Regional and neuraxial anaesthesia

01Core principlesThe concepts and mechanisms needed to understand the subject.

Regional anaesthesia interrupts nerve transmission at a defined anatomical level. A peripheral block targets a nerve or plexus; a fascial-plane injection relies on spread near neural structures; spinal anaesthesia places a small intrathecal dose with rapid dense block; epidural anaesthesia or analgesia places a catheter outside the dura for titratable dosing. These techniques can provide surgical anaesthesia, postoperative analgesia or both, and may reduce systemic opioid exposure. A technically successful block still needs a complete anaesthetic and rescue plan.

Choice starts with the operation, required distribution and duration, patient priorities, comorbidity and consequences of failure. Consent covers what the patient will experience, possible supplementation or general anaesthesia, common temporary effects, serious neurological or infectious complications and practical protection of an insensate limb. Baseline neurological findings should be documented so that later change is interpretable.

Bleeding risk is about both probability and consequence. The joint ESAIC/ESRA guideline treats neuraxial and deep non-compressible procedures differently from superficial compressible blocks. Intervals depend on the specific antithrombotic, dose, renal clearance and timing of catheter insertion and removal. A normal routine coagulation screen does not demonstrate absence of a direct oral anticoagulant effect.

Safety continues after injection. Staff must recognise block regression, excessive spread, motor impairment, urinary retention, hypotension, local-anaesthetic toxicity and evolving nerve injury. A dense block does not explain every new pain or weakness. The review must integrate surgical causes such as compartment syndrome, haematoma, positioning injury and direct nerve trauma.

Key points

Distinguish peripheral nerve block, fascial-plane block, spinal anaesthesia and epidural anaesthesia: each has different onset, spread, duration, failure pattern and bleeding consequence.
Before needling, confirm indication, alternatives, consent, side and site, infection, neurological baseline, drug allergies, total local-anaesthetic plan and an agent-specific anticoagulant interval.
Treat a high neuraxial block as an evolving airway and circulation emergency: call for help, give 100% oxygen, support ventilation, treat hypotension and bradycardia, and reassure an aware patient.
Use asepsis, ultrasound where it improves localisation, fractionated injection with repeated aspiration where appropriate, and monitoring proportionate to sedation and the possibility of conversion to general anaesthesia.
Document technique, level, drug, concentration, total dose, additives, catheter depth, complications and a postoperative plan for block checks, limb protection and escalation.
Children, pregnancy, critical illness and major organ failure change anatomy, physiology and toxicity risk and require their own specialist pathways.

02Mechanisms and patternsImportant relationships and how to distinguish them.

Expected block

Map sensory level, motor effect, onset and distribution against the intended nerve or dermatomes and the planned surgical stimulus.

Failed or patchy block

Incomplete distribution, delayed onset or breakthrough pain requires reassessment of anatomy, catheter position, dose limits and a safe alternative anaesthetic plan.

High neuraxial blockRed flag

Ascending numbness, hypotension, bradycardia, dyspnoea, arm weakness and impaired consciousness may progress rapidly to apnoea.

Neuraxial compressionRed flag

New back pain with progressive motor, sensory or sphincter dysfunction is a neurological emergency requiring urgent imaging and surgical discussion.

Peripheral nerve injury

Persistent weakness, paraesthesia or neuropathic pain beyond expected block duration needs documented examination and an agreed follow-up pathway.

Compartment syndromeRed flag

Disproportionate escalating pain, pain on passive stretch, tense swelling or neurological change requires immediate surgical assessment even when regional analgesia is present.

Red flags requiring action

Difficulty breathing, inability to speak normally, arm weakness, bradycardia or hypotension after spinal or epidural dosing suggests a high or total neuraxial block and requires immediate airway and circulatory support.
New severe spinal pain, motor weakness, sensory loss or bladder and bowel dysfunction after neuraxial intervention may represent an epidural haematoma or abscess; urgent neurological assessment and MRI must not wait for routine ward review.
Tinnitus, metallic taste, circumoral paraesthesia, agitation, seizure, conduction disturbance or cardiovascular collapse during or after injection may be local-anaesthetic systemic toxicity.
Never apply one anticoagulant interval to every block: neuraxial and deep non-compressible blocks carry greater bleeding consequence than superficial compressible techniques, and timing changes with agent, dose, renal function and traumatic puncture.
Pain out of proportion, increasing analgesic requirement or pain on passive stretch despite a functioning lower-limb block can indicate compartment syndrome and needs urgent surgical assessment.
A block on the wrong side, wrong site or wrong patient is prevented by an active stop-before-you-block check immediately before needle insertion.

03Interpreting evidenceInformation, measurements and their limitations.

Reasoning sequence

Consider the information, its meaning and its limitations before deciding what follows.

01
Medication and last-dose record
Why
Determine whether antithrombotic timing is compatible with the exact planned technique.
Interpretation and limitations
Check agent, dose, indication, renal function, last administration and catheter plan against current drug-specific guidance; do not infer safety from the medicine class alone.
02
Baseline neurological examination
Why
Document relevant power, sensation and pre-existing neuropathy before regional intervention.
Interpretation and limitations
A postoperative change is compared with this baseline, expected anatomical block and surgical or positioning risks rather than automatically attributed to the needle.
03
Block level and motor assessment
Why
Confirm that spread is adequate for surgery and not rising to a dangerous level.
Interpretation and limitations
Bilateral ascending block with cardiorespiratory change is an emergency; a patchy distribution suggests failure or malposition and should not be repeatedly dosed without recalculating total exposure.
04
Urgent spinal MRI
Why
Identify compressive neuraxial haematoma or abscess in a patient with concerning neurological change.
Interpretation and limitations
Imaging is time critical and should be arranged with simultaneous senior anaesthetic, radiology and spinal surgical escalation; routine observation is unsafe when deficits progress.
05
Coagulation testing when indicated
Why
Assess a defined haemostatic problem rather than provide generic clearance for a block.
Interpretation and limitations
Routine PT and APTT can be normal despite clinically important DOAC concentrations, so exact drug timing and specialist assays may be required.

