Lower Extremity Regional Anesthesia in the Orthopedic Patient David Freeze

Anatomy of Peripheral Nerves Neuron is responsible for conduction of nerve impulses Longest cells in the body

Common Medications Tetracaine (Class: Esters) - Bupivacaine (Class: amides) most common Ropivacaine (Class: amides) Cocaine is a natural anesthetic

Local Anesthetic Short Acting (45-90 minutes) 2-chloroprocaine Intermediate Acting (90-180 minutes) Lidocaine, mepivacaine Long Acting (4-18 hours) Bupivacaine, ropivacaine, levobupivacaine)

What Impacts duration of a block Lipid solubility Degree of vascularity of the tissue Presence of vasoconstrictors that prevent vascular uptake – epinephrine Greater lipid solubility increases the affinity of the drug causing greater potency and duration of action

Smaller Nerve fibers are more susceptible to the effects of local anesthesia Myelinated fibers are more easily blocked than unmyelinated because the local anesthesia pools near axonal membrane

Adverse Effects Systemic Toxicity Symptoms Cardiac Toxicity Mild: Lightheadedness, dizziness, visual or auditory disturbances, disorientation, drowsiness, metallic taste Severe: shivering, muscular twitching tremors, hypotension, sinus brady, cardiac collapse, cardiac dysrhythmias, resp. dep.

Avoid Adverse Effects Toxicity is typically avoided by appropriate selection of medication, dose, and concentration. Technique is also critical Slow incremental injections with frequent aspirations

Lower Extremity Blocks Common Blocks: Adductor Canal Spinal Sciatic Femoral Nerve

Spinal Neuraxial Block Space in the cerebrospinal fluid that surrounds the spinal cord Bupivacaine 3-4 hrs Tetracaine 5-6 hrs

Femoral Nerve Block Insertion at Groin Femoral Nerve innervates L2 to L4 Covers anterior, medial, and interior but spares lateral and posterior Greater Pain control Increased risk of falls

Adductor Canal Insertion at Mid thigh Preserves most of the motor function of the quadriceps Reduces risk of falls

Sciatic Nerve Insertion anterior or gluteal Ideal for Lower Leg Surgery BKA Achilles Tendon Repair Tibial or Fibula Surgery Foot

References American Society of Regional Anesthesia and Pain Medicine. (2016). Regional anesthesia for surgery. Retrieved from https://www.asra.com/page/41/regional-anesthesia-for-surgery New York School of Regional Anesthesia (NYSORA). (2016). Regional anesthesia. Retrieved from http://www.nysora.com/