Continuous spinal anaesthesia

Surgical approach (if relevant)

Not a surgical operation, technique used to provide neuraxial anaesthesia/analgesia for surgery.
Typical procedures where CSA may be chosen: hip fracture fixation/hemiarthroplasty, major lower limb vascular surgery, lower abdominal surgery in high-risk patients, obstetrics (rare, selected cases).

Anaesthetic management (overview)

Type of anaesthesia: neuraxial regional (continuous intrathecal local anaesthetic titration) ± light sedation, GA backup plan required.
Airway: usually spontaneous ventilation with standard monitoring, have airway equipment ready. If conversion to GA: ETT or SGA depending on aspiration risk and surgical requirements.
Duration: can be prolonged (hours) because block is titratable/extendable via intrathecal catheter, useful when duration uncertain.
How painful: provides dense surgical anaesthesia, postoperative analgesia possible with low-dose intrathecal LA/opioid (practice varies, many use CSA primarily for intra-op anaesthesia).
Key physiological issue: sympathectomy → hypotension/bradycardia, avoid large initial dose, incremental dosing and proactive haemodynamic strategy.

Definition and rationale

CSA = placement of a catheter into the intrathecal space to allow incremental dosing of local anaesthetic (± opioid) to achieve and maintain a desired block height.
Rationale: compared with single-shot spinal, CSA allows titration (smaller aliquots), potentially less abrupt sympathectomy, adjustable duration, and ability to manage unpredictable surgical duration.
Distinguish from epidural: intrathecal doses are much smaller, onset is rapid, block is denser, and risk profile differs (e.g., PDPH, high spinal).

Indications (typical FRCA framing: when is CSA advantageous?)

High-risk patients where avoiding GA is desirable and haemodynamic stability is critical: severe aortic stenosis (controversial, requires expert titration), severe LV dysfunction, severe respiratory disease.
- Key point for viva: neuraxial techniques in fixed cardiac output lesions require extreme caution, CSA may be chosen by experts because it can be titrated, but it is not automatically “safe”.
Elderly/frail with hip fracture where single-shot spinal may cause profound hypotension, CSA can be used to incrementally reach T10–T12 (or as required) with smaller doses.
Surgery of uncertain duration where a dense neuraxial block is required and epidural may be unreliable/slow: complex lower limb/vascular procedures.
When epidural is difficult or has failed but neuraxial is still desired (case-dependent).

Contraindications

Same as other neuraxial techniques: patient refusal, infection at site, uncorrected hypovolaemia, raised ICP due to mass lesion, true LA allergy, inability to cooperate/position (relative).
Anticoagulation/antiplatelets: follow current national guidance for neuraxial procedures, intrathecal catheter increases concern because removal is also a neuraxial intervention—plan insertion and removal timing.
- Viva emphasis: always state you will check the latest guideline and document timing of last dose and planned catheter removal.
Relative: severe aortic stenosis/fixed cardiac output lesions, severe pulmonary hypertension—requires senior decision-making, invasive monitoring consideration, and incremental dosing.

Equipment and set-up

Standard neuraxial asepsis: hat/mask, sterile gown/gloves, chlorhexidine in alcohol (allow to dry), sterile drapes.
CSA catheter options:
- Microcatheter (very small-bore intrathecal catheter) inserted via spinal needle (historically associated with cauda equina syndrome when used with hyperbaric 5% lidocaine and maldistribution, rarely used in many settings).
- Standard epidural catheter placed intrathecally via a Tuohy needle (intentional dural puncture) — easier to handle but larger dural hole → higher PDPH risk.
Filters/connection: use a bacterial filter and secure, clearly label as INTRATHECAL to prevent wrong-route injection, minimise dead space and ensure staff awareness.
Monitoring: standard AAGBI monitoring, consider arterial line for high-risk patients or anticipated haemodynamic lability.
Resuscitation readiness: vasopressors drawn up (phenylephrine/metaraminol/ephedrine), atropine/glycopyrrolate, intralipid, airway/ventilation equipment.

Technique (stepwise)

Consent: include neuraxial risks (failure, hypotension, high spinal, PDPH, infection, bleeding/haematoma, nerve injury) and CSA-specific issues (catheter misplacement, dosing errors, prolonged CSF leak).
Position: sitting or lateral, identify interspace (often L3/4 or L4/5).
Needle insertion and CSF confirmation, then advance catheter a short distance into intrathecal space.
- Avoid excessive catheter advancement (aim minimal length intrathecally, e.g., ~2–3 cm) to reduce risk of nerve root irritation/knotting (practice varies by kit).
Aspirate gently to confirm free-flowing CSF before each dose, inject incremental aliquots with time to assess effect (e.g., every 3–5 min).
Secure catheter, label clearly, document drug concentrations and total intrathecal dose.

