Neuraxial Anaesthesia in Obstetrics

Quick Answer

What is it? Neuraxial anaesthesia encompasses epidural, spinal, and combined spinal-epidural (CSE) techniques for labour analgesia and caesarean delivery. These techniques provide superior pain relief with minimal fetal drug exposure compared to systemic opioids.

Why does it matter? Neuraxial techniques are the gold standard for labour analgesia and caesarean anaesthesia. They reduce maternal catecholamine levels, improve placental perfusion, and provide optimal operating conditions. Epidural analgesia does not increase caesarean section rates [1].

Key points:

• Epidural analgesia: catheter technique for continuous labour analgesia, takes 10-20 minutes to establish
• Spinal anaesthesia: single-shot for caesarean delivery, rapid onset (2-5 minutes), dense block
• CSE technique: combines rapid spinal onset with epidural catheter for duration and postoperative analgesia
• Contraindications: coagulopathy, thrombocytopenia <100 × 10⁹/L, infection at site, patient refusal [2]
• Hypotension (incidence 50-80%) treated with phenylephrine preferred over ephedrine [3]

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Indigenous Health Considerations

Aboriginal and Torres Strait Islander Maternity Care

Aboriginal and Torres Strait Islander women experience significant disparities in maternity care access and outcomes. These women are three times more likely to die in childbirth compared to non-Indigenous women, with higher rates of preterm birth, low birth weight, and perinatal mortality [4]. Geographic isolation presents profound barriers—many remote communities lack epidural services entirely, requiring emergency air evacuation for obstetric emergencies.

Cultural safety fundamentally influences pain management choices. Traditional Aboriginal concepts of pain differ from Western biomedical models; pain is often endured stoically without complaint, potentially masking severe distress [5]. Healthcare providers may misinterpret this stoicism as absence of pain, leading to inadequate analgesia provision. Understanding that silence does not equate to comfort is essential for equitable care.

Historical trauma from forced removals and ongoing systemic racism creates justified mistrust of medical institutions [6]. Many Aboriginal women fear hospitals as places where children were historically removed. This trauma-informed perspective requires patient, relationship-based approaches to analgesia discussions. Rushing consent processes or presenting epidural as the "superior" choice without acknowledging cultural perspectives breaches cultural safety.

Epidural analgesia rates among Aboriginal women remain significantly lower than the general population [7]. This disparity reflects complex factors including late presentation in labour, language barriers, and inadequate interpreter services. Visual aids and translated consent materials are essential. Family-centred decision-making models align with Aboriginal cultural values—excluding mothers, aunties, and grandmothers from discussions contravenes cultural protocols.

Birth on Country holds profound spiritual significance for many Aboriginal women. The disruption caused by transfer to distant tertiary facilities for epidural access creates substantial psychological distress. Supporting culturally safe birth choices while ensuring emergency access requires innovative models including telehealth consultation, fly-in fly-out anaesthetic services, and well-resourced regional maternity units.

Māori Maternity Care (Aotearoa New Zealand)

Māori women experience maternity care disparities reflecting broader health inequities. Māori maternal mortality rates are 1.6× higher than non-Māori, with higher rates of obesity, diabetes, and hypertensive disorders complicating pregnancy [8]. These comorbidities increase obstetric risk and may influence anaesthetic technique selection.

Whānau-centred care models align with Māori concepts of interconnected wellbeing. The birthing woman exists within whānau, hapū, and iwi contexts; individual autonomy differs from Western individualistic frameworks [9]. Decision-making regarding epidural analgesia often involves wider whānau consultation, and excluding family members breaches tikanga (customary practices).

Marae-based or culturally grounded maternity units demonstrate improved outcomes for Māori women, yet most lack 24-hour epidural services [10]. This creates tension between cultural birthing preferences and access to optimal analgesia. Developing kaupapa Māori (Māori approach) pain management strategies that integrate traditional rongoā (healing) with Western medicine supports holistic care.

Language barriers persist despite te reo Māori revitalisation efforts. Medical terminology including "epidural," "spinal," and "caesarean" requires careful explanation in accessible language. Interpreters should be offered even when English appears proficient—labour pain and stress impair second-language comprehension.

Historical experiences of racism within maternity care generate ongoing mistrust. Māori women report feeling judged, stereotyped, and excluded from decision-making in mainstream maternity services [11]. Building trust through consistent, respectful care relationships enables genuine informed consent for neuraxial techniques. Cultural humility—acknowledging limitations in understanding Māori perspectives—creates space for authentic partnership.

Shared Indigenous Considerations

Both Aboriginal and Māori populations demonstrate higher rates of obesity, increasing technical challenges for neuraxial blockade. Body mass index >35 kg/m² increases epidural failure rates and catheter dislodgement risk [12]. Ultrasound-guided insertion techniques improve success rates in this population, yet equipment and training availability varies.

Higher prevalence of coagulopathy from liver disease, thrombocytopenia from hypertensive disorders, and anticoagulation for cardiac conditions complicates neuraxial decisions. Thorough pre-labour assessment enables advance planning, reducing emergency decision-making during labour crisis.

