliding your finger from side to side as you attempt to locate the point of maximum pulsation may give an inaccurate result; lift and reposition your finger laterally to each new location.

• If the artery is not entered when the needle has reached an appropriate depth, do not try to reposition the needle by moving the tip to one side or another; this can damage tissue. Instead, withdraw the needle almost to the skin surface before changing the angle and direction of insertion.

• Never inject drugs into an arterial line.

• During cardiopulmonary arrest or other conditions of low blood pressure and hypoxia, arterial blood may be dark and not pulsatile and may be mistaken for venous blood.

• Avoid pushing too hard on the artery while palpating the pulse during needle insertion; doing so may compress the artery and make it harder to cannulate.

• Some arterial lines are sensitive to wrist position; be alert to changes in the pressure and/or waveform with patient movement. The wrist may need to be immobilized in the most satisfactory position.