Caesarean Section Anaesthesia

Quick Answer

Caesarean section is the most common major surgical procedure in Australia, with approximately 30-35% of births delivered by caesarean section. Neuraxial anaesthesia (spinal, epidural, or combined spinal-epidural) is preferred for 90-95% of elective and 70-80% of emergency caesarean sections due to maternal safety profile, reduced fetal drug exposure, and patient satisfaction. Spinal anaesthesia provides rapid onset (2-5 minutes), profound sensory block (T4 level), and is the technique of choice for most caesarean sections. Standard spinal dose is 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. General anaesthesia is reserved for urgent/emergent deliveries (fetal distress with insufficient time for neuraxial block), contraindications to neuraxial anaesthesia (coagulopathy, patient refusal), or failed neuraxial block. Key considerations include left uterine displacement (15-30° tilt) to prevent aortocaval compression, phenylephrine as first-line vasopressor for spinal-induced hypotension (50-100 μg IV bolus), aspiration prophylaxis (sodium citrate 0.3 M 30 mL PO, ranitidine 50 mg IV, metoclopramide 10 mg IV), and fetal monitoring throughout. Indigenous women have higher rates of emergency caesarean sections, gestational diabetes, and pre-eclampsia, requiring culturally safe communication, experienced anaesthetic teams, and consideration of traditional birth practices alongside emergency medical care. [1-10]

Pathophysiology

Physiological Changes in Pregnancy Relevant to Caesarean Section

Cardiovascular Changes:

• Increased blood volume: 40-50% increase (1500 mL) by third trimester
• Cardiac output: 30-50% increase (stroke volume and heart rate)
• Aortocaval compression: Supine position compresses IVC and aorta, reducing venous return and cardiac output by 20-30%
• Plasma volume expansion: Dilutional anaemia (physiological anaemia of pregnancy)
• Reduced SVR: Vasodilation due to progesterone, prostaglandins
• Implications:
  • Left uterine displacement mandatory (15-30° left lateral tilt)
  • Rapid onset of hypotension with neuraxial blockade
  • Higher risk of haemorrhage (hypervolaemia masks blood loss initially)

Respiratory Changes:

• Minute ventilation: 30-50% increase (tidal volume, not respiratory rate)
• Functional residual capacity: 20% reduction (elevated diaphragm)
• Oxygen consumption: 20-30% increase (fetal and maternal metabolic demands)
• Airway changes:
  • Capillary engorgement of airway mucosa (increased bleeding risk with intubation)
  • Breast enlargement (difficult laryngoscopy)
  • Increased risk of difficult intubation (1:300 vs. 1:2000 non-pregnant)
• Implications:
  • Rapid desaturation during apnoea (reduced FRC, increased O₂ consumption)
  • Difficult airway management
  • Need for experienced anaesthetist for general anaesthesia

Gastrointestinal Changes:

• Reduced lower oesophageal sphincter tone: Progesterone effect
• Delayed gastric emptying: Especially in labour, with opioids, or in obesity
• Increased gastric acidity: Gastrin production increased
• Implications:
  • High risk of aspiration (Mendelson syndrome)
  • Mandatory aspiration prophylaxis (antacids, H2 blockers, prokinetics)
  • Rapid sequence induction if general anaesthesia required

Haematological Changes:

• Hypercoagulable state: Increased clotting factors, reduced fibrinolysis
• Platelet count: May decrease (gestational thrombocytopenia)
• Implications:
  • Risk of thromboembolism (DVT, PE)
  • Thromboprophylaxis required post-caesarean
  • Coagulation assessment before neuraxial blockade

Fetal Physiology and Drug Transfer

Placental Transfer:

• Lipophilic drugs: Cross placenta easily (most anaesthetic agents)
• Ionized drugs: Limited transfer (muscle relaxants, highly ionized opioids)
• Protein binding: Reduced transfer with high protein binding
• Molecular weight: Smaller molecules cross more easily

Fetal Effects of Maternal Drugs:

General Anaesthesia Agents:

• Induction agents (propofol, thiopental): Rapid placental transfer, fetal sedation
• Muscle relaxants (rocuronium, succinylcholine): Poor placental transfer (ionized, quaternary ammonium)
• Opioids (fentanyl, morphine): Cross placenta, neonatal respiratory depression
• Volatile agents (sevoflurane, isoflurane): Rapid transfer, dose-dependent fetal effects
• Implications:
  • Minimize induction-to-delivery interval (I-D interval) to reduce fetal drug exposure
  • Neuraxial preferred (minimal fetal drug exposure)
  • Neonatal resuscitation team present

