2024.2 Day 1 VIVA 3

Obstetric Anaesthesia

A 32-year-old patient presents with headaches. She is 37 weeks pregnant. She has had a previous Lower Segment Caesarean Section for breech under uneventful spinal anaesthesia.

She has been assessed by the Rural Generalist Obstetrician, who is concerned about preeclampsia.

Her blood pressure is 170/105. The cardiotocography (CTG) is nonreassuring.

The obstetrician would like to perform a Category 2 Emergency Caesarean Section.

Please outline your pre-anaesthetic assessment for this patient.

Immediate Priorities:

• ABCDE Approach:

  • Airway: Assess for edema (Mallampati changes — predictor of difficult intubation).

  • Breathing: Check SpO₂; signs of pulmonary edema (rales, tachypnea).

  • Circulation: Control BP urgently, establish 2x large bore IVs.

  • Disability: Neuro signs (severe headache, visual aura, hyperreflexia = eclampsia risk).

  • Exposure: Assess fluid status (urine output, pedal edema), proteinuria.

Preeclampsia-Specific Evaluation:

• Bloods:

  • FBC (platelets)

  • Coagulation (PT/APTT)

  • U&E (renal impairment), uric acid

  • LFTs (AST/ALT → HELLP syndrome detection)

Seizure Prophylaxis:

• Magnesium sulfate:

  • Loading: 4g IV over 5–10 min.

  • Infusion: 1g/hr maintenance.

  • Monitor reflexes, urine output (>25 mL/hr).

  • Calcium gluconate available for Mg toxicity.

BP Management:

• IV Labetalol 20 mg bolus or Hydralazine 5mg IV.

• Aim: SBP <160, DBP <110 mmHg.

• Avoid rapid BP drop → fetal compromise.

Anaesthetic Plan:

• Neuraxial if safe:

  • Platelets >75 ×10⁹/L, no coagulopathy.

  • CSE ideal for faster onset.

• GA if contraindications:

  • Edematous airway → videolaryngoscope available.

  • RSI: thiopentone + suxamethonium (avoid ketamine → hypertensive crisis).

Her platelets are 68. Would you proceed with neuraxial anaesthesia?

• No — platelet count <75 ×10⁹/L is a contraindication.

• Proceed with GA (RSI). Neuraxial increases epidural hematoma risk.

Justification:

• OAA guidelines advise against neuraxial anaesthesia <75k platelets unless trends/stability known.

• Risk of catastrophic spinal hematoma.

How would you modify induction for severe hypertension (BP 200/120)?

• Control BP urgently: Labetalol 20–80 mg IV; consider GTN infusion if refractory.

• Minimise laryngoscopy-induced surges with alfentanil 10mcg/kg IV pre-intubation.

Justification:

• Hypertensive surges risk cerebral haemorrhage or aortic dissection.

• Safe, smooth induction prevents catastrophic events.

The CTG shows recurrent decelerations. How does this change your plan?

• Expedite delivery.

• Choose GA without delay — avoid time-consuming neuraxial attempt.

• Prepare NICU team for compromised neonate.

Justification:

• Maternal and fetal compromise shifts priority to rapid delivery — anaesthetic choice must adapt.

You induce GA and the surgeon reports heavy bleeding post-delivery. Outline your management.

1. Hemorrhage Protocol:

• Alert: Senior anaesthetist and obstetrician. Activate massive transfusion protocol.

• Fluids: Begin with balanced crystalloids, move quickly to PRBCs.

• Blood Products:

  • PRBCs for Hb <80 g/L

  • FFP 15 mL/kg if INR >1.5

  • Cryoprecipitate if fibrinogen <1.5 g/L

  • Platelets if <50 ×10⁹/L

2. Uterotonic Strategy:

• First-line: Oxytocin 5 IU IV slowly + infusion 40 IU over 4 hr.

• Second-line: Carboprost 250 mcg IM (avoid ergometrine → hypertensive crises).

• Third-line: Tranexamic acid 1 g IV (within 3 hrs of bleeding onset).

3. Monitoring:

• Invasive arterial line (if not already in place).

• ABG: lactate, ionized calcium.

4. Surgical Backup:

• B-Lynch suture, uterine artery ligation.

• Hysterectomy if bleeding uncontrolled.

The BP drops to 80/40 post-oxytocin. Your response?

