2024.2 Day 1 VIVA 11

Obstetric Anaesthesia

A 25-year-old female presents to Scenarioville with ultrasound-confirmed perforated appendicitis.

She has a temperature of 38.5°C, a heart rate of 110 bpm, blood pressure of 95/55 mmHg, and pain rated at 7/10.

She has a viable 28-week intrauterine pregnancy, has had an uneventful antenatal course and has no past medical history. Her BMI is 30.

Specialists at a tertiary hospital recommend an emergency laparoscopic appendectomy at Scenarioville, with additional staff and retrieval services on standby for potential neonatal emergencies.

Outline your pre-operative assessment and optimisation.

Immediate Resuscitation:

• IV access x2 (14G), bloods (FBC, UEC, LFTs, lactate, VBG)

• Fluid bolus (500ml crystalloid) → target urine output >0.5ml/kg/hr

• IV paracetamol + limited opioids (e.g., fentanyl 50mcg) for pain

Airway Assessment:

• Mallampati, thyromental distance - anticipate difficult intubation (BMI 30 + pregnancy)

• Prepare videolaryngoscope + difficult airway trolley

Fetal Considerations:

• Obstetric consult for CTG monitoring

• Avoid aortocaval compression - left uterine displacement

Medication Safety:

• Antibiotics: Ceftriaxone + metronidazole (TGA Category B1/B2)

• Avoid NSAIDs (risk of premature ductus arteriosus closure)

Consent Discussion:

• Risks: Premature labour (5-10%), fetal loss (1-2%), aspiration

• Benefits: Source control outweighs risks

Walk me through your antibiotic selection process for this patient.

• Ceftriaxone (Category B1) and metronidazole (Category B2) as first-line for perforated appendicitis in pregnancy. These cover typical gut flora while having the safest fetal profiles.

• Avoid aminoglycosides unless absolutely necessary due to potential ototoxicity (Category D). The choice balances maternal sepsis management with fetal safety.

• Dosing would be weight-based, with renal adjustment if needed, and timed to achieve optimal tissue levels before incision.

How would you modify your approach if the patient had a known difficult airway?

• Perform an awake videolaryngoscopy-assisted intubation with topical airway anesthesia

• Have a second experienced anaesthetist present

• Prepare a surgical airway kit and ensure the obstetric team is ready for emergency fetal delivery if prolonged hypoxia occurs

• Use lower dose induction agents to maintain spontaneous ventilation until airway secured

• The key is maintaining oxygenation while minimizing fetal compromise.

Discuss your fluid management strategy in detail.

Restore perfusion without causing pulmonary edema, which is particularly risky in pregnancy.

• Start with a 500ml crystalloid bolus, reassessing response

• Target a urine output >0.5ml/kg/hr but avoid over-resuscitation

• Use balanced crystalloids rather than normal saline to avoid hyperchloremic acidosis

• Consider early arterial line for beat-to-beat monitoring if persistent hypotension

• Have vasopressors prepared (phenylephrine infusion) for refractory hypotension

How would you adjust your plan if this was a 16-week pregnancy?

The principles of maternal resuscitation and source control remain paramount.

• Less concern about aortocaval compression - may not need left tilt until after 20 weeks

• Lower fetal risk from medications, but still avoid known teratogens

• Surgical approach might be more challenging due to uterine size

• Fetal monitoring would be less crucial as viability is lower

Describe your anaesthetic plan for laparoscopic appendectomy.

• Induction:

  • RSI: Thiopentone 4-5mg/kg + suxamethonium 1.5mg/kg

  • Cricoid pressure until tube placement confirmed

  • Avoid propofol >2mg/kg (risk of maternal hypotension)

• Ventilation:

  • Target EtCO2 32-35 mmHg (mimic normal pregnancy)

  • Peak pressures <30 cmH2O - reduce insufflation pressure if needed

• Haemodynamics:

  • Phenylephrine infusion (50-100mcg/min) to maintain MAP >65mmHg

  • Limit IV fluids (risk of pulmonary edema)

• Surgical Coordination:

  • Open (Hasson) technique for pneumoperitoneum

  • CO2 insufflation <12mmHg

Detail your management if the patient becomes hypotensive during pneumoperitoneum.