Neuraxial Anaesthesia:

• Minimal fetal drug exposure: Local anaesthetic in epidural space, limited systemic absorption
• Advantage: Preferred for fetal safety
• Exception: Intrathecal morphine crosses placenta minimally but provides prolonged postoperative analgesia

Clinical Presentation

Assessment for Caesarean Section Anaesthesia

Preoperative Assessment Domains:

1. Urgency Classification:

• Category 1 (Immediate threat to life): Immediate delivery (<30 minutes) — general anaesthesia usually required
• Category 2 (Maternal/fetal compromise): Urgent delivery (<75 minutes) — neuraxial if feasible, general if not
• Category 3 (No compromise): Elective — neuraxial preferred
• Category 4 (At convenience): Scheduled — neuraxial

2. Airway Assessment:

• Critical assessment: Mallampati score, thyromental distance, neck mobility
• Risk factors: Obesity, short neck, airway masses, prior difficult intubation
• Implications: If general anaesthesia required, airway difficulty may necessitate awake fibreoptic intubation

3. Cardiovascular Status:

• Blood pressure: Baseline, hypertension (pre-eclampsia), hypotension risk
• Cardiac history: Cardiac disease, arrhythmias, valvular disease
• Volume status: Hypovolaemia (haemorrhage), adequate preload for neuraxial blockade

4. Coagulation Status:

• Platelet count: Essential before neuraxial (target >80 × 10⁹/L)
• INR/APTT: If on anticoagulation or liver disease
• Bleeding history: Easy bruising, bleeding gums, menorrhagia

5. Fetal Status:

• Fetal heart rate pattern: Category I (normal), II (indeterminate), III (abnormal)
• Fetal presentation: Cephalic, breech, transverse
• Estimated fetal weight: Macrosomia, growth restriction
• Multiple pregnancy: Twins, triplets (higher risk)

6. Previous Anaesthetic History:

• Previous caesarean: Type of anaesthesia, complications
• Neuraxial complications: PDPH, failed block, neurological injury
• General anaesthesia: Difficult intubation, awareness, PONV

7. Medical Comorbidities:

• Pre-eclampsia: Hypertension, proteinuria, thrombocytopenia
• Diabetes: Gestational or pre-existing
• Obesity: BMI, difficult airway, technical challenges
• Cardiac disease: Valvular, cardiomyopathy, congenital
• Other: Asthma, renal disease, neurological conditions

Management

Neuraxial Anaesthesia for Caesarean Section

Spinal Anaesthesia (Most Common):

Indications:

• Elective caesarean section
• Most urgent caesarean sections (if time allows)
• Patient preference for awake delivery
• Reduced fetal drug exposure desired

Contraindications:

• Coagulopathy (platelets <80 × 10⁹/L, INR >1.4)
• Infection at insertion site
• Patient refusal
• Severe hypovolaemia
• Increased intracranial pressure
• Severe aortic stenosis or fixed cardiac output states

Technique:

Preparation:

1. Informed consent: Explain spinal anaesthesia, benefits, risks, alternatives
2. IV access: Large-bore IV (16G) for fluid resuscitation
3. Monitoring: ECG, SpO₂, BP (continuous or q2-5min)
4. Positioning: Sitting or lateral decubitus
5. Left uterine displacement: 15-30° left lateral tilt (critical)
6. Preload: 500-1000 mL crystalloid (limited efficacy, may cause fluid overload)
7. Aspiration prophylaxis: Sodium citrate 0.3 M 30 mL PO, ranitidine 50 mg IV, metoclopramide 10 mg IV

Spinal Insertion:

1. Identify L3-L4 or L4-L5 interspace: Tuffier's line
2. Skin preparation: Chlorhexidine, sterile drape
3. Local anaesthesia: 1% lignocaine
4. Spinal needle: 25-27G pencil-point (Whitacre or Sprotte)
5. CSF return: Confirm correct placement (clear fluid)
6. Drug injection: Slow, steady injection
7. Position: Immediate supine with left uterine displacement

Standard Spinal Dose:

• Hyperbaric bupivacaine 0.5%: 2.2-2.5 mL (11-12.5 mg)
• Fentanyl: 10-20 μg (lipid-soluble, rapid onset)
• Morphine: 100-200 μg (preservative-free, prolonged postoperative analgesia)

Alternative Dosing:

• Bupivacaine: 10-15 mg (reduce dose in obesity, short stature, elderly)
• Adjuncts: Clonidine 15-30 μg (prolongs block), dexmedetomidine 3-5 μg

Onset and Duration:

