Spinal anaesthesia for caesarean section

12 min read Last updated April 9, 2026

Categories of Caesarean Section

CategoryUrgencyDefinitionDecision-to-deliveryExamples
Category 1EmergencyImmediate threat to life of woman or fetus≤ 30 minutesAcute severe fetal bradycardia, uterine rupture, cord prolapse
Category 2UrgentMaternal or fetal compromise not immediately life-threatening≤ 75 minutesSuboptimal CTG, severe pre-eclampsia
Category 3Scheduled (urgent but stable)No maternal or fetal compromise, but early delivery required≤ 24 hoursFailed induction of labour, failure to progress
Category 4ElectiveDelivery timed to suit woman and servicePlanned (no specific target)Elective LSCS

Surgical approach

  • Positioning and prep
    • Supine with left uterine displacement (tilt or wedge) to reduce aortocaval compression, arms abducted or tucked, diathermy pad, urinary catheter often after block established
    • Skin prep (chlorhexidine/alcohol per local policy), drapes, time-out, prophylactic antibiotics usually before skin incision (local policy may vary)
  • Incision and entry
    • Usually Pfannenstiel transverse skin incision, open rectus sheath, blunt separation of recti, enter peritoneum
    • Lower uterine segment transverse incision, delivery of fetus, cord clamped, placenta delivered
  • After delivery
    • Uterotonics (e.g., oxytocin) given, uterine tone assessed, haemostasis, closure of uterus, fascia, skin
    • Potential surgical issues affecting anaesthesia: exteriorisation of uterus (pain/nausea), traction on peritoneum, bleeding/atony, need for conversion to GA, hysterectomy in catastrophic haemorrhage

Anaesthetic management (overview)

  • Type of anaesthesia
    • Regional:
      • Single-shot spinal is commonest for elective CS
      • Consider CSE for prolonged/complex cases
  • Duration
    • Typical surgical time 30–60 min (longer if adhesions, obesity, placenta accreta spectrum, multiple previous CS)
    • Spinal surgical anaesthesia usually ~90–120 min depending on dose and adjuncts
  • How painful
    • Intra-op: should be pain-free, may feel pressure/traction, peritoneal traction and uterine exteriorisation can cause discomfort/nausea
    • Post-op: moderate pain, multimodal analgesia required (intrathecal opioid + paracetamol/NSAID)

Aims and required block

  • Provide rapid, dense surgical anaesthesia with maternal safety and neonatal wellbeing
  • Target sensory level: T4 (nipple line) to cover peritoneal traction, assess bilaterally with cold/light touch, motor block expected
  • Maintain uteroplacental perfusion: avoid hypotension, hypoxia, hyperventilation (if GA), and aortocaval compression

Pre-op assessment and preparation

  • History:
    • Urgency category
    • Fasting status
    • Previous neuraxial/GA issues
    • Haemorrhage risk (placenta praevia/accreta, multiple CS)
    • Co-morbidities (pre-eclampsia, cardiac disease)
    • Anticoagulants / antiplatelets
    • Sepsis / fever
    • Neurological disease
  • Examination:
    • Airway
    • Back anatomy
    • Baseline BP
    • Signs of hypovolaemia / bleeding
    • Neuro baseline if relevant
  • Investigations:
    • Hb / platelets as indicated
    • Group &amp, save/crossmatch depending on haemorrhage risk
  • Consent: benefits/risks/alternatives (spinal vs CSE vs GA), specific risks: hypotension, high/total spinal, PDPH, nerve injury, infection, bleeding/epidural haematoma, failure/conversion to GA, pruritus/N&amp,V/resp depression from opioids
  • Monitoring and access:
    • Standard monitors
    • Left uterine displacement
    • 1 large-bore IV cannula (consider 2 if haemorrhage risk)
    • Vasopressors drawn up and labelled

Contraindications and cautions

  • Absolute:
    • Patient refusal
    • Infection at site
    • Uncorrected hypovolaemia / major haemorrhage
    • True allergy to LA
    • Raised ICP due to mass lesion
    • Severe coagulopathy / neuraxial haematoma risk
  • Relative/cautions:
    • Sepsis
    • Fixed cardiac output lesions (e.g., severe aortic stenosis)
    • Severe pulmonary hypertension
    • Severe thrombocytopenia or evolving coagulopathy
    • Severe fetal compromise where time-to-delivery mandates GA
    • Spinal deformity / previous surgery
  • Platelets: no single universal threshold, consider trend, cause, bleeding history, and local guideline, involve senior/haematology if uncertainty

