Regional and Neuraxial Anaesthesia, Local Anaesthetics, Preoperative Assessment and Monitoring

4th Year MBBS • Neuroscience

Connect anaesthetic planning, regional techniques, local-anaesthetic action and patient monitoring for rapid revision.

1. THE TOPIC IN ONE CONNECTED FLOW

Safe anaesthesia begins with understanding the patient and the operation, then choosing the most suitable general, regional or local technique. Regional techniques depend on reversible interruption of nerve conduction by local anaesthetics, while monitoring helps detect physiological disturbance or systemic drug toxicity early.

Preoperative Evaluation

History + medical status + airway + operative needs

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Risk & Planning

ASA status + general versus regional choice

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Technique Selected

Spinal • epidural • caudal • nerve block • infiltration

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Local Anaesthetic

Enters nerve → blocks voltage-gated Na⁺ channels

→

Functional Block

Action potentials fail → pain and sensation interrupted

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Monitoring & Safety

Oxygenation + ventilation + circulation + temperature

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Outcome

Effective anaesthesia while minimizing haemodynamic or systemic toxicity

2. KEY CLINICAL CONNECTIONS

Neuraxial Technique Choice

Spinal injection into CSF → close contact with nerve roots → rapid, dense block with a relatively small drug quantity.

Epidural catheter → slower onset but repeat dosing possible → useful when duration must be extended.

Local Anaesthetic Pharmacology

Voltage-gated Na⁺ channel blockade → failure of depolarization → reversible interruption of nerve conduction.

Smaller sensory/autonomic fibers → blocked before large motor fibers → differential nerve blockade.

Safety & Monitoring

Sympathetic neuraxial block → vasodilatation → hypotension → blood-pressure monitoring becomes essential.

Excess systemic local anaesthetic → CNS and cardiac Na⁺ channel effects → seizures, arrhythmia or cardiovascular collapse.

3. AIM HIGH-YIELD INTEGRATION REVIEW

⭐ Preoperative history + ASA status → estimate physical risk → guide anaesthetic technique and monitoring intensity.

Spinal block → drug enters subarachnoid CSF → rapid dense neuraxial effect; epidural block → drug remains outside dura → slower but extendable block.

Combined spinal–epidural → rapid spinal onset + epidural catheter → fast initial anaesthesia with the option of prolongation.

⭐ Local anaesthetic → intracellular Na⁺ channel blockade → action potential failure → reversible loss of sensation.

Esters → mainly plasma esterase hydrolysis; amides → mainly hepatic metabolism → liver dysfunction can increase amide accumulation.

EMLA = lignocaine + prilocaine → lowered melting point of the eutectic mixture → topical anaesthesia of intact skin.

⭐ Adrenaline + lignocaine → local vasoconstriction → slower systemic absorption + longer action + less operative bleeding.

1:200,000 adrenaline = 5 µg/mL; 1:80,000 = 12.5 µg/mL → the smaller denominator represents the more concentrated solution.

Regional and Neuraxial Anaesthesia, Local Anaesthetics, Preoperative Assessment and Monitoring

1. THE TOPIC IN ONE CONNECTED FLOW

2. KEY CLINICAL CONNECTIONS

3. AIM HIGH-YIELD INTEGRATION REVIEW

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