Drugs and dosing (principles + example regimens)

Principle: use small intrathecal aliquots and titrate to effect, avoid a large initial bolus.
Local anaesthetic choices: bupivacaine (common), levobupivacaine, ropivacaine, hyperbaric vs isobaric affects spread and predictability.
Example incremental bupivacaine dosing (adult): 0.5% plain or heavy in 0.2–0.5 mL aliquots (1–2.5 mg) every 3–5 min until target block achieved, typical total dose often lower than single-shot spinal for similar surgery, but varies widely with patient and target height.
- For hip surgery, a pragmatic target may be around T10 (variable by procedure), assess sensory level and motor block.
Intrathecal opioid: fentanyl (e.g., 10–25 micrograms) may improve block quality and reduce LA requirement, morphine provides prolonged analgesia but increases risk of delayed respiratory depression and pruritus—use with appropriate monitoring and local policy.
Test dose concept: because intrathecal placement is confirmed by CSF, a traditional epidural test dose is not required, however, a very small initial aliquot is effectively a functional test to avoid sudden high block.

Physiology and haemodynamic management

Mechanism of hypotension: sympathetic blockade → venodilation (↓ venous return) ± arterial dilation (↓ SVR) → ↓ CO, bradycardia from cardioaccelerator fibre blockade (T1–T4) and reduced venous return (Bezold–Jarisch reflex).
Prevention/management: incremental dosing, left uterine displacement if pregnant, judicious fluid (avoid overload in frail/heart failure), early vasopressors, treat bradycardia promptly.
- Vasopressor choice: phenylephrine (SVR), metaraminol (SVR + some inotropy), ephedrine (HR/CO) depending on physiology and heart rate.
High spinal recognition: rapid ascending sensory block, upper limb tingling/weakness, dyspnoea, hypotension, bradycardia, nausea, reduced consciousness, treat immediately.

Complications (CSA-specific emphasis)

High/total spinal: risk increased if dosing errors or rapid boluses, manage with airway support, ventilation, vasopressors, atropine, and GA if required.
PDPH: risk depends on dural hole size, potentially higher if using Tuohy with intrathecal epidural catheter. Manage with conservative measures and consider epidural blood patch when indicated.
Neurological injury: direct trauma, neurotoxicity, cauda equina syndrome (historical association with microcatheters + concentrated lidocaine + maldistribution). Avoid high concentrations/large doses, use appropriate solutions and incremental dosing.
Infection: meningitis/arachnoiditis—strict asepsis, minimise duration, monitor for fever/back pain/neurological symptoms.
Intrathecal catheter issues: migration, kinking, knotting, breakage, difficult removal, manage with gentle traction, patient repositioning, seek senior help and follow local policy if resistance or breakage.
Drug error/wrong-route injection: catastrophic if epidural doses given intrathecally, mitigate with labelling, dedicated line, restricted access, and team briefing.

Postoperative care

Monitoring: haemodynamics until block regresses, motor/sensory checks, urinary retention risk.
If intrathecal opioid used: respiratory rate/sedation monitoring per local policy (especially with morphine).
Catheter removal: treat as neuraxial catheter removal—consider anticoagulation timing, document intact catheter tip, observe for neurological symptoms after removal.

Comparison with alternatives (useful in viva)

Single-shot spinal: simple, rapid, reliable, but fixed dose/duration and potentially abrupt sympathectomy.
Epidural: titratable and can provide postop analgesia, slower onset, less dense block, higher failure rate in some settings, larger doses and risk of systemic toxicity.
CSE: combines rapid onset spinal with epidural top-ups, avoids intrathecal catheter but retains epidural catheter benefits, still has sympathectomy from spinal dose.
Peripheral nerve blocks: avoid sympathectomy, may be preferable in severe cardiac disease, may not provide complete surgical anaesthesia for some operations and can be time-consuming.

Test yourself…

Describe continuous spinal anaesthesia and how it differs from an epidural.

Core definition + practical differences examiners expect.

CSA uses an intrathecal catheter to deliver incremental intrathecal local anaesthetic (± opioid) to achieve/maintain block.
Compared with epidural: much smaller doses, rapid onset, denser block, higher risk of high spinal if dosing error, PDPH risk may be higher if large dural puncture used.
Epidural has slower onset, larger volumes, segmental block, and can be used for prolonged postop analgesia, systemic toxicity risk is more relevant with epidural dosing.

List indications for continuous spinal anaesthesia and justify its use in a frail elderly patient with a hip fracture.

Focus on titration and haemodynamic control.

Indications: high-risk patients where GA undesirable, uncertain surgical duration, need for dense neuraxial block with controllable height, selected cases after epidural failure/difficulty.
Hip fracture/frail: incremental intrathecal dosing may reduce abrupt sympathectomy vs single-shot spinal, can stop once adequate level reached, can extend block if surgery prolonged.
Must still plan for hypotension/bradycardia and have vasopressors ready, consider invasive monitoring depending on comorbidity.

Outline how you would perform continuous spinal anaesthesia safely (step-by-step).

A structured approach scores well: consent, equipment, asepsis, placement, dosing, securing, documentation.

