Arterial Line Placement

Updated: Sep 21, 2022
  • Author: Sarah Ogle, DO, MS; Chief Editor: Vincent Lopez Rowe, MD, FACS  more...
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Arterial line placement is a common procedure in various critical care and some anesthetic settings. Intra-arterial blood pressure (BP) measurement is more accurate than measurement of BP by noninvasive means, especially in the critically ill. [1] Intra-arterial BP management allows rapid recognition of BP changes, which is especially vital for patients receiving continuous infusions of vasoactive drugs. Arterial cannulation allows repeated arterial blood gas samples to be drawn.

Arterial line placement is a safe procedure. Major complications occur in fewer than 1% of placements. [2]  Risks can be minimized with appropriate knowledge of the anatomy and procedural skills. Arterial lines can be placed in the radial, ulnar, brachial, axillary, posterior tibial, femoral, and dorsalis pedis arteries.

In both adults and children, the most common site of cannulation is the radial artery. [2, 3, 4] The superficial and consistent anatomic location of the radial artery affords easier access, facilitates care, and yields fewer complications. [4]  

The femoral artery is the second most common site for arterial cannulation. One advantage of femoral artery cannulation is that the vessel is larger than the radial artery and has stronger pulsation. Additional advantages include decreased risks of thrombosis and of accidental catheter dislodgment. [5]  

There has been debate over whether radial or femoral arterial line placement more accurately measures BP and mean arterial pressure (MAP); however, both sites provide reliable data. [6, 7, 8]  The arterial cannulation site is patient-specific and is determined on the basis of the anatomy, the risks and benefits, and the indication for the procedure.



Indications for arterial line placement are as follows:

  • Continuous direct BP monitoring - Arterial catheter MAP measurements are even more accurate than sphygmomanometric BP readings in patients who are morbidly obese, are very thin, have severe extremity burns, or are hypotensive [9]
  • Frequent blood sampling ( arterial blood gas sampling)

Placement of an arterial line can help prevent complications associated with repeated arterial puncture (eg, pain, hematoma).



Absolute contraindications for arterial line placement are as follows [9, 10] :

Relative contraindications are as follows [9, 10] :

  • Anticoagulation
  • Coagulopathy
  • Inadequate collateral flow
  • Infection at the cannulation site
  • Partial-thickness burn at the cannulation site
  • Previous surgery in the area
  • Synthetic vascular graft

Technical Considerations


The radial artery originates in the cubital fossa from the brachial artery (see the image below). It traverses the lateral aspect of the forearm and gives rise to the palmar arches that provide vascular flow for the hand. At the wrist, the radial artery sits proximal and medial to the radial styloid process and just lateral to the flexor carpi radialis (FCR) tendon.

Anatomy of radial artery. Anatomy of radial artery.

The initial puncture site for radial arterial cannulation should be as distal as possible on the wrist. A common location is over the radial pulse at the proximal flexor crease of the wrist. The puncture site should be at least 1 cm proximal to the styloid process so as to prevent puncture of the retinaculum flexorum and the small superficial branch of the radial artery.

The femoral artery originates at the inguinal ligament from the external iliac artery (see the image below). The artery passes under the inguinal ligament at approximately the midpoint between the anterior superior iliac spine and the pubic tubercle. It lies medial to the femoral nerve and lateral to the femoral vein and lymphatics.

Anatomy of femoral triangle. Anatomy of femoral triangle.

To facilitate control of bleeding and prevent bleeding into the pelvis, the femoral artery should always be accessed approximately 2.5 cm below the inguinal ligament. The artery is more easily palpable at this location and can be compressed. 

Best practices

The following measures and recommendations may facilitate placement of an arterial line:

  • Ultrasonographic (US) guidance is recommended for identifying and accessing the target vessel, especially at the femoral location
  • Doppler US alone can also facilitate arterial cannulation
  • Appropriately position the patient and feel arterial pulsation before initiating arterial line placement
  • Flush the needle introducer with heparinized flush to facilitate flashback of blood up to the needle hub upon entry into the artery
  • Puncture the radial artery in a slight lateral-to-medial direction to stabilize it against the FCR tendon
  • After arterial puncture or decannulation, maintain pressure over the puncture site for at least 5 minutes (or possibly longer if the patient is coagulopathic or anticoagulated)
  • Make a small skin incision at the site of needle puncture to allow easier passage of the catheter through the skin and help prevent catheter kinking during advancement [3]
  • When using a catheter-over-needle technique, be sure to advance the needle 2 mm after flash to ensure catheter placement inside the lumen
  • When using a Seldinger technique, do not dilate the artery; to minimize bleeding and vessel injury, dilate only the soft-tissue tract
  • If the guide wire cannot be passed into the artery, try rotating the needle 90-180° in an attempt to eliminate an intimal flap blocking passage of the wire
  • To avoid creating false passages, do not force advancement if passage of a guide wire or catheter meets resistance 
  • When it proves difficult to advance the catheter into the lumen, consider the “liquid stylet” method: Fill a 10-mL syringe with 5 mL of sterile normal saline, attach it to the catheter hub, aspirate 1-2 mL of blood into the syringe, and then slowly inject the syringe contents into the vessel as the catheter is advanced behind the fluid wave [11]
  • If several attempts at cannulation fail, the artery may spasm, making further attempts more difficult; if this occurs, allow the artery to recover for a short time before reattempting cannulation; subcutaneous infiltration of lidocaine or similar anesthetic around the puncture site may reduce vessel spasm [3]
  • Check the pulse waveform on the monitor to ensure that a good waveform is obtained; a pulse waveform that appears dampened initially may be secondary to arterial spasm; if this occurs, wait for the arterial spasm to resolve
  • Consider adding papaverine 30 mg/250 mL to the arterial line fluid, this may prolong the patency of peripheral arterial catheters in children and neonates [12, 13]
  • Regularly inspect the area for signs of ischemia, and remove the catheter at the first signs of circulatory compromise or clot formation; do not flush the catheter in an attempt to remove clots
  • To reduce the complication rate, remove the catheter as soon as it is no longer necessary [14]