Arterial access

Arterial access may be required for arterial blood gas (ABG) sampling, arterial line insertion, or as an entry point for other endovascular procedures (e.g., coronary angiography). ABG sampling is commonly performed by puncturing the radial or femoral artery. An arterial line may be placed for continuous blood pressure monitoring or frequent ABG sampling. Contraindications include inadequate circulation, Raynaud syndrome, thromboangiitis obliterans, and full thickness burns. Prior to arterial access, an appropriate site should be selected (most commonly the radial artery) and necessary equipment should be brought to the bedside. Complications include bleeding, AV fistula formation, hematoma formation, and pseudoaneurysm.

See “ABG analysis” for the interpretation of ABG findings.

• Arterial blood gas (ABG) sampling: arterial blood drawn for the purposes of ABG analysis, typically from the radial arteries or an indwelling arterial catheter.
• Arterial line: an indwelling catheter that enters via the skin and terminates within an artery (e.g., the radial artery)

• ABG sampling: monitoring acid-base disturbances and the partial pressures of oxygen and carbon dioxide
• Arterial line
  • Continuous invasive blood pressure monitoring
  • Frequent ABG sampling

Absolute contraindications ^[1]

• Inadequate circulation
• Raynaud syndrome
• Thromboangiitis obliterans
• Full thickness burns

Relative contraindications ^[1]

• Coagulopathy
• Overlying infection
• Atherosclerosis
• Inadequate collateral flow (see modified Allen test)
• Partial thickness burns

We list the most important contraindications. The selection is not exhaustive.

Common puncture sites

• ABG sampling: radial, brachial, and femoral arteries
• Arterial line: radial and femoral arteries

Modified Allen test

Clinical applications

• May be performed prior to radial artery puncture to assess collateral circulation in the hand.
• Not routinely recommended for single radial artery puncture. ^[1][2]
• An abnormal result is suggestive of inadequate collateral blood flow; consider an alternative puncture site.

Steps

1. The patient elevates their hand and makes a tight fist.
2. Apply pressure to the radial and ulnar arteries to occlude palmar perfusion.
3. Release pressure from the ulnar artery as the patient releases their fist.
4. Observe the palm for 15 seconds:
   • Normal: The palm becomes flushed within 5 seconds.
   • Abnormal: The palm remains pale for 5–15 seconds.

The following applies to adults.

ABG sampling

• Ultrasound machine (optional)
• Nonsterile gloves
• Antiseptic solution
• Heparinized syringe (3 mL)
• Small gauge needle
  • Radial artery: 22-gauge, 1.25-inch needle
  • Femoral artery: 20-gauge, 2.5-inch needle
• End cap
• Adhesive bandage

Arterial line placement

• Ultrasound machine (optional)
• Sterile ultrasound probe cover (optional)
• Sterile gloves
• Surgical mask
• Antiseptic solution
• Local anesthetic (e.g., 1% lidocaine)
• Arterial catheter setup (e.g., needle-catheter assembly, guidewire kit, Arrow® kit)
• Needle driver
• Nonabsorbable suture, size 3-0 or 4-0
• Pressure transducer tubing

The following applies to adults.

Radial artery puncture

1. Position the wrist in mild dorsiflexion
2. Prep the skin; create a sterile field if arterial line insertion is indicated.
3. Consider securing the wrist with tape.
4. Locate the radial artery using either palpation or ultrasound guidance.
5. Consider single point local anesthesia for the skin above the insertion site.
6. Puncture the skin with the needle at a 30–45° angle to the skin.
7. Advance the needle along the course of the pulsating artery until blood flashback is observed.
8. Continue steps for ABG sampling or arterial line insertion as required.

ABG sampling from the radial artery ^[1]

1. Follow steps for radial artery puncture using a bevel-up needle.
2. Once blood flashback is visible, allow the syringe to fill on its own.
3. Remove the needle and apply firm pressure to the puncture site for 3–5 minutes.
4. Remove excess air from the syringe by gently depressing the plunger and place an end cap.

Radial arterial line insertion

The technique for arterial line placement depends on the site selected and the equipment available and is performed under sterile conditions.

Arterial catheter with a built-in guidewire

The Arrow® kit is an example of a commonly used device for this purpose.

1. Follow steps for radial artery puncture using the needle-guidewire-catheter assembly.
2. Once blood flashback is observed, stabilize the needle and advance the guidewire into the vessel using the wire guide handle.
3. Advance the catheter over the wire into the vessel.
4. While removing the needle and guidewire, apply occlusive pressure over the proximal artery to avoid blood loss.
5. Attach the pressure transducer tubing to the catheter.
6. Secure the catheter with sutures and apply a sterile dressing.

Direct over-the-needle technique (no guidewire)

1. Follow steps for radial artery puncture using the available needle-catheter assembly.
2. Once blood flashback is observed, advance the catheter over the needle into the artery.
3. While withdrawing the needle, apply occlusive pressure over the proximal artery to avoid blood loss.
4. Attach the pressure transducer tubing to the catheter.
5. Secure the catheter in place with sutures and apply a sterile dressing.

• See “Arterial blood gas analysis.”
• See “Invasive hemodynamic monitoring.”

Radial artery puncture

• Consider local anesthesia to reduce pain. ^[3]
• Optimize wrist dorsiflexion to isolate the radial artery and increase accessibility. ^[1]
• Consider switching to an alternate site if repeatedly unsuccessful at the first site. ^[4]
• Consider ultrasound guidance to increase success. ^[5]
• If there is poor blood flashback despite proper needle alignment and angulation, consider pulling the needle back a few millimeters.

Radial arterial line placement

• Secure the wrist and identify the radial artery before establishing a sterile field.
• Once blood flashback is noted, lower the angle of the catheter before advancing to facilitate catheter insertion.
• Avoid cannulation too close to the wrist joint to reduce the risk of catheter dislodgement or mechanical failure due to flexion. ^[6]

• Bleeding
• Hematoma
• Infection
• Thrombosis
• AV fistula
• Pseudoaneurysm

We list the most important complications. The selection is not exhaustive.