Femoral Artery Cannulation 

Arterial puncture is the current standard for blood gas acid-base analysis and invasive blood pressure monitoring. Continuous blood pressure transduction with intra-arterial cannulation is the accepted standard for monitoring blood pressure in patients who are critically ill. However, arterial puncture is not without risks, and it requires appropriate knowledge of the anatomy and procedural skills.

After the radial artery, the femoral artery is the second most common site for arterial cannulation. It has several benefits when compared to the radial artery; namely, it is larger and easily accessible with stronger pulsation. Importantly, the femoral artery pressure is also a more accurate measure of central arterial pressure than can be obtained at more peripheral sites, such as the radial artery.^{[1, 2]} See Radial Artery Cannulation for more information and an illustrated description of that technique.

Anatomy

The iliac arteries pass below the inguinal ligaments and, at this point, become the femoral arteries, located within the femoral triangle (see image below).

This is the ideal location for access to, and cannulation of, the femoral artery. To prevent bleeding complications, the femoral artery should always be accessed approximately 1 inch below the inguinal ligament, where it can be easily compressed. The femoral artery is bordered medially by the femoral vein and laterally by the femoral nerve. Normally, the femoral arterial pulsation can be palpated midway between the anterior superior iliac spine and the pubic symphysis.

Arterial blood sampling

• When frequent monitoring of blood gases as well as electrolytes and other blood/serum tests are necessary, arterial lines are not only less painful for patients but are more convenient for health practitioners.
• They can prevent complications such as hematomas and scar tissue formation that are associated with repeated arterial puncture.

Continuous blood pressure monitoring

• Patients who are critically ill require accurate, real-time continuous blood pressure monitoring that can be obtained from an arterial catheter rather than relying on frequent sphygmomanometer readings. The arterial catheter mean arterial pressure measurements almost always correlate more accurately with mean aortic root pressure and can be continually monitored.
• Arterial catheter mean arterial pressure measurements are even more accurate than sphygmomanometry blood pressure readings in patients who are morbidly obese, are very thin, have severe extremity burns, or have very low blood pressures.^[3]

Absolute contraindications

• No absolute contraindications
• Potential risks inherent in the procedure should be weighed against potential benefits.

Relative contraindications

• Infection, burn, or skin breakdown overlying the site of desired cannulation
• Previous surgical arterial grafts in the area of cannulation
• Post-thrombolysis (In this case, the radial artery is the desired location for cannulation.)
• Severe coagulopathy or disseminated intravascular coagulation (DIC)
• Severe atherosclerosis
• Decreased palpable pulse or bruit

• In a conscious patient, using a small amount of 1% lidocaine without epinephrine to anesthetize the skin overlying the femoral artery reduces the discomfort and pain associated with the procedure. However, in critically ill or unconscious patients, this step may be bypassed to save time.
• Injections of lidocaine with epinephrine may cause constriction of blood vessels, which could make cannulation more difficult.
• For more information, see Local Anesthetic Agents, Infiltrative Administration.

• Several commercial kits containing all required supplies are available for arterial cannulation (catheter-over-needle technique). Such kits include Arrow AK-04510 (20-gauge [ga], 50-in catheter) and Arrow UM-04018 (18-ga, 6-in catheter). Both these kits are manufactured by Arrow International Inc, a division of Teleflex Medical, Research Triangle Park, NC.
• Commercial kits for the Seldinger technique (catheter-over-wire) are not generally available in the United States. Recommended equipment for the Seldinger technique includes the following:

  • Sterile gloves (latex-free)
  • Chlorhexidine for skin sterilization
  • Sterile drapes or towels
  • Syringe, 3-5 mL, with 25-ga, 1-in needle, for anesthesia
  • 1% lidocaine without epinephrine
  • Needle, 18 or 20 ga, 1.5 or 3 in, for arterial puncture (18-ga spinal needle will suffice)
  • Guidewire, 45 cm (0.64 mm diameter); should have straight soft tip on one end and J tip on other end
  • Plastic spring wire insertion adapter to straighten J tip end of guidewire for insertion into plastic catheter
  • Scalpel, No. 11 blade
  • Indwelling catheter, 20 ga, 5 in; or 18 ga, 6 in
  • Pressure transducer
  • Pressure tubing
  • Silk suture, 2-0 or 3-0
  • Needle driver
  • Adhesive tape
  • Gauze

• The patient should be supine with the leg externally rotated.

Femoral artery cannulation is commonly accomplished by using one of two methods: catheter-over-needle and catheter-over-wire. With either technique, meticulous attention must be paid to preparation of the cannulation site with chlorhexidine to minimize the risk of infection and to firmly securing the final intra-arterial catheter with sutures.^{[4, 5, 6]}

Catheter-over-needle technique

The catheter-over-needle cannulation is shown below. This technique can be combined with the catheter-over-wire technique if a longer catheter is desired.

