Spinal Anaesthesia
Spinal anaesthesia involves injection of local anaesthetic into the subarachnoid space producing rapid, dense sensory and motor block with predictable dermatomal distribution. Mechanism: Local anaesthetic acts on...
What matters first
Spinal anaesthesia involves injection of local anaesthetic into the subarachnoid space producing rapid, dense sensory and motor block with predictable dermatomal distribution. Mechanism: Local anaesthetic acts on...
Total spinal with cardiovascular collapse and respiratory failure
2 Feb 2026
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96 cited sources
Clinical board
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Urgent signals
Safety-critical features pulled from the topic metadata.
- Total spinal with cardiovascular collapse and respiratory failure
- High spinal causing severe hypotension and bradycardia
- Post-dural puncture headache (PDPH) preventing ambulation
- Cauda equina syndrome from neurotoxicity
Exam focus
Current exam surfaces linked to this topic.
- ANZCA Final Written
- ANZCA Final Clinical Viva
- ANZCA Final Medical Viva
Content status and exam context
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Clinical explanation and evidence
Quick Answer
Spinal anaesthesia involves injection of local anaesthetic into the subarachnoid space producing rapid, dense sensory and motor block with predictable dermatomal distribution. Mechanism: Local anaesthetic acts on nerve roots and spinal cord blocking sodium channels, with small unmyelinated C fibers (pain) blocked before large myelinated A fibers (motor). Technique: Midline or paramedian approach at L3-L4 or L4-L5 interspace (below conus medullaris which ends at L1-L2 in adults), using 25-27G pencil-point needles (Whitacre, Sprotte) to reduce PDPH risk. Standard caesarean section dose: Hyperbaric bupivacaine 0.5% 2.2-2.5 mL (11-12.5 mg) with fentanyl 10-20 μg and morphine 100-200 μg for postoperative analgesia. Onset: 2-5 minutes (faster than epidural), duration 90-180 minutes depending on drug/dose. Hypotension occurs in 15-30% due to sympathetic blockade (T4-L1), managed with left uterine displacement, fluid preload 500-1000 mL, phenylephrine 50-100 μg IV bolus or infusion 50-100 μg/min. PDPH incidence 1-2% with modern needles, treated with epidural blood patch (15-20 mL autologous blood) if severe/persistent. Contraindications: Patient refusal, coagulopathy (platelets <80 × 10⁹/L), infection at site, severe hypovolaemia, increased ICP. Indigenous patients have higher rates of obesity and OSA increasing technical difficulty and PDPH risk, requiring careful positioning and culturally sensitive consent processes. [1-10]