Pregnant Female with Mitral Stenosis Posted for LSCS (Anaesthetic Management)

Pathophysiology - Why MS is Dangerous in Pregnancy

Pre-operative Assessment

• Mild: MVA >1.5 cm² - usually well tolerated
• Moderate: MVA 1.0-1.5 cm²
• Severe: MVA <1.0 cm² - very high risk

• NYHA functional class
• Echo: MVA, mean transmitral gradient, pulmonary artery pressure (PAP), LA size, LV function
• Rhythm (sinus vs AF)
• Evidence of pulmonary oedema / right heart failure
• Current medications: beta-blocker, diuretics, digoxin, anticoagulants
• WHO risk class (severe MS = WHO class III-IV; class IV = contraindicated)

Key Anaesthetic Goals (LSCS)

Choice of Anaesthesia

Option 1: Epidural Anaesthesia (PREFERRED for planned/elective LSCS)

• Advantages:
  • Slow onset - allows gradual haemodynamic adaptation
  • No tachycardia from pain (superior analgesia)
  • Avoids GA hazards (airway difficulty in pregnancy, risk of aspiration)
  • Can be extended if surgery prolongs
• Key technique:
  • Titrated slow epidural top-up (not rapid bolus)
  • Avoid hypotension - treat with phenylephrine (not ephedrine - ephedrine causes tachycardia)
  • Avoid adrenaline-containing local anaesthetic solutions (risk of tachycardia)
  • Level T4-T6
• Contraindicated: if patient is fully anticoagulated (heparin/LMWH - observe timing windows)

Option 2: Spinal Anaesthesia

• Used for: emergency LSCS when epidural not in place
• Risk: sudden onset sympathectomy → precipitous hypotension → reflex tachycardia → acute decompensation
• Precautions if used:
  • Low-dose spinal (hyperbaric bupivacaine 7.5-10 mg, not full 12.5 mg)
  • Consider CSE (combined spinal-epidural) to allow titration
  • Phenylephrine infusion prophylactically (NOT ephedrine)
  • Vasopressor ready immediately
  • Have invasive arterial monitoring
  • Avoid adrenaline in spinal solution

Option 3: General Anaesthesia

• Last resort - associated with highest risk in this scenario
• When unavoidable: coagulopathy, patient refusal of regional, failed regional, haemorrhage
• Risks specific to MS:
  • Laryngoscopy/intubation → sympathetic surge → tachycardia → decompensation
  • Positive pressure ventilation → ↓ venous return → compromised preload
  • Most induction agents cause vasodilation (avoid ketamine - causes tachycardia)
• If GA required:
  • Preoxygenation, rapid sequence induction
  • Induction: etomidate (most haemodynamically stable) or low-dose ketamine is contraindicated (tachycardia); thiopentone with caution
  • Opioid (fentanyl/remifentanil) at induction to blunt laryngoscopy response
  • Maintain with volatile agents (sevoflurane preferred - minimal cardiac depression at low MAC)
  • Esmolol or IV metoprolol to control HR if tachycardia occurs intraoperatively

Monitoring

• ECG (continuous - detect AF early)
• SpO2
• Invasive arterial line (arterial line is standard for moderate-severe MS - beat-to-beat BP monitoring)
• CVP line (in severe MS with RV dysfunction)
• Consider pulmonary artery catheter / intra-operative TOE (transoesophageal echo) in the most severe cases
• Hourly urine output

Intraoperative Precautions

1. Positioning: strict left lateral tilt (15°) until delivery
2. IV fluids: restrict; avoid aggressive fluid loading (crystalloid co-load maximum 500-1000 mL)
3. Oxytocin: give as slow infusion (5-10 units over 30 min), NOT as IV bolus - causes hypotension, reflex tachycardia, and pulmonary vasoconstriction. Avoid ergometrine (causes pulmonary vasoconstriction and hypertension)
4. Vasopressors: phenylephrine preferred (pure alpha-agonist, reflex bradycardia actually beneficial) over ephedrine
5. Prophylactic antibiotics: standard
6. Antibiotic endocarditis prophylaxis: not routinely recommended unless high-risk features, per current AHA/ESC guidelines

Postoperative Management

• HDU/ICU monitoring for at least 24-48 hours - the puerperium is the highest-risk period
• Autotransfusion after delivery (uterine contraction returns ~500 mL to circulation) - highest risk for flash pulmonary oedema
• Frusemide 20-40 mg IV if signs of fluid overload
• Continue HR control medications (beta-blockers, digoxin if AF)
• Continue anticoagulation (AF + MS = very high thromboembolic risk; also LMWH for VTE prophylaxis post-LSCS)
• Strict fluid balance
• Elective ventilation in ICU if severe pre-existing pulmonary hypertension or RV failure

Drug Summary for Intraoperative Use

Quick Reference: What to AVOID

Key Takeaways

1. Slow heart rate = top priority in all phases
2. Epidural is the anaesthesia of choice for planned LSCS
3. Phenylephrine over ephedrine for vasopressor support
4. Puerperium (immediate post-delivery period) is the most dangerous phase - volume redistribution can cause acute pulmonary oedema even after uncomplicated surgery
5. Multidisciplinary team: cardiologist, maternal-fetal medicine, anaesthetist, neonatologist - ideally planned delivery at a tertiary centre

Recent evidence: A 2025 review (Naik SA et al., Ann Afr Med, PMID: 40038558) specifically addresses anaesthetic management of LSCS in parturients with valvular heart disease and is consistent with the above framework.