• Determine the location of the vessel by palpation of the arterial pulse approximately 1 inch below the inguinal ligament.
• Prepare the overlying skin with chlorhexidine.
• Anesthetize the skin with a 10-mm intradermal wheal of local anesthetic.
• Identify the course of the vessel by palpating with the index and middle finger of the nondominant, gloved hand.
• Puncture the skin at an angle of 45 degrees to the skin and vessel (see image below).Insertion of 20-ga, 1.75-in catheter over needle into the femoral artery. Note the 45-degree insertion angle.
• Advance the needle slowly until pulsating blood flow is appreciated. Continuation of pulsating blood indicates that the needle continues to be within the arterial lumen.
• If flow ceases, slowly retract the needle in case both walls of the vessel have been punctured. If withdrawal does not produce blood flow and the needle must be redirected, first withdraw the needle to just below the level of the dermis and then reintroduce it.
• If the artery is not easily punctured or if difficult cannulation is anticipated (eg, obese patient), the artery can be located using Doppler ultrasonography.
• Make a small nick in the skin at the site of the needle entry to facilitate passage of the catheter through the skin.
• Advance the needle-catheter assembly through the skin until a flash of blood is obtained. This indicates that the needle, which protrudes beyond the catheter tip, has entered the artery.
• Advance the needle-catheter complex an additional 2 mm to ensure that the catheter tip has entered the artery.
• Advance the catheter into the vessel while holding the needle stationary.
• Remove the needle (see image below). Successful artery cannulation is confirmed by pulsatile blood flow from the catheter when the needle is removed. Removal of needle after artery has been cannulized and catheter has been inserted into the artery lumen.
• Suture the catheter in place to ensure immobilization.
• Apply a sterile dressing with the date of placement over the catheter.

Catheter-over-wire technique

The second technique for femoral artery cannulation is the Seldinger technique, also known as catheter-over-wire. This technique is not commonly used in the United States because commercial kits are not available.^[3]

• Prepare and anesthetize the skin, locate the vessel, and insert the needle as described above in the catheter-over-needle technique (see image below). Seldinger technique. Puncture of femoral artery with an 18-ga, 3-in hollow introducer needle (note 45-degree insertion angle).
• Once the needle is in the artery, use a guidewire insertion adapter to advance the guidewire through the lumen of the needle (see image below). Ensure that the guidewire passes easily, without resistance.^[7] Seldinger technique. Guidewire being inserted into the femoral artery lumen.
• After the guidewire has been advanced to within several centimeters of the end of the needle, remove the needle over the wire, taking care never to let go of the wire.
• Make a small nick in the skin at the site of the guidewire to facilitate passage of the catheter through the skin (see image below). A 2-mm incision is made next to the guidewire with a No. 11 scalpel blade.
• Make sure that the wire fits tightly into the end of the catheter so the catheter will enter the arterial lumen smoothly (this may be problematic, especially in patients with synthetic femoral grafts and in patients with advanced atherosclerosis).
• Advance the catheter over the guidewire and into the vessel (see image below).Insertion of 20-ga, 5-in catheter over the guidewire into the femoral artery.
• Remove the guidewire, leaving the catheter in place. Successful artery cannulation is confirmed by pulsatile blood flow from the catheter when the wire is removed.
• Suture the catheter in place to ensure immobilization.
• Apply a sterile dressing with the date of placement over the catheter.

Combination technique

The initial insertion of the catheter-over-needle technique should be performed with a 2.5-in catheter. Often, a longer 5-in catheter is desirable, to ensure permanent placement of the catheter. In such a case, the 5-in catheter may be inserted initially and advanced over the needle once continuing arterial flow persists. However, not infrequently, the longer catheter, when inserted via the catheter-over-needle technique, presents difficulty in cannulating the artery. In this case, the catheter-over-needle technique can be combined with the catheter-over-wire technique as follows:

• Employ the catheter-over-needle technique with a 2.5-in catheter, as described above.
• When the artery is cannulated, remove the needle and insert a guidewire into the catheter (see image below).Insertion of guidewire through catheter into femoral artery lumen.
• Remove the 2.5-in catheter from over the wire, leaving only the guidewire in place.
• Insert a longer 5-in catheter over the guidewire (see image below).Final placement of 20-ga, 5-in catheter into the femoral artery (note the yellow plastic spring wire insertion adapter).
• Remove the guidewire once the catheter is confirmed in the arterial lumen.

• The radial artery is preferred for securing arterial blood and for cannulation to provide continuous blood pressure monitoring and arterial blood sampling. If the radial artery cannot be cannulated, the femoral artery offers a viable alternative.
• The catheter-over-needle technique is preferred for radial artery cannulation but can also be used alone for femoral artery cannulation. It can also be combined with the Seldinger (over-the-wire) technique if a longer indwelling catheter is desired.
• The contraindications of femoral artery cannulation are few, and complications are unusual.
• Sterile technique and appropriately securing the catheter are the 2 most important aspects of femoral artery cannulation.

• Arterial cannulation is generally a safe procedure. The primary complications, however, are infection, bleeding, superficial hematoma formation, arterial injury and thrombosis.
• The risk of infection at the catheter site increases with the length of time the catheter is in place.^[8] This risk can be minimized with strict attention to sterile technique when placing the catheter and prompt removal when the catheter is no longer required.
• Bleeding from the cannulation site can be minimized with direct pressure at the site, and arterial injury can be minimized with correct procedural technique.
• More serious complications, such as femoral artery dissection, nerve injury, and intraperitoneal hemorrhage, have been reported but are exceedingly rare when correct procedural techniques are employed.^[9]