• Onset: 2-5 minutes
• Peak: 10-15 minutes
• Surgical block: T4 level required (test with pinprick or temperature sensation)
• Duration: 90-150 minutes (adequate for most caesarean sections)
• Postoperative analgesia: 12-24 hours from intrathecal morphine

Advantages:

• Rapid onset (2-5 minutes)
• Profound sensory block (reliable T4 level)
• Minimal fetal drug exposure
• Patient awake and aware
• Reduced risk of aspiration compared to general
• Reduced thromboembolism risk (vs. general)

Disadvantages:

• Hypotension (15-30% incidence)
• Limited duration (if prolonged surgery, may need conversion to general)
• Post-dural puncture headache (rare with modern needles)
• Unable to extend block if insufficient (unlike epidural)

Epidural Anaesthesia:

Indications:

• Labour epidural already in place (extension for caesarean)
• Prolonged surgery anticipated
• Contraindication to spinal (patient preference, severe aortic stenosis)
• Postoperative epidural analgesia desired

Contraindications: Same as spinal

Technique:

Extension of Labour Epidural:

1. Check catheter: Aspirate for blood/CSF, ensure functioning
2. Test dose: 3 mL lidocaine 1% + adrenaline
3. Top-up: 15-20 mL 2% lidocaine OR 0.5% bupivacaine in divided doses
4. Opioid: Fentanyl 50-100 μg or morphine 3-5 mg
5. Time to surgical block: 15-20 minutes (slower than spinal)

De novo Epidural:

1. Insert catheter: As for labour epidural (L3-L4)
2. Test dose: 3 mL lidocaine 1% + adrenaline
3. Loading dose: 15-20 mL local anaesthetic (lidocaine 2% or bupivacaine 0.5%)
4. Opioid: Fentanyl 50-100 μg or morphine 3-5 mg
5. Time: 20-30 minutes to surgical block

Advantages:

• Can extend block if insufficient (top-up via catheter)
• Prolonged duration (useful for long surgeries)
• Postoperative analgesia via catheter
• Slower onset (less hypotension)

Disadvantages:

• Slower onset (15-30 minutes vs. 2-5 minutes for spinal)
• Less reliable block (patchy, may need general conversion)
• Higher failure rate (5-10% vs. <1% for spinal)
• Not suitable for emergent caesarean (time delay)

Combined Spinal-Epidural (CSE):

Indications:

• High-risk patient (may need prolonged surgery or postoperative analgesia)
• Difficult airway (if spinal fails, epidural catheter available for top-up rather than general)
• Patient preference for rapid onset with backup

Technique:

1. Epidural needle insertion: L3-L4
2. Spinal component: Insert 25-27G spinal needle through epidural needle
3. Intrathecal injection: Bupivacaine 10-12.5 mg + fentanyl 10-20 μg + morphine 100-200 μg
4. Epidural catheter: Insert after spinal needle removed
5. Advantage: Rapid spinal onset with epidural backup

Complications and Management:

Hypotension:

Incidence: 15-30% (spinal), 5-10% (epidural)

Mechanism:

• Sympathetic blockade → vasodilation → venous pooling → decreased venous return → reduced cardiac output
• More severe with spinal (more dense block)
• Exacerbated by aortocaval compression in supine position

Prevention:

• Left uterine displacement: 15-30° left lateral tilt (critical, reduces incidence by 50%)
• Fluid preload: 500-1000 mL crystalloid (limited efficacy, may cause fluid overload in pre-eclampsia)
• Vasopressor prophylaxis: Phenylephrine infusion (50-100 μg/min) or ephedrine (5-10 mg IV)

Management:

1. Left uterine displacement: Increase tilt, manual uterine displacement
2. Fluid bolus: 500-1000 mL crystalloid (caution in pre-eclampsia)
3. Vasopressors:
   • Phenylephrine (first-line): 50-100 μg IV bolus, repeat PRN
   • Ephedrine: 5-10 mg IV bolus (alternative, may cause fetal tachycardia)
4. Oxygen: 100% via face mask if maternal hypoxia
5. Monitor fetus: Continuous CTG if hypotension severe/prolonged

High Block/Total Spinal:

Incidence: <1%

Mechanism:

• Excessive cephalad spread of local anaesthetic
• Can occur with:
  • Excessive dose (reduce in obesity, short stature)
  • Hyperbaric solution in head-down position
  • Intrathecal catheter migration (epidural top-up entering subarachnoid space)

Signs:

