General anaesthesia for caesarean section

Surgical approach

Usually lower segment caesarean section (LSCS)
- Skin incision: typically Pfannenstiel (transverse suprapubic) or Joel-Cohen; occasionally midline vertical if urgent/complex
- Entry: open rectus sheath, separate rectus, enter peritoneum; bladder flap may be created
- Uterine incision: transverse lower segment; deliver fetus; clamp/cut cord; placenta delivered
- Uterotonics after delivery (e.g. oxytocin); uterine closure; haemostasis; close abdomen
Key surgical timepoints relevant to anaesthesia
- Decision-to-delivery interval (category 1 urgency) drives need for rapid RSI and minimising delays
- After delivery: analgesia options broaden (opioids/NSAIDs), and uterotonics/haemorrhage risk increase

Anaesthetic management (overview)

Type of anaesthesia: General anaesthesia (usually when neuraxial contraindicated/failed or extreme urgency)
Airway: Cuffed ETT with rapid sequence induction (RSI); second-generation SGA as rescue if failed intubation
Typical duration: ~45–90 minutes (variable with complexity/adhesions/haemorrhage)
How painful: Major abdominal surgery (high pain without multimodal analgesia; consider neuraxial opioids only if neuraxial used)
Aims: maternal oxygenation/aspiration prevention, haemodynamic stability, uteroplacental perfusion, neonatal wellbeing, readiness for haemorrhage

Indications for GA in Caesarean section

Category 1 CS (immediate threat to life of woman/fetus) where neuraxial would delay delivery
Contraindications to neuraxial: coagulopathy/anticoagulation, thrombocytopenia (context-specific), infection at site, raised ICP from mass lesion, patient refusal
Failed/patchy neuraxial block requiring conversion (time-critical or inadequate analgesia)
Maternal factors: inability to lie flat, severe haemorrhage/shock, some complex cardiac/respiratory disease (case-dependent), severe anxiety/trauma

Obstetric physiology relevant to GA

Airway: mucosal oedema, friability, weight gain, breast enlargement → higher difficult/failed intubation risk
Respiratory: ↓FRC, ↑O2 consumption → rapid desaturation during apnoea; mild chronic respiratory alkalosis
GI: reduced LOS tone + delayed gastric emptying in labour/opioids → aspiration risk; treat all as full stomach
Cardiovascular: aortocaval compression supine → hypotension, reduced uteroplacental perfusion; increased CO and blood volume (but haemorrhage can be concealed)
Pharmacology: MAC reduced ~30%; increased sensitivity to IV agents; placental transfer of lipophilic drugs (timing matters)

Preoperative assessment and preparation

Rapid focused assessment: indication/urgency category, fasting status, airway (Mallampati, mouth opening, neck movement), previous anaesthetic/neuraxial history
Comorbidities: pre-eclampsia/HELLP, obesity, diabetes, asthma, cardiac disease; check BP control and symptoms (headache, visual change, epigastric pain)
Bloods: Hb, platelets, coagulation if indicated; group & save/crossmatch based on risk (placenta praevia/accreta, abruption, anaemia)
Aspiration prophylaxis (time permitting): sodium citrate 0.3 M 30 mL, H2 blocker (ranitidine/famotidine), metoclopramide; continue left uterine displacement
Team brief: roles, urgency, neonatal team present, haemorrhage plan, difficult airway plan; ensure functioning suction and anaesthetic machine check
IV access: at least one wide-bore cannula (consider two for high haemorrhage risk); arterial line if severe pre-eclampsia/major haemorrhage anticipated

Monitoring and positioning

Standard monitoring: ECG, NIBP (frequent cycling), SpO2, ETCO2, agent monitoring; temperature if prolonged/haemorrhage
Position: 15° left tilt or manual uterine displacement; head-up if feasible for preoxygenation
Preoxygenation: tight mask, 100% O2; aim EtO2 ≥ 0.9 (or 3–5 min tidal breathing / 8 vital capacity breaths if time-critical)

Induction and airway (RSI in obstetrics)

Plan A: RSI with cricoid pressure (applied correctly, released if impairs ventilation/laryngoscopy); prepare difficult airway equipment and second anaesthetist/ODP support
Induction agent: propofol (beware hypotension) or thiopentone (traditional; haemodynamically stable); ketamine if shocked (caution: hypertension in pre-eclampsia)
Neuromuscular blocker: succinylcholine 1–1.5 mg/kg (rapid onset) or rocuronium 1.0–1.2 mg/kg with sugammadex available
Intubation: cuffed ETT; confirm with capnography; secure tube well (surgical drapes, breast interference). Consider smaller tube (6.5–7.0) if airway oedema
Failed intubation: follow OAA/DAS obstetric difficult airway principles—prioritise oxygenation; early second-generation SGA; consider waking if feasible; if cannot intubate/cannot oxygenate → front-of-neck access

