Describe Techniques of Local & Regional Anaesthesia in detail.

Overview

Local anaesthetics can be delivered by many techniques, from numbing the skin surface to blocking whole regions of the body. These regional techniques can provide anaesthesia for surgery and analgesia while avoiding, or supplementing, general anaesthesia — useful in patients unfit for GA and for postoperative pain relief.

Surface, Infiltration & Field Block

Topical/surface anaesthesia: LA applied to mucous membranes or skin (e.g. EMLA cream before cannulation, topical to the airway or eye). Local infiltration: LA injected directly into the tissues to be incised (e.g. Suturing a wound). Field block: LA injected around the operative area to block the nerves supplying it.

Nerve & Plexus Blocks

Peripheral nerve block: LA injected around a specific nerve to anaesthetise its territory (e.g. Ulnar, femoral, ankle blocks). Plexus block: a whole plexus is blocked (e.g. brachial plexus block for arm surgery). Ultrasound guidance has greatly improved the accuracy and safety of these blocks.

Intravenous Regional Anaesthesia (bier’s Block)

Bier’s block (IVRA) anaesthetises a limb by injecting LA (usually prilocaine/lignocaine, never bupivacaine) intravenously into a limb exsanguinated and isolated by a tourniquet — the LA diffuses into the tissues to produce anaesthesia while the tourniquet is inflated. It is used for short procedures on the forearm/hand.

Advantages of Regional Techniques

Beyond simply numbing an area, regional techniques carry genuine advantages that explain their popularity: they can provide excellent operating conditions and prolonged postoperative analgesia while avoiding the risks of general anaesthesia — airway instrumentation, the cardiorespiratory depression of general anaesthetic agents, and postoperative nausea and drowsiness — which is particularly valuable in the elderly, the patient with significant comorbidity, and the day-case setting. They can be used as the sole anaesthetic, in combination with general anaesthesia, or purely for analgesia, and the growth of ultrasound guidance has made many nerve and plexus blocks faster, more reliable and safer to perform.

Complications Common to the Techniques

Whatever the specific method, the regional techniques share a set of potential complications that must be anticipated: systemic toxicity from an excessive dose or intravascular injection, direct nerve injury or intraneural injection, bleeding or haematoma at the site, infection, and failure or an incomplete block requiring supplementation or conversion to general anaesthesia. Careful patient selection and consent, aseptic technique, aspiration before injection, incremental dosing with the patient awake enough to report symptoms, and increasingly the use of ultrasound guidance all reduce these risks, and full resuscitation facilities are always available whenever a significant block is performed.

Ultrasound guidance has improved success and safety of nerve blocks.

• LA techniques: topical/surface, infiltration, field block, nerve/plexus block, IV regional (Bier’s).
• Provide anaesthesia/analgesia, avoiding or supplementing GA; ultrasound improves nerve blocks.
• EMLA for skin; infiltration for minor surgery; brachial plexus block for arm.
• Bier’s block: exsanguinate + tourniquet + IV prilocaine/lignocaine (never bupivacaine).
• Don’t release the Bier’s tourniquet early — risk of systemic toxicity.