Resuscitation takes priority over diagnosis, however echo and arterial line monitoring should be considered in turn.

• First reduce insufflation pressure to ≤10mmHg

• Increase phenylephrine infusion rate

• Give a small fluid bolus (100-200ml) if likely hypovolemic

• Check for signs of venous gas embolism (mill-wheel murmur, sudden EtCO2 drop)

• Consider temporary Trendelenburg position if embolism suspected

How would you modify ventilation for this obese pregnant patient?

The balance is between minimisation of volutrauma with maximisation of oxygenation.

• Use lung-protective ventilation (6-8ml/kg ideal body weight)

• Apply PEEP 5-8cmH2O to prevent atelectasis

• Maintain slight respiratory alkalosis (PaCO2 28-32mmHg) to compensate for fetal acidosis

• Perform regular recruitment maneuvers

• Monitor airway pressures closely to avoid barotrauma

What would you do if you couldn't achieve adequate surgical exposure with 12mmHg insufflation?

• First discuss with the surgeon whether they can proceed at lower pressure

• Consider brief increases to 14-15mmHg only when absolutely necessary for critical steps

• Compensate by increasing phenylephrine to maintain perfusion

• Monitor fetal heart rate closely during periods of higher pressure

• Consider converting to open procedure if exposure remains inadequate

Describe your approach if the patient develops bronchospasm during the case.

In the event of life-threatening bronchospasm, I'd prepare for emergency delivery to improve maternal ventilation.

• First deepen anaesthesia with volatile agent

• Give salbutamol via ETT adapter

• Consider IV magnesium (2g over 20 minutes) for refractory cases

• Rule out mechanical causes (ETT malposition, pneumothorax)

• Monitor fetal heart rate closely as hypoxia affects the fetus first

Outline your post-op management plan at Scenarioville.

• Monitoring:

  • HDU for 24hrs - hourly vitals, continuous CTG if >26 weeks

  • Fetal assessment: Daily growth scans if prolonged admission

• Analgesia:

  • Paracetamol 1g q6h + tramadol 50mg q6h (Category C but low-risk)

  • Avoid morphine PCA (risk of neonatal respiratory depression)

• Complications Surveillance:

  • Preterm labour: Tocolytic (nifedipine) if contractions

  • Sepsis: Repeat cultures, adjust antibiotics

• Retriage Planning:

  • Coordinate with retrieval team for neonatal ICU transfer if delivery imminent

Detail your postoperative analgesia regimen and alternatives.

It is critical to avoid NSAIDs completely in third trimester. Therefore:

• First-line:

  • Regular paracetamol 1g q6h2. Tramadol 50mg q6h PRN (maximum 400mg/day)

  • Consider transversus abdominis plane (TAP) block if expertise available

• Second Line:

  • Low-dose ketamine infusion (0.1mg/kg/hr)

  • Fentanyl PCA (lower fetal risk than morphine)

How would you manage new-onset preterm labor postoperatively?

• Consult obstetrics

• Start tocolysis with nifedipine (first-line in sepsis as it doesn't cause pulmonary edema)

• Give betamethasone for fetal lung maturation if <34 weeks

• Optimize maternal oxygenation and perfusion

• Prepare for possible emergency delivery

What monitoring would you insist on if HDU beds aren't available?

Minimum requirements would be:

• 1:1 nursing in recovery for first 4 hours

• Hourly vitals including SpO2

• Continuous CTG if >26 weeks

• Strict fluid balance monitoring

• Emergency call system for rapid response to deterioration

Document the suboptimal situation but accept it's the best available.

How would you modify care if the retrieval team is delayed?