Maintenance of anaesthesia (pre- and post-delivery)

Ventilation: controlled ventilation to normocapnia (avoid hypocapnia → reduced uterine blood flow; avoid hypercapnia → acidosis)
Anaesthetic: volatile (e.g. sevoflurane) in O2/air; aim adequate depth to prevent awareness (higher risk in obstetrics). Consider processed EEG if available
Before delivery: minimise opioids/benzodiazepines to reduce neonatal respiratory depression; consider small opioid only if maternal indication (e.g. fentanyl in severe hypertension) balancing neonatal effects
After delivery: give opioid (e.g. fentanyl/morphine), paracetamol, NSAID if not contraindicated; consider wound infiltration/TAP block; antiemetics
Uterine tone: volatile agents can reduce tone dose-dependently; keep volatile at minimum effective; coordinate with obstetrician if atony/PPH

Haemodynamic management and uterotonics

Maintain maternal BP close to baseline to preserve uteroplacental perfusion; treat hypotension promptly (fluids + vasopressors)
Vasopressors: phenylephrine (preferred in neuraxial; also useful in GA) vs ephedrine (more fetal acidosis association). Use titrated boluses/infusion as needed
Oxytocin: give after delivery (local protocol; often slow IV bolus then infusion). Watch for hypotension, tachycardia, nausea
If uterine atony/PPH: additional uterotonics (ergometrine—avoid in severe hypertension/pre-eclampsia; carboprost—caution asthma; misoprostol) + escalate haemorrhage protocol

Analgesia and antiemesis

Multimodal: paracetamol + NSAID (if no contraindication) + opioid after delivery; consider regional adjuncts (TAP block, wound infiltration)
Antiemetics: ondansetron, dexamethasone (after delivery if concerned), cyclizine/metoclopramide as appropriate; aspiration risk persists post-op

Emergence and postoperative care

Extubation: fully awake, head-up/left tilt, suction thoroughly; consider aspiration risk and airway oedema; ensure neuromuscular reversal complete
Post-op destination: recovery with close obs; HDU/ICU if severe pre-eclampsia, major haemorrhage, ongoing respiratory/cardiac issues
Postpartum haemorrhage vigilance: uterine tone, lochia, vitals; maintain normothermia, correct coagulopathy, monitor Hb/ABG if needed
Thromboprophylaxis: early mobilisation, LMWH timing per local policy (especially if neuraxial used—less relevant in pure GA but still postpartum VTE risk)

Special situations

Severe pre-eclampsia/HELLP: anticipate difficult airway (oedema), labile BP; avoid ergometrine; consider arterial line; cautious fluid; magnesium therapy potentiates NMB
Obesity: ramped position, aggressive preoxygenation (CPAP/PEEP), early airway adjuncts, consider videolaryngoscopy first-line; higher aspiration and desaturation risk
Placenta praevia/accreta: major haemorrhage risk—crossmatch, cell salvage (with obstetric filters/local protocol), large-bore access, warming, consider GA with arterial/central access; plan for hysterectomy/IR balloons
Conversion from neuraxial to GA: treat as full stomach; ensure adequate preoxygenation; anticipate hypotension from sympathectomy + induction; communicate timing with surgeons
Awareness risk: light anaesthesia pre-delivery, urgency, haemodynamic constraints—use end-tidal agent targets, avoid long periods without volatile, consider TIVA only with robust monitoring and experience

You are called for a category 1 caesarean section for fetal bradycardia. Talk through your anaesthetic plan for GA from arrival in theatre to incision.

Structure: preparation → positioning/preoxygenation → RSI → confirmation → maintenance/communication.

Rapid assessment: urgency, allergies, comorbidities (esp. pre-eclampsia), fasting status; quick airway assessment and plan for difficulty
Call for help early; allocate roles; ensure neonatal team present; brief obstetrician about induction timing and readiness
Monitoring on, left uterine displacement, head-up if possible; suction checked; difficult airway trolley and second-generation SGA immediately available
Aspiration prophylaxis if time: sodium citrate; do not delay for full regimen in category 1
Preoxygenate with tight seal 100% O2 aiming EtO2 ≥0.9; consider PEEP/CPAP if obese
RSI: induction agent (propofol/thiopentone; ketamine if shocked) + sux or roc; apply cricoid pressure correctly; intubate (consider videolaryngoscope)
Confirm tube with capnography; secure; start volatile; ventilate to normocapnia; maintain BP with vasopressors
Communicate ‘safe to start’ once airway secured and stable; minimise opioids until delivery unless maternal indication

Why is general anaesthesia higher risk in obstetrics? Give key risks and how you mitigate them.

High-yield domains: airway/aspiration, rapid desaturation, awareness, haemorrhage, neonatal depression.