Postpartum haemorrhage rates are elevated in both populations, potentially requiring urgent intervention under neuraxial blockade or conversion to general anaesthesia. The increased blood loss combined with higher baseline anaemia prevalence necessitates vigilant monitoring and preparedness.

Research exclusion has historically rendered Indigenous women invisible in obstetric anaesthesia literature. Most trials exclude non-English speakers, remote residents, and those with comorbidities—systematically excluding the most vulnerable [13]. This evidence gap perpetuates disparities through guidelines based on homogenous, low-risk populations. Anaesthetists must advocate for inclusive research and apply clinical judgment when evidence does not reflect their diverse patient populations.

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Clinical Overview

Physiological Changes in Pregnancy

Pregnancy induces profound physiological adaptations affecting neuraxial anaesthesia:

Cardiovascular System

• Increased cardiac output (40-50% increase by third trimester)
• Decreased systemic vascular resistance (afterload reduction)
• Aortocaval compression from gravid uterus in supine position (becomes critical after 20 weeks)
• Increased intravascular volume (1000-1500 mL expansion)

Respiratory System

• Functional residual capacity reduced 20% (upward displacement of diaphragm)
• Minute ventilation increased 30-40% (progesterone-driven)
• Respiratory alkalosis (PaCO₂ 28-32 mmHg) with compensatory metabolic alkalosis
• Airway oedema and increased vascularity (more challenging intubation)

Haematological System

• Hypercoagulable state (increased fibrinogen, Factors VII, VIII, X; reduced protein S)
• Dilutional anaemia (haemodilution exceeds red cell mass increase)
• Platelet count may decrease 10% (gestational thrombocytopenia usually >100 × 10⁹/L) [14]

Gastrointestinal System

• Reduced lower oesophageal sphincter tone
• Delayed gastric emptying (especially during labour)
• Increased gastric acidity
• Risk of aspiration with general anaesthesia

Neurological System

• Epidural venous engorgement reduces epidural space volume
• Increased susceptibility to local anaesthetic toxicity
• Altered pharmacokinetics (decreased protein binding, increased volume of distribution)

Epidural Analgesia for Labour

Indications

• Maternal request (primary indication—pain relief is sufficient reason)
• Prolonged labour (reducing maternal exhaustion)
• Hypertensive disorders (reducing catecholamine surge)
• Breech presentation or twins (preparing for emergency caesarean)
• Cardiac disease (reducing cardiac stress)
• Anticipated difficult airway (safer than general anaesthesia if caesarean required)

Contraindications

Absolute:

• Patient refusal or inability to consent
• Coagulopathy or therapeutic anticoagulation
• Thrombocytopenia <100 × 10⁹/L (some centres accept >80 × 10⁹/L) [15]
• Infection at insertion site (cellulitis, abscess)
• Systemic sepsis with bacteraemia
• Raised intracranial pressure
• Severe hypovolaemia

Relative:

• Thrombocytopenia 100-150 × 10⁹/L (individual risk assessment)
• Fixed cardiac output states (aortic stenosis, hypertrophic cardiomyopathy)
• Prior spinal surgery at insertion level
• Neurological disease (multiple sclerosis, spinal cord injury—consultant decision)

Technique

1. Preparation:

   • Informed consent including risks (see below)
   • Intravenous access (16-18G cannula)
   • Standard monitoring (BP, SpO₂, ECG, fetal heart rate)
   • Fluid preload (10-20 mL/kg crystalloid or colloid) [16]
   • Positioning: lateral decubitus or sitting flexed

2. Insertion:

   • Skin preparation with chlorhexidine or povidone-iodine
   • Sterile technique (mask, hat, sterile gloves, drapes)
   • Loss of resistance to saline or air for epidural space identification
   • Recommended levels: L3-L4 or L4-L5
   • Epidural catheter threaded 3-5 cm into space
   • Test dose: 3 mL local anaesthetic with adrenaline (1:200,000) to exclude intrathecal or intravascular placement

3. Maintenance:

   • Initial bolus: 10-15 mL local anaesthetic (bupivacaine 0.25% or ropivacaine 0.2%)
   • Patient-controlled epidural analgesia (PCEA) preferred:
     • Background infusion: 8-12 mL/hr
     • Bolus: 4-6 mL
     • Lockout: 10-20 minutes
   • Alternatively: programmed intermittent epidural boluses (PIEB) 8-12 mL every 45-60 minutes
   • Addition of opioid (fentanyl 2 μg/mL or sufentanil 0.5 μg/mL) improves quality and reduces motor block

Advantages:

• Superior pain relief (VAS <3/10 in 90% of patients)
• Allows maternal participation in birth
• Reduces maternal catecholamines, improving uteroplacental perfusion
• Provides surgical anaesthesia if caesarean required
• Can be continued for postoperative analgesia after vaginal delivery (perineal infiltration)

Disadvantages:

• Requires anaesthetic expertise and presence
• Prolonged second stage (approximately 15-30 minutes longer)
• Increased instrumental delivery rate (controversial; may reflect confounding by indication)
• Motor block affecting ambulation
• Hypotension requiring treatment
• Potential for serious complications (see below)