Technique: performing the spinal

  • Position: sitting or lateral, optimise flexion, maintain left uterine displacement as soon as supine
  • Asepsis: full sterile technique, allow chlorhexidine to dry, sterile gloves, drapes, minimise contamination
  • Interspace: typically L3/4 or L4/5, midline or paramedian, use pencil-point needle (e.g., 25–27G Whitacre/Sprotte) to reduce PDPH
  • Drug choice:
Normal height&nbsp,Heavy marcaine 2.6ml + 400mcg diamorphine
Short height&nbsp,2.4ml + 300 mcg diamorphine
Placental extractionPrilocaine 20mg/ml, 2.5-3ml +/- Fentayl 20mcg
  • After injection:
    • Position supine with left uterine displacement,
    • Frequent BP monitoring
  • Block assessment:
    • Motor block
    • Cold/light touch to T4 bilaterally
    • Check sacral sparing, confirm before incision
    • Be vigilant for rapid cephalad spread/high spinal symptoms

Physiology and haemodynamics

  • Pregnancy increases susceptibility to hypotension:
    • Aortocaval compression + sympathetic blockade → ↓SVR, ↓venous return, ↓CO
    • Uteroplacental circulation is pressure-dependent (no autoregulation)
  • Hypotension consequences:
    • Maternal nausea/vomiting
    • Dizziness
    • Reduced uteroplacental perfusion → fetal acidaemia if severe/prolonged
  • Prevention and treatment
    • Left uterine displacement
    • Early vasopressor, and fluid co-load (crystalloid at time of spinal)

Vasopressors and fluids

  • Preferred first-line vasopressor in many UK units: phenylephrine (maintains fetal acid-base, may reduce maternal HR/CO).
    • Alternatives: metaraminol, ephedrine (more fetal acidosis association)
  • Phenylephrine dosing examples (local protocols vary):
    • Prophylactic infusion (e.g., 25–50 micrograms/min) titrated to maintain SBP near baseline,
    • Boluses 50–100 micrograms for hypotension
  • Metaraminol: bolus 0.25–0.5 mg IV titrated, infusion strategies exist, useful if bradycardic hypotension or phenylephrine causes problematic bradycardia
  • Ephedrine: bolus 3–6 mg IV, consider if hypotension with bradycardia and concern about uterine blood flow, but be aware of fetal acidosis association
  • Fluids: crystalloid co-load (e.g., 500–1000 mL) at time of spinal, avoid fluid overload in pre-eclampsia/cardiac disease, consider colloid only per local policy/risk-benefit

Uterotonics

  • Uterotonics are used for:
    • Active management of third stage of labour
    • Treatment of postpartum haemorrhage (PPH)
  • Escalation is typically:
    • Oxytocin → Ergometrine/Synthometrine → Carboprost → Misoprostol
DrugDoseRouteMaximum doseKey comments / cautions
Oxytocin5 IU slow IV bolusIVTypically 10 IU bolus, then infusion (e.g. up to 40 IU over 4 hours)First-line. Rapid administration → hypotension, tachycardia, flushing
Ergometrine0.5 mgIM or slow IV0.5 mg (may repeat once cautiously)Avoid in pre-eclampsia, hypertension, cardiac disease (vasoconstriction → severe hypertension)
Synthometrine (oxytocin + ergometrine)1 ampouleIM1 dose (avoid repeat dosing)Potent. Same cautions as ergometrine (avoid in PET)
Carboprost (15-methyl PGF₂α)0.25 mg every 15 minIM2 mg total (8 doses)Avoid in asthma (bronchospasm). SE: diarrhoea, vomiting
Misoprostol (PGE₁ analogue)600–1000 microgramsPR (or oral/sublingual)1000 microgramsUseful if others unavailable. SE: pyrexia, shivering

Intra-operative management

  • Monitoring:
    • NIBP frequent until stable
    • ECG
    • SpO2
    • Consider invasive BP if severe disease/major haemorrhage risk
  • Nausea/vomiting:
    • Treat hypotension first
    • Antiemetics (ondansetron, cyclizine, metoclopramide) as needed
    • Consider that uterine exteriorisation/traction can trigger symptoms
  • Uterotonics:
    • Oxytocin can cause hypotension/tachycardia
    • Give as slow IV dose/infusion per local policy
    • Be prepared for haemodynamic changes and treat promptly

