Background
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
Indications for arterial line placement are as follows:
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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]
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Frequent blood sampling ( arterial blood gas sampling)
Placement of an arterial line can help prevent complications associated with repeated arterial puncture (eg, pain, hematoma).
Contraindications
Absolute contraindications for arterial line placement are as follows [9, 10] :
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Absent pulse
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Thromboangiitis obliterans (Buerger disease)
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Full-thickness burns over the cannulation site
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Inadequate circulation to the extremity
Relative contraindications are as follows [9, 10] :
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Anticoagulation
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Coagulopathy
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Inadequate collateral flow
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Infection at the cannulation site
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Partial-thickness burn at the cannulation site
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Previous surgery in the area
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Synthetic vascular graft
Technical Considerations
Anatomy
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.
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.
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:
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Ultrasonographic (US) guidance is recommended for identifying and accessing the target vessel, especially at the femoral location
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Doppler US alone can also facilitate arterial cannulation
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Appropriately position the patient and feel arterial pulsation before initiating arterial line placement
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Flush the needle introducer with heparinized flush to facilitate flashback of blood up to the needle hub upon entry into the artery
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Puncture the radial artery in a slight lateral-to-medial direction to stabilize it against the FCR tendon
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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)
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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]
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When using a catheter-over-needle technique, be sure to advance the needle 2 mm after flash to ensure catheter placement inside the lumen
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When using a Seldinger technique, do not dilate the artery; to minimize bleeding and vessel injury, dilate only the soft-tissue tract
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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
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To avoid creating false passages, do not force advancement if passage of a guide wire or catheter meets resistance
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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]
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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]
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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
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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
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To reduce the complication rate, remove the catheter as soon as it is no longer necessary [14]
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Anatomy of radial artery.
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Anatomy of femoral triangle.
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Wrist position for radial artery line placement.
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Modified Allen test. Return of perfusion to hand after release of compression of ulnar artery.
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Radial artery cannulation. Positioning of hand.
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Radial artery cannulation. Palpation of radial artery.
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Radial artery cannulation (catheter over needle). Catheter introduction through skin.
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Radial artery cannulation (catheter over needle). Puncture of radial artery.
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Radial artery cannulation (catheter over needle). Catheter advanced into radial artery.
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Radial artery cannulation (catheter over needle). Arterial line tubing attached to radial artery catheter.
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Radial artery cannulation (Seldinger). Catheter-over-wire arterial line kit.
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Radial artery cannulation (Seldinger). Palpation of radial artery.
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Radial artery cannulation (Seldinger). Puncture of skin with finder needle.
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Radial artery cannulation (Seldinger). Puncture of radial artery with return of blood.
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Radial artery cannulation (Seldinger). Introduction of guide wire into radial artery.
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Radial artery cannulation (Seldinger). Skin incision over needle.
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Radial artery cannulation (Seldinger). Advancement of catheter over guide wire.
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Radial artery cannulation (Seldinger). Attachment of arterial line tubing to catheter.
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Femoral artery cannulation (modified Seldinger). Catheter-over-wire arterial line kit.
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Radial artery cannulation (modified Seldinger). Catheter and wire assembled.
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Radial artery cannulation (modified Seldinger). Wire advancement through catheter.
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Allen test. Examiner occludes both radial and ulnar arteries while patient makes fist.
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Allen test. Radial and ulnar arteries remain occluded after hand is opened.
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Allen test. Pressure on ulnar artery is released, and time to observed return of color to hand is measured.
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Radial artery cannulation (modified Seldinger). Radial artery catheter kit.
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Radial artery cannulation (modified Seldinger). Radial artery catheter.
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Positioning of wrist for radial artery cannulation.
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Radial artery cannulation (modified Seldinger). Radial artery prepared and draped in sterile fashion.
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Radial artery cannulation (modified Seldinger). Introduction of radial artery catheter.
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Radial artery cannulation (modified Seldinger). Angle of introduction of radial artery catheter.
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Radial artery cannulation (modified Seldinger). Flashback of blood into radial artery catheter hub.
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Radial artery cannulation (modified Seldinger). Radial artery catheter entering artery.
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Radial artery cannulation (modified Seldinger). Advancement of guide wire into radial artery.
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Radial artery cannulation (modified Seldinger). Advancement of guide wire into radial artery.
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Radial artery cannulation (modified Seldinger). Stabilization of catheter while introducer is removed.
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Radial artery cannulation (modified Seldinger). Stabilization of catheter while introducer is removed.
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Radial artery cannulation (modified Seldinger). Pressure transducer attached to radial artery catheter.
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Radial artery cannulation (modified Seldinger). Radial artery cannula sutured in place.
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Radial artery cannulation (modified Seldinger). Sterile dressing applied over radial artery cannula.
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Radial artery cannulation (modified Seldinger). Inline 3-way stopcocks attached for blood sampling.
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Angiocatheter used for radial artery cannulation in infants and small children.
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Radial artery cannulation (catheter over needle). Introduction of angiocatheter into radial artery.
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Radial artery cannulation (catheter over needle). Flashback of blood into angiocatheter hub.
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Radial artery cannulation (catheter over needle). Needle entering radial artery with bevel facing up.
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Radial artery cannulation (catheter over needle). Stabilization of catheter while needle introducer is removed.
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Radial artery cannulation (catheter over needle). Pressure transducer attached to radial artery catheter.
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Radial artery cannulation (catheter over needle). Radial artery catheter secured in place with Steri-Strips.
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Radial artery cannulation (catheter over needle). Sterile dressing applied over radial artery cannula.
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Femoral artery cannulation (catheter over needle). Insertion of 20-gauge 1.75-in. catheter over needle into femoral artery. Note 45° insertion angle.
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Femoral artery cannulation (catheter over needle). Removal of needle after artery has been cannulated and catheter has been inserted into lumen of artery.
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Femoral artery cannulation (combination technique). Insertion of guide wire through catheter into femoral artery lumen.
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Femoral artery cannulation (combination technique). Final placement of 20-gauge 5-in. catheter into femoral artery (note yellow plastic spring wire insertion adapter).
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Femoral artery cannulation (Seldinger). Puncture of femoral artery with 18-gauge 3-in. hollow introducer needle. Note 45° insertion angle.
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Femoral artery cannulation (Seldinger). Guide wire being inserted into femoral artery lumen.
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Femoral artery cannulation (Seldinger). 2-mm incision is made next to guide wire with No. 11 scalpel blade.
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Femoral artery cannulation (Seldinger). Insertion of 20-gauge 5-in. catheter over guide wire into femoral artery.
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Equipment setup for ultrasound-guided radial arterial line placement.
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Ultrasound probe with sterile sheath.
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External view of ultrasound-guided short-axis view.
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Identification of radial artery in short-axis view. Yellow circle surrounds radial artery.
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Identification of radial artery with color Doppler ultrasonography.
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External view of ultrasound-guided long-axis view.
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Identification of radial artery with long-axis view. Yellow arrows highlight radial artery.
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Short-axis view of needle entering soft tissue and targeting radial artery. Red arrow identifies radiopaque needle near radial artery.
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Long-axis view of needle entering soft tissue and targeting radial artery. Yellow arrows highlight radial artery. Red stars identify radiopaque needle near radial artery.
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Needle within radial artery in short-axis view. Red arrow identifies radiopaque needle within lumen of radial artery.
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Long-axis view of needle within lumen of radial artery. Yellow arrows highlight radial artery. Red stars identify radiopaque needle within lumen of radial artery.