Spinal Anaesthesia for Caesarean Delivery

Indications

• Elective or emergency caesarean delivery (preferred technique)
• Operative vaginal delivery requiring analgesia
• Removal of retained placenta
• Perineal repair (occasionally)

Contraindications Same as for epidural, plus:

• Severe fetal distress requiring immediate delivery (decision-to-incision time critical)
• Inadequate time to establish block (though spinal is typically faster than GA)

Technique

1. Preparation:

   • Left uterine displacement (15-30° left lateral tilt) or wedge to prevent aortocaval compression
   • IV access and crystalloid co-load (rapid administration concurrent with block establishment) [17]
   • Standard monitoring
   • Positioning: sitting or lateral decubitus

2. Injection:

   • Spinal needle (typically 25-27G pencil-point) at L3-L4 or L4-L5
   • Hyperbaric bupivacaine 0.5%: 2.0-2.5 mL (10-12.5 mg)
   • Additives:
     • Fentanyl 10-25 μg (improves intraoperative comfort)
     • Morphine 100-200 μg (provides 18-24 hour postoperative analgesia)
     • Clonidine or diamorphine (alternative adjuncts)

3. Assessment:

   • Sensory block to T4 (nipple level) using pinprick or cold sensation
   • Block achieved within 2-5 minutes
   • Motor block (Bromage score 3—unable to lift extended leg)

Management of Hypotension:

• Prophylactic phenylephrine infusion (25-100 μg/min) or intermittent boluses (50-100 μg) [18]
• Ephedrine (5-10 mg boluses) if maternal heart rate <60 bpm (phenylephrine causes reflex bradycardia)
• Left uterine displacement essential
• Fluid co-loading (crystalloid or colloid 500-1000 mL during block establishment)
• Treat when systolic BP <100 mmHg or >20% below baseline, or symptoms present

Combined Spinal-Epidural (CSE) Technique

The CSE technique combines rapid onset of spinal blockade with flexibility of epidural catheter:

Technique

1. Epidural needle inserted (standard technique)
2. Spinal needle passed through epidural needle into intrathecal space
3. Spinal dose injected (bupivacaine 1-2 mg, fentanyl 10-15 μg for labour; full dose for caesarean)
4. Spinal needle removed
5. Epidural catheter threaded and secured
6. Rapid analgesia achieved (within 2-3 minutes) while epidural catheter available for top-ups or duration extension

Advantages:

• Faster onset than epidural alone (especially beneficial in advanced labour)
• Reduced local anaesthetic doses used initially (lower total drug exposure)
• Epidural catheter available if spinal block inadequate or wears off
• Can extend block for prolonged procedures or postoperative analgesia

Disadvantages:

• Slightly more technically demanding
• Risk of epidural catheter migration into intrathecal space (rare, 0.01-0.1%)
• Theoretical risk of spinal dose tracking up epidural needle hole ("spinal barbotage")

Use in Labour:

• Particularly useful when rapid analgesia required (late first stage, multiparous, distress)
• Low-dose intrathecal component (bupivacaine 1-2.5 mg, fentanyl 10-15 μg) provides analgesia without significant motor block
• Epidural component activated when spinal component recedes (usually 1-2 hours)

Use in Caesarean:

• Standard technique in many centres
• Spinal component provides rapid, reliable surgical block
• Epidural catheter allows block extension if duration >90-120 minutes
• Postoperative analgesia via epidural or catheter removed after intrathecal morphine

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Complications of Neuraxial Techniques

Maternal Complications

Fetal and Neonatal Effects

Local Anaesthetics

• Minimal placental transfer with neuraxial doses (compared to systemic administration)
• No significant neonatal neurobehavioural effects observed
• Continuous epidural infusion does not increase fetal acidosis [20]

Opioids

• Epidural fentanyl: minimal transfer, no neonatal depression at standard doses
• Intrathecal morphine: delayed respiratory depression in neonate not observed with maternal doses <0.3 mg
• Pethidine (systemic): active metabolite norpethidine accumulates; prolonged half-life in neonate; avoid repeated dosing [21]

Hypotension Effects

• Untreated maternal hypotension reduces uteroplacental perfusion
• Effective vasopressor treatment (phenylephrine or ephedrine) maintains fetal wellbeing
• No difference in Apgar scores or umbilical cord pH between phenylephrine and ephedrine when hypotension treated effectively [22]

Serious Neurological Complications

Epidural Haematoma

• Incidence: 1:150,000-1:250,000 in obstetric patients (lower than general population due to young, healthy population)
• Risk factors: coagulopathy, anticoagulation, thrombocytopenia, difficult insertion (multiple attempts, vascular trauma)
• Presentation: new severe back pain, neurological deficit (motor > sensory), bladder/bowel dysfunction
• Management: urgent MRI diagnosis within 4-6 hours; surgical decompression if confirmed [23]

Epidural Abscess

• Incidence: 1:50,000-1:100,000
• Risk factors: prolonged catheter duration, breach of sterility, immunocompromise (diabetes, steroids)
• Presentation: back pain, fever, neurological deficit, raised inflammatory markers
• Management: MRI diagnosis, broad-spectrum antibiotics, surgical drainage if neurological compromise

