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PART 1: Mitral Stenosis (MS) in Pregnancy Posted for Emergency LSCS - Anaesthetic Considerations and Management

Pathophysiology Relevant to Anaesthesia

• Heart rate (HR) is the most critical variable - tachycardia reduces diastolic filling time, escalates LA pressure, and precipitates pulmonary oedema
• Preload dependence - the stenotic valve requires maintained preload to generate adequate forward flow; however, fluid overload raises LA pressure
• Pulmonary hypertension - secondary to chronic LA hypertension; manipulation of PVR determines right heart stability
• Fixed cardiac output - the patient cannot increase CO in response to the haemodynamic demands of pregnancy, labour, and surgery
• Atrial fibrillation - loss of atrial kick and fast ventricular rate causes dramatic haemodynamic deterioration

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Preoperative Assessment (Emergency - Time-Compressed)

• NYHA class, exercise tolerance
• Symptoms: dyspnoea, orthopnoea, haemoptysis, palpitations
• Onset/duration of any AF
• Current medications (digoxin, beta-blockers, diuretics, anticoagulants)

• ECG - look for AF, P-mitrale (bifid P in sinus rhythm), RVH, right axis deviation
• Echocardiogram - mitral valve area (MVA) defines severity:
  • Mild MS: MVA >1.5 cm²
  • Moderate MS: MVA 1.0-1.5 cm²
  • Severe MS: MVA <1.0 cm²
  • Also assess: LA size, PAP, pulmonary pressures, LV function, TR
• CXR - cardiomegaly, pulmonary oedema, Kerley B lines
• ABG if hypoxic
• Full blood count, coagulation profile (if on anticoagulants), renal function
• SpO2

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Haemodynamic Goals for Anaesthesia in MS

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Multidisciplinary Team Preparation

• Anaesthesiologist (senior/consultant), obstetrician, cardiologist on standby
• Neonatologist for baby
• ICU/HDU bed arranged for postoperative care
• IABP/ECMO team on standby in severe cases with PHT
• Blood bank alert

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Monitoring (Invasive Monitoring is Essential)

• Intra-arterial line (A-line) - beat-to-beat BP, beat-to-beat arterial waveform, ABG access
• Central venous catheter - CVP monitoring, vasopressor/inotrope infusion
• SpO2, ETCO2, ECG (5-lead), temperature
• Continuous urine output (Foley catheter)
• Fetal heart rate monitoring until delivery

• Pulmonary artery catheter (rarely used now) - PCWP monitoring
• Transoesophageal echocardiography (TOE/TEE) if available - most valuable real-time haemodynamic monitor

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Choice of Anaesthetic Technique

Option 1: Epidural Anaesthesia (PREFERRED for emergency LSCS in stable/moderate MS)

• Slow, titrated onset - gradual sympathectomy, avoids sudden vasodilation
• Allows incremental dosing to maintain haemodynamic stability
• Avoids airway manipulation and intubation stress (which causes tachycardia)
• Better postoperative analgesia - prevents pain-induced tachycardia
• Epidural catheter can be used for labour analgesia if patient was in labour

• Position: left lateral decubitus (15° tilt after sitting for epidural) - avoid supine hypotension
• Level: L2-L3 interspace
• Test dose: 3 ml of 2% lignocaine + adrenaline (1:200,000)
• Incremental doses: 0.5% bupivacaine in 5 ml aliquots to achieve T4-T6 level
• Slow titration is the key - target level T4 (allows handling of uterus without pain)
• Supplement with epidural fentanyl (50-100 mcg) for analgesia and to reduce bupivacaine dose
• Manage hypotension with small doses of phenylephrine (vasopressor of choice - does not increase HR) or noradrenaline; avoid ephedrine (causes tachycardia)
• IV crystalloid judiciously - avoid fluid bolus loading (worsens MS)

Option 2: Combined Spinal-Epidural (CSE) - Cautious Use

• Preferred if time is critical and epidural titration is slow
• Use low-dose spinal: 1.5-2 ml of 0.5% heavy bupivacaine (7.5-10 mg) + fentanyl 15-25 mcg intrathecally
• Establish epidural catheter simultaneously for supplementation
• Risk: even low-dose spinal can cause abrupt vasodilation in severe MS - have vasopressors ready

Option 3: General Anaesthesia (for truly emergent situations, failed regional, or severe PHT)

• Patient refusal of regional
• Coagulopathy (anticoagulants - not reversed)
• True emergency (category 1 LSCS - <30 min decision-to-delivery)
• Failed regional block
• Severe pulmonary hypertension with haemodynamic instability

• Blunt intubation response (tachycardia from laryngoscopy is dangerous)
• Avoid all tachycardia-inducing drugs

