MD Anaesthesia PG Exam Answer

QUESTION 1: Patient with Multiple Sclerosis (MS) Posted for Emergency LSCS - Anaesthetic Considerations and Detailed Management

Introduction

Pathophysiology Relevant to Anaesthesia

• MS lesions render demyelinated axons susceptible to neurotoxic injury from local anaesthetics
• Autonomic dysfunction is common - predisposing to haemodynamic instability under both regional and general anaesthesia
• Uhthoff's phenomenon: heat increases conduction block in demyelinated fibres - core temperature rise worsens neurological symptoms intraoperatively
• Disease-modifying therapies (DMTs - fingolimod, natalizumab, rituximab, ocrelizumab) have immunosuppressive effects relevant to infection risk and drug interactions

Preoperative Assessment

• Type of MS: Relapsing-Remitting (RRMS), Secondary Progressive (SPMS), or Primary Progressive (PPMS)
• Current functional status - Motor deficits, spasticity, bulbar involvement, degree of weakness
• Baseline MRI findings (upper vs. lower motor neuron lesion pattern)
• Cognitive and autonomic status - bladder dysfunction, postural hypotension, dysautonomia
• Respiratory function - spirometry, if bulbar involvement or severe weakness is present

• DMTs: fingolimod causes bradycardia and may affect heart rate response to haemorrhage
• Steroids (may have received recent methylprednisolone for relapse)
• Baclofen (antispastic) - abrupt withdrawal can precipitate seizures and worsening spasticity
• Amantadine, modafinil (fatigue management)
• Antiepileptics (carbamazepine, gabapentin) - drug interactions with anaesthetics

• Gestational age, indication for emergency LSCS, fetal wellbeing
• Degree of urgency (Category 1, 2, 3 LSCS)
• Placental status, estimated blood loss risk
• Antenatal steroid exposure

Key Anaesthetic Concerns

Choice of Anaesthesia

A. Regional Anaesthesia (Preferred for LSCS in MS)

• Lower concentration of local anaesthetic in the CSF compared to spinal
• Titrated, incremental dosing minimizes the total LA exposure to an already demyelinated cord
• Avoids the pulsatile high-concentration CSF exposure of single-shot spinal
• Provides excellent postoperative analgesia - reduces postoperative stress (a relapse trigger)

• Bupivacaine 0.5% hyperbaric (for spinal) - use lowest effective dose
• Levobupivacaine or ropivacaine for epidural (less neurotoxic profile)
• Avoid high concentrations of lidocaine intrathecally (transient neurological symptoms more likely)
• Chloroprocaine epidurally - caution (associated with neurotoxicity in high concentration)

B. General Anaesthesia (If Regional Contraindicated or Failed)

• Severe coagulopathy
• Patient refusal
• Failed regional block
• Category 1 LSCS with insufficient time
• Significant bulbar dysfunction (risk of aspiration with impaired airway reflexes)
• Patient with respiratory failure

• Upregulation of extrajunctional nicotinic acetylcholine receptors in denervated muscles leads to exaggerated potassium efflux
• Risk of life-threatening hyperkalaemia
• A case of succinylcholine-induced hyperkalaemia specifically in MS has been documented (Miller's Anesthesia 10e)
• Safer alternative: Rocuronium 1.2 mg/kg for RSI (with sugammadex reversal available)
• Use of rocuronium/sugammadex in MS has been reported safely (Staikou & Rekatsina, Saudi J Anaesth 2017)

• All volatiles are acceptable
• Avoid hyperthermia - aim for normothermia or mild hypothermia (active cooling blanket, cool IV fluids)
• Isoflurane, sevoflurane are commonly used

• Pre-oxygenation: 3 minutes tidal volume or 8 deep breaths at 100% FiO2
• Cricoid pressure
• Propofol 1.5-2 mg/kg (or thiopentone 4-5 mg/kg) + Rocuronium 1.2 mg/kg
• Video laryngoscope preferred (anticipate difficult airway - pregnancy + possibly bulbar symptoms)
• Intubation confirmed with ETCO2

• Volatiles (sevoflurane/isoflurane) + N2O or air (avoid high N2O for fetal concerns)
• TIVA (propofol + remifentanil) is an acceptable alternative
• Neuromuscular monitoring mandatory - avoid residual block
• Reversal with sugammadex preferred over neostigmine

Intraoperative Management

• Standard ASA/AAGBI monitoring: ECG, SpO2, NIBP (5-minute cycle), EtCO2, temperature
• Invasive arterial line if significant autonomic dysfunction or haemodynamic instability anticipated
• Neuromuscular monitor (Train-of-Four) mandatory if NMBA used

• Left lateral tilt (15 degrees) until delivery to relieve aortocaval compression
• Careful pressure area protection - sensory-impaired skin is vulnerable to pressure injury

• Normothermia or slight hypothermia preferred
• Avoid pyrexia - core temperature >37.5°C worsens demyelination conduction block (Uhthoff phenomenon)
• Use warming blankets only if temperature falls below 36°C
• Cool IV fluids, avoid excess warming devices