Pre-op: assess contraindications (including anticoagulation), consent, IV access, baseline observations, vasopressors prepared, GA backup plan.
Asepsis and positioning, identify L3/4 or L4/5, insert needle, confirm CSF, advance catheter minimally intrathecally, confirm CSF aspiration.
Dose incrementally with small aliquots, allowing time to assess block height, monitor BP/HR closely, treat hypotension early.
Secure and label INTRATHECAL, document drug, concentration, total dose, communicate to theatre team to prevent wrong-route injection.

What dosing regimen would you use for CSA and how would you avoid a high spinal?

Examiners want principles rather than one fixed recipe.

Use very small aliquots (e.g., bupivacaine 0.5% in 0.2–0.5 mL increments) with 3–5 min between doses, stop at target level.
Avoid rapid boluses, reassess after each aliquot, maintain verbal contact, monitor BP/HR continuously, be ready with vasopressors and airway support.
Consider opioid adjunct (e.g., fentanyl 10–25 micrograms) to reduce LA requirement, be mindful of respiratory depression if using morphine.

A patient becomes hypotensive and bradycardic after intrathecal top-ups. Explain the physiology and give a management plan.

Classic neuraxial physiology viva.

Sympathetic blockade → venodilation (↓ preload) and arterial dilation (↓ SVR) → ↓ CO, bradycardia from reduced venous return and/or T1–T4 blockade.
Immediate actions: call for help, check block height, left lateral tilt if pregnant, oxygen, ensure IV access/fluids running.
Treat: vasopressor (phenylephrine/metaraminol/ephedrine guided by HR and physiology), atropine for significant bradycardia, consider adrenaline in severe collapse.
If high/total spinal suspected: airway support, ventilation, GA induction if needed, ongoing vasopressor/inotrope support.

Discuss complications specific to continuous spinal anaesthesia and how you would reduce them.

Focus on PDPH, high spinal, infection, catheter issues, and drug error.

High/total spinal: avoid large boluses, incremental dosing, close monitoring, clear documentation of total dose.
PDPH: minimise dural trauma, consider catheter choice, counsel patient, manage with hydration/caffeine/simple analgesia and consider epidural blood patch when indicated.
Infection: strict asepsis, minimise duration, sterile handling, monitor for meningism/fever/neurological symptoms.
Catheter problems (migration/knotting/breakage): minimal insertion length, secure well, gentle removal, escalate if resistance.
Wrong-route injection: label INTRATHECAL, dedicated line, team briefing, restrict access, standardised drug preparation.

How would you manage a suspected high spinal during CSA?

This is a high-yield crisis algorithm question.

Stop intrathecal dosing, call for help, assess ABC.
Airway/breathing: high-flow oxygen, support ventilation, early intubation if reduced consciousness/apnoea.
Circulation: left tilt if pregnant, rapid vasopressor boluses (metaraminol/phenylephrine) and consider adrenaline for severe hypotension, treat bradycardia with atropine, IV fluids as appropriate.
Reassure/communicate, ongoing monitoring, consider ICU/HDU post-event.

Continuous spinal anaesthesia in severe aortic stenosis: discuss the pros, cons, and how you would make it safer if chosen.

Examiners want balanced risk discussion and a cautious plan.

Major concern: sympathectomy → ↓ SVR and ↓ coronary perfusion pressure, fixed stroke volume limits compensation, risk of ischaemia/collapse.
Potential advantage of CSA: very small incremental doses may allow controlled block height and avoid sudden haemodynamic change (but not guaranteed).
If proceeding: senior anaesthetist, invasive arterial BP, vasopressors ready (often phenylephrine/noradrenaline strategy), avoid hypovolaemia, incremental dosing with low target height, clear GA rescue plan.
Alternative strategies: peripheral nerve blocks, GA with tight haemodynamic control, or combined approaches depending on surgery and patient.

A nurse asks to give a top-up through the neuraxial catheter. What systems do you put in place to prevent wrong-route injection in CSA?

Human factors + practical steps are key.

Label catheter and filter clearly as INTRATHECAL, use distinctive colour/labels per local policy, keep line visible and separate from IV lines.
Only anaesthetist administers intrathecal doses, pre-brief team, document explicitly, use standard concentrations and pre-drawn syringes where possible.
Use checklists/double-checks for drug, concentration, route, and dose, minimise distractions during dosing.

Discuss PDPH risk in CSA and how you would manage a post-dural puncture headache after CSA.

Show you understand risk factors and escalation.

Risk factors: larger dural puncture (e.g., Tuohy), young age, female, pregnancy, previous PDPH, CSA with larger catheter/needle may increase risk vs pencil-point spinal.
Diagnosis: postural headache (worse upright, better supine) ± neck stiffness, photophobia, nausea, exclude red flags (fever, neuro deficit).
Management: hydration, simple analgesia, caffeine (local policy), advice and follow-up, if severe/persistent: epidural blood patch after assessment and consent, document and safety-net.