04Applied reasoningWorked examples connecting principles to decisions.

01Worked case: anticoagulationEpidural requested in an anticoagulated adultAn adult scheduled for major abdominal surgery takes an antithrombotic and requests epidural analgesia.

1Identify the exact drug, dose, indication, renal function, last dose, other haemostatic abnormalities and both the procedural bleeding risk and consequence of neuraxial bleeding.
2Use the current agent-specific neuraxial table for insertion and catheter removal; if the interval is unmet, choose an alternative analgesic technique rather than improvising a shortened gap.
3Record postoperative thromboprophylaxis timing, catheter observations and who authorises removal and restart so that prescriptions cannot inadvertently overlap an unsafe catheter window.
4If traumatic puncture occurs or neurological symptoms develop, stop routine progression, seek senior advice and arrange urgent assessment under the applicable escalation pathway.

02Block emergencyHigh central neuraxial blockSoon after spinal or epidural dosing the patient becomes hypotensive, bradycardic and breathless with ascending weakness.

1Call for help, stop neuraxial dosing, give 100% oxygen, reassure the patient and assess airway, breathing, circulation and block level continuously.
2Support ventilation with airway manoeuvres, a supraglottic airway or tracheal intubation as physiology dictates, using a reduced hypnotic dose if consciousness is already impaired.
3Give rapid intravenous fluid and titrated vasopressor or anticholinergic therapy, start CPR if required, and plan monitored ongoing care after stabilisation.

03Post-block reviewUnexpected weakness after expected regressionMotor function fails to return on the expected trajectory or a new focal deficit appears after surgery.

1Stop any infusion, examine and map power and sensation, inspect the site and limb, and review block drugs, surgery, positioning, anticoagulation and timing.
2Escalate progressive, bilateral, severe or sphincter-associated findings immediately and arrange urgent spinal imaging when neuraxial compression is possible.
3Document findings and times, communicate with surgical and neurological services, and ensure follow-up until the deficit resolves or a definitive plan is active.

05Relevant medicines and safetySpecific regimens and precautions where medicines are relevant.

Produces reversible interruption of sensory and sometimes motor conduction at the intended neural structure.

Local anaesthetic for regional block

Select agent, concentration and volume for the target and keep the cumulative dose within the product-specific limit.

Reduce exposure in frailty or organ dysfunction, account for all infiltration and infusion sources, aspirate and inject incrementally where appropriate, and keep lipid rescue immediately available.

Restores vascular tone while airway, ventilation, volume status and excessive block spread are assessed.

Vasopressor for neuraxial hypotension

Use small titrated intravenous boluses or an infusion selected for heart rate and haemodynamic context.

Avoid a fixed universal dose; severe bradycardia, haemorrhage, anaphylaxis and high block require cause-specific resuscitation and senior anaesthetic support.

06Checking understandingVerify the reasoning, revisit uncertainties and apply feedback.

During block placement and onset, use clinical observation with pulse oximetry, blood pressure and ECG, adding capnography whenever verbal responsiveness is lost or deep sedation is likely.
Record sensory distribution, motor power, haemodynamics, pain and sedation at intervals matched to the technique and continue until the expected trajectory is clear.
For epidural infusions, inspect the catheter and prescription, total local-anaesthetic and opioid delivery, block height, motor effect, respiratory status and urinary function.
Protect an insensate limb from heat, pressure, falls and unsupported weight bearing, and give the patient explicit duration and contact advice.
Escalate any progressive neurological deficit, unexpectedly dense block, uncontrolled pain or cardiorespiratory deterioration rather than waiting for the next scheduled observation.

07Special situationsVariants, exceptions and circumstances that change the usual approach.

Compression changes risk

A superficial site that can be compressed is not equivalent to a neuraxial or deep plexus site where a small haematoma can cause major injury.

Removal is another procedure

An epidural catheter removal needs the same deliberate antithrombotic timing and postoperative restart plan as insertion.

Function tests analgesia

Pain assessment should ask whether the patient can breathe deeply, cough, mobilise and participate in recovery, while recognising new surgical pain patterns.

Baseline prevents attribution error

Recording pre-existing neuropathy and weakness helps distinguish block effect from surgical, positional or evolving compressive injury.

Specialist contexts remain separate

Obstetric, paediatric and critically ill patients have distinct physiology, drug handling, staffing and rescue needs that routine adult guidance cannot establish.

08Common pitfallsFrequent interpretation and management errors.

01
Proceeding with neuraxial needling from a normal PT or APTT without identifying a recently taken direct oral anticoagulant.
02
Repeatedly topping up an ineffective block without recalculating cumulative local-anaesthetic dose or preparing an alternative anaesthetic.
03
Assuming a regional technique prevents compartment syndrome from being detected or explains disproportionate escalating pain.
04
Removing an epidural catheter without linking the time to the last and next anticoagulant doses.
05
Leaving an insensate limb without protection, mobilisation restrictions or a route for urgent advice.
06
Applying adult elective guidance unchanged to pregnancy, children or critical illness.

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