Nerve Injury

• Direct trauma from needle/catheter: usually transient (weeks to months)
• Cauda equina syndrome (rare): permanent injury from intrathecal local anaesthetic toxicity
• Anterior spinal artery syndrome: ischaemic injury from hypotension plus vascular compression
• Most injuries resolve within 6-12 months; permanent injury <1:100,000 [24]

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Specific Clinical Scenarios

Pre-Eclampsia and Eclampsia

Neuraxial techniques are preferred in pre-eclampsia when coagulation permits:

Advantages:

• Avoids airway manipulation (difficult intubation more common due to airway oedema)
• Reduces catecholamine surge and blood pressure lability
• Allows controlled delivery of antihypertensives
• Provides excellent postoperative analgesia

Considerations:

• Thrombocytopenia common—check platelet count within 6 hours of neuraxial placement
• If platelets 80-100 × 10⁹/L: individual assessment, informed consent, consider bleeding time or TEG/ROTEM
• Coagulopathy (INR >1.4, aPTT prolonged) contraindicates neuraxial
• Severe hypertension treated before block establishment (systolic >160 or diastolic >110 mmHg)
• Magnesium sulfate therapy potentiates neuromuscular blockade
• Reduced drug requirements (magnesium enhances block; lower local anaesthetic doses needed)

Cardiac Disease in Pregnancy

Neuraxial techniques beneficial in most cardiac conditions:

Physiological Benefits:

• Reduces systemic vascular resistance (afterload reduction beneficial in regurgitant lesions)
• Reduces myocardial oxygen demand (pain relief)
• Reduces catecholamine surge (avoiding tachycardia and hypertension)
• Allows controlled, incremental haemodynamic changes

Specific Lesions:

• Regurgitant lesions (MR, AR): epidural/spinal beneficial; afterload reduction reduces regurgitation
• Stenotic lesions (AS, MS): caution required; slow, controlled epidural establishment; avoid rapid sympathectomy; consider CSE with reduced spinal dose or continuous spinal
• Cardiomyopathy: epidural beneficial; avoid phenylephrine if low EF (increases afterload); use ephedrine or metaraminol
• Pulmonary hypertension: neuraxial generally preferred over GA; avoid hypoxia and hypercarbia; maintain preload; cautious fluid management

Technical Approach:

• Slow establishment with titrated doses
• Avoid high blocks (maintain cardiac sympathetic fibres T1-T4)
• Invasive monitoring (arterial line) for moderate-severe disease
• Multidisciplinary planning with cardiology and obstetrics

Morbid Obesity

Obesity presents technical and physiological challenges:

Technical Challenges:

• Difficult surface anatomy identification (iliac crests, spinous processes)
• Greater skin-to-epidural space distance (often 8-12 cm vs 4-6 cm in normal BMI)
• Higher epidural failure rates and catheter migration [25]

Solutions:

• Ultrasound-guided insertion (improves success rates, identifies midline, measures depth) [26]
• Longer needles (12.5 cm Tuohy needles available)
• Sitting position often preferred for landmark identification
• CSE technique (rapid onset confirms intrathecal placement; catheter backup if needed)
• Secure catheter meticulously (longer catheter in space, tunneling, sterile occlusive dressing)

Physiological Considerations:

• Greater aortocaval compression effect
• Increased risk of hypotension (more extensive venous pooling)
• Reduced functional residual capacity (desaturation risk if high block)
• Difficult airway (SA safer than GA if possible)
• Higher aspiration risk (increased gastric volume, reduced LES tone)
• Thromboembolism risk (chemoprophylaxis timing with neuraxial removal)

Coagulopathy and Anticoagulation

Thromboprophylaxis in pregnancy complicates neuraxial timing:

Unfractionated Heparin (UFH)

• Prophylactic (5,000-10,000 units BD): safe to proceed; delay next dose until after block
• Therapeutic IV infusion: stop 4-6 hours before; check aPTT normal; restart 1 hour after catheter removal
• Therapeutic subcutaneous: variable absorption; check aPTT; consider 12-hour window

Low Molecular Weight Heparin (LMWH)

• Prophylactic dose (e.g., enoxaparin 40 mg daily): withhold 12 hours before neuraxial; restart 4 hours after catheter removal [27]
• Therapeutic dose (e.g., enoxaparin 1 mg/kg BD): withhold 24 hours before; anti-Xa level may guide; restart 4 hours after catheter removal

Warfarin

• Stop 5 days before; INR <1.4 required for neuraxial
• Bridge with UFH if high thromboembolism risk

Direct Oral Anticoagulants (DOACs)

• Generally avoided in pregnancy; if present: 48-72 hour washout required (renal function dependent)

Thrombocytopenia

• 100 × 10⁹/L: generally accepted as safe

• 80-100 × 10⁹/L: individual assessment; consider TEG/ROTEM; informed consent
• <80 × 10⁹/L: generally contraindicated; consider general anaesthesia
• HELLP syndrome: platelet nadir typically 24-48 hours post-delivery; neuraxial catheter can remain if placed before platelet fall

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Indigenous Health and Obstetric Anaesthesia

Cultural Safety in Labour Pain Management

Effective neuraxial anaesthesia provision for Indigenous women requires cultural safety integration across all care phases.