Maternal Stabilization

• Ensure airway patency and adequate oxygenation (SpO₂ >95%) with supplemental O₂ via non-rebreather mask

• Maintain systolic BP >100 mmHg using crystalloid boluses (250-500ml) and phenylephrine infusion if needed

• Continuous ECG monitoring for arrhythmias secondary to sepsis or electrolyte imbalances

Fetal Protection

• Administer betamethasone 12mg IM immediately if delivery appears imminent (<48 hours)

• Position in full left lateral tilt to optimize uteroplacental perfusion

• Continuous CTG monitoring with obstetric review q2h for signs of fetal compromise

Neonatal Preparedness

• Set up resuscitation area with:

  • Pre-warmed radiant warmer and dry towels

  • Neopuff T-piece resuscitator with 100% O₂

  • Umbilical catheterization kit for emergency vascular access

• Prepare medications:

  • Adrenaline 1:10,000 dilution

  • 10% glucose for potential neonatal hypoglycemia

Resource Optimization

• Mobilise all available staff:

  • Assign most experienced clinician to neonatal resuscitation

  • Utilise anesthetic nurses for maternal monitoring

• Improvised equipment:

  • Use syringe pumps for precise medication administration if infusion pumps unavailable

  • Consider manual ventilation with Mapleson C circuit if mechanical ventilator needed

Communication Strategy

• Designate a team leader to coordinate care

• Establish hourly updates with retrieval team regarding ETA

• Document all interventions thoroughly for handover

The key principles are:

• Maternal physiology takes precedence - a stable mother gives the fetus the best chance

If delivery becomes unavoidable, I would prioritise:

1. Neonatal thermoregulation (dry, warm, wrap in plastic)

2. Ventilation support (5 inflation breaths followed by 30-60/min if apneic)

3. Chest compressions if HR remains <60 bpm after 30s of effective ventilation

Rationale for Key Decisions:

• Betamethasone is prioritized as it takes 24h for full effect on fetal lung maturation

• Left lateral position improves uterine perfusion by ~30% compared to supine

• T-piece resuscitator is preferred over self-inflating bags for preterm neonates

6 Key Learning Points

1. Maternal Stability is Paramount

   • Fetal outcomes depend on maternal physiology – always prioritise ABC (Airway, Breathing, Circulation) before fetal interventions.

2. TGA Pregnancy Categories Guide Medication Safety

   • Use Category B antibiotics (e.g., ceftriaxone) and avoid teratogens (e.g., NSAIDs in 3rd trimester).

3. Pneumoperitoneum Pressures Affect Fetal Wellbeing

   • Limit CO₂ insufflation to ≤12 mmHg to reduce fetal acidosis risk.

4. Neuraxial Contraindications in Thrombocytopenia

   • Platelets <75 × 10⁹/L = avoid spinal/epidural → proceed with GA and RSI.

5. Postoperative Vigilance is Critical

   • Preeclampsia/sepsis can worsen postpartum – monitor for 24hrs in HDU.

6. Adapt to Resource Limitations Without Compromising Safety

   • Improvise with available equipment (e.g., T-piece resuscitator for preterm neonates) while awaiting retrieval.

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6 Key Phrases Examiners Expect

1. "Maternal resuscitation comes first – the fetus depends on maternal stability."

   • Demonstrates prioritization in obstetric emergencies.

2. "I avoid ergometrine due to hypertensive risks in preeclampsia."

   • Shows knowledge of context-specific contraindications.

3. "I’ll use phenylephrine to maintain uteroplacental perfusion during hypotension."

   • Highlights physiological understanding of pregnancy hemodynamics.

4. "Magnesium is for seizure prophylaxis, not just treatment."

   • Reinforces guideline-based management of preeclampsia.

5. "I’ve prepared for the worst while hoping for the best – all equipment is checked."

   • Reflects anticipatory planning in resource-limited settings.

6. "I document resource limitations but maintain the highest standard possible."

   • Balances realism with professional responsibility.