Regional Anesthesia Lecture Notes

Introduction

• Channel: Medical System Fictionalist
• Focus: Anesthesiology (Video 7 - Regional Anesthesia)
• Recap: Previous video on airway management

Key Concepts

• Anesthesia vs Analgesia:
  • Anesthesia includes analgesia, hypnosis, and muscle relaxation.
  • Analgesia: Pain relief without unconsciousness.

Premedication

• Question: Should patients be pre-medicated to prevent aspiration?
• Answer: No, most patients are at very low risk of aspiration syndrome.

Anesthesia Care Phases

1. Preoperative
2. Intraoperative
3. Postoperative

Types of Anesthesia

• General
• Regional (Today’s Focus)
  • Types:
    • Neuraxial (Spinal and Epidural)
    • Limb Blocks
• Local

Neuraxial Anesthesia

• Definition: Blocks nerves at the spinal cord axis (median plane)
• Subtypes:
  • Spinal
  • Epidural
    • Further Divisions:
      • Thoracic
      • Lumbar
      • Caudal (through the sacral hiatus)
• History: Once called conduction anesthesia.

Embryology Review

• Development Stages:
  • Fertilization
  • Cleavage
  • Blastulation
  • Implantation
  • Bilaminar Embryo (Epiblast, Hypoblast)
  • Trilaminar Embryo (Endoderm, Mesoderm, Ectoderm)
• Ectoderm Development:
  • Nervous system (under primitive streak influence)
  • CNS: Brain and spinal cord
  • PNS: Cranial and spinal nerves
  • Segmented spinal cord: Cervical, Thoracic, Lumbar, Sacral, Coccygeal
• Mesoderm Development:
  • Notochord → Nucleus Pulposus (intervertebral disc)
  • Spinal Cord Anatomy: Surrounded by vertebral canal, contains CSF in the spinal canal.

CSF Flow Pathway

• Brain: Ventricles (Lateral → Third → Fourth)
  • Production: Ependymal cells of the choroid plexus.
  • Flow: Interventricular foramina (Monroe) → Third ventricle → Cerebral aqueduct (Silvius) → Fourth ventricle → Subarachnoid space.
• Spinal Cord: Subarachnoid space continues around spinal cord.

Spinal Anatomy and Procedure

• Spinal Cord Regions:
  • Cervical, Thoracic, Lumbar, Sacral
• Meninges: Dura mater, Arachnoid mater, Pia mater (CSF in subarachnoid space)
  • Neuraxial Space Injections:
    • Epidural: Above dura
    • Spinal: Subarachnoid (between arachnoid and pia)

Procedure Details

• Epidural Injection:
  • Layers: Skin, Subcutaneous tissue, Supraspinous ligament, Interspinous ligament, Ligamentum flavum, Epidural space
• Spinal Injection:
  • Enter subarachnoid space (CSF presence confirms entry)
  • Levels: Between L3 and L5 to avoid spinal cord injury (ends at L1-L2)

Complications and Considerations

• Hypotension: Due to sympathetic block
• Meningeal Layers: Epidural above dura, Spinal in subarachnoid (
• Injection Techniques:
  • Hyperbaric, Isobaric, Hypobaric solutions (based on density to CSF)
• Patient Positioning: Important for accurate injection (lateral decubitus/jackknife/etc.)
• Spinal vs Epidural:
  • Spinal: Shorter duration, stronger block, higher post-dural headache risk.
  • Epidural: Longer administration, more control, used in combination with general anesthesia.

Post-Dural Puncture Headache

• Cause: Dura puncture and CSF leak.
• Symptoms: Frontal/occipital headache, diplopia, photophobia.
• Treatment: Bed rest, fluids, pain meds, caffeine, blood patch.

Summary

• Applications: Lower abdomen, pelvis, lower limbs, labor
• Contraindications: Patient refusal, bleeding disorders, infections, increased intracranial pressure
• Patient Care: Monitor for complications, ensure correct positioning, advise patients (e.g., on hypotension risk).