Difficult/failed intubation more common (oedema, weight gain, breast enlargement) → plan, ramping, videolaryngoscopy, early SGA rescue, skilled help
Rapid desaturation (↓FRC, ↑O2 consumption) → meticulous preoxygenation, head-up, PEEP/CPAP, minimise apnoea time
Aspiration risk (full stomach, reduced LOS tone) → RSI, cricoid pressure (appropriate use), cuffed ETT, extubate awake
Awareness risk (light anaesthesia pre-delivery, urgency) → ensure end-tidal volatile targets, avoid prolonged ‘gas off’, consider depth monitoring
Haemorrhage/atony and haemodynamic instability → large-bore IV, blood availability, uterotonic plan, early activation of major haemorrhage protocol
Neonatal depression from drugs/hypoxia/hypotension → optimise maternal oxygenation/BP, minimise pre-delivery opioids, rapid delivery, neonatal team ready

Describe your approach to failed intubation during GA for caesarean section.

Prioritise oxygenation; follow local/DAS obstetric difficult airway algorithm; decide continue vs wake based on maternal/fetal status and ability to oxygenate.

Declare failed intubation early; call for help; maintain cricoid only if not impeding ventilation/laryngoscopy
Reoxygenate; optimise: head-up/ramped, suction, airway adjuncts, two-person mask technique, consider gentle ventilation
Limit laryngoscopy attempts; change technique/operator; consider videolaryngoscope if not already used
If cannot intubate but can oxygenate: insert second-generation SGA; confirm capnography; decide whether to proceed with surgery vs wake (consider category, fetal status, aspiration risk, surgical factors)
If cannot oxygenate (CICO): proceed to emergency front-of-neck access per DAS; stop surgery if possible; 100% O2; call ENT support
Post-event: document, debrief, inform patient, safety-net for aspiration/pulmonary complications; plan future anaesthesia

How do you minimise the risk of awareness during GA for caesarean section?

Obstetrics is a high-risk group due to urgency and deliberate opioid minimisation pre-delivery.

Avoid long delays between induction and volatile delivery; ensure vaporiser on and circuit primed where appropriate
Use adequate end-tidal volatile concentration (MAC reduced in pregnancy but still ensure sufficient depth); monitor end-tidal agent continuously
Consider a small dose opioid if haemodynamics allow and fetal considerations acceptable (especially if prolonged time to delivery)
Use neuromuscular monitoring and avoid paralysis without adequate hypnotic
Consider processed EEG monitoring in high-risk cases (e.g. haemodynamic instability limiting volatile, obesity, prior awareness)
Post-op: ask about recall; manage suspected awareness promptly and follow local policy

Discuss choice of neuromuscular blocker for obstetric RSI: suxamethonium vs rocuronium.

Compare onset, conditions, contraindications, reversal, and context of failed airway.

Suxamethonium: fastest onset/offset; excellent intubating conditions; contraindications include hyperkalaemia risk states, MH susceptibility; myalgia/bradycardia rare with single dose
Rocuronium (1.0–1.2 mg/kg): comparable onset at high dose; longer duration may be disadvantage in failed airway unless sugammadex immediately available and drawn up
In obstetrics, key is oxygenation and a robust failed intubation plan; rocuronium is reasonable if sugammadex availability and team familiarity are assured
Magnesium therapy (pre-eclampsia) potentiates non-depolarising block → adjust dosing and monitor

A woman with severe pre-eclampsia requires emergency caesarean section under GA. What are your key concerns and modifications?

Think: airway oedema, hypertensive response, magnesium, fluid balance, uterotonics, organ dysfunction.

Airway: anticipate difficulty (oedema); consider videolaryngoscope first-line; smaller ETT; gentle instrumentation
Haemodynamics: blunt intubation response (opioid after delivery if possible; consider short-acting agents per local practice); treat severe hypertension; avoid hypotension compromising uteroplacental flow
Magnesium: potentiates NMB and can cause respiratory depression; monitor reflexes/respiratory status; adjust relaxant and use nerve stimulator
Fluids: cautious due to pulmonary oedema risk; consider arterial line; early vasopressors rather than fluid loading
Uterotonics: avoid ergometrine if severe hypertension; use oxytocin carefully (slow) and alternatives as needed
Coagulation/platelets: check for HELLP; plan blood products; consider HDU/ICU post-op

How do anaesthetic drugs and maternal physiology affect the neonate during GA for caesarean section?

Neonatal status depends on uteroplacental perfusion, maternal oxygenation/CO2, and drug transfer.

