Regional Anesthesia and Acute Pain Medicine
Regional anesthesia: anatomy, dose, and rescue
Know neuraxial anatomy (epidural versus intrathecal space, ligamentum flavum, dermatomes), local anesthetic onset and duration, adjuvants, and ultrasound principles. For peripheral blocks, identify nerves, fascia, and danger structures; use hydrodissection and incremental injection with aspiration. Understand LAST prevention and treatment: stop injection, call for help, secure the airway, give lipid emulsion 1.5 mL/kg bolus then infusion, and support circulation. Anticoagulation and neuraxial guidelines are high-yield.
Traps: a negative aspiration does not exclude intravascular placement. Test doses are imperfect, especially for intrathecal detection. Do not add epinephrine to every block without considering end-arterial risk. Bupivacaine is more cardiotoxic than lidocaine. A dense block can mask compartment syndrome or neurologic injury.
Worked example: a 70-kg patient scheduled for interscalene block. Maximum bupivacaine 0.25% at 2 mg/kg = 140 mg. Since 0.25% = 2.5 mg/mL, that is 56 mL-far more than needed. Use 10–20 mL and calculate cumulative dose if other blocks are planned.
Rule of thumb: calculate the maximum dose before drawing up, inject incrementally, and have lipid emulsion immediately available.