• Block above T4 (respiratory difficulty)
• Arm weakness/paralysis (block above cervical levels)
• Respiratory distress/apnoea (phrenic nerve paralysis C3-C5)
• Loss of consciousness (if total spinal)
• Cardiovascular collapse (sympathetic blockade + hypoxia)

Management:

1. Call for help: Immediate assistance
2. Airway support: 100% oxygen, face mask, may need intubation/ventilation
3. Left uterine displacement: Critical
4. Fluid resuscitation: 1000-2000 mL crystalloid
5. Vasopressors: Aggressive phenylephrine/ephedrine to maintain BP
6. Supportive care: Until block regresses (90-150 minutes)
7. Delivery: Expedite if safe, otherwise support until block resolves

Inadequate Block:

Incidence: 5-10% (epidural), <1% (spinal)

Causes:

• Spinal: Insufficient dose, inadequate baricity, patient positioning
• Epidural: Catheter malposition, insufficient volume, patchy spread, tachyphylaxis

Management:

1. Allow time: Wait 15-20 minutes for full block development
2. Positioning: Supine or head-down to encourage spread
3. Supplement: Local infiltration by surgeon (lignocaine 1% with adrenaline)
4. Conversion: If persistent pain, convert to general anaesthesia (ketamine 0.5 mg/kg IV, propofol TCI, sevoflurane, remifentanil infusion)
5. Epidural top-up: If catheter in place, additional 5-10 mL local anaesthetic

Pruritus:

Incidence: 30-60% with intrathecal opioids

Mechanism:

• Opioid effect on medullary itch centres
• Not allergic reaction

Management:

• Reassurance: Not harmful, resolves with opioid metabolism
• Naloxone: 40-80 μg IV (reverses opioid effect, may reduce analgesia)
• Antihistamines: Minimal efficacy (not histamine-mediated)
• Propofol: 10-20 mg IV (effective, mechanism unknown)

Nausea and Vomiting:

Incidence: 10-30% (spinal)

Causes:

• Hypotension (reduced cerebral perfusion triggers vomiting centre)
• Opioid side effect
• Surgical manipulation
• Anxiety

Management:

1. Treat hypotension: Most common cause
2. Anti-emetics:
   • Ondansetron 4 mg IV
   • Dexamethasone 4-8 mg IV
   • Droperidol 1.25 mg IV (if severe)
3. Propofol: 20-30 mg IV (effective for both nausea and pruritus)

Urinary Retention:

Incidence: 30-50%

Mechanism:

• S2-S4 blockade (sacral parasympathetic block)
• Reduced detrusor muscle function

Management:

• Indwelling catheter: Usually placed intraoperatively, removed when block resolves
• Postoperative monitoring: Ensure voiding before discharge

Post-Dural Puncture Headache (PDPH):

Incidence: 1-2% with 25-27G needles (higher with larger needles, multiple attempts)

Mechanism:

• CSF leak through dural puncture → intracranial hypotension → traction on pain-sensitive structures

Management:

• Conservative: Hydration, caffeine, analgesics
• Epidural blood patch (EBP) if severe/persistent: 15-20 mL autologous blood into epidural space

General Anaesthesia for Caesarean Section

Indications:

• Urgent/emergent delivery: Insufficient time for neuraxial block (<15-20 minutes)
• Contraindications to neuraxial: Coagulopathy, patient refusal, infection
• Failed neuraxial block: Persistent pain despite supplementation
• Maternal preference: After informed discussion (rarely appropriate)

Contraindications:

• Known difficult airway (relative — may need awake fibreoptic)
• Severe respiratory disease
• High aspiration risk (full stomach, not fasted)

Technique:

Preparation:

1. Aspiration prophylaxis: Sodium citrate 0.3 M 30 mL PO, ranitidine 50 mg IV, metoclopramide 10 mg IV
2. Positioning: Left uterine displacement (15-30° left lateral tilt)
3. Monitoring: ECG, SpO₂, BP, capnography (ETCO₂), fetal monitoring until delivery
4. Surgical readiness: Surgeon and assistant scrubbed, instruments ready
5. Neonatal team: Paediatrician, resuscitation equipment, warming station
6. Airway equipment: Difficult airway cart available, videolaryngoscope

Rapid Sequence Induction:

Preoxygenation:

• 100% oxygen via face mask for 3-5 minutes
• Head-up position (reduces aspiration risk, improves FRC)

Induction:

1. Cricoid pressure: 10 Newtons (assistant applies)
2. Propofol: 2-3 mg/kg IV (or thiopental 4-5 mg/kg)
3. Succinylcholine: 1.5 mg/kg IV (rapid onset, short duration)
4. Intubation: Direct laryngoscopy, ETT size 7.0-7.5 mm
5. Confirm placement: Capnography, auscultation
6. Release cricoid pressure: After intubation confirmed

