2024.1 Day 1 VIVA 2

Obstetric Anaesthesia

You are asked to provide analgesia for a primigravida on labour ward, who is in early labour. Her pregnancy has been uncomplicated to date.

She is currently 38 weeks gestation and her bloods and ultrasound are unremarkable. Her BMI is 34. She is otherwise well, takes no medications and has no known allergies.

Please outline your consent discussion, including the potential risks and complications you will discuss with her.

Initial approach:

• Assess understanding, concerns, and expectations

• Explain purpose: pain relief while maintaining participation in birth

• Clarify timing is appropriate in labour course

Benefits:

• Gold-standard labour pain relief (90-95% effective)

• Preservation of consciousness and participation

• Avoids systemic opioid effects (maternal sedation, neonatal depression)

• Convertible to surgical anaesthesia if needed

• Allows rest during prolonged labour

Procedure description:

• Sitting/lateral position with curved back

• Aseptic technique, local anaesthetic infiltration

• L3/4 or L4/5 approach with 18G Tuohy needle

• Test dose (3ml 2% lidocaine with adrenaline)

• Low-dose infusion (0.1% bupivacaine + 2μg/ml fentanyl)

• Continuous monitoring post-insertion

Risks:

• Common (>1%):

  • Hypotension (10-20%) with IV fluid management

  • Pruritus (20-30%) from opioid component

  • Shivering, transient paraesthesia

  • Urinary retention requiring catheterization

• Uncommon:

  • PDPH (1:100) - typically self-limiting, may need blood patch

  • Inadequate analgesia (10%) - may need adjustment or replacement

• Rare but serious:

  • Local anaesthetic toxicity (<1:10,000)

  • Infection/epidural abscess (<1:50,000)

  • Permanent neurological injury (<1:100,000)

Alternatives:

• Remifentanil PCA (shorter-acting opioid)

• Nitrous oxide (Entonox)

• Non-pharmacological: breathing techniques, water birth, massage

This patient has BMI 34. How does this modify your discussion?

Technical considerations:

• Potentially more challenging landmark identification

• May use pre-procedure ultrasound for accurate placement

• Longer Tuohy needle potentially required (10cm vs standard 8cm)

Risk modifications:

• Slightly higher displacement/migration risk

• May require deeper insertion (5-7cm vs standard 4-5cm)

• No increased risk of neurological complications

• More significant hypotension due to aortocaval compression

The patient heard epidurals slow labour. How would you respond?

Modern evidence-based response:

• Contemporary low-dose mixtures preserve motor function

• No clinically significant prolongation (2022 Cochrane review)

• May actually facilitate labour by reducing maternal stress hormones

• NICE guidelines support early epidural placement

• No increased caesarean section rate (robust meta-analysis data)

Her husband has heard that you can get permant neurological injury from epidurals and asks what the risk of this is?

• Acknowledge concern with empathy

• Differentiate between:

  • Temporary motor block (expected, resolves when epidural wears off)

  • Permanent injury (extremely rare: <1:100,000)

• Contextualise with everyday risks (car accident, lightning strike)

• Emphasis on monitoring for early intervention if issues arise

When is the optimal timing for an epidural?

Modern guidance (NICE):

• No minimum cervical dilation requirement

• Provide when requested, regardless of labour stage

• Early placement advantages:

  • Technical ease before intense pain

  • Avoids urgent placement later

  • Gradual titration minimizes motor block

  • Reduces maternal stress hormones

Your patient with epidural analgesia now requires Category 3 caesarean section. Your assessment reveals predominantly unilateral block. Outline your management.

Initial assessment:

• Check block level bilaterally (cold/pinprick testing)

• Assess block quality (sharp/dull discrimination)

• Evaluate motor function (Bromage score)

• Review catheter insertion depth and fixation

• Establish timeline (30-minute window for Category 3)

Block optimisation strategy:

• Patient repositioning:

  • Lateral position with unblocked side dependent

  • 15° head-down tilt if appropriate

• Epidural manipulation:

  • Consider withdrawing catheter 0.5-1cm if deep insertion

  • Aspirate to check for CSF/blood

• Top-up regimen:

  • 15-20ml of 2% lidocaine with 1:200,000 adrenaline, or

  • 15-20ml of 0.5% levobupivacaine with fentanyl 50-100μg

  • Fractionated administration (5ml aliquots)

  • Test block adequacy at 5-minute intervals

Contingency planning:

• Successful top-up: proceed with surgery

• Partial improvement:

  • Supplemental IV analgesia (ketamine, fentanyl)

  • Consider local infiltration by surgeon

• Inadequate block:

  • Time permitting: CSE or spinal at different interspace

  • Limited time: convert to general anaesthesia

  • Document conversion rationale clearly

Monitoring during top-up:

• Continuous BP measurements q2min

• Continuous ECG, SpO₂

• Left lateral tilt/wedge

• Phenylephrine infusion readiness

• Fetal heart rate monitoring

Block remains patchy after top-up. Next steps?

Time-sensitive decision tree:

• If 15+ minutes available: replace epidural or perform new spinal

• If <15 minutes or ongoing fetal concerns: proceed to GA

• Document failed regional, consent for GA

• Ensure RSI preparation and difficult airway equipment

What specific considerations for obese patients apply here?