Pre-Labour Education: Many Indigenous women, particularly from remote communities, have limited exposure to epidural concepts. Culturally tailored antenatal education improves informed consent quality and reduces fear. Visual materials depicting Indigenous women receiving epidural analgesia normalises the experience [28].

Consent Processes: Standardised consent forms and medical terminology create barriers for women with English as second or third language. Interpreter services must be offered even when women appear conversational in English—labour pain, stress, and fatigue significantly impair language comprehension. Family-centred consent models respect collective decision-making cultures [29].

Intrapartum Care: Continuous labour support from culturally matched carers improves outcomes and satisfaction. Aboriginal and Māori midwifery workforce development enables this. For women transferred from remote communities for epidural access, maintaining connection to family and cultural support is essential—birthing alone in unfamiliar tertiary hospitals creates trauma.

Postpartum Considerations: Neuraxial opioid analgesia (intrathecal morphine) provides superior post-caesarean analgesia, enabling earlier mobilisation and breastfeeding establishment. Supporting early breastfeeding aligns with traditional infant feeding practices. Medication safety education regarding intrathecal morphine and sedation monitoring must be culturally accessible.

Addressing Healthcare System Barriers

Geographic Inequity: Remote Indigenous communities rarely have 24-hour anaesthetic coverage. Women requiring epidural must be evacuated, often by air, generating fear and separation distress. Telemedicine consultation enables advance decision-making; well-resourced regional units reduce transfer requirements; culturally safe retrieval services minimise trauma [30].

Institutional Racism: Implicit and explicit racism within maternity services creates justified distrust. Stereotyping regarding pain tolerance, drug-seeking behaviour, or compliance affects analgesia provision. Mandatory cultural safety training, Indigenous health workforce development, and accountability mechanisms address systemic racism [31].

Research Exclusion: Obstetric anaesthesia research historically excluded Indigenous women, limiting evidence base for these populations. Higher comorbidity burdens, language diversity, and geographic isolation render standard trial criteria exclusionary. Anaesthetists must advocate for inclusive research design and apply clinical judgment when guidelines reflect homogenous populations.

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SAQ Practice Questions

SAQ 1: Combined Spinal-Epidural Technique (25 marks)

A 28-year-old woman (G2P1) is in established labour at 7 cm cervical dilatation. She is experiencing severe pain and requests rapid analgesia. The midwife requests a combined spinal-epidural (CSE) technique.

a) Describe the CSE technique and explain its advantages in this clinical scenario (10 marks)

b) What are the potential complications of CSE, and how would you prevent/manage them? (9 marks)

c) After 4 hours, the patient requires caesarean delivery for fetal distress. Outline your management of the epidural component (6 marks)

Model Answer

a) CSE Technique and Advantages (10 marks)

Technique (5 marks):

• Epidural needle (Tuohy) inserted using loss of resistance to saline or air technique at L3-L4 or L4-L5 interspace
• Spinal needle (25-27G pencil-point) passed through epidural needle into intrathecal space ("needle-through-needle" technique)
• Confirmation of subarachnoid placement by free flow of CSF
• Intrathecal injection: bupivacaine 1-2.5 mg (0.5-1.0 mL of 0.25% solution) plus fentanyl 10-15 μg [32]
• Spinal needle withdrawn; epidural catheter threaded 3-5 cm into epidural space
• Epidural catheter aspirated and test dose given (3 mL local anaesthetic with 1:200,000 adrenaline) to exclude intrathecal or intravascular placement
• Epidural component activated when spinal analgesia recedes (typically 1-2 hours)

Advantages in this scenario (5 marks):

• Rapid onset of analgesia (2-3 minutes vs 10-20 minutes for epidural alone)—critical in advanced labour at 7 cm
• Reduced local anaesthetic doses initially (intrathecal component uses small volume); beneficial for minimizing total drug exposure
• Reliable analgesia (intrathecal component provides dense block) while epidural catheter ensures duration and flexibility
• Patient at 7 cm with severe pain requires immediate relief; CSE faster than standard epidural loading
• Epidural catheter available if spinal component inadequate or if emergency caesarean required later
• Lower total local anaesthetic dose may reduce motor block and enable more ambulation

b) CSE Complications (9 marks)

Complications specific to CSE:

• Intrathecal catheter migration (epidural catheter enters intrathecal space through dural puncture hole): 0.01-0.1% incidence; presents as unexpectedly high/extensive block; prevent by limiting catheter insertion depth (3-5 cm); manage with supportive care, airway management if high block [33]
• Spinal dose tracking up epidural needle hole (theoretical "spinal barbotage"): minimal clinical significance; prevent by careful positioning and slow injection
• Dural puncture headache: same risk as epidural if dural puncture occurs during epidural needle insertion; reduced with spinal needle separate from epidural puncture

General neuraxial complications applicable to CSE:

