Femoral nerve block
Overview
The femoral nerve block involves injecting local anesthetic adjacent to the femoral nerve just below the inguinal ligament to achieve peri-and postoperative analgesia for a variety of surgical interventions, to include anterior cruciate ligament repair, patella surgery and/or quadriceps tendon repair. The femoral nerve block is often used in combination with obturator and sciatic nerve blocks for various lower extremity surgeries.
Anatomy
The femoral nerve originates from the posterior cords of the lumbar plexus at the level of L2-L4. It runs under the inguinal ligament 1-2 cm lateral to the femoral artery and vein, separated from them by the iliopectineal ligament. Distal to the inguinal ligament the femoral nerve lies deep to the fascia iliaca. The femoral nerve gives rise to many cutaneous branches as it moves distally including the saphenous nerve. [1]
Indications
Generally, peripheral nerve blocks are indicated when neuraxial anesthesia is contraindicated, analgesics have failed or when the side effects of general anesthesia and oral medications should be avoided. Examples of such situations are patients that are at a high risk for respiratory depression related to general anesthesia, have severe cardiac disease, need or desire to avoid systemic medications, have bacteremia, and/or have an intolerance or lack of response to oral medications.[2]
Regional blocks may be considered as an alternative to neuraxial anesthesia when neuraxial anesthesia is contraindicated. In addition, blocks contribute to a multimodal anesthetic/analgesic strategy thereby lessening the burden of general anesthetics and systemic analgesics such as opioids.[3]
If the duration of post operative pain is expected to be less than or equal to 24 hours a single injection of local anesthetic may be used. For postoperative pain expected to exceed 24 hours a continuous infusion catheter may be inserted into the perineural space using the same technique as single injection.[3]
Specifically, the femoral nerve block is indicated for postoperative analgesia of the anterior thigh and knee. However, the femoral nerve block only provides analgesia to the superficial areas of the anterior thigh, as such it is typically combined with other nerve blocks such as obturator and sciatic nerve blocks for more complete lower leg anesthesia. [4]
Contraindications
Absolute contraindications:
- Allergy to local anesthetic
- Unwilling or unable to cooperate
- Presence of overlying infection at site of injection[2]
Relative contraindications:
- Pre-existing neuropathy involving distribution of block
- Coagulopathies
- Pharmacologic anticoagulation[2][5]
Sedation
Procedural sedation can be considered for patients undergoing femoral nerve block. Commonly used medications include midazolam and fentanyl. ketamine, propofol, and dexmedetomidine may be considered for sedation as well.[2]
Choice of Local Anesthetic
The specific local anesthetic chosen depends on several factors such as desired onset, duration, and degree of conduction block. Some local anesthetics commonly used for the femoral nerve block include:[2]
Lidocaine and mepivacaine 1% to 1.5% -- surgical anesthesia onset in 20-30 minutes with surgical anesthesia duration of 2-3 hours[4]
Ropivacaine 0.5% and Bupivacaine 0.375%-0.5% -- slower onset, and produce less motor blockade, but produce surgical anesthesia that lasts 6-8 hours[4]
Lower doses of local anesthetic should be considered in patients with low body weight, older patients, patients with a history of liver, kidney, or cardiac insufficiency, patients who are pregnant, and patients with diabetic peripheral neuropathy.[6]
Adjuncts
Epinephrine
The addition of epinephrine to local anesthetics serves as a marker of intravascular injection by increasing heart rate/blood pressure. Epinephrine slows reabsorption of local anesthetic due to its vasoconstrictive effect on surrounding vasculature thereby extending the duration of conduction block as well as reducing peak plasma levels.[3]
Alpha 2 agonists
Clonidine as well as dexmedetomidine may be used as adjuncts to extend the anesthetic duration of blocks by 2 to 5 hours respectively. Care must be taken in patients with pre-existing bradycardia and hypotension as these medications lower heart rate and may cause hypotension and sedation at higher doses.[7][8]
Dexamethasone
Prolongs analgesic effect of local anesthetic by an average of 8 hours with minimal undesirable side effects. Of note, dexamethasone may crystalize when combined with ropivacaine.[3]
Buprenorphine
Has been shown to extend the analgesic effects of local anesthetics by 5-10 hours with minimal adverse effects, however, increased nausea and vomiting have been reported.[9]
Technique
With the patient in the supine position, slightly abduct and externally rotate the thigh. Using a linear ultrasound probe identify the femoral nerve and surrounding landmarks in cross section by positioning the probe near the femoral crease. The femoral nerve is appreciated as a hyperechoic bundle of fascicles superficial to the hyperechoic iliopsoas muscle and lateral to the femoral artery. Insert the block needle and advance within the plane of imaging from lateral to medial until it punctures the fascia iliaca with a distinct pop. Inject 10-30 ml of local anesthetic to create a circumferential spread around the nerve.[4]
Complications
