Arterial access

Last updated: February 21, 2023

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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.

Absolute contraindications [1]

Relative contraindications [1]

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

Common puncture sites

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.


  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

Arterial line placement

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.

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]

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

  1. Roberts JR. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. Elsevier ; 2018
  2. Barone JE, Madlinger RV. Should an Allen Test Be Performed Before Radial Artery Cannulation?. J Trauma. 2006; 61 (2): p.468-470. doi: 10.1097/01.ta.0000229815.43871.59 . | Open in Read by QxMD
  3. Gonella S, Clari M, Conti A, et al. Interventions to reduce arterial puncture-related pain: A systematic review and meta-analysis. Int J Nurs Stud. 2022; 126 : p.104131. doi: 10.1016/j.ijnurstu.2021.104131 . | Open in Read by QxMD
  4. Nuttall G, Burckhardt J, Hadley A, et al. Surgical and Patient Risk Factors for Severe Arterial Line Complications in Adults. Anesthesiology. 2016; 124 (3): p.590-597. doi: 10.1097/aln.0000000000000967 . | Open in Read by QxMD
  5. Genre Grandpierre R, Bobbia X, Muller L, et al. Ultrasound guidance in difficult radial artery puncture for blood gas analysis: A prospective, randomized controlled trial. PLoS ONE. 2019; 14 (3): p.e0213683. doi: 10.1371/journal.pone.0213683 . | Open in Read by QxMD
  6. Imbrìaco G, Monesi A, Spencer TR. Preventing radial arterial catheter failure in critical care — Factoring updated clinical strategies and techniques. Anaesthesia Critical Care & Pain Medicine. 2022; 41 (4): p.101096. doi: 10.1016/j.accpm.2022.101096 . | Open in Read by QxMD

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