Failed/patchy spinal and conversion plan

  • Recognise early: inadequate level, unilateral block, sacral sparing, pain on incision/traction, stop surgery if possible and reassess
  • Immediate actions: confirm test modality and dermatomes, optimise position, consider time (some blocks ascend slowly), treat anxiety and hypotension
  • Options depending on urgency and circumstances
    • Repeat spinal (with caution): only if clear failure (e.g., no block) and safe to do so, reduce dose to avoid high/total spinal, document and involve senior
    • Convert to epidural/CSE top-up if catheter present (not applicable to single-shot spinal unless CSE used)
    • Proceed to GA if inadequate block and delivery cannot be delayed, follow obstetric GA/failed intubation plans, consider aspiration risk

Complications and management

  • Hypotension
    • Left uterine displacement, vasopressor bolus/infusion, fluid co-load, treat bradycardia if present, consider other causes (haemorrhage, aortocaval compression, high spinal)
  • High/total spinal
    • Features: rapidly rising block, arm/hand tingling, dyspnoea, inability to speak, hypotension, bradycardia, nausea, LOC, may progress to apnoea
    • Management: call for help, left uterine displacement, 100% O2, support ventilation (BVM) early, treat hypotension/bradycardia (phenylephrine/metaraminol, atropine, consider epinephrine in extremis), prepare RSI and intubation, reassure patient if awake, consider intralipid only if LAST suspected (rare with spinal doses)
  • Local anaesthetic systemic toxicity (LAST)
    • Very unlikely with standard intrathecal bupivacaine doses, consider if inadvertent IV injection (more relevant to epidural) or large doses used, treat per AAGBI/RA-UK lipid rescue guidance
  • PDPH
    • Postural headache ± neck stiffness, photophobia, tinnitus, risk reduced with pencil-point small gauge, treat with hydration, simple analgesics, caffeine (limited), and consider epidural blood patch if severe/persistent
  • Neurological injury / infection / haematoma
    • Rare, red flags: severe back pain, progressive motor weakness, sensory changes, sphincter dysfunction, fever, urgent senior review and MRI if concern for epidural haematoma/abscess, time-critical decompression for haematoma
  • Intrathecal opioid side effects
    • Pruritus (common), nausea, urinary retention, delayed respiratory depression risk with intrathecal morphine—ensure appropriate post-op monitoring and naloxone availability

Special situations

  • Pre-eclampsia
    • Spinal is usually safe
    • Hypotension may be less pronounced due to higher SVR, but avoid fluid overload
    • Consider invasive BP if severe
    • Check platelets/trend and coagulation if indicated
    • Magnesium therapy increases risk of hypotonia/resp depression with sedatives/opioids
  • Obesity
    • Difficult positioning/landmarks
    • Consider ultrasound
    • Anticipate difficult airway even for spinal case
    • Ensure ramping and airway plan
    • Higher risk of high block if repeat dosing
    • Consider CSE for flexibility
  • Placenta praevia/accreta spectrum (PAS)
    • High haemorrhage risk
    • Consider CSE/epidural or GA depending on plan
    • Invasive monitoring
    • Large-bore access
    • Blood products
    • Cell salvage, major haemorrhage protocol

Test yourself…

Talk me through how you would provide spinal anaesthesia for an elective caesarean section.

Structure: preparation → technique → confirmation → haemodynamic strategy → analgesia and post-op plan.

  • Preparation: confirm indication/urgency, consent (including conversion to GA), aspiration prophylaxis, IV access, baseline BP, vasopressors drawn up, left uterine displacement ready, antibiotics per policy
  • Technique: asepsis, sitting/lateral, L3/4 or L4/5, 25–27G pencil-point, confirm free CSF, inject hyperbaric bupivacaine + opioid, lay supine with tilt
  • Assess block: cold/light touch to T4 bilaterally before incision, manage anxiety, avoid excessive sedation
  • Haemodynamics: prophylactic phenylephrine infusion or boluses, crystalloid co-load, treat hypotension promptly, manage bradycardia
  • Analgesia: intrathecal morphine if appropriate, regular paracetamol + NSAID, antiemetics, post-op monitoring for respiratory depression
What level of block is required for caesarean section and how do you test it?

Examiners want: level, modality, bilateral assessment, and relevance to peritoneal traction.

  • Aim for sensory block to T4 (nipple line) to cover peritoneal traction and uterine manipulation
  • Test bilaterally using cold (ice/ethyl chloride) or light touch, pinprick may be unreliable and unpleasant, document dermatomal level
  • Assess progression over time, be cautious of sacral sparing/unilateral block, confirm before incision
Why does spinal anaesthesia cause hypotension in pregnancy, and why is it important?

Core physiology + fetal implications.

  • Sympathetic blockade → vasodilation (↓SVR) and venous pooling (↓venous return) → ↓CO
  • Aortocaval compression worsens venous return when supine, pregnancy reduces CSF volume and increases spread
  • Uteroplacental blood flow is pressure-dependent (no autoregulation): severe/prolonged maternal hypotension can cause fetal hypoxia/acidaemia, maternal symptoms include nausea/vomiting
How would you prevent and treat spinal-induced hypotension for caesarean section?