Local Anesthetic Systemic Toxicity
Local Anesthetic Systemic Toxicity (LAST) is a potentially fatal condition caused by high plasma levels of local anesthetics. LAST is most often a result of direct intravascular injection of local anesthetic during regional anesthesia or less commonly from the reabsorption of local anesthetic from peripheral tissues following regional anesthesia. Signs of LAST include tinnitus, perioral numbness, seizures, hypotension, bradycardia, cardiac arrhythmias, and cardiac arrest. If suspected, LAST must be treated emergently with intravenous lipid emulsion therapy.[10]
Nerve Injury
Nerve injury or neurologic complications described by patients as tingling, pain, pressure, or pins and needles may last for weeks or months and are associated with up to 8.2% of peripheral nerve blocks.[11][12]
Bleeding
Bleeding following regional anesthesia is very rare. Factors such as compressibility of site, patient body habitus and pharmacologic anticoagulation must be considered when assessing bleeding risk.[13]
Infection
Single injection nerve blocks are not generally associated with infection, however, continuous nerve blocks with indwelling catheters result in infection in up to 3% of patients.[10][14]
Allergic Reaction
Allergies to local anesthetics are rare. Far more likely are allergies to additives and
preservatives added during the manufacturing process. Such additives include para-aminobenzoic acid, metabisulfite, and methylparaben.[15]
- ↑ Refai, Nader A.; Black, Asa C.; Tadi, Prasanna (2023), "Anatomy, Bony Pelvis and Lower Limb: Thigh Femoral Nerve", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 32310525, retrieved 2023-09-14
- ↑ 2.0 2.1 2.2 2.3 2.4 Emelife, Patrick Ifesinachi; Eng, Matthew R.; Menard, Bethany L.; Myers, Andrew S.; Cornett, Elyse M.; Urman, Richard D.; Kaye, Alan D. (2018-06). "Adjunct medications for peripheral and neuraxial anesthesia". Best Practice & Research Clinical Anaesthesiology. 32 (2): 83–99. doi:10.1016/j.bpa.2018.06.011. Check date values in:
|date=(help) - ↑ 3.0 3.1 3.2 3.3 Albrecht, E.; Chin, K. J. (2020-01). "Advances in regional anaesthesia and acute pain management: a narrative review". Anaesthesia. 75 (S1). doi:10.1111/anae.14868. ISSN 0003-2409. Check date values in:
|date=(help) - ↑ 4.0 4.1 4.2 4.3 Miller, R. D.; Pardo, M. C. (2011). Basics of Anesthesia. Elsevier/Saunders.
- ↑ Horlocker, Terese T.; Vandermeuelen, Erik; Kopp, Sandra L.; Gogarten, Wiebke; Leffert, Lisa R.; Benzon, Honorio T. (2018-04). "Regional Anesthesia in the Patient Receiving Antithrombotic or Thrombolytic Therapy: American Society of Regional Anesthesia and Pain Medicine Evidence-Based Guidelines (Fourth Edition)". Regional Anesthesia and Pain Medicine. 43 (3): 263–309. doi:10.1097/AAP.0000000000000763. ISSN 1098-7339. Check date values in:
|date=(help) - ↑ Steinfeldt, T.; Volk, T.; Kessler, P.; Vicent, O.; Wulf, H.; Gottschalk, A.; Lange, M.; Schwartzkopf, P.; Hüttemann, E.; Tessmann, R.; Marx, A. (2015-11). "Peripheral nerve blocks on the upper extremity: Technique of landmark-based and ultrasound-guided approaches". Der Anaesthesist. 64 (11): 846–854. doi:10.1007/s00101-015-0091-x. ISSN 0003-2417. Check date values in:
|date=(help) - ↑ Popping DM, Elia N, Marret E, Wenk M, Tramer MR. Clonidine as an adjuvant to local anesthetics for peripheral nerve and plexus blocks: A meta-analysis of randomized trials. Anesthesiology 2009;111(2): 406–415
- ↑ Abdallah FW, Brull R: Facilitatory effects of perineural dexmedetomidine on neuraxial and peripheral nerve block: a systematic review and meta-analysis. Br J Anaesth 2013;110(6):915–925.
- ↑ NYSORA (2018-06-08). "Analgesic Adjuvants in the Peripheral Nervous System". NYSORA. Retrieved 2023-09-14.
- ↑ 10.0 10.1 Joshi, Girish; Gandhi, Kishor; Shah, Nishant; Gadsden, Jeff; Corman, Shelby L. (2016-12). "Peripheral nerve blocks in the management of postoperative pain: challenges and opportunities". Journal of Clinical Anesthesia. 35: 524–529. doi:10.1016/j.jclinane.2016.08.041. Check date values in:
|date=(help) - ↑ Widmer, B., Lustig, S., Scholes, C. J., Molloy, A., Leo, S. P., Coolican, M. R., & Parker, D. A. (2013). Incidence and severity of complications due to femoral nerve blocks performed for knee surgery. The Knee, 20(3), 181-185.
- ↑ Fredrickson, M. J., and D. H. Kilfoyle. "Neurological complication analysis of 1000 ultrasound guided peripheral nerve blocks for elective orthopaedic surgery: a prospective study." Anaesthesia 64.8 (2009): 836-844.
- ↑ Tsui, Ban C. H.; Kirkham, Kyle; Kwofie, M. Kwesi; Tran, De Q.; Wong, Patrick; Chin, Ki Jinn; Sondekoppam, Rakesh V. (2019-11). "Practice advisory on the bleeding risks for peripheral nerve and interfascial plane blockade: evidence review and expert consensus". Canadian Journal of Anesthesia/Journal canadien d'anesthésie. 66 (11): 1356–1384. doi:10.1007/s12630-019-01466-w. ISSN 0832-610X. Check date values in:
|date=(help) - ↑ Ilfeld, Brian M. (2011-10). "Continuous Peripheral Nerve Blocks: A Review of the Published Evidence". Anesthesia & Analgesia. 113 (4): 904–925. doi:10.1213/ANE.0b013e3182285e01. ISSN 0003-2999. Check date values in:
|date=(help) - ↑ Šimurina, Tatjana (2019). "Local Anesthetics and Steroids: Contraindications and Complications - Clinical Update". Acta Clinica Croatica. doi:10.20471/acc.2019.58.s1.08.
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