• Hypotension: 50-80% incidence with spinal component; prevent with left uterine displacement, fluid co-load, prophylactic phenylephrine infusion; treat with phenylephrine boluses or ephedrine if bradycardic [34]
• Local anaesthetic toxicity: test dose essential; intravascular injection presents with tinnitus, metallic taste, seizures; treat with intralipid emulsion 20%, airway management, cardiovascular support
• High/total spinal: excessive dose or cephalad spread; presents with respiratory difficulty, hypotension, loss of consciousness; manage with airway support, ventilation, cardiovascular support, delivery if possible
• Neurological injury: rare (<1:10,000); epidural haematoma or abscess presents with back pain and neurological deficit; urgent MRI and surgical decompression if confirmed
• Pruritus: opioid-related; common (30-50%); treat with naloxone, antihistamines
• Urinary retention: catheterise bladder

c) Epidural Conversion for Caesarean (6 marks)

Assessment (2 marks):

• Confirm epidural catheter position and functioning (test block with 3 mL lidocaine 2% with adrenaline)
• Check sensory level (should cover at least T10 for labour; need T4 for caesarean)
• Assess motor block (should be minimal for top-up; if dense block present, reduce incremental doses)

Top-up technique (3 marks):

• Rapid sequential dosing: 5 mL aliquots of lidocaine 2% or bupivacaine 0.5% with adrenaline (1:200,000)
• Doses given every 2-3 minutes to total 15-20 mL
• Alternative: chloroprocaine 3% for rapid onset if urgent (3-5 minutes to surgical block)
• Aim for T4 sensory block (nipple level) using pinprick testing
• Addition of fentanyl 50-100 μg or diamorphine 2.5-5 mg improves block quality and provides postoperative analgesia
• Check block adequacy before surgical incision (light touch sensation, pinprick, cold)

Backup plan (1 mark):

• If block inadequate after 20-30 minutes or patient pain: convert to spinal or general anaesthesia
• Spinal: hyperbaric bupivacaine 2.0-2.5 mL with fentanyl 10-25 μg and morphine 100-200 μg
• General anaesthesia: rapid sequence induction with cricoid pressure (aspiration risk)

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SAQ 2: Thrombocytopenia and Neuraxial Blockade (20 marks)

A 32-year-old woman with pre-eclampsia is labouring at term. Her platelet count is 95 × 10⁹/L (falling from 145 × 10⁹/L 48 hours ago). She is requesting epidural analgesia for severe labour pain.

a) What are the risks of neuraxial blockade in this patient? (6 marks)

b) Outline your decision-making process and what additional investigations you would consider (8 marks)

c) If you decide to proceed with neuraxial blockade, what specific precautions would you take? (6 marks)

Model Answer

a) Risks of Neuraxial Blockade (6 marks)

Epidural haematoma risk:

• Thrombocytopenia increases risk of spontaneous or procedure-related epidural haematoma
• Platelets <100 × 10⁹/L associated with increased bleeding risk; <80 × 10⁹/L generally considered contraindication [35]
• Obstetric population has lower baseline risk than general population due to age and health, but pre-eclampsia increases vascular fragility
• Epidural haematoma incidence approximately 1:150,000-1:250,000 in obstetrics; thrombocytopenia increases this risk
• Neurological deficit may be permanent if not decompressed within 4-8 hours

Trend concerns:

• Falling platelet count (145 → 95 × 10⁹/L in 48 hours) suggests HELLP syndrome or worsening pre-eclampsia
• Platelets may continue to fall post-procedure; catheter removal may be complicated by ongoing thrombocytopenia
• Risk of procedure-related bleeding versus benefit of analgesia must be weighed

General neuraxial risks:

• Standard risks apply (hypotension, infection, nerve injury) but thrombocytopenia increases bleeding-related complications

b) Decision-Making and Investigations (8 marks)

History and examination (2 marks):

• Assess for bleeding history (gingival bleeding, epistaxis, petechiae, bruising)
• Medication history (aspirin, low molecular weight heparin, anticoagulants)
• Obstetric history (previous pre-eclampsia, HELLP, obstetric haemorrhage)
• Clinical assessment of HELLP syndrome (right upper quadrant pain, nausea, malaise)

Investigations (3 marks):

• Coagulation profile: PT/INR, aPTT, fibrinogen
• Thromboelastography (TEG) or rotational thromboelastometry (ROTEM) if available—assesses clotting dynamics better than standard tests [36]
• Liver function tests (LDH, AST, bilirubin) for HELLP diagnosis
• Renal function (pre-eclampsia involvement)
• Repeat platelet count to confirm trend
• Group and save serum (cross-match if delivery imminent)

Risk assessment (3 marks):

• Platelets 95 × 10⁹/L is borderline; many centres accept >80-100 × 10⁹/L for neuraxial
• Falling count is concerning; HELLP syndrome typically platelet nadir 24-48 hours post-delivery
• No other coagulopathy (normal INR, aPTT) reduces risk
• If TEG/ROTEM shows normal clot formation, supports neuraxial safety
• Individualised informed consent: discuss risks (haematoma, paralysis), benefits (analgesia, avoids GA if caesarean), alternatives (remifentanil PCA, entonox, non-pharmacological)
• Multidisciplinary discussion with obstetrics and haematology if uncertain
• Document decision-making process clearly

c) Precautions if Proceeding (6 marks)

Technical precautions (3 marks):

