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Step 26 · Subspecialty

Regional Anesthesia — The Basics

Nerve blocks, epidurals, spinals and caudals — what they are and what you'll see.

7 min read

The TL;DR

  • Regional places local anesthetic near nerves to numb a region — sole anesthetic or combined with GA, and great for post-op pain.
  • Peripheral nerve blocks (landmarks/stimulator/ultrasound) numb a nerve or extremity.
  • Epidural: a catheter in the epidural space via loss-of-resistance; level + volume set the analgesia level.
  • Spinal: a thin needle into the CSF, confirmed by CSF return — faster and denser than an epidural.
  • Always test an epidural for intrathecal/intravascular placement before dosing; dilute only with preservative-free solutions.

01The techniques

Regional anesthesia bathes nerves in local anesthetic to numb a region — as the sole anesthetic, layered with sedation/GA, or for post-op pain control. Three you'll meet:

  • Peripheral nerve block — find the nerve with landmarks, a nerve stimulator, or ultrasound, then deposit local nearby. Most common for extremity surgery.
  • Neuraxial — epidural and spinal (below).
  • Caudal — a pediatric favorite (epidural space via the sacral hiatus).

If you dilute regional medications, use preservative-free solutions — preservatives near nerves can cause damage.

Pearls
  • NYSORA (nysora.com) has excellent free anatomy and block videos — see the procedures before you assist.

02Epidural — what you'll see

A needle is advanced in the back to the epidural space, then a catheter is threaded in. The needle passes: skin → subcutaneous tissue → supraspinous ligament → interspinous ligament → ligamentum flavum → epidural space (go too far → dura → "wet tap," CSF). The level (lumbar→cervical) and the volume of local set the analgesia level.

Roughly what happens: 1. Sterile prep and drape; local at the entry point. 2. A Tuohy needle is advanced to the interspinous ligament; stylet out; a loss-of-resistance syringe (air/saline) is attached. 3. Advance with pressure on the plunger until loss of resistance = the epidural space. 4. Thread the catheter through the needle (never pull it back through — it can shear); remove the needle, leaving ~3–4 cm in the space. 5. Test dose (e.g., lidocaine with epinephrine) checks for intrathecal (would cause a profound block) and intravascular (tachycardia from the epi, or CNS symptoms) placement. 6. Dose, then secure with a clear dressing.

Common mistakes
  • Pulling the catheter back through the Tuohy needle — it can shear off in the patient.

03Spinal & caudal

Spinal — medication placed into the CSF (the dural sac). Similar setup to an epidural but with a thin needle; correct placement is confirmed by CSF dripping from the needle. Faster and denser than an epidural, but a single shot.

Caudal — used in infants/children, usually after they're under GA. The epidural space is reached through the sacral hiatus (the covering ligament calcifies after childhood, making caudals hard in adults). A needle/IV catheter is advanced at ~45° until resistance "gives," then flattened and advanced; aspirate (no CSF/blood) and inject.

Concepts adapted for AnesthesiaHub from “Anesthesia Made Easy” (Jeff Steiner, DO, MBA) and standard anesthesia references, re-expressed in this site's own words. Educational use only — always verify doses against primary sources and your institution's protocols.

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