Maintenance:

• Volatile anaesthetic: Sevoflurane 0.5-1 MAC or isoflurane
• 50% N₂O / 50% O₂: After delivery (reduces volatile requirement, speeds emergence)
• Opioid: Fentanyl 1-2 μg/kg IV or morphine 0.1-0.2 mg/kg IV (after delivery)
• Muscle relaxation: Rocuronium 0.6 mg/kg IV (intubation), 0.2 mg/kg maintenance

Emergence:

• Reverse neuromuscular block: Sugammadex 2-4 mg/kg IV (or neostigmine 0.05 mg/kg + glycopyrrolate 0.01 mg/kg)
• Extubation: Awake, following commands, adequate respiratory effort
• Recovery: Left lateral position, high-dependency monitoring

Complications:

Failed Intubation:

Incidence: 1:300 in obstetric patients (vs. 1:2000 general population)

Risk factors:

• Obesity
• Short neck
• Breast enlargement
• Airway oedema (preeclampsia, prolonged labour)

Management:

1. Call for help: Immediate assistance
2. Face mask ventilation: 100% oxygen, two-person technique, oral airway
3. LMA insertion: If face mask inadequate
4. Fibreoptic intubation: If LMA unsuccessful, time permits
5. Surgical airway: Emergency cricothyrotomy if cannot ventilate
6. Decision: Proceed with surgery vs. wake patient up (depends on fetal status)

Aspiration:

Incidence: Rare (0.1-0.2%) with proper prophylaxis

Mechanism:

• Gastric contents enter airway during induction/emergence
• Mendelson syndrome (chemical pneumonitis from acidic aspiration)

Prevention:

• Aspiration prophylaxis (antacids, H2 blockers, prokinetics)
• Rapid sequence induction with cricoid pressure
• Head-up position
• Avoid excessive sedation postoperatively

Management:

1. Suction: Immediate oropharyngeal suctioning
2. 100% oxygen: Ventilate with high FiO₂
3. Bronchoscopy: Remove particulate matter
4. Steroids: Controversial, may reduce inflammation
5. Antibiotics: If infection suspected
6. Supportive care: ICU admission if severe

Awareness:

Incidence: 0.2-0.5% (higher in obstetrics due to reduced MAC, avoidance of opioids before delivery)

Risk factors:

• Light anaesthesia (reduced MAC in pregnancy)
• Avoidance of opioids before delivery (fetal depression)
• Rapid surgery (reduced time for anaesthetic depth)

Prevention:

• Adequate volatile concentration (sevoflurane 0.5-1 MAC)
• Depth of anaesthesia monitoring (BIS) if available
• Nitrous oxide after delivery
• Opioid after delivery (reduces volatile requirement)

Management:

• Reassurance, psychological support
• Document and discuss with patient
• Referral to psychology if PTSD symptoms

Neonatal Depression:

Cause:

• Placental transfer of induction agents, opioids, muscle relaxants
• More common with general than neuraxial

Prevention:

• Minimize induction-to-delivery interval (I-D interval)
• Neuraxial preferred (minimal fetal drug exposure)
• Neonatal team present for resuscitation

Management:

• Neonatal resuscitation per NRP guidelines
• Airway suctioning, positive pressure ventilation
• Chest compressions if HR <60 bpm
• Epinephrine 0.1-0.3 mL/kg 1:10,000 IV if refractory

Aspiration Prophylaxis

Standard Protocol:

Non-particulate Antacid:

• Sodium citrate 0.3 M: 30 mL PO immediately pre-op
• Mechanism: Neutralizes gastric acid, raises pH to >2.5
• Reduces risk: Mendelson syndrome if aspiration occurs

H2 Receptor Antagonist:

• Ranitidine: 50 mg IV (or 150 mg PO 1 hour pre-op)
• Cimetidine: 200-400 mg IV
• Famotidine: 20 mg IV
• Mechanism: Reduces gastric acid secretion
• Timing: IV 30-60 minutes pre-op (PO 1-2 hours pre-op)

Prokinetic:

• Metoclopramide: 10 mg IV
• Mechanism: Increases gastric emptying, increases LES tone
• Reduces: Gastric volume, aspiration risk

Additional Measures:

• Head-up position: 15-30° (reduces aspiration risk, improves FRC)
• Rapid sequence induction: Reduces time from loss of consciousness to intubation
• Cricoid pressure: Prevents gastric insufflation during mask ventilation