• Experienced operator to minimise attempts and trauma
• Midline approach (paramedian potentially higher bleeding risk)
• Ultrasound guidance to identify midline and minimise attempts
• Avoid multiple attempts (increases vascular trauma risk)
• Test dose with adrenaline to detect intravascular placement (would indicate bleeding into epidural space if catheter in vessel)
• Limit catheter depth in space (3-4 cm) to reduce vascular trauma

Monitoring and management (2 marks):

• Continuous neurological monitoring post-procedure (motor function, sensation, sphincter tone)
• Document baseline neurological examination
• Regular platelet count monitoring (4-6 hourly if falling trend)
• Plan for catheter removal: ensure platelets >80 × 10⁹/L before removal; if urgent removal needed with low platelets, consider platelet transfusion [37]
• Immediate MRI available if any neurological concern (back pain, motor weakness, bladder dysfunction)
• Low threshold for neurosurgical consultation if epidural haematoma suspected

Alternative plan (1 mark):

• Have backup analgesia plan (remifentanil PCA) if neuraxial contraindicated or fails
• Early communication with obstetrics regarding delivery timing and mode

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SAQ 3: Spinal Anaesthesia for Caesarean (25 marks)

A healthy 30-year-old primigravid woman at term is scheduled for elective caesarean delivery. She has no significant medical history.

a) What are the advantages of spinal anaesthesia compared to general anaesthesia for caesarean delivery? (8 marks)

b) Describe your technique for establishing spinal anaesthesia for this patient (10 marks)

c) The patient experiences hypotension (BP 80/50 mmHg, HR 58 bpm) following spinal injection. How would you manage this? (7 marks)

Model Answer

a) Advantages of Spinal Anaesthesia (8 marks)

Maternal advantages:

• Avoidance of airway instrumentation (reduced risk of failed intubation, aspiration, airway trauma); crucial given difficult airway incidence 1:300-1:500 in obstetrics vs 1:2,000 in general population [38]
• Awake mother can witness birth and have immediate skin-to-skin contact with baby
• Reduced postoperative analgesic requirements (intrathecal morphine provides 18-24 hour analgesia)
• Reduced thromboembolism risk compared to GA (earlier mobilisation, reduced hypercoagulable response)
• Lower maternal mortality compared to GA (historical data; though modern GA safety improved, SA remains safer)

Fetal/neonatal advantages:

• Minimal drug transfer to fetus (compared to systemic maternal anaesthesia drugs)
• Better Apgar scores and umbilical cord pH compared to GA with emergency caesarean (particularly with prolonged decision-to-delivery interval) [39]
• Reduced neonatal respiratory depression (no systemic opioids, no volatile agents)
• No uterine relaxation from volatile agents (preserved uterine tone reduces bleeding)

Other advantages:

• Rapid, reliable onset (2-5 minutes to surgical block)
• Dense motor and sensory block provides excellent surgical conditions
• Technically straightforward in experienced hands
• Cost-effective (no volatile agents, airway equipment)

b) Spinal Anaesthesia Technique (10 marks)

Preparation (3 marks):

• Informed consent: explain procedure, expected sensations (warmth, heaviness), potential complications (hypotension, shivering, nausea, pruritus, post-dural puncture headache, rare neurological complications)
• IV access: 16-18G cannula; fluid co-load 500-1000 mL crystalloid (or colloid) administered rapidly concurrent with block establishment (more effective than preloading) [40]
• Monitoring: continuous pulse oximetry, ECG, non-invasive BP (1-3 minute intervals), fetal heart rate
• Positioning: left lateral decubitus or sitting; left uterine displacement essential (15-30° wedge or tilt)
• Theatre setup: emergency drugs (phenylephrine, ephedrine, atropine), airway equipment (mask, oropharyngeal airways, laryngoscope, endotracheal tubes), suction
• Surgical team scrubbed and ready (rapid sequence can proceed immediately after block confirmed)

Spinal injection (4 marks):

• Skin preparation with chlorhexidine or povidone-iodine; sterile draping
• Identify L3-L4 or L4-L5 space (iliac crest line = L4 spinous process)
• Local anaesthetic infiltration at intended puncture site
• Spinal needle (25-27G pencil-point, e.g., Whitacre or Sprotte) inserted midline
• Identification of subarachnoid space by free flow of CSF
• Hyperbaric bupivacaine 0.5%: 2.0-2.5 mL (10-12.5 mg) injected slowly (over 30-60 seconds) [41]
• Additives: fentanyl 10-25 μg (improves intraoperative comfort); morphine 100-200 μg (provides postoperative analgesia)
• Needle withdrawn; sterile dressing applied; patient positioned supine with left tilt

Block assessment (2 marks):

• Assess sensory block to T4 (nipple level) using pinprick or alcohol swab (cold)
• Test both sides; block should be bilateral and symmetrical
• Allow 2-5 minutes for block to establish; reassess if inadequate
• Ensure block height adequate before surgical incision (prevents intraoperative pain requiring conversion to GA or supplementation)

Intraoperative management (1 mark):

• Continuous verbal contact with patient
• Monitor for hypotension, nausea, anxiety
• Treat hypotension promptly to maintain uteroplacental perfusion
• Supplemental oxygen via nasal cannulae or face mask if desired

c) Management of Hypotension (7 marks)