• Vasopressor of choice: Phenylephrine (first line) or noradrenaline for spinal hypotension - maintain MAP ≥65 mmHg and systolic BP within 20% of baseline
• Autonomic dysreflexia (if cervical or high thoracic MS lesions): precipitated by uterine contractions, catheterization, surgical stimulation - manage with deepening anaesthesia, antihypertensives

• Avoid hypotension - preferably phenylephrine infusion preemptively with spinal/epidural
• Warm IV fluids to normothermia range

• Standard 5 IU slow IV bolus after delivery + infusion 10-40 IU in 500 mL
• Note: oxytocin causes vasodilation and hypotension - slower infusion preferred, especially in autonomic dysfunction

Postoperative Management

• Recovery in a monitored setting (HDU/ICU) if significant preoperative weakness or respiratory dysfunction
• Neurological assessment documented immediately post-procedure (vital for medicolegal baseline)
• Continue regular medications - especially baclofen, antispasmodics; do NOT abruptly stop
• Adequate analgesia: multimodal - paracetamol, NSAIDs (after 24h), epidural infusion, TAP block if GA used
• Avoid NSAIDs if renal function impaired (common with DMTs)
• DVT prophylaxis: early mobilization, compression stockings, LMWH (as per obstetric protocol)
• Temperature monitoring: treat any fever early (lactated Ringer's cooling, antipyretics)
• Physiotherapy: early mobilization to prevent worsening of pre-existing weakness

• The postpartum period (first 3 months) carries the highest risk of MS relapse due to immune reconstitution
• Inform the neurology team prior to LSCS - early restarting of DMTs after delivery recommended
• Breastfeeding and DMT compatibility must be discussed with neurology
• Patient counselling regarding relapse signs

Summary Box: Key Points for MS + Emergency LSCS

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

Introduction

• Acute appendicitis (most common)
• Acute cholecystitis
• Maternal trauma
• Ovarian torsion/adnexal pathology
• Cancer (cervical, breast, colorectal)
• Cardiac surgery (rarely)
• Neurosurgery (intracranial aneurysm, tumour)

Physiological Changes of Pregnancy Relevant to Anaesthesia

• Mucosal engorgement (oestrogen) - nasal, oropharyngeal, laryngeal oedema from second trimester
• Increased Mallampati score, friable mucosa
• Increased risk of difficult/failed intubation (8x greater than non-pregnant)
• Use video laryngoscope routinely after second trimester

• FRC reduced by 20% (raised diaphragm)
• Oxygen consumption increased 20%
• Rapid oxygen desaturation on apnoea - prolonged pre-oxygenation mandatory
• PaCO2 reduced to 28-32 mmHg (compensated respiratory alkalosis) - maternal target EtCO2 = 28-34 mmHg

• Blood volume +45% (plasma > red cell mass = dilutional anaemia)
• Cardiac output +40-50% by term
• SVR reduced (progesterone-mediated vasodilation)
• Aortocaval compression by gravid uterus from 20 weeks - LEFT LATERAL TILT mandatory
• Supine hypotensive syndrome: compression of IVC reduces venous return and CO by 30%

• Delayed gastric emptying (progesterone effect on lower oesophageal sphincter tone) from 18-20 weeks
• Increased intragastric pressure (gravid uterus)
• High aspiration risk - full stomach protocol applies from second trimester
• Aspiration prophylaxis: sodium citrate 30 mL PO + ranitidine/pantoprazole preoperatively

• GFR increased 50% - lower creatinine baseline
• Hepatic metabolism altered - unpredictable drug pharmacokinetics
• MAC of volatile agents reduced by up to 30% (progesterone)

Goals of Anaesthetic Management

1. Maternal safety first - adequate oxygenation, ventilation, haemodynamic stability
2. Fetal wellbeing - avoid hypoxia, hypotension, acidosis, and uteroplacental insufficiency
3. Avoid teratogenicity - no anaesthetic drug proven teratogenic in humans at clinical doses
4. Prevent preterm labour - minimise surgical stress, avoid hypoxia, consider tocolysis
5. Minimise fetal drug exposure - prefer regional where possible

Timing of Surgery

Preoperative Assessment

• Gestational age and fetal viability (viable = >24-26 weeks)
• Obstetrician consultation - document FHR before procedure
• Aspiration risk assessment
• Baseline neurological, cardiorespiratory, renal status
• Coagulation (physiological hypercoagulability)
• Labs: FBC, coagulation, crossmatch, renal function, LFTs
• Informed consent: teratogenicity (low risk), preterm labour, fetal loss risk

Premedication and Aspiration Prophylaxis

• Sodium citrate 0.3M, 30 mL PO - clear antacid, immediately before induction
• Ranitidine 150 mg PO or pantoprazole 40 mg PO/IV - 1-2 hours before
• Metoclopramide 10 mg IV - improves gastric emptying, increases lower oesophageal sphincter tone
• Avoid sedative premedication - risk of neonatal respiratory depression if delivery imminent

