Complications of Regional Anesthesia

Overview & Classification - The Initial Rundown

Complications are classified by:

• Scope of Effect:
  • Systemic: Affecting entire body (e.g., LAST, high spinal).
  • Local: At injection site (e.g., nerve injury, hematoma).
• Timing of Onset:
  • Immediate: During or soon after block.
  • Delayed: Hours to weeks later.

Common risk factors (📌 PPA):

• Patient: Coagulopathy, pre-existing neuropathy, systemic illness.
• Procedure: Technique, multiple attempts, needle type.
• Anesthetic: Drug choice, total dose, vasoconstrictors.

⭐ Most complications are preventable with meticulous technique and careful patient selection.

Local Anesthetic Systemic Toxicity (LAST) - When LAs Go Rogue

• Definition: Systemic adverse reaction due to high blood concentrations of local anesthetic.
• Pathophysiology: Dose-dependent Na+ channel blockade in CNS & cardiovascular system (CVS).
• Susceptible LAs: Bupivacaine > Ropivacaine > Lidocaine (potency & cardiotoxicity).
• CNS Symptoms:
  • Early: Tinnitus, metallic taste, perioral numbness, dizziness, visual disturbances, muscle twitching, agitation.
  • Late: Seizures, unconsciousness, coma, respiratory arrest.
  • 📌 Mnemonic for CNS signs (LAST): Lips numb/tingling, Agitation/Auditory changes, Seizures/Slurred speech, Twitching.
• CVS Symptoms: Initial hypertension/tachycardia → bradycardia, hypotension, ventricular arrhythmias (VT/VF), asystole, cardiac arrest.
• Risk Factors:
  • High dose or rapid injection.
  • Site of injection (vascularity): IV > Tracheal > Intercostal > Caudal > Epidural > Brachial plexus > Sciatic/Femoral > Subcutaneous.
  • Patient factors: Extremes of age, pregnancy, cardiac/hepatic/renal dysfunction, low protein.
• Prevention:
  • Use lowest effective dose.
  • Aspirate before & during injection.
  • Incremental injection (3-5 mL, wait 15-30s).
  • Ultrasound guidance.
  • Test dose for epidurals.
  • Adhere to maximum recommended doses (e.g., Bupivacaine ~2 mg/kg).
• Management:
  • STOP LA injection immediately.
  • Call for help (get LAST kit).
  • ABCs: Maintain Airway (100% O2), ensure adequate Breathing (ventilate if needed), support Circulation.
  • Seizure control: Benzodiazepines (e.g., Midazolam 0.05-0.1 mg/kg IV). Avoid large doses of propofol if CVS unstable.
  • Lipid Emulsion Therapy (Intralipid 20%): Administer at first sign of severe LAST (arrhythmias, refractory seizures, rapid progression).
    • Bolus: 1.5 mL/kg (lean body mass) over 1 minute.
    • May repeat bolus 1-2 times for persistent CVS instability.
    • Infusion: 0.25 mL/kg/min.
    • Continue infusion for at least 10 minutes after hemodynamic stability.
    • Maximum total dose: approx. 10-12 mL/kg in the first 30 minutes.

⭐ Lipid emulsion therapy (Intralipid 20%) is a critical and specific antidote for severe Local Anesthetic Systemic Toxicity (LAST).

Neurological Complications (PDPH, Nerve Injury, CES, TNS) - Brain & Nerve Blues

• Post-Dural Puncture Headache (PDPH)

  • Patho: CSF leak → ↓ICP.
  • Symptoms: Postural headache (↑upright), neck stiffness, nausea, photophobia, tinnitus.
  • Risk Factors: 📌 NEEDLE: Needle (large/cutting Quincke 22G > pencil-point Whitacre 27G), Experience↓, Earlier PDPH, Dural punctures (multiple), Low CSF (young, female, pregnancy).
  • Prevention: Small (25-27G), pencil-point (Whitacre, Sprotte); bevel parallel dural fibers.
  • Treatment: Conservative (hydration, analgesics, caffeine); Epidural Blood Patch (EBP).

  ⭐ Pencil-point needles (Whitacre, Sprotte) ↓ PDPH vs. cutting (Quincke).

• Direct Nerve Injury

  • Mechanism: Needle trauma, intraneural injection, LA neurotoxicity.
  • Symptoms: Persistent paresthesia, motor/sensory deficit.
  • Prevention: Ultrasound, nerve stimulator; avoid injection on paresthesia/high pressure.

• Cauda Equina Syndrome (CES) ⚠️

  • Symptoms: 📌 SADDLE: Saddle anesthesia, Anal tone↓, Dysfunction (bowel/bladder), Lower limb weakness, Emergency.
  • Causes: High LA conc., maldistribution, hematoma. (Old: microcatheters).

• Transient Neurological Symptoms (TNS)

  • Symptoms: Buttock/lower limb pain/dysaesthesia post-spinal.
  • LA: Lidocaine. Self-limiting.

Hematoma, Infection & Catheter Issues - Site-Specific Setbacks

• Spinal/Epidural Hematoma: Neurological emergency!
  • Risks: Coagulopathy, anticoagulants (check specific timing guidelines!), traumatic tap, indwelling catheter.
  • Symptoms: 📌 PAIN (Progressive deficit, Acute onset, Incontinence, Numbness), severe back/radicular pain, progressive motor/sensory deficits, bowel/bladder dysfunction.
  • Dx: Urgent MRI.
  • Rx: Neurosurgical consultation for decompressive laminectomy within 8-12 hours.
• Infection (Epidural Abscess, Meningitis):
  • Risks: Poor asepsis, immunocompromise, prolonged catheterization.
  • Sx: Fever, localized back pain/tenderness, erythema, neuro deficits.
  • Dx: MRI, CSF analysis. Rx: Antibiotics, surgical drainage (if abscess).
• Catheter Issues: Breakage, knotting, migration, occlusion, shearing.
• Allergic Reactions: Rare with amides; esters (PABA metabolite) more common.
• Backache: Common, usually musculoskeletal, transient.

⭐ Spinal epidural hematoma is a neurological emergency requiring prompt diagnosis (MRI) and surgical decompression, ideally within 8-12 hours, to maximize chances of neurological recovery.

High‑Yield Points - ⚡ Biggest Takeaways

• LAST: CNS excitation (seizures) then depression, CVS toxicity (arrhythmias). Treat with lipid emulsion.
• PDPH: Postural headache, worse upright. Epidural blood patch for severe, persistent cases.
• Nerve Injury: Paresthesia, motor deficits from direct trauma, hematoma, or chemical irritation.
• Epidural Hematoma/Abscess: Back pain, fever, progressive neurological deficits. Urgent MRI and intervention.
• Total Spinal Anesthesia: Apnea, profound hypotension, unconsciousness. Immediate airway management.
• Pneumothorax: Risk with supraclavicular/intercostal blocks. Sudden dyspnea, chest pain.