Thromboprophylaxis

Risk Factors for VTE Post-Caesarean:

• Pregnancy-induced hypercoagulable state
• Reduced mobility post-surgery
• Obesity
• Age >35
• Multiple pregnancy
• Pre-eclampsia
• Previous VTE
• Thrombophilia

Prophylaxis:

Mechanical:

• Compression stockings: Reduce venous stasis
• Intermittent pneumatic compression: In theatre and postoperatively
• Early ambulation: As soon as safe

Pharmacological:

• Low molecular weight heparin (LMWH):
  • Enoxaparin: 40 mg SC daily (prophylactic dose)
  • Dalteparin: 5000 units SC daily
• Unfractionated heparin: 5000 units SC q8-12h (if LMWH unavailable)
• Timing: Start 4-6 hours post-op if no bleeding concerns
• Duration: 7-10 days (or 6 weeks if high risk)

Contraindications to Pharmacological Prophylaxis:

• Active bleeding
• Platelets <50 × 10⁹/L
• Coagulopathy (INR >1.5)
• Epidural catheter in situ (wait 4 hours after catheter removal)

Indigenous Health Considerations

Aboriginal and Torres Strait Islander Women:

Higher Risk Profile:

• Higher rates of emergency caesarean sections (30-35% vs. 25-30% non-Indigenous)
• Higher rates of gestational diabetes and pre-eclampsia
• Higher rates of obesity (technical challenges with neuraxial blockade)
• Higher rates of preterm birth
• Higher rates of stillbirth and neonatal mortality

Cultural Safety:

• Involvement of Aboriginal midwives and health workers
• Cultural protocols around birth and family involvement
• Communication strategies (plain language, visual aids, interpreter if needed)
• Respect for traditional birth practices (Birthing on Country where safe)
• Family involvement in decision-making

Access and Equity:

• Geographic barriers for remote communities (transfer delays)
• Limited epidural availability in some remote settings
• Culturally safe postoperative care
• Follow-up coordination with Aboriginal health services

Māori Health Considerations (New Zealand)

Cultural Safety:

• Whānau involvement in decision-making
• Tikanga (cultural protocols) around birth
• Karakia (prayer) may be requested before procedures
• Respect for tapu (sacredness) of birth
• Whenua (placenta) cultural significance

Health Equity:

• Higher rates of pre-eclampsia and gestational diabetes
• Geographic isolation affecting access to services
• Cultural adaptation of communication strategies
• Māori Health Worker involvement

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ANZCA Final Exam Focus

SAQ Patterns

Caesarean section anaesthesia appears regularly in ANZCA Final Written Examination. Common SAQ themes include:

Technique-Focused Questions:

• "Describe the technique for spinal anaesthesia for elective caesarean section." (2020)
• "What are the contraindications to neuraxial anaesthesia for caesarean section?" (2021)
• "Compare spinal versus general anaesthesia for caesarean section."

Complication-Focused Questions:

• "How would you manage hypotension following spinal anaesthesia for caesarean section?"
• "Describe the management of high block/total spinal."
• "What are the causes and management of inadequate neuraxial block?"

Pharmacology Questions:

• "Explain the standard spinal drug regimen for caesarean section and the rationale for each component."
• "Describe aspiration prophylaxis for caesarean section."
• "What is the management of failed intubation during general anaesthesia for caesarean section?"

Indigenous Health Questions:

• "What specific considerations apply to caesarean section anaesthesia for Aboriginal women?"
• "How would you ensure cultural safety in obstetric anaesthesia for Indigenous patients?"

Marking Scheme Priorities:

• Technique description (spinal dose, positioning, monitoring)
• Contraindications (absolute vs. relative, coagulation thresholds)
• Complication management (hypotension, high block, inadequate block)
• Aspiration prophylaxis protocol
• General anaesthesia technique (RSI, cricoid pressure, difficult airway)
• Indigenous health considerations
• Fetal monitoring and neonatal considerations

Clinical Viva Themes

The Clinical Viva frequently includes caesarean section scenarios:

Scenario Types:

• Emergency caesarean section for fetal distress
• Failed neuraxial block management
• Hypotension management
• High block/total spinal management
• Difficult airway in obstetric patient
• Pre-eclampsia with thrombocytopenia requiring anaesthesia

Examiner Expectations:

• Systematic technique description
• Knowledge of contraindications
• Understanding of complication management
• Dosing and pharmacology knowledge
• Aspiration prophylaxis protocol
• General anaesthesia technique
• Indigenous health considerations
• Team leadership and communication

Common Viva Questions:

• "Describe how you would perform spinal anaesthesia for caesarean section."
• "What is the standard spinal drug regimen?"
• "What are the contraindications to spinal anaesthesia?"
• "How would you manage hypotension after spinal anaesthesia?"
• "What is high block and how would you manage it?"
• "What are the causes of failed intubation in obstetrics?"
• "Describe aspiration prophylaxis for caesarean section."
• "How would you manage a Category 1 caesarean section?"