Choice of Anaesthesia

A. Regional Anaesthesia (Preferred)

• Minimises fetal drug exposure
• Avoids airway instrumentation
• Allows continuous fetal monitoring
• Lower aspiration risk

B. General Anaesthesia

• 3 minutes tidal breathing at 100% FiO2 (FRC reduced, rapid desaturation)
• 8 vital capacity breaths as alternative in emergency
• Apply cricoid pressure during pre-oxygenation

• Propofol 2 mg/kg (or thiopentone 4-5 mg/kg) + Succinylcholine 1.5 mg/kg or Rocuronium 1.2 mg/kg
• Cricoid pressure - maintained until cuff inflated and confirmed
• Video laryngoscopy preferred - higher difficult airway rate
• Failed intubation protocol (DAS obstetric guidelines) must be known

• Volatile agent (sevoflurane/isoflurane) acceptable - maintain 0.5-1 MAC
• Target EtCO2 28-34 mmHg (avoid hyperventilation - causes uterine vasoconstriction and fetal hypoxia; avoid hypoventilation - fetal CO2 retention and acidosis)
• FiO2 sufficient to maintain SpO2 >95%; avoid maternal hypoxia (immediate fetal consequence)
• Avoid N2O in first trimester (inhibits methionine synthetase, theoretical folate metabolism concern) and long procedures
• Maintain normotension - MAP within 20% of baseline; treat hypotension promptly with phenylephrine

• All NMBAs have very low placental transfer (ionised, high molecular weight)
• Succinylcholine: safe in absence of contraindication; standard RSI doses
• Vecuronium, rocuronium, cisatracurium: all acceptable
• Reversal: neostigmine + glycopyrrolate (glycopyrrolate does not cross placenta; preferred over atropine)
• Sugammadex: limited safety data in pregnancy - use if sugammadex was used for RSI (mandatory with high-dose rocuronium)

Intraoperative Management

• Left lateral tilt (15-degree wedge under right hip) from 18-20 weeks onwards
• Prevents aortocaval compression - maintains venous return and uteroplacental flow
• During laparoscopy: Trendelenburg position increases aortocaval compression; use carefully

• Previable fetus (<24 weeks): Doppler FHR before and after procedure
• Viable fetus (>24 weeks): Electronic FHR + contraction monitoring before, during (if feasible), and after procedure
• Under GA: loss of FHR variability expected; fetal bradycardia is more concerning
• Intraoperative FHR monitoring allows identification of reversible factors

• EtCO2 28-34 mmHg (mirrors normal pregnancy PaCO2)
• Tidal volume 6-8 mL/kg IBW
• Avoid hypocapnia (PaCO2 <28): causes uterine vasoconstriction, fetal acidosis
• Avoid hypercapnia: fetal CO2 retention

• Maintain MAP >65 mmHg and systolic within 20% of baseline
• Vasopressor: phenylephrine infusion (first-line for spinal/regional hypotension in pregnancy)
• Treat hypotension aggressively - uterine blood flow is not autoregulated; any fall reduces placental perfusion

• Pneumoperitoneum pressure ≤15 mmHg (standard pressure further compromises venous return in pregnancy)
• Left lateral tilt essential
• Entry technique: open Hasson preferred over Veress needle (reduces uterine injury risk)
• CO2 absorbs across peritoneum - monitor EtCO2 carefully, adjust ventilation

Drug Safety in Pregnancy

Postoperative Management

• Multimodal: paracetamol (safe all trimesters) + regional technique (TAP block, epidural) + short-term opioids
• NSAIDs: avoid after 32 weeks (premature ductus arteriosus closure); use with caution in 2nd trimester
• Opioid use: monitor neonate if used near delivery - naloxone available

• Continuous FHR and uterine contraction monitoring postoperatively
• Monitor for preterm labour - obstetrician involvement essential
• Tocolysis: if preterm contractions occur, consider terbutaline, nifedipine; consult obstetrics

• Pregnancy is hypercoagulable + surgical immobility = very high DVT risk
• LMWH (enoxaparin) 12h postoperatively + TED stockings + pneumatic compression devices

• Obstetrician to perform fetal biophysical profile/Doppler after surgery
• Neonatology team alerted if gestational age is at the limits of viability

Summary: Key Principles - Non-Obstetric Surgery in Pregnancy

Recent Evidence Update

• Ioannopoulos et al., Eur J Anaesthesiol 2025 (PMID 40017411) - Systematic review: neuraxial anaesthesia/analgesia does NOT significantly increase postpartum MS relapse rates. Supports use of epidural/spinal in MS parturients when indicated.
• Monanian et al., Medicina 2025 (PMID 40282988) - Review of anesthetic management in pregnant patients for non-obstetric surgery: reaffirms regional anaesthesia preference, RSI principles, fetal monitoring guidelines, and the safety of currently used anaesthetic agents.
• Zeleke et al., Ann Med Surg 2024 (PMID 38846888) - Systematic review on perioperative management during pregnancy: no anesthetic agent currently in use is teratogenic at clinical doses; second trimester safest surgical window.