Immediate assessment (1 mark):

• Confirm BP measurement (80/50 mmHg); check for symptoms (nausea, light-headedness, dyspnoea)
• Heart rate 58 bpm indicates reflex bradycardia from baroreceptor response to hypotension (spinal-induced sympathectomy)

Immediate treatment (4 marks):

• Left uterine displacement (maximise venous return; confirm wedge in place)
• Fluid bolus: rapid administration of remaining crystalloid/colloid (if preload not complete)
• Phenylephrine: preferred first-line vasopressor in obstetrics; gives 50-100 μg IV bolus; repeat every 1-2 minutes as needed; can start infusion at 25-50 μg/min [42]
• Ephedrine: appropriate given bradycardia (HR 58 bpm); gives 5-10 mg IV bolus; repeat every 2-3 minutes; ephedrine has both α and β effects, increasing heart rate and cardiac output
• Target: maintain systolic BP >100 mmHg or within 20% of baseline; treat symptoms

Alternative/adjunctive measures (2 marks):

• If refractory hypotension: ensure left tilt adequate, check for aortocaval compression (consider Trendelenburg position temporarily), increase phenylephrine dose
• Atropine 0.3-0.6 mg IV if severe bradycardia (<50 bpm) or haemodynamic compromise
• Consider reduced spinal dose or combined spinal-epidural in future high-risk cases
• If patient symptomatic despite treatment and ongoing hypotension: consider delivery to relieve aortocaval compression (if caesarean not yet started)

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Viva Voce Scenarios

Viva Scenario 1: Epidural Failure

Examiner: "You have been called to see a patient in labour with an epidural that isn't working effectively. She is still experiencing significant pain despite the epidural being in situ for 2 hours. How would you approach this?"

Model Answer:

"I would approach this systematically to identify the cause and provide effective analgesia. Epidural failure occurs in 5-15% of cases and requires methodical troubleshooting.

Firstly, I would assess the clinical situation: confirm the patient's pain location, character, and whether it's unilateral or bilateral. Ipsilateral pain often indicates unilateral block from catheter migration; sacral pain may indicate inadequate caudal spread.

I would check the catheter:

• Inspect the insertion site and dressing—has the catheter been displaced?
• Aspirate the catheter to check for CSF (intrathecal placement) or blood (intravascular placement)
• Give a test dose of 3 mL lidocaine 2% with adrenaline—if rapid onset with dense motor block, catheter is intrathecal; if tachycardia, it may be intravascular

I would assess the block clinically: test sensory level with pinprick or cold; check motor block using Bromage scale. A patchy or unilateral block suggests suboptimal catheter position.

For management, I have several options:

1. If catheter appears correctly placed but block inadequate: give additional local anaesthetic bolus (5-10 mL of 0.25% bupivacaine or 0.2% ropivacaine) in incremental doses; consider repositioning patient to encourage spread
2. If unilateral block: withdraw catheter 1-2 cm and re-test; lateral position with painful side down may improve spread
3. If catheter intravascular or intrathecal: remove and re-site
4. If catheter completely ineffective: consider replacing entirely, possibly using CSE technique for rapid relief
5. Alternative: if re-siting not possible or declined, consider remifentanil PCA for labour analgesia

Throughout, I would reassure the patient, explain my actions, and ensure she understands the plan."

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Viva Scenario 2: High Spinal

Examiner: "Five minutes after spinal anaesthesia for caesarean delivery, the patient reports difficulty breathing and has difficulty speaking. Her blood pressure is 70/40 mmHg and she is anxious. What is your diagnosis and immediate management?"

Model Answer:

"This presentation is highly suggestive of a high or total spinal anaesthesia. The respiratory difficulty and inability to speak indicate involvement of the phrenic nerve roots (C3-C5) affecting diaphragmatic function, while the severe hypotension reflects extensive sympathetic blockade affecting cardiac accelerator fibres.

My immediate management priorities are:

1. Airway and breathing: Call for help immediately. This patient may require intubation and ventilation. I would administer 100% oxygen, support ventilation with bag-valve-mask if necessary, and prepare for rapid sequence induction with cricoid pressure given full stomach status. Position supine with left tilt to maximise functional residual capacity.

2. Circulation: Left uterine displacement is essential to relieve aortocaval compression. I would give rapid fluid bolus (crystalloid or colloid) and vasopressors aggressively—both phenylephrine and ephedrine may be needed to counteract profound vasodilation. Atropine for bradycardia if present. Invasive arterial pressure monitoring if time permits.

3. Delivery: If the block is established and fetal heart rate acceptable, proceed with surgery quickly to deliver the baby, which will relieve aortocaval compression and improve venous return. If fetal distress or block inadequate for surgery, convert to general anaesthesia immediately.

4. Specific measures for high spinal: Head-down position may reduce cephalad spread of hyperbaric solution if still in early stages. However, once established, supportive care is the mainstay.

Throughout, I would reassure the patient, explain what is happening, and continuously monitor neurological status. Recovery typically occurs as the spinal regresses—duration depends on drug used and dose. Postoperatively, high-dependency monitoring is required until respiratory function normalises."

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ANZCA Syllabus Mapping

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