Tips & Tricks for Ultrasound-Guided Fascia Iliaca Compartment Block
01 Secure a longer medium-gauge needle (e.g. an 18 gauge lumbar puncture needle to perform the procedure).
02 Use the 13-10MHz linear array transducer to map out the important anatomical structures. In larger patients, you may need to use the 5-3MHz curvilinear array transducer. Try to directly visualize the femoral artery, femoral vein, femoral nerve bundle, iliospsoas muscle, fascia iliaca, and fascia lata.
03 Scan with your probe resting in a transverse fashion just below the patient’s inguinal crease on the affected side.
04 Remember the mnemonic NAVEL. From lateral to medial, you should see the Nerve, Artery, Vein, an Empty Space, and then the Lymphatic channels.
05 Arteries will appear as thick-walled, round, pulsatile anechoic vascular structures. Veins will have more of an oval shape to them and have thinner walls. Nerves will appear as hypoechoic fascicles embedded within a more hyperechoic perineurium and endoneurium. When nerves are grouped together and viewed in a transverse plane, they appear as “honeycombs”. Distal nerves that are innervating smaller sites may have smaller amounts of myelinated axons, and therefore can be mistaken as tendons. When in doubt, trace the course of the target structure to determine its origin.
06 Nerve blocks should not be used in patients who have an allergy to anesthetic agents, in those with active infection at the site of injection, in patients who are at risk for compartment syndrome, in uncooperative patients who won’t tolerate the procedure, in those with a pre-existing neurological deficit, and in those with are extremely obese thereby precluding adequate visualization of the important target structures. Note that anticoagulation use is a relative contraindication.
07 Once you have found your landmarks and tissue planes under ultrasound guidance, make sure you are looking at the fascia iliacus. The Sartorius muscle crosses the iliopsoas just after it passes over the edge of the ileum and can confuse the picture. Use your probe to find the bright white ilium bone. The muscle lying in contact with the bone and directly overlying it is the iliacus muscle, and the fascial layer above it is the iliacus fascia.
08 Pull up 40-50 mL of your anesthetic of choice. Insert your needle in plane with the ultrasound transducer and aim towards the area just below the fascia iliacus. You will feel two pops. The first pop will be felt as you penetrate through the fascia lata. You will feel a second pop after you poke through the fascia iliaca. Once your needle is inserted underneath the fascia iliacus, inject 40-50 mL’s of anesthetic in a superomedial angle towards the edge of the ileum to bathe all of the nerve fibers traversing downwards to the femoral nerve.
09 Monitor the spread of the muscle fibers and nerve bundles as the anesthetic is instilled. If you are running into resistance during the anesthetic injection, redirect the needle so that it is not aimed directly into any muscle bellies.
10 Pain relief should peak by 20-30 minutes after the injection.
Brady Pregerson manages a free on-line EM Ultrasound Image Library and is the editor of the Emergency Medicine Pocketbook series. For more information visit EMresource.ORG.
Teresa S. Wu is the Associate Residency Director, and Director of Ultrasound and Simulation Programs and Fellowships, for the Maricopa Emergency Medicine Program in Phoenix, Arizona.