Arterial Line Placement

Updated: Mar 26, 2018
  • Author: Alex Koyfman, MD; Chief Editor: Vincent Lopez Rowe, MD  more...
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Arterial line placement is a common procedure in various critical care 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 permits the rapid recognition of BP changes that is vital for patients on continuous infusions of vasoactive drugs. Arterial cannulation also allows repeated arterial blood gas samples to be drawn without injury to the patient.

Overall, arterial line placement is considered a safe procedure, with a rate of major complications that is below 1%. [2] It is not entirely without risks, however, and it requires appropriate knowledge of the anatomy and procedural skills. Arterial lines can be placed in multiple arteries, including 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, [3, 4]  primarily because of the superficial nature of the vessel and the ease with which the site can be maintained. Additional advantages of radial artery cannulation include the consistency of the anatomy and the low rate of complications. [5]

After the radial artery, 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 removal, [6] though the overall complication rate remains comparable. [2]

There has been considerable debate over whether radial or femoral arterial line placement more accurately measures BP and mean arterial pressure (MAP) [7, 8] ; however, both approaches seem to perform well for this function. [9] In determining the need for and optimal location of arterial line placement, one must consider the risk and benefits of the procedure for each patient.



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 have very low blood pressures [10]
  • Inability to use indirect BP monitoring (eg, in patients with severe burns or morbid obesity)
  • Frequent blood sampling

Placement of an arterial line can also help prevent complications associated with repeated arterial puncture (eg, hematomas and scar tissue formation).



Absolute contraindications for arterial line placement are as follows [3, 11] :

Relative contraindications are as follows [3, 11] :

  • 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 tendon.

Anatomy of radial artery. Anatomy of radial artery.

For the radial artery, the initial puncture site should be as distal as possible. A common location is over the radial pulse at the proximal flexor crease of the wrist. In any case, the puncture site should be at least 1 cm proximal to the styloid process so as to keep from puncturing 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). It 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, where it can be easily compressed. Normally, the femoral arterial pulsation can be palpated midway between the anterior superior iliac spine and the pubic symphysis.

Best practices

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

  • Always position the patient appropriately and feel arterial pulsation before initiating arterial line placement
  • Before starting the procedure, 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; this allows the artery to be stabilized against the flexor carpi radialis tendon
  • After arterial puncture or decannulation, maintain pressure over the puncture site for at least 5 minutes (or possibly longer if the patient is in a hypocoagulable state)
  • 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 [4]
  • To avoid creating false passages, refrain from forcing further advancement if passage of a guide wire or catheter meets with 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 [12]
  • 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]
  • 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 [13, 14]
  • 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 [2]