Either an integrated catheter-over-guidewire device or an angiocatheter (catheter-over-needle) is used to thread a catheter into the radial artery.
The radial artery is the most frequent site used for arterial catheterization.
Ultrasound guidance, when equipment and trained personnel are available, is helpful in cannulating nonpalpable arteries (eg, due to hypotension or a small artery).
(See also Vascular Access and How To Do Ultrasound-Guided Radial Artery Catheter Insertion.)
Indications
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
Contraindications
Absolute contraindications:
An artery that is neither palpable nor detectable by ultrasound (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 over the femoral artery as an arterial cannulation site in these situations; prolonged pressure (eg, 10 minutes or more) may be needed to stop bleeding or hematoma formation at the site.
Local anatomic distortion (traumatic or congenital)
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 risk 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
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 be removed as soon as they are no longer needed, and their transparent, occlusive dressings should be left undisturbed..
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.
Equipment
Sterile procedure, barrier protection:
Antiseptic solution (eg, chlorhexidine, povidone-iodine, isopropyl alcohol)Antiseptic solution (eg, chlorhexidine, povidone-iodine, isopropyl alcohol)
Sterile drapes, towels
Sterile head caps, masks, gowns, gloves
Face shields
Radial artery cannulation:
Arm board, gauze roll, and tape
Local anesthetic (eg, 1% lidocaine without epinephrine, 25-gauge needle, 3-mL syringe)Local anesthetic (eg, 1% lidocaine without epinephrine, 25-gauge needle, 3-mL syringe)
Sterile gauze (eg, 10 cm × 10 cm squares)
3-mL and 5-mL syringes
Cannulation device based on equipment availability or operator preference
Integrated catheter and guidewire device; separate needle, guidewire, and catheter
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)
Chlorhexidine patch, transparent occlusive dressingChlorhexidine patch, transparent occlusive dressing
Having 1 or 2 assistants is helpful.
Additional Considerations
Arterial catheterization is performed 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 the brachial or dorsalis pedis arteries peripherally, and the femoral or axillary arteries centrally.
Relevant Anatomy
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.
Positioning
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 placement allows the natural movement of your dominant hand to insert the catheter in a proximal direction.
Step-by-Step Description of Procedure
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 ascertain the presence of ulnar artery flow by palpation or Doppler evaluation to evaluate for collateral flow (1).
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.
Prepare the equipment and the sterile field
Assemble the arterial pressure–monitoring equipment: Place the IV saline bag within the pressure bag (unpressurized), connect the arterial pressure tubing to the saline bag, and squeeze residual air from the bag into the line. Hang the bag, pinch the drip chamber to fill it halfway with fluid, and run solution through the tubing to flush the air out. Connect (plug in) the pressure transducer to the pressure monitor. Situate the transducer at the level of the heart (ie, lateral to the intersection of the mid-axillary line and fourth intercostal space). Open the transducer to air, set the transducer signal to zero on the monitor, and then close the transducer to air. Ensure all air is flushed from the tubing. Remove all vent caps and replace with sealed caps at all the ports. Then pressurize the bag to 300 mm Hg. Throughout the process, maintain sterility of all connecting points of the tubing.
Place sterile equipment on sterilely covered equipment trays.
Test the cannulation equipment if using an integrated catheter and guidewire device: Rotate the catheter about the needle and slide the guidewire into and out of the needle to verify smooth motion.
Attach the transducer tubing to the blood pressure transducer and flush the tubing with sterile normal saline.
Swab the ventral wrist area of skin with antiseptic solution over the volar surface of distal radius where the radial pulse is palpable.
Allow the antiseptic solution to dry for at least 1 minute.
Place sterile towels around the site.
Put on a sterile mask and hat.
Put on a sterile gown and gloves.
Anesthetize the cannulation site
Draw the local anesthetic into a syringe (eg, 3 mL 1% lidocaine into 3 mL syringe)Draw the local anesthetic into a syringe (eg, 3 mL 1% lidocaine into 3 mL syringe)
Inject 1 to 2 mL of anesthetic into the skin and subcutaneously along the anticipated needle insertion path. Do not make a skin bleb so big that it obscures palpation of the radial artery.
Maintain gentle negative pressure on the syringe plunger as you advance the needle, to identify intravascular placement and prevent an intravascular injection.
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 distal radius 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 an integrated 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 a peripheral venous 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.
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 formation.
Assess the blood return
Place a gauze square under the cannulation device at the insertion site.
Observe the reservoir or barrel of the device to verify pulsatile blood flow. If needed, slightly advance or withdraw the device until the pulsatile flow is evident, which confirms intra-arterial placement.
Continuously hold the cannulation device motionless at this spot.
Thread the arterial catheter
Integrated catheter-over-wire technique:
Thread the guidewire through the needle and into the artery. Do not force the guidewire; it should slide smoothly.
If the guidewire meets resistance, it may have passed into or through the arterial wall. Remove the catheter-over-wire device as a unit, use gauze pads to apply pressure to the area for 10 minutes (to help prevent bleeding and hematoma formation), and start over at a new insertion site with a new catheter-over-wire device.
Securely hold the needle hub and slide the catheter, using a twisting motion, over the needle and guidewire and into the artery.
Angiocatheter technique:
The insertion method is essentially the same as starting an IV in a peripheral vein.
Further decrease the angle of insertion and advance the angiocatheter an additional 2 mm to ensure that the catheter tip has entered the lumen. This step is done because the needle tip slightly precedes the catheter tip.
Securely hold the needle hub and slide the catheter over the needle and into the artery; it should slide smoothly.
If the catheter meets resistance, slowly withdraw the needle followed by the catheter, stopping immediately and trying to re-advance the catheter if blood flow resumes. If the catheter cannot be inserted, withdraw it and start over. Never withdraw the catheter back over the needle or reinsert the needle back into the catheter (doing so may shear off the end of the catheter within the patient). Likewise, never withdraw the guidewire through the needle. Use gauze pads for about 10 minutes to apply external pressure to the area.
Sometimes the catheter cannot be advanced although it is in the lumen; try to advance the catheter while flushing it with fluid from a syringe.
Connect the arterial line
Attach the pressure tubing (which has been pre-flushed with saline) to the catheter hub and verify an arterial pressure waveform on the monitor screen.
Dress the site
Use gauze to wipe all blood and fluid from the site, being careful not to disturb the catheter.
Suture the catheter in place at the insertion site. To avoid skin necrosis, tie air loops in the skin and then tie the suture tails to the catheter hub.
Apply a transparent occlusive dressing. Chlorhexidine-impregnated discs at the insertion point are commonly placed before the dressing.Apply a transparent occlusive dressing. Chlorhexidine-impregnated discs at the insertion point are commonly placed before the dressing.
Loop the arterial tubing and tape it to the skin away from the insertion site to help prevent accidental traction on the tubing from dislodging the catheter.
Write the date and time of cannulation on the dressing.
Warnings and Common Errors
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 laterally; this movement can damage tissue. Instead, withdraw the needle almost to the skin surface before changing the angle and direction of insertion.
Never inject medications 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.
Tips and Tricks
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 arterial waveform with patient movement. The wrist may need to be immobilized in the most satisfactory position.
Reference
1. Golamari R, Gilchrist IC. Collateral Circulation Testing of the Hand- Is it Relevant Now? A Narrative Review. Am J Med Sci 2021;361(6):702-710. doi:10.1016/j.amjms.2020.12.001