• Stop oxytocin infusion → potent vasodilator.

• Administer phenylephrine 50–100 mcg boluses.

• Initiate fluid and blood resuscitation.

Justification:

• Hypotension from oxytocin is common → must manage swiftly to maintain organ perfusion.

Blood gas shows Hb 65, fibrinogen 1.2. What’s your action?

• Transfuse 2 units PRBCs and 2 pools cryoprecipitate immediately.

• Recheck bloods in 30 mins.

Justification:

• Low fibrinogen = critical coagulopathy → drives ongoing hemorrhage if not corrected.

The surgeon requests ergometrine. How do you respond?

• Politely decline: ergometrine causes hypertensive crisis in preeclampsia.

• Offer carboprost or tranexamic acid instead.

Justification:

• Patient safety trumps surgical preference.

• Ergometrine risks stroke or cardiac ischemia.

You have exhausted theblood products in Scenarioville. Plan?

• Prioritize crystalloids initially.

• Accept permissive hypotension (SBP >90 mmHg) until blood arrives.

Justification:

• Aggressive fluid resuscitation alone risks dilutional coagulopathy — balance essential.

She’s stable post-op. Outline your postoperative management.

1. Monitoring:

• HDU/ICU care for 24 hours minimum.

• Hourly BP and neurological checks.

• Strict fluid balance monitoring.

2. Medications:

• Continue magnesium sulfate infusion for 24 hrs post-op.

• Start oral antihypertensives: labetalol or nifedipine.

• LMWH thromboprophylaxis if platelets >50 ×10⁹/L (start 12 hrs after surgery).

3. Complication Surveillance:

• Pulmonary edema → monitor O₂ sats, restrict fluids.

• HELLP syndrome → monitor LFTs and platelets 6hrly.

• AKI risk → urine output and creatinine checks.

When would you stop magnesium?

• After 24hrs if no seizures, stable neurology, urine output >0.5mL/kg/hr.

Justification:

• Early cessation risks rebound eclamptic seizures

Her urine output is 20ml/hr. Your action?

• Assess fluid balance, renal function (U&E, creatinine).

• Exclude hypovolemia, consider diuretics if overload confirmed.

Justification:

• Preeclampsia-induced AKI or pulmonary edema can develop post-op.

Midwife suggests discharge at 6 hours — your response?

• Decline. Minimum 24hr monitoring is mandatory due to risk of postpartum eclampsia and pulmonary edema.

Justification:

• Visual "wellness" is deceptive in severe preeclampsia.

Platelets 45 — would you give LMWH?

• No.

• Mechanical thromboprophylaxis only until platelets >50 ×10⁹/L.

• Consult hematology if persistent.

Justification:

• LMWH in thrombocytopenia risks major bleeding events.

Key Learning Points

1. Prioritize Multisystem Assessment in Preeclampsia

   • Evaluate airway (edema risk), neurology (eclampsia signs), hematology (platelets/coagulation), and renal/hepatic function before anaesthesia.

2. Magnesium is First-Line for Seizure Prophylaxis

   • Administer 4g IV load → 1g/hr infusion, monitoring for toxicity (loss of reflexes, respiratory depression).

3. Avoid Ergometrine in Hypertensive Patients

   • Use oxytocin + carboprost for uterine atony—ergometrine worsens hypertension and is contraindicated.

4. Thrombocytopenia Contraindicates Neuraxial Anaesthesia

   • Platelets <75 × 10⁹/L = avoid spinal/epidural. Opt for GA with RSI and airway precautions.

5. Postpartum Monitoring is Critical

   • Preeclampsia can worsen for 24–48hrs post-delivery. Monitor for eclampsia, pulmonary edema, and HELLP syndrome in HDU.

Key Phrases

1. "Preeclampsia is a multisystem disorder—my assessment covers airway, neurology, and end-organ function."

2. "Magnesium is for seizure prophylaxis, not just treatment of eclampsia."

3. "I avoid ergometrine due to its hypertensive effects in preeclampsia."

4. "Platelets <75 × 10⁹/L contraindicate neuraxial techniques—I’d proceed with GA."

5. "Oxytocin causes vasodilation; phenylephrine boluses treat hypotension post-delivery."

6. "Preeclampsia can deteriorate postpartum—24hrs of close monitoring is essential."