Neuraxial Anesthesia Troubleshooting
Regional Anesthesia · 7 min read
Neuraxial blocks fail in 5-10% of cases (failed level, partial block, patchy block). Recognizing why + how to rescue is what separates competent from confident regional anesthesia practice.
Failed spinal — diagnose by waiting + testing
After spinal injection, wait 5-15 min before declaring failure. TEST: cold/temperature → wide gradient = block taking effect; pinprick at expected dermatomes; motor block at lower extremities. If at 15-20 min still no block: re-inject is OPTION (controversial — risk of high spinal if combined with already-given dose; some recommend waiting 30 min minimum, then small re-dose at lower level). Convert to GA is the safer rescue. CSF flow visible on initial spinal? If unclear, was likely SUBDURAL (false 'flow') → high level + asymmetric block + hypotension. Subdural: support + observe; resolves slowly.
Patchy spinal — usually adequate for surgery
Patchy block (some dermatomes spared) is most often INADEQUATE LA SPREAD. If patient comfortable on test stimulus → proceed; if uncomfortable → add IV adjuncts (ketamine 0.3 mg/kg, dexmedetomidine 0.5 mcg/kg, midazolam, fentanyl) and proceed; if completely inadequate → convert to GA. Do NOT inject MORE local through spinal needle (already removed) and do NOT chase with epidural unless pre-planned.
Total spinal — emergency
Total spinal: rapid ascent of block to cervical/cranial nerves → diaphragm paralysis (C3-C5), hypotension (sympathectomy + decreased venous return), bradycardia (cardioaccelerator T1-T4 blocked + Bezold-Jarisch reflex), unconsciousness, dilated unreactive pupils. EMERGENCY: airway support (intubate), 100% O₂, fluid bolus, vasopressors (phenylephrine, norepi, vasopressin), atropine for bradycardia, leg elevation/Trendelenburg controversial. Resolves over 1-3 hours. Causes: subdural injection, intrathecal injection of epidural-intended dose, very rapid ascent in pregnant patient.
Failed epidural — multifactorial
Failed epidural causes: (1) incorrect needle placement (too lateral, too shallow, in epidural fat pocket); (2) patchy spread of LA in epidural space (catheter near nerve root vs free); (3) inadequate volume; (4) catheter migration; (5) loss of catheter through skin during patient movement. RESCUE: re-bolus 5-10 mL 0.25% bupivacaine + observe 10 min; if patchy, add IV adjuncts; if completely inadequate, replace catheter (one level higher/lower) or convert to GA. For OB labor analgesia: combined spinal-epidural (CSE) reduces failed epidural rate.
Post-dural puncture headache (PDPH)
PDPH: positional headache (worse upright, better supine) starting 12-72 h post-spinal/epidural. Mechanism: CSF leak through dural puncture → low CSF pressure → traction on meninges. RISK: pencil-point needles (Sprotte, Whitacre) ~1-2%, cutting (Quincke) 5-25% (size + age dependent). PRESENTATION: bilateral occipital/frontal headache, can have neck stiffness, photophobia, nausea, transient hearing/visual changes. CONSERVATIVE: bed rest, hydration, caffeine 300-500 mg/day, NSAIDs. SUMATRIPTAN limited evidence. EPIDURAL BLOOD PATCH (definitive): 15-20 mL autologous blood injected one level below original puncture; 60-90% complete relief; consider in severe persistent PDPH.
Hypotension during neuraxial — manage actively
Hypotension after spinal: 80-90% incidence in cesarean. Severity correlates with sympathetic block extent. PROPHYLAXIS: phenylephrine infusion 25-100 mcg/min titrated to baseline, co-load crystalloid 1-2 L, leftward uterine displacement. TREATMENT: bolus phenylephrine 50-100 mcg, ephedrine 5-10 mg if bradycardic (rare in non-OB). For routine non-OB spinal: ephedrine 5-10 mg first-line (treats both HR + BP), phenylephrine 50-100 mcg if reflex tachycardia. Treat aggressively — fetal/elderly patient outcomes suffer from sustained hypotension.
References
- · Hadzic Regional Anesthesia 2e
- · Miller's Anesthesia 9e Ch 45
- · Ngan Kee Anesth Analg 2010 — Phenylephrine for spinal hypotension