1. Preoxygenation: 100% O2 for 3-5 min (SpO2 >94% mandatory, FRC reduced in pregnancy)
2. Antacid prophylaxis: sodium citrate 30 ml PO + IV ranitidine/metoclopramide
3. Pre-induction beta-blockade: esmolol 0.5-1 mg/kg IV (short-acting, controls intubation tachycardia; monitor fetal HR after delivery), or metoprolol 1-2 mg IV
4. Fentanyl 2-3 mcg/kg IV (2-3 min before induction) - blunts laryngoscopy response
5. Induction agent: Etomidate 0.2-0.3 mg/kg (haemodynamic stability) - preferred. Ketamine and thiopentone are alternatives but ketamine increases HR (AVOID in MS); thiopentone can cause vasodilation
6. Muscle relaxant: Rocuronium 1 mg/kg (RSI dose) - succinylcholine 1.5 mg/kg acceptable (use with caution - increases HR with repeated doses)
7. Sellick's cricoid pressure during RSI
8. Laryngoscopy - rapid and smooth; topical lignocaine 4% spray or IV lignocaine 1.5 mg/kg 3 min before intubation to blunt response
9. Intubate with 7-7.5 mm cuffed ETT

• O2:N2O (50:50) or O2:air - avoid high N2O (fetal concerns, debated)
• Isoflurane/sevoflurane at low MAC (0.5-1 MAC) - reduce in pregnancy (MAC reduced 25-30%)
• IV fentanyl infusion for analgesia
• Atracurium for neuromuscular blockade (non-depolarising)
• Avoid halothane (sensitises to arrhythmias)
• Control ventilation: maintain normocarbia (EtCO2 32-35 mmHg) - hypercarbia increases PVR

• Oxytocin: give as SLOW infusion (10 units in 500 ml NS over 4-8 hours) - avoid bolus; oxytocin bolus causes profound vasodilation, hypotension, reflex tachycardia - can be catastrophic in MS
• Ergometrine/Syntometrine: CONTRAINDICATED in MS (causes severe hypertension and pulmonary oedema)
• Carboprost (prostaglandin F2α): use with caution - can cause pulmonary vasoconstriction
• Misoprostol: safer alternative uterotonic in MS

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Drugs to AVOID in MS

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Special Situations

If Patient is in AF at Presentation:

• Rate control is priority: IV digoxin (slow), or IV metoprolol 1-5 mg (titrated)
• Esmolol infusion (50-300 mcg/kg/min) for acute control
• DC cardioversion if haemodynamically unstable AF in emergency (50-100 J synchronised)
• Anticoagulation if AF >48 hours (risk of embolism)

If Pulmonary Oedema is Present:

• IV furosemide 40 mg
• Sit patient upright, oxygen
• Controlled ventilation if severe
• Proceed to emergency LSCS once stabilised or if fetal distress mandates immediate delivery

If Severe PHT (PAP >50% systemic or >50 mmHg):

• Very high-risk - maternal mortality up to 50%
• Consider inhaled NO (20 ppm) - reduces PVR without systemic vasodilation
• Sildenafil pre-loaded if time permits
• Vasopressors: phenylephrine preferred, noradrenaline second
• Avoid RV afterload increase (hypercarbia, hypoxia, acidosis)

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Postoperative Management

• ICU/HDU mandatory - haemodynamic instability peaks in puerperium (autotransfusion effect)
• Continue arterial line monitoring for 24-48 hours
• Analgesic plan: epidural catheter left in situ for continued analgesia (prevents tachycardia from pain); IV paracetamol + IV opioids as needed
• Continue beta-blocker therapy
• Anticoagulation: restart when surgically safe
• Monitor for: pulmonary oedema, arrhythmia, cardiac failure, DVT/PE
• Fluid balance strictly negative postoperatively
• DVT prophylaxis

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PART 2: Non-Obstetric Surgery in the Pregnant Patient - Anaesthetic Considerations and Management

Epidemiology

• Approximately 1-2% of pregnant women require non-obstetric surgery during pregnancy
• Most common indications: acute appendicitis, cholecystitis, ovarian cysts, trauma, adnexal masses, cardiac surgery
• Emergency surgery cannot be deferred - should proceed regardless of trimester

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Physiological Changes of Pregnancy Relevant to Anaesthesia

Respiratory System

Cardiovascular

Gastrointestinal

• Reduced LES tone, raised intra-abdominal pressure = increased aspiration risk
• Aspiration precautions from 16-18 weeks (many practitioners from first trimester or whenever uterus becomes intra-abdominal)
• Delayed gastric emptying during active labour (NOT in non-labouring pregnant patients - gastric emptying is normal)

Haematological

• Hypercoagulable state - increased risk DVT/PE
• Reduced plasma cholinesterase (affects suxamethonium - duration prolonged)
• Physiological anaemia (dilutional)

Renal

• Increased GFR - faster clearance of renally excreted drugs
• Physiological glycosuria

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Timing of Surgery

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Teratogenicity of Anaesthetic Drugs

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Fetal Considerations

1. Avoid teratogens (especially 1st trimester)
2. Maintain uteroplacental perfusion
3. Prevent preterm labour
4. Avoid fetal asphyxia