Expect: left tilt, vasopressors, fluids, targets, and bradycardia management.

  • Prevent: left uterine displacement, crystalloid co-load, start prophylactic phenylephrine infusion or be ready with boluses, frequent BP monitoring
  • Treat: vasopressor bolus/infusion titrated to maintain SBP near baseline, treat bradycardia (atropine) and consider epinephrine if cardiovascular collapse
  • Reassess: ensure tilt adequate, exclude high spinal or haemorrhage, communicate with obstetricians
Compare phenylephrine and ephedrine for obstetric spinal hypotension.

A common FRCA theme: maternal CO/HR effects and fetal acid-base.

  • Phenylephrine: pure alpha agonist → ↑SVR, may cause reflex bradycardia and reduced maternal CO, associated with better fetal acid-base compared with ephedrine in many studies
  • Ephedrine: mixed alpha/beta → maintains HR/CO but crosses placenta and increases fetal metabolic rate, associated with more fetal acidosis
  • Practical: phenylephrine often first-line, ephedrine may be useful when hypotension is accompanied by significant bradycardia (depending on local practice)
A woman becomes breathless and says she cannot move her arms after the spinal. What is happening and what will you do?

This is high/total spinal until proven otherwise.

  • Diagnosis: high/total spinal with cervical/thoracic spread causing hypotension, bradycardia, respiratory compromise, consider differential (anxiety, local anaesthetic toxicity, pulmonary embolus) but treat as high spinal immediately
  • Immediate management: call for help, left uterine displacement, 100% oxygen, support ventilation early with bag-mask, prepare for RSI and intubation
  • Circulation: aggressive vasopressor therapy, treat bradycardia (atropine), consider epinephrine in severe hypotension/cardiac arrest, start CPR if needed with manual uterine displacement/tilt
  • Communication: reassure if conscious, inform obstetric team, consider urgent delivery if maternal resuscitation compromised
Your spinal seems inadequate at skin incision. How do you manage a failed or patchy spinal for caesarean section?

Key: stop, assess, decide based on urgency, avoid high spinal from repeat dosing.

  • Stop surgery if possible, assess block level bilaterally with appropriate modality, check time since injection and patient position
  • If no block at all: consider intrathecal failure, repeat spinal may be reasonable with reduced dose and senior input, avoid repeating full dose
  • If partial/patchy: options limited with single-shot spinal—often proceed to GA if urgent, if non-urgent, consider waiting briefly, repositioning, or conversion strategies per local policy
  • Analgesia/sedation alone is not a substitute for surgical anaesthesia, avoid masking pain with heavy sedation in a full-stomach patient
What are the complications of intrathecal morphine in caesarean section and how do you monitor/manage them?

Expect pruritus, N&amp,V, urinary retention, and delayed respiratory depression with monitoring requirements.

  • Common: pruritus, nausea/vomiting, treat with antiemetics, low-dose naloxone infusion if troublesome pruritus (local policy), or antihistamines (sedating)
  • Serious: delayed respiratory depression (hours after), ensure appropriate post-op observations (RR, sedation score, SpO2) per local guideline, have naloxone available
  • Other: urinary retention, counsel patient and coordinate catheter management
Outline the causes, diagnosis, and management of PDPH after obstetric spinal anaesthesia.

A frequent FRCA viva topic.

  • Cause: CSF leak through dural puncture → intracranial hypotension and meningeal traction, risk increased with cutting needles and larger gauge, reduced with pencil-point needles
  • Diagnosis: postural headache (worse upright, relieved supine) ± neck stiffness, photophobia, tinnitus, exclude other causes in postpartum (pre-eclampsia, meningitis, intracranial pathology)
  • Management: conservative (analgesia, hydration, caffeine with caution) and early anaesthetic review, epidural blood patch for severe or persistent symptoms after discussion of risks/benefits
Discuss spinal anaesthesia for caesarean section in a woman with severe pre-eclampsia.

Examiners want: safety, haemodynamics, fluids, coagulation, magnesium, monitoring.

  • Spinal is usually appropriate, hypotension may be less pronounced but still treat promptly, avoid fluid overload, consider invasive BP if severe features
  • Check platelets and trend, consider coagulation if HELLP suspected, follow local neuraxial thresholds and senior involvement
  • Magnesium therapy: potentiates neuromuscular weakness and respiratory depression with sedatives/opioids, be cautious with additional CNS depressants

0 comments