Maternal hypoxia or hypotension reduces uteroplacental oxygen delivery → fetal hypoxia/acidosis; maintain oxygenation and BP
Hypocapnia can reduce uterine blood flow; hypercapnia causes fetal acidosis—aim normocapnia
Induction agents cross placenta but single bolus usually acceptable; prolonged induction-to-delivery time increases neonatal depression risk
Opioids/benzodiazepines pre-delivery can depress neonatal respiration and tone; minimise until delivery unless maternal indication
Volatile agents: minimal direct neonatal depression at typical concentrations, but can cause maternal hypotension and uterine relaxation at higher doses
Ensure neonatal resuscitation team present; anticipate need for PPV/CPAP if maternal opioids or fetal compromise

Outline your management of suspected aspiration during GA for caesarean section.

Immediate priorities: oxygenation, airway protection, suction, ventilation strategy, and escalation.

Call for help; head-down/left tilt if feasible; suction oropharynx; secure airway with cuffed ETT (if not already)
Suction through ETT; consider bronchoscopy if particulate matter; optimise oxygenation/PEEP; treat bronchospasm
Consider whether to proceed with surgery vs wake depending on urgency and maternal status
Post-op: CXR not routine unless symptomatic; monitor for pneumonitis/ARDS; antibiotics only if infection suspected (not prophylactic for chemical pneumonitis)
Document, explain to patient, and arrange follow-up

What are the common causes of hypotension during GA for caesarean section and how do you treat it?

Think: aortocaval compression, induction drugs, haemorrhage, high volatile, anaphylaxis, sepsis.

Aortocaval compression → left uterine displacement/manual displacement
Induction-related vasodilation/myocardial depression → reduce dose if shocked, use vasopressors early
Haemorrhage (concealed) → assess surgical field/uterine tone, quantify loss, activate haemorrhage protocol, transfuse guided by labs/TEG/ROTEM if available
High volatile concentration → reduce agent, supplement with opioids after delivery, consider adjuncts
Treat: oxygen, check depth, fluids judiciously, phenylephrine/ephedrine boluses or infusion; consider adrenaline if anaphylaxis

Discuss the conduct of general anaesthesia for caesarean section. Include preparation, induction, maintenance, and postoperative care.

A complete answer should show a safe RSI-based technique, awareness of obstetric risks, and a coherent plan for haemorrhage and neonatal considerations.

Preparation: urgency category; airway assessment; aspiration prophylaxis; IV access; blood availability; team brief; neonatal team; difficult airway plan and equipment
- Positioning: left uterine displacement; head-up for preoxygenation; ramping if obese
Induction: preoxygenation to EtO2 ≥0.9; RSI with propofol/thiopentone (ketamine if shocked) + sux/roc; cricoid pressure; intubate and confirm with capnography
- Have plan for failed intubation and CICO; early second-generation SGA rescue
Maintenance: volatile in O2/air; controlled ventilation to normocapnia; maintain BP (vasopressors); minimise opioids until delivery; avoid excessive volatile (uterine atony)
- Awareness prevention: monitor end-tidal agent; avoid prolonged low agent concentrations; consider depth monitoring
After delivery: opioid + multimodal analgesia; oxytocin per protocol; antiemetics; manage haemorrhage risk; temperature management
Emergence/post-op: extubate awake; monitor for aspiration/airway oedema; PPH surveillance; VTE prophylaxis; HDU/ICU if indicated; documentation and debrief if complications

Outline the reasons why failed intubation is more common in obstetrics and describe strategies to reduce morbidity and mortality.

Examiners expect physiology + systems + practical airway steps.

Why more common: airway oedema/friability, weight gain, reduced FRC/rapid desaturation, urgency/time pressure, less opportunity for optimisation, breast enlargement hindering laryngoscopy, higher BMI prevalence
Reduce risk: antenatal airway flagging; early epidural in high-risk labour; senior involvement; videolaryngoscope availability and training; ramped positioning; optimal preoxygenation (EtO2 target, CPAP/PEEP)
Reduce harm: strict attempt limits; prioritise oxygenation; early second-generation SGA; clear proceed vs wake decision-making; readiness for front-of-neck access; simulation and drills; post-event follow-up

Describe the anaesthetic considerations for caesarean section in a woman at high risk of major obstetric haemorrhage (e.g. placenta accreta).

Expect a major haemorrhage plan and multidisciplinary preparation.

Pre-op planning: MDT (obstetrics, anaesthesia, haematology, neonatology, IR/urology), consent for hysterectomy, availability of blood products and massive transfusion protocol
Access/monitoring: 2 large-bore cannulae, arterial line, consider central access; warming; frequent labs/ABG; TEG/ROTEM if available
Anaesthetic technique: GA often preferred for anticipated prolonged surgery/haemorrhage; secure airway early; consider controlled hypotension only with extreme caution (uteroplacental perfusion)
Blood conservation: cell salvage (local protocol), tranexamic acid early if bleeding, minimise hypothermia/acidosis/hypocalcaemia; calcium replacement during massive transfusion
Post-op: ICU/HDU; ongoing bleeding/coagulopathy surveillance; analgesia plan; thromboprophylaxis balancing bleeding risk