Regional anesthesia

Editor-in-Chief: Santosh Patel M.D., FRCA [mailto:santosh.patel@pat.nhs.uk]

Overview
Regional anesthesia, is anesthesia or (anaesthesia) affecting only a large part of the body, such as a limb. Regional anaesthetic techniques can be devided in central and peripheral techniques. The central techniques include so called neuroaxial blocks epidural anaesthesia, spinal anaesthesia, the peripheral techniques can be further devided in plexus blocks like e.g. the brachial plexus blocks, and single nerve blocks. Regional anesthesia may be performed as a single shot or with a continuous catheter through which medication is given over a prolonged period of time, e.g continuous peripheral nerve block. Last but not least, regional anesthesia can be provided by injecting local anesthetics directly into the veins of an arm (provided the venous flow is impeded by a tourniquette.) This is called intravenous regional techniques (Bier block).

Regional anaesthesia generally involves the introduction of local anaesthetics to block the nerve supply to a specific part of the body, such as a limb, so patients cannot feel pain.

Indications and applications
Regional anaesthesia may provide anaesthesia (absence of pain) to allow a surgical operation, or provide post-operative pain relief. Various brachial plexus blocks exist for shoulder and arm procedures. Methods similar to routine regional anaesthetic techniques are also often used for treating chronic pain.

In labour and childbirth, epidural or combined spinal epidurals provide effective pain relief. Regional anaesthesia is now more common than general anaesthesia for caesarian section procedures.

Relationship to other anaesthetic techniques
Unlike general anaesthesia, patients may remain awake during the procedure, resulting in reduced side-effects and enabling the surgeon to converse with the patient during the procedure if required. However, many patients prefer to receive sedation either during the block, the procedure, or both.

There is a spectrum of complexity between simple local anaesthetic infiltration and major regional blocks, such as the 'central neuraxial blocks' (spinal and epidural), with nerve blocks lying in the middle. Nerve blocks affecting major peripheral nerves such as the femoral nerve and sciatic nerve are also sometimes viewed as regional anaesthetic techniques.

Complications
Unlike a minor local anaesthetic infiltration to allow a wound to be sutured, or a skin lesion to be excised, regional anaesthesia may involve large doses of local anaesthetic, or administration of the local anaesthetic very close to, or directly into the central nervous system. Therefore there is a risk of complications from local anaesthetic toxicity (such as seizures and cardiac arrest) and for a syndrome similar to spinal shock.

Most regional anaesthetic techniques, even in expert hands, have a failure rate of 1-10%. Therefore general anaesthesia may become necessary even when a procedure was initial planned to be conducted under a regional technique.

For these reasons, regional anaesthesia is only ever conducted in an environment that is fully equipped and staffed to provide safe general anaesthesia should this be needed.