Technical adaptations:

• Ultrasound guidance for replacement if needed

• Longer spinal needle if converting to spinal

• Extended lateral position time for drug spread

Physiological considerations:

• Higher oxygen requirements (preoxygenation crucial)

• More profound hypotension risk

• Increased risk of rapid desaturation if GA needed

• Consider arterial line if BMI >40

Explain the rationale for adrenaline in your top-up mixture.

Multi-purpose additive:

• Prolongs neural blockade via vasoconstriction

• Reduces systemic absorption of local anaesthetic

• Improves quality of sensory block

• Acts as inadvertent IV injection marker (tachycardia)

• Counteracts epidural-induced hypotension

• May accelerate onset (debated in literature)

How would you manage significant hypotension after top-up?

Structured approach:

• Maintain left lateral tilt/wedge (15°)

• Phenylephrine boluses (50-100μg) titrated to effect

• Consider phenylephrine infusion (25-50μg/min)

• Judicious fluid management (crystalloid boluses)

• Continuous maternal BP + fetal heart monitoring

• Treatment threshold: 20% drop from baseline or <90mmHg systolic

Despite your top-up, the patient reports sharp pain at peritoneal entry during caesarean. Detail your immediate and subsequent management.

Immediate actions (first 60 seconds):

• Clear communication: "I need to give you general anaesthesia"

• Request surgical pause if safe (communicate with surgeon)

• Rapid analgesia bridging:

  • Ketamine 10-20mg IV (sub-dissociative dose)

  • Fentanyl 50-100μg if fetus already delivered

• Call for immediate assistance (second anaesthetist)

• Prepare for rapid sequence induction

Pre-induction preparation:

• Position: head-up ramp for obese patient

• Preoxygenation: 3 minutes tight-fitting mask, 100% O₂

• Target EtO₂ >0.9 or SpO₂ >95% during 30s apnea test

• Equipment check:

  • Functioning IV access (16G or larger)

  • Suction immediately available

  • Difficult airway equipment ready (video laryngoscope)

  • ETT size 6.5-7.5 with bougie

RSI procedure:

• Cricoid pressure by trained assistant

• Induction agents:

  • Propofol 2-3mg/kg ideal body weight or

  • Thiopentone 4-5mg/kg ideal body weight

• Suxamethonium 1.5mg/kg total body weight

• Laryngoscopy: video laryngoscope first attempt

• ETT confirmation: capnography + bilateral auscultation

• Maintain cricoid until confirmation

Post-intubation management:

• Maintenance: sevoflurane 1-1.5 MAC in O₂/air

• Neuromuscular blockade: rocuronium

• Uterotonic: oxytocin 5IU slow bolus then infusion

• Analgesia post-delivery:

  • Fentanyl 100-200μg

  • Morphine 0.1mg/kg

  • Paracetamol 1g

• Antiemetics: dexamethasone 8mg + ondansetron 4mg

Critical documentation:

• Reason for conversion

• Difficult/easy intubation

• Drugs administered

• Neonatal condition

• Post-operative plan

What is your management for failed intubation in this scenario?

Structured DAS-OAA algorithm:

• Declare "Failed intubation" to team

• Maintain oxygenation (two-person technique)

• Second attempt only by senior with different approach

• If second attempt fails, insert second-generation LMA

• Consider:

  • Proceed with surgery if ventilation adequate

  • Wake if ventilation inadequate AND stable maternal/fetal condition

  • Emergency front-of-neck access if cannot intubate/cannot oxygenate

How do you minimise fetal exposure to anaesthetic agents?

Key strategies:

• Minimize induction-to-delivery time (<10 minutes ideal)

• Maintain maternal MAP >65mmHg (phenylephrine preferred)

• Use lowest effective concentration of volatile agent (0.8-1.0 MAC)

• Avoid high-dose opioids before delivery

• Ensure adequate uterine displacement

• Optimize maternal oxygenation (target PaO₂ >100mmHg)

• Consider depth of anaesthesia monitoring

What do you do with the epidural catheter after GA?

Evidence-based approach:

• Leave in situ if functioning and uncontaminated

• Use for post-operative analgesia:

  • PCEA with 0.1% bupivacaine + fentanyl

  • Test proper placement before relying on it

• Remove if:

  • Signs of infection

  • Malposition confirmed

  • Patient preference after discussion

• Document removal and catheter integrity

The patient develops uterine atony after delivery. Anaesthetic management?

Multi-modal approach:

• Reduce volatile concentration (uterine relaxant) and consider switching to propofol TIVA anaesthetic.

• Support hemodynamics:

  • Phenylephrine for MAP >65mmHg

  • Consider arterial line for unstable patient

Facilitate uterotonic administration:

• Oxytocin infusion (30IU in 500ml at 167ml/hr or 40IU in 1L at 125mL/hr)

• Carboprost/ergometrine as requested

• Prepare for massive haemorrhage:

  • Additional large-bore IV access

  • Blood products availability

  • Cell salvage consideration

  • Point-of-care coagulation testing

Key Study Points

• Consent completeness: Address both common and rare complications with contextualization

• Unilateral block: Position dependent side down before assessing top-up efficacy

• GA conversion: Clear communication and immediate action prevent traumatic experience

• Decision-making: Balance maternal wishes with safety priorities

• Documentation: Critical for both medical and medico-legal purposes

Critical Phrases to Include:

• "Adequate regional anaesthesia requires sensory block to T4 dermatome"

• "Pain during caesarean section always requires immediate intervention"

• "Physiological changes of pregnancy significantly impact anaesthetic management"

• "Failed intubation protocol prioritises oxygenation over securing definitive airway"