Regional Anesthesia and Nerve Blocks

Regional anaesthesia produces loss of sensation in a circumscribed region of the body by interrupting nerve conduction without affecting consciousness. A nerve block — the deposition of local anaesthetic at or near a nerve, plexus, or the neuraxis — is the central technique, and the field encompasses both neuraxial approaches and peripheral nerve blocks.

Definition

Regional anaesthesia is the reversible interruption of nerve conduction to a region of the body by depositing local anaesthetic at or near peripheral nerves, plexuses, or the neuraxis, producing analgesia or anaesthesia without loss of consciousness.

Scope

This topic covers the principles common to regional techniques: the conduction block produced by local anaesthetics, the distinction between neuraxial and peripheral approaches, the role of guidance methods, and the core safety considerations, particularly neurologic complications and bleeding risk in anticoagulated patients. It is the orienting topic under which neuraxial and peripheral techniques are detailed; it offers no procedural or dosing instructions.

Core questions

• Which neural target corresponds to the region to be anaesthetised?
• How do neuraxial and peripheral approaches differ in distribution and risk?
• What safety frameworks govern neurologic and bleeding complications?

Key concepts

• Conduction block
• Local anaesthetic pharmacology
• Neuraxial versus peripheral block
• Plexus and single-nerve blocks
• Local anaesthetic systemic toxicity
• Neurologic complications
• Anticoagulation and neuraxial risk

Mechanisms

Local anaesthetics diffuse across the nerve membrane and block voltage-gated sodium channels, preventing the rise of the action potential and thereby interrupting conduction in the targeted fibres. The clinical effect depends on where the agent is placed: in the epidural or subarachnoid space it produces a segmental, bilateral neuraxial block, while around a peripheral nerve or plexus it anaesthetises that nerve's territory. Smaller, less myelinated fibres carrying pain are generally affected before larger motor fibres, producing the differential block exploited in analgesia.

Clinical relevance

Regional anaesthesia is a reference concept for understanding how localised analgesia and anaesthesia are achieved and what determines their safety. The entry describes the field's structure and the society advisories that frame it, for educational orientation rather than as guidance for performing blocks or managing patients.

Evidence & guidelines

Safety in regional anaesthesia is structured by ASRA advisories on neurologic complications and on regional anaesthesia in patients receiving antithrombotic or thrombolytic therapy. Systematic reviews of ultrasound-guided regional anaesthesia describe its effect on block success and characteristics, and reviews by Marhofer and colleagues summarise the role of imaging in the field.

History

Regional anaesthesia developed from the introduction of injectable local anaesthetics in the late nineteenth century and matured through the twentieth century with neuraxial and plexus techniques; the recent adoption of ultrasound guidance, reviewed by Marhofer and colleagues, marked a major methodological shift.

Seminal works

• marhofer-2005
• liu-2009
• neal-2015
• horlocker-2018

Frequently asked questions

What is the difference between regional anaesthesia and a nerve block?

Regional anaesthesia is the broad concept of anaesthetising a region by interrupting nerve conduction; a nerve block is the specific act of depositing local anaesthetic at or near a nerve, plexus, or the neuraxis to achieve it.

Does regional anaesthesia affect consciousness?

No. By design it interrupts conduction in peripheral nerves or the neuraxis to numb a region while the patient remains awake, although sedation may be used separately.