Key Points for Examination Success

1. Spinal technique is foundational — know dose, positioning, monitoring
2. Left uterine displacement is critical — 15-30° tilt, prevents hypotension
3. Contraindications — coagulopathy, infection, patient refusal
4. Hypotension management — phenylephrine first-line, left tilt, fluids
5. Aspiration prophylaxis — sodium citrate, ranitidine, metoclopramide
6. General anaesthesia technique — RSI, cricoid pressure, difficult airway preparation
7. Failed intubation management — LMA, face mask, wake vs. proceed decision
8. Indigenous health — cultural safety, higher risk profile, access issues

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Assessment Content

SAQ Practice Question 1 (20 marks)

Question:

A 32-year-old primigravida (75 kg) at 39 weeks gestation is scheduled for elective caesarean section due to breech presentation. She has no medical comorbidities and her platelet count is 220 × 10⁹/L.

(a) What are the advantages and disadvantages of spinal versus general anaesthesia for elective caesarean section? (6 marks)

(b) Describe the spinal anaesthesia technique and drug regimen you would use. (8 marks)

(c) What aspiration prophylaxis would you administer? (6 marks)

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Model Answer:

(a) Spinal vs. General Anaesthesia (6 marks)

Spinal Anaesthesia Advantages [1.5 marks]

1. Maternal safety: Reduced risk of aspiration, airway complications, awareness
2. Minimal fetal drug exposure: Local anaesthetic in epidural space, limited systemic absorption
3. Patient awake: Mother can witness birth, immediate skin-to-skin contact
4. Reduced thromboembolism risk: Less hypercoagulable state compared to general
5. Postoperative analgesia: Intrathecal morphine provides 12-24 hours analgesia
6. Reduced PONV: Less nausea/vomiting compared to general

Spinal Anaesthesia Disadvantages [1.5 marks]

1. Hypotension: 15-30% incidence (sympathetic blockade)
2. Limited duration: 90-150 minutes (may need conversion to general if prolonged surgery)
3. Technically demanding: Requires skill, positioning, sterile technique
4. Complications: PDPH, high block, neurological injury (rare)
5. Patient refusal: Some patients prefer to be asleep
6. Contraindications: Coagulopathy, infection, hypovolaemia

General Anaesthesia Advantages [1.5 marks]

1. Rapid onset: 2-3 minutes from induction to surgical readiness
2. Reliable: No risk of inadequate block or patchy analgesia
3. No neuraxial complications: No PDPH, no neurological injury risk
4. Patient preference: Some patients prefer to be unconscious
5. Emergency use: Category 1 caesarean section (insufficient time for neuraxial)

General Anaesthesia Disadvantages [1.5 marks]

1. Aspiration risk: High risk in pregnancy (reduced LES tone, delayed gastric emptying)
2. Airway complications: Difficult intubation more common (1:300 vs. 1:2000)
3. Fetal drug exposure: Placental transfer of induction agents, opioids, volatile agents
4. Maternal risks: Awareness, failed intubation, aspiration pneumonia
5. Postoperative issues: Pain, PONV, delayed recovery
6. Reduced mother-baby bonding: Mother unconscious at delivery

(b) Spinal Anaesthesia Technique and Drug Regimen (8 marks)

Preparation [2 marks]

1. Informed consent [0.5 marks]

   • Explain spinal anaesthesia, benefits, risks, alternatives
   • Document consent

2. IV access and monitoring [0.5 marks]

   • 16-18G IV cannula
   • ECG, SpO₂, BP (continuous or q2-5min initially)
   • Fetal monitoring until delivery

3. Positioning and preload [0.5 marks]

   • Left uterine displacement (15-30° left lateral tilt) — critical to prevent hypotension
   • Sitting or lateral decubitus position
   • Preload: 500-1000 mL crystalloid (limited efficacy, may cause fluid overload)

4. Aspiration prophylaxis [0.5 marks]

   • Sodium citrate 0.3 M 30 mL PO
   • Ranitidine 50 mg IV
   • Metoclopramide 10 mg IV

Technique [3 marks]