• Maintain maternal MAP >65-80 mmHg (or within 20% of baseline)
• Treat hypotension immediately with phenylephrine (vasoconstrictor of choice in pregnancy - preserves uteroplacental blood flow without increasing HR); noradrenaline also acceptable
• Avoid ephedrine as first-line (increases fetal acidosis compared to phenylephrine - COMET trial)
• Avoid hyperventilation (PaCO2 <25 mmHg causes uterine vasoconstriction and fetal hypoxia)
• Avoid hypoventilation (PaCO2 >45 mmHg causes fetal respiratory acidosis)
• Target maternal PaCO2: 32-35 mmHg (normal in pregnancy)

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Anaesthetic Technique

Regional vs General Anaesthesia

• Minimises fetal drug exposure
• Maintains maternal airway reflexes
• Reduces aspiration risk
• Provides postoperative analgesia
• Better outcome data in obstetric population

• Increased sensitivity to local anaesthetics (25-30% dose reduction)
• Increased risk of hypotension - treat aggressively with phenylephrine
• Lipid rescue should be available at all times (increased toxicity risk)

• Rapid sequence induction from 16-18 weeks (or earlier by many guidelines)
• Preoxygenation: 3-5 min 100% O2 (or 4 vital capacity breaths) - essential given reduced FRC
• Cricoid pressure (Sellick's manoeuvre) - until ETT confirmed
• Use smaller ETT (6.5-7.0 mm) - mucosal oedema
• Antacid prophylaxis: sodium citrate 30 ml, ranitidine 150 mg oral or 50 mg IV, metoclopramide 10 mg IV (30-60 min before)
• Induction agent: propofol/thiopentone - standard doses; propofol infusion (TIVA) or volatile maintenance both acceptable
• Neuromuscular monitoring essential (altered pharmacokinetics)
• Reverse with sugammadex (rocuronium) or neostigmine - note neostigmine can stimulate uterus; use glycopyrrolate (not atropine) as anticholinergic

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Airway Management in Pregnant Patient

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Positioning

• Left lateral tilt (15°) from 16-18 weeks (or when uterus palpable above umbilicus)
• Prevents aortocaval compression by gravid uterus
• Use a wedge under right hip or tilt the operating table

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Monitoring

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Specific Drug Considerations

• Do NOT use prophylactically
• Use only if evidence of preterm labour develops intraoperatively or postoperatively
• Indomethacin (1st/2nd trimester), nifedipine, or atosiban (2nd/3rd trimester)
• Volatile agents (isoflurane, sevoflurane) have uterine relaxing properties - slightly protective

• Cephalosporins, penicillins - safe in pregnancy
• Tetracyclines, quinolones - avoid
• Metronidazole - 2nd and 3rd trimester only for most indications

• Low molecular weight heparin (LMWH) for DVT prophylaxis - safe
• Avoid warfarin (teratogenic in 1st trimester; crosses placenta)

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Laparoscopic Surgery in Pregnancy - Special Considerations

• Safe in all trimesters - evidence supports safety
• Position: reverse Trendelenburg to displace uterus; use left tilt
• Pneumoperitoneum pressure: keep ≤15 mmHg (lower if possible - 10-12 mmHg preferred)
• CO2 insufflation causes: hypercapnia (absorbed CO2), fetal respiratory acidosis if maternal ventilation not adjusted
• Increase minute ventilation to maintain EtCO2 32-35 mmHg
• Open Hasson technique preferred for trocar insertion (avoids uterine injury)
• FHR monitoring before and after procedure

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Postoperative Care

• Fetal monitoring: CTG for minimum 2 hours postoperatively (longer if surgery was prolonged or complicated)
• Uterine activity monitoring for 24 hours
• Multimodal analgesia: paracetamol + regional techniques preferred; opioids as needed (with caution near term)
• NSAIDs: Avoid after 28-32 weeks (risk: premature closure of ductus arteriosus)
• DVT prophylaxis: early mobilisation, compression stockings, LMWH
• Monitor for preterm labour symptoms

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Key Points Summary Table

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References

• Creasy & Resnik's Maternal-Fetal Medicine (Mitral Stenosis in Pregnancy section)
• Misra MK et al. "Mitral stenosis and pregnancy: Current concepts in anaesthetic practice." Indian J Anaesth (PMC2991654)
• Lal AK et al. "Anesthetic Management of Cesarean Sections in Parturients with Valvular Heart Disease." Can J Anaesth 2025 (PMC12103142)
• "Anesthetic Management of the Pregnant Patient Undergoing Non-Obstetric Surgery." J Med Life 2025 (PMC12028341)
• Braunwald's Heart Disease, 12e
• WFSA Update in Anaesthesia - Anaesthesia for non-obstetric surgery during pregnancy (PMC9947972)
• ACOG Practice Bulletin on non-obstetric surgery in pregnancy