Regional anesthesia

1. Brachial Plexus Block (for upper limb anesthesia)

• Injection site:
  • Interscalene block: At the level of C6, between the anterior and middle scalene muscles.
  • Supraclavicular block: Above the clavicle, near the brachial plexus trunks.
  • Infraclavicular block: Below the clavicle near the cords of the brachial plexus.
  • Axillary block: Near the axillary artery, at the level of the axilla.
• Clinical relevance: Used for surgeries of the shoulder, arm, forearm, and hand.
• Key point: Interscalene block can cause phrenic nerve paralysis (C3-C5), leading to diaphragmatic hemiparalysis.

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Epidural anesthesia

• Mechanism: Local anesthetics (bupivacaine) ± opioids (fentanyl) into L3-L4/L4-L5 epidural space; blocks Na+ channels at nerve roots (dura remains intact).
• Layers Traversed: Skin -> Subcutaneous -> Supraspinous lig. -> Interspinous lig. -> Ligamentum flavum (loss of resistance) -> Epidural space.
• Indications: Labor analgesia, post-op pain control, chronic pain management.
• Contraindications: Patient refusal, severe coagulopathy/thrombocytopenia (platelets < 70k-80k -> epidural hematoma risk), uncorrected shock, site infection, ↑ ICP.
• Test Dose (Lidocaine + Epinephrine):
  • Intravascular placement: Tachycardia (>20 bpm spike) & HTN.
  • Intrathecal placement: Rapid sensory/motor block.
• Physiological Effects: Loss of sympathetic tone below block level -> venodilation/arterial dilation -> maternal hypotension (↓ SVR/preload) -> ↓ uteroplacental blood flow -> fetal late decelerations/bradycardia. c
• Complication Management:
  • Maternal Hypotension: Left lateral tilt (relieves IVC compression), IV fluid bolus, IV Phenylephrine or Ephedrine.
  • Post-Dural Puncture Headache (PDPH): Due to accidental dural puncture (“wet tap”); postural headache (worse standing, better lying flat); Rx: Conservative (fluids, caffeine) -> Epidural blood patch if refractory.
  • Epidural Hematoma/Abscess: Progressive lower extremity weakness, back pain, bowel/bladder dysfunction; Dx: Urgent Spine MRI; Rx: Emergency surgical decompression (laminectomy).
  • Local Anesthetic Systemic Toxicity (LAST): Accidental IV injection; CNS signs (perioral numbness, metallic taste, seizures) -> CV collapse/cardiac arrest; Rx: 20% Lipid emulsion therapy (Intralipid). c
  • High/Total Spinal Block: Accidental intrathecal dose -> ascending paralysis, respiratory arrest (C3-C5 block); Rx: Immediate intubation, vasopressors.
• Obstetric Impact: Prolongs 2nd stage of labor (pushing phase); does NOT increase C-section rate; can be placed at any cervical dilation.

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3. Spinal Anesthesia

• Injection site:
  • Into the subarachnoid space, usually at L3-L4 or L4-L5 interspace.
• Clinical relevance: Used for lower limb, pelvic, and lower abdomen surgeries.
• Key point: Fast onset and denser block; risk of hypotension due to sympathetic blockade.

Feature	Epidural	Spinal (Subarachnoid)
Site	Epidural space (outside dura)	Subarachnoid space (mixes with CSF)
Level	Any level	Below L2 (avoid cord damage)
Onset	Slow (10–20 min)	Rapid (< 5 min)
Volume	High volume required	Low volume required
Duration	Continuous (catheter)	Finite (single shot)
Primary Use	Labor, Post-op pain	C-Section, TURP, Lower limb surgery

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4. Sciatic Nerve Block

• Injection site:
  • Posteriorly in the gluteal region or mid-thigh.
• Clinical relevance: Used for anesthesia of the lower limb below the knee.
• Key point: Useful in foot and ankle surgeries.

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5. Femoral Nerve Block

• Injection site:
  • Just distal to the inguinal ligament, lateral to the femoral artery and vein. The nerve lies lateral to the femoral artery in the femoral triangle.
• Clinical relevance:
  • Provides anesthesia to the anterior thigh, knee, and medial leg (via saphenous nerve branch).
  • Frequently used in surgeries involving the anterior thigh, knee arthroscopy, or for pain control after femur fractures.
• Anatomical landmarks:
  • Needle insertion usually at the level of the femoral triangle, found using the inguinal ligament superiorly, sartorius muscle laterally, and adductor longus muscle medially.
  • Palpate femoral artery, insert needle just lateral to artery.

6. Digital Nerve Block

• Injection site:
  • At the base of the fingers, near the digital nerves.
• Clinical relevance: For finger surgeries.
• Key point: Avoid intravascular injection to prevent systemic toxicity.