5. Identify interspace [0.5 marks]

   • Tuffier's line (intercristal line) — connects highest points of iliac crests (L4)
   • Choose L3-L4 or L4-L5 interspace

6. Skin preparation and local [0.5 marks]

   • Chlorhexidine scrub, sterile drape
   • 1% lignocaine subcutaneous and intradermal

7. Spinal needle insertion [0.5 marks]

   • 25-27G pencil-point needle (Whitacre or Sprotte)
   • Insert through skin wheal, advance to ligamentum flavum
   • Continue through dura, confirm CSF return (clear fluid)

8. Drug injection [1 mark]

   • Hyperbaric bupivacaine 0.5%: 2.2-2.5 mL (11-12.5 mg)
   • Fentanyl: 10-20 μg (lipid-soluble opioid for intraoperative analgesia)
   • Morphine: 100-200 μg (preservative-free, provides 12-24 hours postoperative analgesia)
   • Inject slowly over 10-15 seconds

9. Positioning after injection [0.5 marks]

   • Immediately supine with left uterine displacement
   • Head-down position (10-15°) if block needs to spread cephalad
   • Assess sensory block with pinprick or ice (target T4 level)

Monitoring and Management [3 marks]

10. Blood pressure monitoring [0.5 marks]

    • Check BP every 2 minutes for first 20 minutes
    • Target SBP >100 mmHg or within 20% of baseline

11. Hypotension prophylaxis and treatment [1 mark]

    • Phenylephrine: First-line vasopressor
      • Prophylactic infusion: 50-100 μg/min starting with spinal injection
      • OR bolus: 50-100 μg IV for SBP <100 mmHg or >20% drop from baseline
    • Ephedrine: Alternative (5-10 mg IV bolus)
    • Fluids: 500-1000 mL crystalloid bolus if hypotensive

12. Sensory block assessment [0.5 marks]

    • Test with pinprick or temperature sensation every 5 minutes
    • Target: T4 dermatome (nipple level)
    • Minimum: T6 (xiphoid level) for caesarean section

13. Surgical readiness [0.5 marks]

    • Wait 10-15 minutes for peak block effect
    • Confirm T4 block before surgical incision
    • Start surgery when block adequate

14. Intraoperative management [0.5 marks]

    • Continue BP monitoring every 5 minutes
    • Treat nausea (usually hypotension-related)
    • Supplemental oxygen via nasal cannula (2-4 L/min)
    • Reassurance and communication with patient

(c) Aspiration Prophylaxis (6 marks)

Standard Protocol:

1. Non-particulate Antacid — Sodium Citrate [2 marks]

• Dose: Sodium citrate 0.3 M 30 mL PO immediately preoperative
• Mechanism:
  • Neutralizes gastric acid (raises pH >2.5)
  • Reduces risk of chemical pneumonitis (Mendelson syndrome) if aspiration occurs
  • Non-particulate (won't cause pulmonary granulomas if aspirated)
• Timing: Within 20-30 minutes of surgery (short duration of effect)
• Alternative: Bicitra (sodium citrate + citric acid)

2. H2 Receptor Antagonist — Ranitidine [2 marks]

• Dose: Ranitidine 50 mg IV (or 150 mg PO 1-2 hours preoperative)
• Mechanism:
  • Blocks H2 receptors on gastric parietal cells
  • Reduces gastric acid secretion by 60-70%
  • Increases gastric pH, reduces gastric volume
• Timing: IV 30-60 minutes preoperative (onset 30-60 minutes)
• Alternatives:
  • Famotidine 20 mg IV
  • Cimetidine 200-400 mg IV

3. Prokinetic — Metoclopramide [1.5 marks]

• Dose: Metoclopramide 10 mg IV
• Mechanism:
  • Dopamine antagonist (prokinetic)
  • Increases gastric emptying (reduces gastric volume)
  • Increases lower oesophageal sphincter tone (reduces reflux)
  • Central anti-emetic effect
• Timing: 30 minutes preoperative (IV onset 1-3 minutes, peak 30-60 minutes)
• Side effects: Extrapyramidal symptoms (dystonia, akathisia) — rare at this dose

Additional Measures [0.5 marks]

4. Head-up position:

• Position patient 15-30° head-up during preoxygenation and induction
• Reduces aspiration risk by using gravity
• Improves functional residual capacity

5. Rapid sequence induction (if general anaesthesia):

• Cricoid pressure (10 Newtons)
• Rapid intubation to minimize time with unprotected airway
• Avoids mask ventilation (reduces gastric insufflation)

Summary of Aspiration Prophylaxis:

Total: 20 marks

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